Essar Internship Report

(EXPLORATION AND PRODUCTION)
Summer Internship
2014
Internship Report
Date:
14th
May – 27th
June
Submitted by:
Dhaval Patel,
B.Tech, Petroleum Engineering,
Pandit Deendayal Petroleum University

Dhaval Patel, PDPU Page 2
Acknowledgement
I would like to take this opportunity to thank Mr. Pramod Gupta, Vice President, Production, Mr.
Arun Singh, Joint General Manager, Production Department and Mr. Manoj Kumar, HR Head,
Essar Oil Ltd. for giving me the opportunity to do my summer Internship with Essar Oil Ltd.
With deepest regards I would like to thank Mr. Nirav Majethiya , Field Supervisor, Bravo Team,
Instrumentation and Maintenance department and his team, also Mr. Chetan Mishra, Mr. Fayaz
Iqbal, Mr. VishwajitSoni, Mr. Shishir, Mr. Vipul Keswani and Mr. Vishnu for his guidance and
support throughout the internship and ensuring that I smoothly complete my training.
I would also like to thank the entire Production Department for their valuable support and
hospitality throughout the internship. A special thanks to the personnels of various service
providers like Kingston, and Aakash for guiding us at site, wherever possible.
I am greatly indebted to Essar Oil and all its members for their cooperation also thank everyone
at Essar Oil who directly or indirectly guided me in completing my internship

Abstract
An industrial training session was undertaken as a part of co-curricular activity. The
internship was being done in Essar Oil Ltd., Raniganj, CBM block and the duration of the
internship was 42 days (6 weeks) from 14th June to 27th July. Essar is one of the major private
sector companies in India and is planning to develop CBM blocks near Durgapur, West Bengal.
The Essar CBM block is spread over an area of 500 sq. km. located in the coaliferous belt of the
Eastern Raniganj Coalfields.
The main purpose of the internship was to get industrial exposure and field experience
along with proper guidance from the industry people. It will also enhance students knowledge
and gave them a great opportunity to connect to industry and test their academic knowledge and
apply to real fields. It will also help them decide the right carrier path and will help them to
choose projects for their final B.tech year.
Essar Oil Ltd. provided an important opportunity to the students to work closely with the
professionals and to train them in real conditions. The internship included visiting and working
on CBM fields, India’s one of the most dominating Unconventional fields. The students aimed at
getting the maximum out of the internship by field exposures and concentrating on particular
subjects. Essar Oil Limited managed the internship such that students are benefited and gets to
understand all the aspects of CBM and its production. Students were allotted various department
under appropriate guide to explain in details everything related to the operations and to entertain
the queries.

Table Of Content
Acknowledgement…(2)
Abstract…………….(3)
Chapter no. Topic Page no.
1 Induction Session……………………………………………...
1.1 Basics of Coal Bed Methane
1.2 Conventional Gasfield vs CBM field.
1.3 Problems encountered and Important concepts
1.4 Facts known by Interaction or Observations
6
2 Introduction to CBM Reservoir……………………………...
2.1 Coal as a reservoir
2.2 Petrology of coal
2.3 Physical and chemical properties of coal
2.4 Nature of porosity in coal
2.5 Coal cleat and permeability
14
3 Raniganj: Regional Geology………………………………….
3.1 Description of the Block
3.2 Coal Seams of the Block
19
4 Instrumentation and Maintenance………………..................
4.1 Introduction
4.2 Progessive Cavity Pump
4.2 GCS: System and Components
22

4.3 Wellsite: System and Components
4.4 Facts known by Interaction or Observations
5 Workover Operations………………………………………...
5.1 Introduction
5.2 Fishing: Methods, Operations and Various Tools
5.3 Flushing: Methods and Operations
5.4 Rotor/stator failure, causes and solution
5.5 Facts known by interaction and observations
41
6 Literature Reading and Understandings……………………
6.1 Selecting and Preparing a Fieldsite
6.2 Drilling and Casing the Wellbore
6.3 Fracturing a Coalseam
6.4 Treating and Disposing Produced Water
53
7 Health, Safety and Environment…………………..................
8.1 Protective Wear
8.2 Safety- Warning Signs
8.3 Fire Fighting Equipments
58

1. INDUCTION SESSION
An Induction session was conducted on 16th June, Saturday, to make us acquainted with Coal
Bed Methane, Raniganj scenario, operations carried out and various important concepts related
to CBM and its production. Also, various terms were explained and doubts were entertained.
Lectures were taken explaining the basics of CBM, difference between CBM field and Oilfield
and also, various common problems were discussed, along with their solution.
Essar is one of the major private sector companies in India and is planning to develop CBM
blocks near Durgapur, West Bengal. The Essar CBM block is spread over an area of 500 sq. km.
located in the coaliferous belt of the Eastern Raniganj Coalfields.
1.1 Basics of Coal Bed Methane:
Coalbed Methane (CBM) is natural gas (CH4) and it occurs in coals as adsorbed gas.
Coalbed methane is a technology play that requires reservoir understanding and appropriate
technology for all phases of prospect evaluation and field development. CBM Explorers
essentially try getting fix on the following:
•Coal thickness and coal seam continuity
•Gas content
•Permeability
CBM Reservoirs is water saturated & requiring dewatering in initial phase& gas takes time to
come on to the surface .
Consider that the use of CBM could fulfill national goals, such as the following:
• Provide a clean-burning fuel.
• Increase substantially the natural gas reserve base.
• Improve safety of coal mining.
• Decrease methane vented to the atmosphere from coal mines that might affect global
warming.
• Provide a means to use an abundant coal resource that is often too deep to
mine

Various uses of CBM can be given as:
•Power Generation: Lower capital investment and higher operational efficiency
•Auto Fuel: Compressed Natural Gas (CNG)
•Fertilizer Manufacture: As feed stock for urea manufacture & Captive power
•Steel Manufacturing : Better Quality product at lower capital costs
•Fuel for Industries : Economical fuel for cement plants, refractory, steel rolling mills etc
•Other uses : Domestic and industrial supplies
1.2 Conventional Gas field vs CBM field
The above mentioned two fields are different, owing to the below given facts:
 The composition of the rock. Coal is 90 percent organic, whereas conventional gas
formations are nearly 100 percent inorganic.
 The different mechanical properties of coal. Coal is brittle and
weak, and it tends to collapse in the wellbore.
 Coal’s naturally occurring fractures, or cleats. These fractures,
called face cleats and butt cleats, are extensive in coals. Most coal
reservoirs, however, require hydraulic fracturing to stimulate production.
 Coal’s gas storage mechanism. Gas is adsorbed or attached onto the
internal surfaces of the coal, whereas gas is confined in the pore spaces
of conventional rocks.
 The large volumes of water present in the coal seams. Water must be
pumped continuously from coal seams to reduce reservoir pressure

and release the gas.
 The low pressure of coal reservoirs. Backpressure on the wellhead
must be kept low to maximize gas flow. And all produced gas must be
compressed for delivery to a sales pipeline.
 The modest gasflow rates from coal reservoirs. Capital outlays and
operating expenses must be minimized to produce an economical
project.
Figure 1 : Comparison between Conventional and CBM production with time

1.3 Problems Encountered and Important Concepts
The CBM at Raniganj is mainly recovered using Progressive Cavity Pump, an Artificial lift
technique in which motion of Rotor, in side the Stator, displaces the water positively, from well
bottom to well head. The major problems encountered herein are listed below along with there
causes and solution.
Table 1: Problems with pump, their causes and solutions
Problem Cause Solution
High Torque
Sand inside the Stator Flushing
Stator Swelling Change Stator
Dogleg Severity Use of Centralizers
High Gas Pump below the perforation
Low Torque
Loose Fit Change Stator
Breakage of rod Fishing of rod
Unscrew tubing Fishing of tubing
No Water flow Weared Stator Change Stator
No water present Pump lowering
Logging is used to pinpoint the depth intervals where coals are present in a
wellbore. During this process, truck-mounted equipment lowers electronic
instruments down the well. Logging instruments record the characteristics of the
geology over the depth of the well. The logging data is processed and reviewed to
determine the zones (coal seams and other sediments) where natural gas is likely
to be present. This information is used to design the rest of the completions
program for the well
Various type of logs used to determine the depth and thickness of caol seams are:
 Density log
 Gamma ray log
 Neutron log

 Resistivty log- conventional and micrologs
 Mud log
 Caliper log
Adsorption Isotherm is helpful in understanding behavior of CBM, and a typical Adsorption
isotherm can be shown as:
Figure 2 : Langmuir Adsorption Isotherm
Langmuirs adsorption isotherm can be given in the form of equation as:
𝐺𝑠 = (1 − 𝑓𝑎 − 𝑓𝑚)
𝑉𝐿 𝑃
𝑃 𝐿+𝑃

Where, Gs = Gas storage capacity, scf/ton
P = Presure, psia
VL = Langmuir volume constant, scf/ton
PL = Langmuir Pressure constant, psia
fa = Ash content, fraction
fm = Moisture content, fraction
Isotherm: When coals are fully saturated with gas, initial gas content falls on adsorption curve.
However, coal seams are not always gas saturated, in that case the gas content falls below the
curve. Hence, reservoir pressure need to be reduced by dewatering to the critical desorption
pressure level to initiate gas production. Thus, critical desorption pressure is always less than the
initial reservoir pressure. Then the gas production is obtained till the abandonment pressure,
which is the lowest possible pressure beyond which the recovery of coalbed methane is not
economical. Abandonment pressure may vary from 50 to 150 psi, depending upon type of coals
and geological conditions. The gas content corresponding to this pressure is abandonment gas
content, which is recovery of gas is generally not possible. Abandonment gas content may also
vary from 15 to 30% of the original gas content.
Fit: Concept of “Fit” is very important of PCP, where Fit is the clearance between stator and
rotor. Tight fit results into high water slippage, low efficiency of pump and high torque, loose fit
results into low water slippage, high efficiencyof pump and low torque.
Production history: A typical production history of CBM Reservoir shows that CBM gas
production increases to a peak and then gradually reduces, the time span for this peak is de-
watering period. Also, the water production gradually decreases from the start of production and
becomes almost constant from the de-watering period.

Figure 3: Typical Production History Of CBM Reservoir
Typical well scheme in CBM block can be shown as:
Figure 4: Typical casing scheme in CBM block

Various artificial lifts can be used to pump out water. But Total power system efficiency is
usually higher for PCPs than other forms of artificial lift system, as demonstrated by the
following table:
Table 2: Various Artificial lift with their efficiency
System Type Typical efficiency (%)
PCP 60-75
Rod Pump 45-60
ESP 35-40
Gas lift 5-30
Jet Pump 10-25
1.4 Facts known by Interactions and Observations
 Gas from the CBM block is mainly used in fertilizer or steel plants and not sold for
housing purpose.
 Depth of the wells here ranges from 600 to 1800 m.
 The subsurface strata has many layers of coal seam ( 6-7 ) having thickness of 1.5 to 4 m.
 Various colours of pipeline shows: white = water line, yellow = gas line, brown = oil line,
red = fire water line.
 Gas adsorbed in CBM = 6 x gas adsorbed in gas reservoir.
 Maximum DLS used is 3˚/100ft for drilling a directional well.

2. INTRODUCTION TO CBM RESERVOIR
Coalbed methane is a form of natural gas extracted from coal beds. The term refers to
methane adsorbed into the solid matrix of the coal. It is called 'sweet gas' because of its lack of
hydrogen sulfide. The presence of this gas is well known from its occurrence in underground
coal mining, where it presents a serious safety risk.
Coalbed methane is distinct from typical sandstone or other conventional gas reservoir, as the
methane is stored within the coal by a process called adsorption. The methane is in a near-liquid
state, lining the inside of pores within the coal (called the matrix). The open fractures in the coal
(called the cleats) can also contain free gas or can be saturated with water. Unlike much natural
gas from conventional reservoirs, coalbed methane contains very little heavier hydrocarbons
such as propane or butane, and no natural gas condensate. It often contains up to a few percent
carbon dioxide.
2.1 Coal as a reservoir
Coal serves as both source rock and reservoir rock in CBM operations. To thoroughly evaluate
and develop a CBM reservoir internal structure and character of the coal and the strata
surrounding the reservoir must be understood properly. The two most important parameters in
evaluating a coalbed methane prospect are the total gas in-place and the gas deliverability of the
reservoir. These parameters are determined largely by the physical properties of the coal these
parameters are.
•Coal Resource: Number, Thickness, and Extent of Coal Seams
•Coal Rank, Type, and Quality
•Coal Cleats and Natural Fractures
•Gas Content and Composition
•Sorption and Diffusion Properties of Coal
•Coal Cleats and Natural Fractures

•Geologic Structure
•Stress Setting
•Hydrological Characteristics
Figure 5: Internal structure of a Coal seam
2.2 The Petrology of Coal
Coal petrology is the study of the origin, occurrence, and structure of coal. This readily
combustible rock contains more than fifty percent by weight and seventy percent by volume
carbonaceous material. This material includes inherent moisture formed from compaction,
induration and digenesis of variously altered plant remains similar to those in peat. Differences
in the kinds of plant materials (type), in degree of metamorphism rank, and in the range of
impurity (grade), are characteristic of coal and are used to classify coals. Several significant
differences between coal and conventional reservoir rock include: the greater compressibility of
coal, the relatively low effective porosity of coal, and the adsorption of gas onto coals carbon
structure.

As organic material is buried, compressed and dewatered, peat is formed. Peat is a dark
brown residuum produced by the partial decomposition and disintegration of plants that grow in
marshes and swamps. As peat is buried more deeply, heat and pressure progressively drive off
water and volatiles. Peat is then transformed into coal as the carbon content of the fossil organic
material increases through de volatilization.
In this process called coalification, coals increase in rank from lignite, to sub-bituminous,
bituminous and anthracite. Coal rank is important because it directly influences the gas storage
capacity of coal. Several factors influence the rank and type of coal formed the type of organic
material, depositional setting, pH, temperature, reducing potential, depth of burial and time of
burial.
Coal by definition is not a unique substance, but rather a group of sedimentary rocks
comprised primarily of altered vegetal matter. It is a heterogeneous mixture of components.
Mineral matter, water and methane are natural components of coal; their relative proportions are
important influences on the value of coal. Coal composition has evolved in response to
temperature, pressure, and the chemical environment. Though solid in appearance, coal contains
gas and oil-like substances, which are formed during coalification. Part of these substances is
retained in the coal and part of them is expelled.
2.3 Physical and chemical properties of coal
Physical and chemical properties can vary significantly from seam to seam and over a short
distance within a seam. Coal is usually classified by three fundamental characteristics:-
i) Grade: Represents the relative percentage of organic to mineral components.
ii) Type: Represents the various organic constituents.
iii) Rank: Represents the level of maturation reached, ranging from peat through anthracite.
These characteristics are used in classifying coal.
The three levels of coal rank are:

i) Lignite. A brownish-black coal in which the alteration of vegetal material has
proceeded further than in peat, but not so far as sub-bituminous coal, also called
brown coal.
ii) Bituminous. Varieties of soft coal which burn freely with a flame and yield volatile
matter when heated.
iii) Anthracite. A hard black lustrous coal with 92 percent or more fixed carbon (dry,
mineral matter-free), also called hard coal. The permeability of these coals usually is
very low.
2.3 The Nature of Porosity in Coal
Porosity is the portion of the total coal volume that can be occupied by water, helium, or a
similar molecule. The size of pore spaces can range from cleat fractures to intra molecular
interstices.
Coal pores can be classified into three sizes—
i) macropores (>500 Å)
ii) mesopores (20 to 500 Å)
iii) micropores (8 to 20 Å).
Pore volume and average pore size both decrease with rank through low volatile bituminous.
Porosity tends to decrease with rank into the low volatile bituminous stage, then increases as
additional volatiles are lost and pore space is left open. Macroporosity in general, includes
cracks, cleats, fissures, voids in fusinite, etc. Gas in excess of that which can be adsorbed on the
coal surfaces can be present as “free gas” within the porosity of the coal, mostly in the fractures.
Gas can also be dissolved in water moving through the coalbed. Natural gas is soluble, to a
limited degree, in ground water at the pressures and temperatures encountered in most coalbed
methane reservoirs.
2.4 Coal Cleat and Permeability

A prerequisite for economic gas flow rates is sufficient coal permeability. Most gas and
water flows through the coal cleat system and other fractures. Cleat is a miners’ term for the
natural system of vertical fractures which have formed in most coals usually as a result of the
coalification process. Typically, the cleat system in coal comprises two or more sets of sub
parallel fractures which are oriented nearly perpendicular to bedding. The set of fractures called
the face cleat is usually dominant. The spacing of face cleat fractures may range from one tenth
of an inch to several inches. The individual face cleats are relatively planar and persistent. Face
cleat orientation is related to tectonic forces and is believed to form parallel to the maximum
compressive stress. Typically, the butt cleat is perpendicular to the face cleat, but the fractures
tend to be discontinuous and non-planar. Butt cleats commonly terminate against face cleats.
Cleat spacing greatly influences coalbed permeability. Cleat spacing is related to rank,
petrographic composition, mineral matter content, bed thickness and tectonic history. In general,
at any given rank, closer cleat spacing is associated with brighter coal, less mineral matter, and
thinner beds. This correlation means that most medium and low-volatile coals will have good
permeability if the cleats are open. Permeability can be low to non-existent in semi anthracite
and anthracite coals because of the destruction of the cleat. Mineral fillings in cleat may also lead
to low permeability. If a large proportion of the cleats are filled, absolute permeability may be
extremely low. Common minerals in cleat are calcite, pyrite, gypsum, kaolinite, and illite. A
large acid pad is sometimes used at the beginning of a stimulation treatment in areas where
calcite is prevalent in the cleat. However, use acids carefully because many acid/corrosion
inhibitor combinations can damage coal seam permeability.
Figure 6: Structure of Coal block

3. REGIONAL GEOLOGY OF RANIGANJ BASIN
Damodar Valley basin has NW-SE directional orientation. Rocks of both lower and upper
Gondwana represented as Damodar Valley fields. Lower Gondwana consisting of Talchir and
lies unconformably on a basement of Archean metamorphic rocks. Sediments in the Raniganj
basin commenced with the deposition of glacial, peri-glacial sediments of Talchir formation. In
the northern periphery of the basin Talchir formation are exposed and are succeeded by a thick
sequence of coal measures, known as Barakar formation.
In the northern part of the coal field the Barakar sediments covers a large E-W trending tract
and attain maximum development in the north-west. The computed maximum thickness of
Barakar strata is of the order of 750m in this area and towards the eastern and south eastern parts
of the coalfield thickness decreases progressively. The Barakar grade conformably into the
overlying Iron Stone Shale formation also called Barren Measures.
Barren Measures has around 600m thickness in the western part of the basin and in the
eastern part the thickness reduces. The Raniganj formation which overlies the Iron Stone Shale
shows its acme of development in this basin. This formation covers a wide area and shows
thicker development in the western and central parts of the coalfield, where the thickness is
almost 1150m and the thickness decreases progressively towards the east.
3.1 Description of the Block
The Block RG (East)-CBM-2001/1 covers an area of 500sq.km. (approx.) and is located
eastern most part of the Raniganj coalfield area. It falls largely in Barddhaman district, West
Bengal. The block is bounded by Latitude: 23°21’45’’ and 23°41’12’’N and Longitude:
87°14’40’’ and 87°28’46’’E.

Figure 7: Geology of Raniganj basin
3.2 Coal Seams of the Block
The coal seams of Raniganj Formation in the Raniganj Coalfield area have a unique
development pattern over a wide stretch. Previously coal seam correlation was attempted and
resulted in recognition of ten regional coal seams of Raniganj measures, in addition to a
number of local throughout the basin. Synthesis of the large volume of data generated from the
spurt in exploration activities during the post-nationalization period suggests complex multi
directional splitting and merging tendencies of the coal seam. In the east central part of the coal
field the seams are thicker and well developed, and towards west they split, sometimes more
than ones, as a result more number of coal seams are found.
Based on recent analysis and available data, the coal seams of Raniganj Formation grouped into

seven coal horizons broadly, each horizon hosting a number of component coal seams
exhibiting splitting and merging tendencies.
This block RG (East)-CBM-2001/1 is located in the eastern most part of the Raniganj coalfield
area. Beyond the western limit of the block best development of the coal seams are found,
where the thickness is more than 50m. But in the eastern part of the block, there is a local
enhancement of the total coal content to about 60m, as recorded in the boreholes of Panagarh-
Domrasector.
Coal seam correlation of coal seams in this area with standard coal horizons of Raniganj
Formation is tentative.

4. INSTRUMENTATION AND MAINTENANCE
4.1 Introduction
Instrumentation and Maintenance plays a very important role in CBM field, as it uses
artificial lift for producing water from the reservoir, also number of well drilled is large
compared to oilfield leading to a need of appropriate instrumentation and maintenance. The gas
from the CBM block will be supplied to industries in and around Durgapur, West Bengal. Coal
Bed Methane gas from well heads shall be used as feed for the Gas Compression Stations(GCS).
The outlet of the GCS shall be sent to the Main Compression Station(MCS). Mainly Progressive
Cavity pumps are used as Artificial Lift technique, which is explained below as sections, along
with, wellsite, GCS and various problems realted to instrumentation and maintenance.
4.2 Progressive Cavity Pump
A progressive cavity pump is a type of positive displacement pump, which transfers fluid by
means of the progress, through the pump, of a sequence of small, fixed shape, discrete cavities,
as its rotor is turned. PCP systems typically consists of: Surface Drive and Downhole Assembly.
PC pumps comprises of a single helical-shaped rotor that turns inside a double helical elastomer-
lined stator. The stator is attached to the bottom of a production tubing string and in most cases,
the rotot is attached to a drive string that is suspended and rotated by the surface drive.

Figure 8: Schematics of progressive cavity pump
Operating principle: As the rotor turns eccentrically in the stator, a series of sealed cavities
form to move fluid from the intake to the discharge end of the pump. The differential pressure
between the pump intake and discharge provides the lift necessary to move produced fluid to the
surface. The result is a non-pulsating
PCP system have several unique design features and operating characteristic that favor their
selection for many applications :
 High overall system energy efficiency typically in the 55 to 75% range.
 Ability to produce high concentrations of sand or other produced solids.
 Ability to tolerate high percentage of free gas.

 No valves or reciprocating parts to clog, gas lock or wear.
 Good resistance to abrasion.
 Low internal shear rates (limits fluid emulsification through agitation).
 Relatively low power costs and continuous power demand.
 Relatively simple installation and operation.
 Low profile surface equipment.
 Low surface noise level.
Some of the limitations and special considerations are as follows:
 Limited lift capacity (maximum of 3000m). Note that the lift capacity of larger
displacement PC pump is typically much lower.
 Sensitivity to fluid environment.( Stator may degrade)
 Subject to low volumetric efficiency in wells producing substantial quantities of gas.
 Sucker rod strings may be susceptible to fatigue failures.
 Rod string and tubing wear can be problematic in directional and horizontal wells.
 Most system require the tubing to be pulled to replace the pump.
 Vibration problems may occur in high speed application.
 Parrafins control can be an issue in waxy crude application.
The detailed list of equipment required for PC pump operations is given below
a) Bottom Hole Equipment:
• Stator
• Rotor
• No Turn Tool
• Rotor bushing
• Necessary X-overs
• Gas anchors
b) Surface Equipment:
• Flow Tee

• Hollow Shaft drive head
• Intrinsically safe electric motor/hydraulic motor driven by duel fuel engines
• Polished rod
• Polished rod clamp
In Essar CBM block mainly drive heads of KUDU or NETZSCH are used. The nomenclature
describing the NETZSCH drive head is given as:
Figure 9: Nomenclature of NETZSCH Drive Head
Example: NDH 200 DH X 93
Pump geometry: The pump consists of two helices, one inside the other, which constitutes a
helical gear:
 the metal rotor, the internal one, is a simple helix;
 the soft stator, the external one, is a double helix with twice the pitch length of the rotor.

The geometry of the assembly is such that it constitutes a series of identical, separate cavities.
When the rotor is rotated inside the stator these cavities move axially from one end of the stator
to the other, from suction to discharge, creating the pumping action.
Pumps are described by the ratio of lobes created by the rotor and stator geometry. The most
typical pump for oil production is a pump with a 1:2 geometry is referred to as a single lobe
pump and creates geometry as follows:
At any cross-section the number of cavities is equal to the number of lobes on the stator i.e. for a
1:2 geometry there are 2 cavities 180O apart. Cavities are one stator pitch in length. One cavity
starts where the other ends. The pitch of the rotor is one-half that of the stator.
In addition to single lobe pumps some manufacturers have designs for multilobe systems, where
additional lobes are added to the rotor and stator.
Flowrate Calculations for progressive cavity pump:
Figure 10: Parameters of PCP pump for Calculations

At any cross section of the pump the area of fluid is equal to:
Area fluid = 4E x dR
And the volume of fluid per cavity is equal to:
Volume per cavity = 4E x dR x PS
Taking into account units the theoretical pump displacement (single lobe pump) can be
determined from:
PD = 5.94 x 10-1
x dR x PS
where
PD = pump displacement (bbl/day/rpm)
The same equation is applicable for calculating flowrate using metric units if the constant is
changed to 5.7E-6. The flowrate calculated will be in m3/day/rpm.and total flow is calculated as:
Q = PD x RPM
where
Q = flowrate (bbl/day)
RPM = Pump rotational speed (RPM)
The calculated Q will differ from actual production rates at surface due to:
 inefficiency (slip/leakage) in the PCP
 downhole fluid volume will be higher than that at the surface (Bo effect).
Rotor:
The rotor is normally 4140/4150 Carbon steel chrome plated with a coating. The purpose of the
coating is to increase lubricity of the rod in the stator, resist corrosion and resist wear from

solids. The coating is typically chrome but this may change with well conditions.
The function of the rod is to:
 withstand axial roads
 transmit torque to the rotor
In design of a rod system the following issues need to be considered:
 weight of the rod and rotor
 maximum stress in rod (combined torque and load)
 yield Strength of rod material
 operating environment (salt water, H2S)
 fatigue loading
Stator:
Suitability of elastomers to a given application is summarised by the following table:
Table 3: Stator material and their properties
Elastomer Mechanical
properties
Resistance to Temperature
limit(˚C)Abrasives Aromatic H2S CO2
Standard
Nitrile
Excellent Good Medium Good Good 120
Soft Nitrile Good Excellent Poor Good Poor 80
High
Acrylonitrile
Good Medium Good Good Medium 100
Hydrogenated
Nitrile
Good Excellent Medium Excellent Medium 140
Fluorocarbon Medium Poor Very
Good
Good Excellent 130

Efficiency:
The efficiency is the ratio of the power to lift fluids from approximately the fluid level in the
casing divided by the input power to the system.
One simple monitoring process can be the pump efficiency. The formula is:
Ƞ =
𝐵𝑃𝐷, 𝑎𝑐𝑡𝑢𝑎𝑙
𝐵𝑃𝐷
100𝑟𝑝𝑚
x 𝑟𝑝𝑚/100
The simple formula showing what the production is as a % of the no-slip production is a
method of estimating if the pump is too tight or too loose. If the efficiency is over 90% field
experience should be monitored to see if pump is too tight to restart or breaks in the pump or
rods occur. If the n is lower than -80% then experience may show the pump is set too loose in the
shop and after the pump elastomer swells in field operation. It is one way to try to monitor
performance without additional instrumentation.
4.3 Gas Compression Station (GCS)
CBM gas Compression facility receives the CBM gas from cluster of wells located at a
distance of approximately 0.5 to 0.8 kms away from each other. Alternatively cluster wells can
be drilled from well pads using directional drilling techniques.
Gas from about 40 to60 wells at different locations shall be transported to common header of
respective GCS. The pressure in these headers shall be in the range of 0.3 to 2 kg/cm2g and gas
temperature shall be in the range of 20-46˚C. The gas is fully saturated with water. A control
valve shall be provided at upstream to the Knock Out Drum in order to control the suction
pressure of the compressor based on the flow rate.
The free moisture will be removed with the help of Individual Suction Knock out Drums.
CBM gas is compressed from 0.3-1 kg/cm2g using Integral Reciprocating Compressors. A
common Drier is provided to maintain a dew point of -44°C at atmospheric pressure.

The entire system shall be designed for dispatching 4,50,000 SCMD of Dry CBM gas to the
consumers through the trunk line. However the compression capacity will bedecided based on
the productivity of wells connected to the individual GCS
Figure 11: Schematics of a GCS system
Various equipments in the CBM gas compression facility are as follows:
Knock-out Drum (KOD):
KOD shall be sized considering 2% free moisture in the gas stream. For the KOD sizing,
liquid hold-up time to be considered as 10 minutes. Automated draining to be provided on the
KOD. Demister Pad for removal of entrained liquid or carryover of liquid droplets.
Compressor:

Integral Reciprocating Compressor to be designed considering 0.5 kg/cm2g (min.) as
CBM gas inlet pressure. The compressor should be able to compress the CBM gas upto 15.3
kg/cm2g discharge pressure. The individual compressor shall be driven by a dedicatd Gas engine
drive. Under normal operating conditions, the CBM gas from the interstage separator in
Compressor Package shall be used as a fuel for gas engine. However, during start-up, the CBM
gas at the outlet of KOD shall be utilized.
Dryer:
CBM gas feed to the dryer shall be 100% saturated with moisture. Dryer to be designed
to produce dry CBM gas with -44˚C as dew point at atmospheric pressure. The dried CBM gas
shall be used for regeneration and this stream to be recycled at the KOD inlet. Hence the Dryer
upstream system (i.e. KOD, Compressor and interconnecting piping) to be designed considering
additional 15% flow based on Dried CBM gas.
Separator:
Separator to be provided at Compressor discharge. The sizing of separator shall be based on the
liquid hold up to 10 minutes.Automated draining to be provided on the separator.
Compresses Air Vessel:
Compressed Air Vessel to be provided for meeting the compressed air compressed air
requirement for cranking purpose of Gas Engine. The Vessel Shall be sized based on the
compressed air requirement, minimum required pressure and time duration specified by the Gas
engine Vendor.
Safety Valves:
Safety valves to be provided on the vessels to avoid overpressure and vessek rupture. The
sizing basis shall be as per API 521. The outlet of safety valves shall be connected to the
common flare header. While designing the PSVs built up back pressure at the outlet during
relieving conditions to be considered.

4.4 Designof Well Surface Facility
The current production is around 2MMSCMD and is expected to be around 3.5 MMSCMD
in 2014-15 and then gradual decline to 1.5 MMSCMD by 2035-36. Based on this the well
surface facilities have been designed keeping in mind the production capacities, reliability,
expansion possibilities and a design life of 30 years.
Based on the simulation studies the well drilling schedule has been designed. The well can be
either a single vertical or well pad having a vertical well or directional wells. The single vertical
well will be having PCP and well pad will have vertical well with PCP & directional well with
ESP (action plan not yet prepared). The annulus pressure at the well is around 28psi. Daily water
withdrawn is 40-60 m3/day. Well is connected to a skid mounted separator unit via flexible hose
pipes. Strainers are provided in gas line and water line for the removal of coal fines / solid
particles. The skid mounted unit will consist of the following equipment:
 Separator unit with level control
 Gas and water flow measurement equipment
 Back Pressure Regulator
 Float operated Dump Valve/ Mechanical Dump Valve
 4" water surge vessel with suspended ball (Not yet observed)
At each well sites ’V’ cone or orifice meter is used for gas measurement and turbine
meters for water measurement.

Figure 12: Schematics of a wellsite along with legends

Separator Skid:
The Seperator is provided along with the Seperaotr Skid approx. size of 5 meter (length)
× 1.6 meter (Width). From the annulus, gas through high pressure flexible hose (gas line) will
pass by the strainer where coal fines/ particles can be screened out. To the separator through 4"
CSGV (Cast Steel Gate Valve). From the tubing, water through high pressure flexible hose
(water line) can be bypassed by 2 " CSGV to the gas line. The vertical separator dimension are 2
meter (height) and 550 mm(ID). For the separator sizing, liquid hold-uptime to be considered as
10 minutes. Demister Pad for removal of entrained liquid droplets is provided inside the
separator at the top. Pressure Safety Valve is provided which will operate at 3.2 kg/cm2 at
separator. The gas separation takes place inside the separator. Separator cleaning/drain can be
done with 2" CSGV manually. We have below mentioned the existing scheme of level control
for liquid in separator at which was observed by us:
Existing Scheme:
Float operated level controller which will operate dump valve is provided at the
separator. The separatedgas from the top goes to the orifice/cone meter (gas measurement
system), through PCV towards the gas grid. In case of maintenance of PCV/flow meter the gas
can be bypassed through 2" globe valve to the gas grid and to the flare by 2" CSGV. In case of
maintenance of Turbine meter the water can be bypassed through 2" isolation valve and to the
water network through 2" CIGV (Cast Iron Gate Valve).
The skid mounted Vertical water/ gas separator will have the following specifications:
I. Operating : 45 psi
II. Design Pressure: 150 psi
III. Liquid: 250 M3 /day
IV. Gas processing Capacity: 25,000 M3 /day (Max)
V. Pressure Gauge 0-10 kg/cm2 dial size 100 mm 1/2" NPT with SS pigtail siphon. &
Temperature Gauge 0-100 °c with suitable thermo well.
VI. Pressure safety valve 3.2 kg/cm2 with proper safety vent line.
VII. Level switch controller unit which will operate Mechanical dump valve. (Revised
scheme)

VIII. Level switch controller unit which will operate dump valve (old scheme)
IX. Suitable hand hole shall be provided at separator.
X. Water surge vessel (4" dia) in the gas outlet line with float (Ball shaped)
XI. Turbine type meter for water measurement of 1.5 " dia.
XII. Orifice /cone type flow sensor and fitting of gas flow measurement device with RTC for
2" Diameter line pipe.
GG (Gas Generator)/DG (Diesel Generator) Sets:
In the initial stages of dewatering of the well DG is used for the pump/motor energy
consumption. After gas breakout DG is replaced by GG for pump motor and well site
illumination.
Dessicator Unit:
A part of gas is directed to the dessicator unit for the removal of entrained water droplets
in the gas prior to GG set.
Panel Room:
Major electric panels like Electric Harmonic Filter, Feeder Panel, VSD and RTU Panels are
placed.
Water Storage Facility:
Water tanks of 60 m3 for storage of water will be placed at the site.
Type of Valves:
Different type of valves used in the above system are:
 Globe valve
 Ball valve
 Gate valve
 Dump valve
 Non-return valve
 Pressure safety valve

Some of the important valves are explained in the below section:
1. Gate valve:
 Operating mechanism: a wedge-shaped gate slides between matching seats. Seal
is metal-to-metal. In larger sizes some manufactures use a gate that is two
separate plates separated by springs to hold the gate more firmly on the seat.
 Primary Use: liquids and steam. Used in natural-gas applications where a bubble-
tight seal is not required.
 Throttling characteristics: very poor
 Method of actuation: actuators are rarely used on gate valves outside of steam
plants and then they are configured to simulate turning a valve handwheel.
 Flow path: directly through the valve, generally larger than the pipeline ID.
 Advantages: somewhat lower costs.
 Disadvantages: extremely tedious to operate (e g a 12 inch e.g. 12-Grove gate
valve requires almost 100 turns of the handwheel to operate), no provisions for
double-block-and-bleed.
Figure 13: Gate valve

2. Globe valve:
Includes “motor valves”, needle valves, and backpressure valves.
 Operating mechanism: a plug-shaped stem seats in a matching seat that is
oriented 90° (relative to the flow direction) from the pipe centerline.
 Primary Use: throttling any fluid.
 Throttling characteristics: good across almost half the valve travel.
 Method of actuation: actuators in the oil and gas industry are usually
diaphragms.
 Flow path: up through the seat, across the chamber, and down into the outlet.
This flow path causes a pressure drop across even a fully opened valve.
 Flow symmetry: While a globe valve can be installed in either direction, the
manufacturer’s generally recommend that they be installed with the upstream
flow under the seat to minimize the pressure on the stem-packing.
 Advantages: throttling and easy actuation.
Figure 14: Globe valve
3. Butterfly valve:

 Operating mechanism: a flat plate that pivots about its centerline is placed in the
flow. Rotating the plate ¼ turn towards shut will put the plate against the seating
surfaces.
 Primary Use: on/off in applications where considerable leakage is acceptable.
 Throttling characteristics: very poor.
 Method of actuation: quarter-turn piston actuators can be used.
 Flow path: straight through the valve, but the plate in the flow prevents them
from being piggable.
 Flow symmetry: can be installed in either direction.
 Advantages: very inexpensive.
 Disadvantages: poor seal and not piggable.
Figure 15: Butterfly vlave
4. Ball valve:
 Operating mechanism: a drilled ball rotates between seating surfaces. The ball is
coupled to the valve body on the top only.
 Primary Use: low-replacement-cost on/off applications
 Throttling characteristics: poor.

 Method of actuation: quarter-turn piston actuators.
 Flow path: through the ball. Many floating-ball valves have reduced ports so they
are often not easily piggable (e.g., a reduced port valve on Tenneco’s 36- inch
main into New York City requires 3-5 hours for the pig to traverse)
 Flow symmetry: can be installed in either direction.
 Advantages: are cheaper than trunion-mounted ball valves.
 Disadvantages: lack of a body bleed, they have more of a tendency to leak
through (because of lateral ball movement as seals wear), and they have poor
sealing characteristics in very-low dP installations.
Figure 16: Ball valve
4.5 Facts known by Interactions or Observations
 Water level inside the well gives information about setting of the rpm and depth of the
pump. Echometer is used to measure the water level, using gas shots, which can be
manual or automatic.
 When gas sell is less, the pressure in the compressor increases. The limit is 16 kg/cm2,
rest gas in vented and flared.

 GGS-1 has motor driven (using electricity), screw type compressors and GGS-2 has
engine driven (using fuel), reciprocating type compressors.
 Understanding the Display from SCANNER 2000:
SP: Separator Pressure or static pressure (psi)
DP: differential pressure or discharge pressure (psi)
GFR: gas flow rate current (SCM)
GYT: yesterday gas flow rate (SCM) from today’s 0500 hours to yesterday’s 0500 hours
GTT: gas today total (SCM) from today’s 0500 hours till present hours
WFR:gas flow rate current (M3)
WYT:yesterday water flow rate (M3) from today’s 0500 hours to yesterday’s 0500 hours
WTT:water today total (M3) from today’s 0500 hours till present hours
TIME: current time of observing the scanner (hours)
TEMP: working temperature of the separator
 Variable frequency drive reads: Motor current, Motor Speed, Torque, Motor Power,
Voltage. The rpm can be changed from the VFD itself
 There are two type of maintenance: 1. Preventive maintenance: analyse the working
condition, change lubricants and coolants and 2. Breakdown maintenance: Repairing and
changing of instruments after break down
 The gear ratio is the ratio of motor angular velocity to the pump angular velocity, and is
generally between 2 and 4. (i.e. motot ω > pump ω )
 Possible problems in storage tank : leakages, screw or bolt failure, weak foundation, weld
failure.

5. WORKOVER OPERATION
5.1 Introduction:
Workover refers to any kind of well intervention involving invasive techniques, such as
wireline, coiled tubing or snubbing. It can also be described as the process of performing major
maintenance or remedial treatment on a oil or gas well. In all the operations in the CBM block
pump is required to stop and in some of the operations downhole pump is to retrieved. The
operations necessary to retrieve a downhole pump and/or sucker rod string for replacement or
repair. If a tubing-retrievable pump is used, you must pull the tubing string. However, if an insert
pump is used, you may retrieve the pump by pulling the rods. You can retrieve the rotor from a
progressing cavity (PC) pump by pulling the rods, but to retrieve the stator from a PC pump, you
must pull the tubing string.
Figure 17: Workover rig schematics with guying pattern

Drawwork specifications of typical Workover rig at the CBM block:
 Max rotational speed: 550 rpm
 Drum size: 345 mm
 Max. Weight: 2392 kg
 Max. Fast line tension: 80 kN
 Wireline diameter: Φ22 mm
Reasons to perform a workover:
 Sand gets accumulated in the stator resulting into high torque and stator is required to be
cleaned (flushing).
 Sucker rod may fail, either breaks down or unscrews, or the tubing may unscrew, leading
to a need of fishing operation.
 The pump may be required to be lowered owing to the changing water level condition.
 Sand may be accumulated in the wellbore reducing the depth of the well, leading to a
need of sand wash.
 When the production tubing may have become damaged due to operational factors like
corrosion to the point where integrity is threatened.
 Downhole components such as tubing, rotor, stator, NTT or Downhole safety valves may
have malfunctioned.
 Changing reservoir conditions can make the former completion unsuitable, in case of
which workover is required.
The operations under workover can classified as below:
Table 4: Workover Operations
Normal Operations
(Planned Operations)
Maintenance Operations
(Unplanned Operations)
Installation of Pump Sand Wash
Acid Job Flushing Job
Workover Operations

 Change Pump Type
 Change Pump design
Fishing Operations
Procedure for Installation of Pump:
Figure 18: Installation Procedure of PCP
Assemble the PC pump
Connect the PC pump with production tubing
Attach the rotor with sucker rod
Assemble the sucker rod with Centralizer and
Spindle
Connect the rotor with sucker rod
Space Out
Attach the surfacedrivehead to rod stringand
the flow tee
Attach the prime mover drivesystem
Connect the Power supply

Pre-Operation Checks:
 NTT-Check the NTT is working properly
 Stator-Check whether the elsatomer is ok and not damaged
 Stop Bushing-Check the stop bush is not damaged
 Pup Joint-Check whether the threads are ok
 Tubing(2 𝟕
𝟖⁄ ’’ EUE)-Check the tubing are ok and not punctured, also the threads are ok
 Rotor- It is clean and lubricated with proper grease, also no damage is done while
installing it
 Coupling- All threads are ok, also not worn or damaged
 Sucker rod( 𝟕
𝟖⁄ ’’ EUE)- All threads are ok, also not worn or damaged
 Centralizers- Check whether it is rotating freely on the spindle
 Spindle- All threads are ok, also not worn or damaged
 Polish rod- All threads are ok, also not worn or damaged
 Drive Head Assembly- It has proper lubrication and all connections ok
 Well Head- Its clamp is proper holding the tubing or not
5.2 Fishing: Operation and various tools used
The term fishing applies to all operations concerned with the retrieving of equipment or
other objects from the hole. Portions of the drill string, bit, drill string accessories, and
inadvertently dropped hand tools are typical items which may require fishing. The most common
fishing job is that recovering of a portion of the drill string left in the hole due to either its failing
or becoming stuck.
Reasons for fishing operation to be carried out:
 High torque due to sand or stator swelling, can lead to breakage of sucker rod, which
needs to be fished out
 Sucker rod may be unscrewed due to jerk on it or loose joint connection.

 The tubing may be unscrewed due to failure of No Turn Tool (NTT) and continuous
rotation of sucker rod, giving opening turns to tubing.
 Downhole Failure of drill string at the point of weakest joint.
 Overload of the string, due to overestimation of the used string.
 Parting of drill string due to excess overpulling of equipment.
 Mechanical failure of bit.
 Accidental drop of small equipments or foreign materials into the wellbore.
In Essar CBM blocks, fishing is required mainly during the production stage, when the tubing or
sucker rod fails due to high or low torque. (Reasons of high and low torque are mentioned in 1st
chapter.)
Fishing is the only solution to such failures. The main fishing operations observed here are
mainly using same sized tubing or rod to recover the unscrewed tubular. If a sucker rod is
unscrewed, rod is lowered into the borehole and rotated over the failed rod to catch it by the
thread and thus recovered by pulling out. If a sucker rod is broken due to high torque, the tubing
is pulled out along with which the rod is recovered, and it is pulled out of the tubing on the
surface. If a tubing can’t be recovered by same sized threads, a mill taper is used to form thread
inside the tube and then pulled out. Mill Taper is discussed in the below section. Other fishing
occurs during drilling failures, and the fish is recovered by appropriate fishing tool used in
oilfield operations.
Mill Taper:
It is a tool which is used to retrieve tubular fiah like tubing or casing. The mill taper hardfacing is
designed to clean the tubing from inside and to penetrate very gradually. The upper part of the
taper mill is long enough to aloow the addition of stabilizing blades while still remaining easy to
fish. The threads on the tool is generally made of tungsten carbide.

Stepwise Operations for performing Fishing:
 Plan the fishing operation on basis of the type of fish and prevelant conditions.
 Decommission the wellhead over which fishing is to be done, put it in a safe place.
 Install the workover rig, whose selection depends on depth of the well, weight of the
string to be pulled and availability of workover rig.
 Lower the string of appropriate size, till the depth above the top of unscrewed tubing.
 Support the string on the fish, and when the load gauge shows low load, rotate the string
to catch the tubing.
 Once the thread are made, the tubing is ready to be pulled out, (if tubing is not caught in
this way, mill taper should be used at the bottom)
 After pulling the string out, again install the pump, tubing, sucker rod and the drive head
to continue production.
5.3 Sand wash and Flushing Operation:
This operation is mainly used to remove sand which obstructs the proper working of a well.
The sand can be proppants used to hold the fracture open or it can be sand produced during
production. Sand wash and flushing differ from each other because sand wash cleans the well
from sand which is accumulated in the sump (extra depth drilled in a well), and flushing is
the cleaning of stator to continue its smooth operations. CBM field requires Hydraulic
Figure 19: Mill Taper

Fracturing of the coal seam to initiate the production of gas. After the HF operation it
becomes necessary to clean the well from the sand and sand wash is applied. During the
production stage of a well ,it may indicate high torque due to sand production, and its
accumulation over the stator. In that case flushing is done to clean the stator and again
continue its smooth operation.
Reason for performing Flushing/Sand wash
 After Hydraulic fracturing of the formation, the sand(proppant) gets accumulated in the
sump.
 During production the sand produces gradually and starts collecting or sticking to the
stator leading to high torque.
 Incompetent formation can lead to sand production resulting in high torque.
 High flow rate (by high rpm or high pitch of the rotor) can result in high production of
sand and its accumulation.
 Quality of stator can matter at some point of time, if the stator attracts produced sand
particles then accumulation increases and high torque results.
 Loose or tight fit matters as loose fit can let sand to be produced at the surface whereas
tight fit traps those sand particles.
Stepwise Operation to perform Flushing/Sand Wash:
 Plan the flushing or sand wash program on basis of data available and the requirement f
the above mentioned process.
 Decommission the wellhead over which flushing/ sand wash is to be done, put it in a safe
place.
 Install all the required instruments, the tanker carrying water and all the required
equipments for flushing operaitions.
 Commission the workover rig for the operation.
 Lift the rotor above the stator for passing the water through it and into the formation or to
clean the sump and bring it to the surface, (flushing or sand wash respectively)
 Connect the pipeline from the tanker to the tubing inlet from the flow tee.

 In case of flushing, pump in the fluid at atmospheric pressure.
 In case of sand wash connect another pipe at the annulus, and with pressure pump in the
fluid from the tubing.
 Lower the rotor again into the stator and commission the well head over the well and
continue production from the well.
5.4 Rotor/stator failure, causes and solution
Pump failures can be classified into different categories, each representing unique
characteristics. Typical causes of failures can be determined by visually inspecting pump
components and analysing various symptoms of failure.
Following table outlines common rotor and stator observations when a PC pump is removed
from a well.
I. Rotor failure
Table 5: Operational Failures of a Rotor, Visual signs, Possible causes and
Potential Solutions
I Failure Type Visual Signs Possible Causes Potential Solution
1. Rotor surface checking Checkered pattern 1.Heat
2.Lack of lubrication
3.Wear
1.Lowering the pump
2.Operate at lower
RPM
3.Install perforated tag
sub
2. Abrasion / Scoring Score marks 1.Solids 1. Operate at lower
RPM
2.Install extended
slotted tag-sub
3. Base metal wear Worn surface coating 1.Sharp flat edges due to
metal to metal contact
2.Smooth edges due to
prolonged operation in
abrasive environment
1.Re-evaluate space-
out
2.Install larger
displacement pump &
lower the RPM
4. Bent Rotor Rotor is bent 1.Improper handling 1.Ensure proper pull-
out & pull-in
2.Proper lifting &
handling of rotor

5. Broken rotor
(Torsional)
Rough jagged surface
throughout the cross
section of rotor
Due to high torsional stress
caused by
1.Solid entering the pump
2.Swelling of stator
3.Pump-off
4.Over-pressuring the pump
5.Operating it on the tag bar
1. Install extended
slotted tag-sub
2.perform
compatibility test with
stator
3. Operate it at lower
RPM
4.Install larger
pressure rated pump
5.Install high torque
shutdown VFD
6. Pitting Small dimpling on the
rotor
1.Presence of a corrosive
substances
1.Proper flushing after
acid based work-over
2.Add corrosion
inhibitor
3.Rotor with better
corrosion resistance
7. Broken rotor
(Fatigue)
Flat, smooth surface
across the cross-
sectional area
1.A continuous torque and
release of the pump
2.Long run life at higher
RPM
3.Large space out and rotor
is running in smaller ID
4.Landig in highly deviated
section
1.Install the smaller
pump and operate it at
Higher RPM
2.Use larger pump at
low RPM
3.Re-evaluation of the
space-out
4.Move the pump and
use pup joint to land it
in tangent section
8. Worn tag bar Tag bar will have a
flattered pin &
Worn rotor bottom
If the patterns are in
1.Clockwise direction
- Due to improper space-out
2.Counter-clockwise
direction
-Due to anti-clockwise
rotation of pump after
shut in&
Rotor break
1.Re-evaluate space-
out
2.Check whether
higher strength rods
are needed
II. Stator Failure
Table 6: Operational Failures of a Stator, Visual signs, Possible causes and
Potential Solutions

I Failure Type Visual Signs Possible Causes Potential Solution
1. Stators burnt
elastomer
Elastomer is
hardened on the
contact surface of
the stator &
Smell like burnt
rubber
Excessive heat due to
1.Gas
2.Swelling of elastomer
3.Pump off
1.Install pump or tail joints
below the perforation
2.Perform compatibility test
with wellbore fluid on
elastomer
3.Operate it at lower RPM
2. Blisters Blisters on the
surface of stator
when it is brought
to the surface
1.Gas enters the elastomer
under high pressure
2.When pump is shut down
in low fluid level
1.Lower the pump
2.Increase trip time
3. Missing elastomer
(Large pieces)
Large pieces are
missing from
elastomer
1.Exceeded over pressure
rating
2.Large solids
3.Pump off
1.Install pump with higher
pressure rating
2.Install slotted screen
3.Operate it at lower RPM
4. Missing elastomer
(Small pieces)
Missing pieces of
elastomer
throughout the
stator
1.Solids
2.Pump off
1. Install slotted screen
2. Operate it at lower RPM
5. Swollen
elastomer
Smaller ID & High
torque
1.Arometais such as
Benzene, Toluene & Xylene
and
Other incompatible
chemicals injected in the
wellbore
2.Gas entering the elastomer
& 𝐶𝑂2.
1. Perform compatibility
test with wellbore fluid on
elastomer
2.Lower the pump or Install
gas separator
6. Debonded
elastomer
Long intact pieces
of elastomer &
Clean inner wall of
the surface
1.Improper bonding agent
2.Extreme heat due to
I. High bottom hole
Temperature
II. Improper working
of Pump
1.High strength bonding
agent
2.
I. Higher temp.
rated elastomer
II. Pump lowering 0r
Operate it at lower RPM

7. Scoring /
Abrasion
Score marks along
the surface
1. Solid travelling through
pump
2. Higher RPM
1. Install slotted screen
2.Install a larger
displacement pump and
operate it at lower RPM
8. Perforation wash The outer steel
surface of stator
will look worn
1.Flow of solids, gas, and
high pressure fluid
1.Lift the pump above
perforation
2.Install tail pipe
9. High pressure
jetting
Worm like grooves
cut in the direction
opposite to the
flow
1.High pressure fluid
slipping within the pump
1.Install a pump with an
increased no. of stages
2.Re-evaluate the pump
efficiency
10. Rotor head
running in stator
Damaged top of the
stator
1.Improper space-out 1.Re-evaluate space-out
height
5.5 Facts known by interaction and observations:
 Sump is the extra depth drilled for deposit of sand without disturbing the operations of a
pump (50-60 ft). it needs to be cleaned by sand wash if it is filled with sand and creating
operational problems.
 Space out is the distance between staor bottom and tag-bar. The space is given for proper
rotation of the rotor without damage and efficient working. Space out is done by marking
a tag when rotor is rested on the tag-bar and the string is lifted up that much distance and
using pony pony rod is adjusted to the required depth.
The depth of spaceout can be known by the following formula:
Y(cm)=
∆𝒑.𝑳𝒐.𝒌
𝟏𝟎𝟎𝟎
+ d + Lstatic.12.10-6
.(Tfluid – Tair).100
Where,
Δp = actual differential pressure, bar

Lo = length of rod string, m
k = spacing factor from table
d = recommended distance between stop pin and rotor, m
Lstatic = static fluid level, m
Tfluid, Tair = fluid and air temperature, ˚C
 No Turn Tool: Torque anchor is used to take the reactive torque given by the friction
between the rotor and the stator of the helicoidal pump with progessing cavities, to
prevent the tubing from unscrewing. It is mounted under the pump, as a aprt of tubing.
Figure 20: A Typical No Turn Tool (NTT)
 Equipments used on a typical workover rig at the Essar CBM block are: tongs, slips,
swivel, teliscope, elevator, cathead, wench, hydraulic slip and tong.
 Controls on the workover rigs are: croen saver, drum emergency brake, main drum
control, engine setup, engine kill, engine throttle, cathead.
 For efficient working of a rig, the hook load decreases with the wind speed.

6. LITERATURE READING AND UNDERSTANDINGS.
6.1 Selecting and preparing a wellsite
The primary environmental regulations for developing coalbed methane sites in the Black
Warrior Basin are:
• Protecting Wetland Areas
• Disposing Produced Water
• Controlling Non-Point Source (NPS) Pollution
• Preventing Oil Spills
• Protecting Historical Sites
 The impact of wetlands presents the single most critical regulatory issue in establishing
right-of-way for pipelines, roads, and pads. Operating coalbed methane facilities often
requires some activity in wetlands (e.g. an access road or a pipeline system). Coalbed
methane facilities or activities which occur in wetlands are regulated and require a
permit.
 The ability to dispose produced water is key to the successful operation
of a coalbed methane field. If standards are not met, production from the field could be
forced to stop. Therefore, you must carefully plan for the management of produced water
when selecting the field site. Your selection of a field site should be based on a thorough
analysis of water treatment and disposal options
 A pollutant entering a waterbody through a NPDES permitted discharge is called a point
source discharge. However, a pollutant that reaches a waterbody by other means that are
not traceable to an identifiable facility, such as storm water runoff, seepage, percolation,
etc., is called a non-point source discharge. When planning a field site, you should
consider the requirements concerning non-point source pollution and controlling it.
 By properly siting a coalbed methane facility, you can greatly reduce control
requirements and impacts associated with a release event (spill). Any coalbed methane
operation must prepare a Spill Prevention Control and Countermeasure Plan (SPCC) to
prevent the discharge of oil from any facility into or upon any waters of the state.

 To protect any sites having potential historical or cultural significance, you should have
an historical or cultural resource assessment performed on the site before beginning any
development. Such an assessment can identify areas that should not be disturbed and can
help avoid unnecessary problems in developing the site.
6.2 Drilling and Casing the wellbore
To successfully drill and case a coalbed methane well, you must consider several
operational factors not usually encountered with conventional wells. For example, most coalbed
wells in the Black Warrior Basin are drilled into relatively shallow (500-3500 feet), lowpressure
coal formations. Because these formations produce very low rates of gas, project economics
require an extremely efficient and costeffective drilling program. A significant part of this
drilling program will be shaped by the stimulation treatment and completion methods you select
for the wells. Similarly, the unique mechanical properties of coals require that you use
procedures that avoid damaging the coal formation.
By carefully planning your coalbed drilling program, you can help ensure productive,
economical coalbed methane wells.
Figure 22: Planning flowchart for drilling

 Before you can make informed decisions about a drilling program, you must learn as
much as possible about coalbed drilling and production operations in your area. Begin by
collecting any well information available from offset coalbed methane operators.
 After collecting offset well information, you should evaluate any available well logs and
drilling records to determine approximate depths for prospective coal intervals. You
should also attempt to identify any potential problem zones.
 To select the casing string and drilling equipment, you must first determine at which
depths to set casing in the wellbore.
 Before the rest of the drilling program can be designed, you must first determine the sizes
of the hole to be drilled. You should base the hole sizes on the casing program rather than
selecting casing based on a pre-selected hole size.
 When you design a casing string, you must consider three principal forces: burst pressure,
collapse pressure and tensile pressure.
 To select the most effective drilling technique for your area of interest, you must consider
the geologic and reservoir conditions of the coal basin.
 Designing a hydraulics program for the drillstring involves selecting the proper
combination of drilling fluids and drillbits. An optimum drilling hydraulics program can
accelerate drilling rate and lower rig cost. A poorly designed program can slow
penetration, increase cost, and possibly damage the formation.
 Now, the drillstring should be selected. The drillstring includes the drillbit, drill collars,
and drillpipe. In some areas, you may also use stabilizers to control hole deviation.
 Because coals have a low mechanical strength, you must design the cementing program
to prevent the weight of the cement from fracturing the coal formations. You can avoid
fracturing coal formations during cementing by selecting proper cement and additives
and proper cementing techniques.
 After you have designed the casing, drillstring, and hydraulics programs, you can select a
drilling rig.
 Before spudding a well, you must satisfy all state and federal regulatory requirements.

6.3 Fracturing a Coalseam
Though most coals are naturally fractured, you normally need to hydraulically fracture coal
seams to produce economic gas flow rates.
In the reservoir, methane gas is adsorbed onto the surface of the coal. After the reservoir
pressure is lowered and the gas desorbs from the coal, it flows through the natural fractures in the
coal. For gas to flow to the wellbore at economical rates, effective communication must be
established between the natural coal fractures or cleats and the wellbore. The most effective way
to create this communication is by hydraulically fracturing the coal seam.
In fracturing, large volumes of fluid and sand are pumped at high pressure down the
wellbore. The fluid opens a crack in the coal, and after the fluid is removed, the sand remains in
place to keep the new channel open. The resulting proppant-filled fracture provides a flow path
into the wellbore for water and gas. When successful, hydraulic fracturing can greatly increase
methane production from coal seams.
Though much conventional fracturing technology can be applied to coalbed fracturing, many
techniques have been developed specifically for coalbed methane wells. Steps to perform a
hydraulic fracturing operation:
 Performing a Minifracture Test
 Planning a Fracture Treatment Design
 Preparing for a Fracture Treatment
 Performing a Fracture Treatment
 Evaluating a Fracture Treatment
6.4 Treating and disposing produced water
Managing produced water is critical to the successful development of a coalbed methane
project. Some operators have initiate projects and invested great time and money in drilling and
completing wells, but initially failed to sell any gas because of problems in disposing produced
water. Because water treatment and disposal can represent a large portion of daily operating
costs, improper planning
of this operation may result in unexpected costs which can impair the economics of an otherwise
profitable project.

Water disposal problems often stem from not carefully investigating the character of the
produced water, treatment and disposal options available, the costs of the various options, and
the regulatory requirements
that govern those options. A geological and engineering evaluation at the outset of the project
can help prevent many waterrelated problems.
The main issues you should consider in developing a plan to manage produced water:
 Characteristics of Coalbed Methane Produced Water
 Regulations and Permitting for Water Disposal
 Considerations for Designing a Water Disposal System
 Methods for Treating and Disposing Produced Water
7. HEALTH, SAFETY AND ENVIRONMENT.
Health, Safety and environment measures will be one of the most important aspects to be
taken care of during the operations. Some of the relevant provisions of the Oil Mines
Regulations’ 1984 (OMR) and other requirements, shall be followed at the well sites. In the
induction session, special attention was given to health, safety and environment, and its
importance was explained. The issues to be considered during operations on a CBM field are:
Protective wear, warning signs and Fire fighting, which are explained in the below section.
7.1 Protective wear
As per OMR certain essential protective wears are to be provided to persons working at the
well sites. Protective footwear were provided to the workers on the field to protect them against
any accidents. No person shall go into work or allowed to go into work unless he wears
protective footwear of such type as specified by Directorate General of Mines and Safety
(DGMS).
No person shall go into work or be allowed to go into work in a drilling rig or work-over rig
or rig building or rig dismantling or as such other place of work where there is a hazard from

flying or falling objects unless he wears a helmet of such type as may be approved by the
DGMS.
Every person engaged in the operations and every other person who may be exposed to the
risk of injury, poisoning or disease arising from the operations were provided with, depending
upon the risk:
i) suitable protective equipment including respiratory protective equipment, eye
protectors, gloves and aprons;
ii) suitable protective outer clothing for use in rain and extreme weather conditions.
During the training, all these precautions were made compulsory to get a complete field
exposure.
7.2 Safety- Warning Signs
The following warning signs were followed at Essar CBM block:
 Storage area and containers of toxic, corrosive, flammable, poisonous and radioactive
material were properly labeled and appropriately stored according to content.
 Warning signs were posted to denote any hazardous situation.
 Warning signs were posted in areas where the use of personal protective equipment is
required.
 “ No Smoking ” zones were clearly marked surrounding 30 m radius around a well. No
naked light or open flame or spark were permitted within 30metres of any well.
 Identification signs were conspicuously posted to locate emergency equipment.
Various warning signs were used on the field to keep the workers aware and to reduce the
probability of occurrence of any accidents.
7.3 Fire Fighting Equipments
 At every drilling rig at least two foam and two dry chemical type fire- extinguishers were
conveniently located.

 At every work-over rig at least one foam and one dry chemical type fire extinguishers
were provided.
 Foam shall not be used to extinguish electric fires.
 A competent person shall once at least in every three months examine every fire-
extinguisher and shall discharge and refill it as often as may be necessary to ensure that it
is in proper working order.
 A report of every such examination or refilling shall be kept in a bound-paged book kept
for the purpose and shall be signed and dated by the person making the examination or
refilling.
 Use of fire-fighting equipment: Every person employed at any drilling-rig, work-over rig,
well-head installation group gathering station, storage tank or on such work where fire-
fighting equipment may be required to be used, shall be trained in the use of such
equipment; regular fire drills shall be held for this purpose.
Figure 23: Safety and Fire fighting Equipments

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