Coring.pptx

WELCOME TO THE STUDENTS
7th Semester (Mining)
Bogura Polytechnic Institute, Bogura.
Md. Majedur Rahman
B. Sc (Hon’s), M. Sc in Geology & Mining, RU
Instructor (Tech)
Mining and Mine Survey Technology
Bogura Polytechnic Institute, BOGURA.
Presented By
Prepared by Md. Majedur Rahman, E-mail: majedu1r_ru6871@yahoo.com
August 3, 2022 1

Petroleum Well Design & Completion
Course Code No. 69372
Prepared by Md. Majedur Rahman, E-mail:
majedu1r_ru6871@yahoo.com
August 3, 2022 2

Chapter-08
Understand the Coring
8.1 Define coring.
8.2 Describe coring methods.
8.3 Define conventional and wire-line coring.
8.4 State coring tools.
8.5 Sketch coring bits.
8.6 Describe core bit stabilization.
8.7 Describe preservation process of core sample.
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Cores which extract from the formation /reservoir using special coring
tools. once the cores is cut, they are captured and retrieved to the
surface for analysis of different physical parameters.
Oil well coring is a procedure that is meant to remove a small amount
of rock sample from within the oil well. This entails using a core bit to
drill and remove a cylindrical sample of the rock. The core bit is used
with a core barrel and core catcher to drill out a sample that is then
brought up to the surface with the core barrel. The core bit has a hole
in its center so when the coring procedure is undertaken it produces a
small piece of rock.
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8.1 Define coring.

Core sample
A core sample is a cylindrical section of (usually) a naturally occurring
substance. Most core samples are obtained by drilling with special drills into
the substance, for example sediment or rock, with a hollow steel tube called
a core drill. The hole made for the core sample is called the "core bowling". A
variety of core samplers exist to sample different media under different
conditions. More continue to be invented on a regular basis. In the coring
process, the sample is pushed more or less intact into the tube. Removed
from the tube in the laboratory, it is inspected and analyzed by different
techniques and equipment depending on the type of data desired.
Core sample are two type:
1. Disturb sample
2. Undisturbed sample
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Purposes of Coring
The purpose of getting cores is to obtained rock samples of sufficient
size for :
1. making reservoir analysis test to determined porosity,
permeability ,residual oil and water saturation (primary purpose
of coring).
2. To establish the physical character of formation boundry
3. To furnish paleontological data for age and facies correlation
4. To determined the structural attitude of the beds
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Difference between Conventional coring and Side
wall coring
• Conventional coring:
1. Conventional coring provides large samples
2. It is more better and more consistent representation of formation..
3. It is better for heterogeneous rocks or for more complex lithology's
• Side Wall Core :
1. Side wall coring provides smaller samples
2. It is less representative of heterogeneous formation.
3. Within 1 to 2 percent of whole cores for medium to high porosity
formation
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8.2 Describe coring methods.
The coring procedure should follow a systematic approach. In lacustrine
settings, the water depth should be measured using an echo-sounding device
or weighted rope measure. In settings with a particularly diffuse sediment
water interface, the true water depth can be difficult to judge. When coring, a
duel or triplicate core approach should be used to cover boundaries between
core sections. Care should be taken to accurately record the penetration depth
which should be compared against the depth of material sampled to identify
any compression/ loss of material. The location of boreholes should be
measured with GPS and levelled according to a known datum if necessary.
Because the rock is so tough, the core bit, or drag bit in some cases, uses a a
PDC or natural diamond cutting device to cut with. When the cylindrical sample
is cut out, it needs to be safely removed from the well. The core catcher device
grips the bottom of the rock core. Tension is then applied to the drill-string, and
this causes the rock core sample to break away from the rock beneath it. By
holding the core sample, the core catcher serves to prevent it from falling away
and being lost.
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Core analysis has become a long way from the days when reservoir
productivity was determined by blowing through a piece of cable tool
produced core. Our tools and methods for drilling and core analysis have
changed but our interest is not. The reservoir rock properties that
determine hydrocarbon production, the variation in this properties and
how these properties effect ultimate recovery are still of primary
concern. Properly engineered core analysis provides a direct
measurement of these reservoir rock properties and is an essential step
in formation evaluation, reservoir and production engineering.
Fundamental core analysis measurements are unchanged but advances
provide the ability to test at reservoir conditions and to acquire
simultaneous measurements of reservoir related properties.
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Normally the most important information desired from the coring operation
concerns:
• Porosity, which is a measure of the fluid-carrying capacity of the formation.
• Permeability, which indicates whether the formation fluids will be able to
flow at rates fast enough to permit economical production of the
hydrocarbon fluids
• Water saturation
• Hydrocarbon saturations, including the relative percentages of oil and gas.
Rotary coring
Rotary coring equipment has continued to keep abreast of technological
developments in the drilling industry. At the present time there are basically
three types of rotary coring equipment:
1) Conventional coring
2) Wire-line retrievable coring
3) Diamond coring
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Conventional Coring
Conventional coring is a continued development of the original rotary coring
methods. Special equipment required in conventional coring includes a core bit,
which is located on the extreme lower end of the drill stem, and a core barrel, for
retaining the core after it has been cut, which is located immediately above the
core bit.
Wire-line Coring
In order to overcome the previously cited disadvantages of conventional core
drilling, methods have been developed for obtaining a core, bringing the core to
the surface and proceeding with normal drilling operations ,all without removing
the drilling tools from the hole. This is accomplished by inserting the proper
equipment in the lower part of the drill stem by means of a wire line which can be
run inside the drill pipe. This wire-line coring decreased the cost of obtaining cores
and thus many more cores may be obtained than would otherwise be possible. As
the average depth of wells continues to increase, the time and money saved by not
having to remove the drill pipe in order to obtain a core is substantial. The only
special equipment required on the lower end of the drill stem is a core bit. To
obtain a core after the core bit is in place, the core-barrel assembly is forced down
the inside of the drill pipe using drilling mud pressure.
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Diamond Core Drilling
In order to increase both core recovery and penetration rate, use has been
made of a diamond-faced coring bit. Diamond bits may be used to advantage
in coring hard, dense formations where the cost of the coring with roller
cutter bits is high. Although the cost of a diamond core bit may be as much
as fifteen to twenty times the cost of a conventional core bit, the reduction
in the number of round trips and the increased penetration rate in many
cases make the diamond bit more economical.
Side-wall Coring
Side-wall coring is a supplementary coring tool. It can be used in zones
where core recovery by conventional or wire-line methods is, or in zones
where the latter cores were not obtained as drilling processed. Side-wall
cores can be obtained at any time after the formation from which a core is
desired has been penetrated.
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8.3 Define conventional and wire-line coring.
Conventional Coring
Conventional coring is a method of drilling and acquiring rock samples. To retrieve the
core samples, the complete rod string and core barrel assembly has to be removed from
the hole.
Wire-line Coring
Wireline Coring. Coring is to obtain samples of different rock types. Coring is the
technique most often used for geological fieldwork. The assembly used for a core
drilling crown consists of a sleeve reamer
August 3, 2022
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8.4 State coring tools.
• A core drilling tool for drilling rock in underground soil formations which includes an
outside pipe and an inside pipe therein that can be conveyed separately to the surface.
The inside pipe includes a core-receiving receptacle at its lower end, and at its upper end
is provided with a measurement unit for on-site acquisition, processing and storage of
data, such as borehole, core and/or drilling process parameters.
• A way of measuring well conditions downhole by studying samples of reservoir rocks,
core analysis gives the most accurate insight into the porosity and permeability, among
other characteristics, of the well.
• A core is a sample of rock in the shape of a cylinder. Taken from the side of a drilled oil or
gas well, a core is then dissected into multiple core plugs, or small cylindrical samples
measuring about 1 inch in diameter and 3 inches long. These core plugs are then dried
and measured.
• In order to complete a core sample, drilling must be halted at the top of the subsurface
of the reservoir. The drillstring is removed from the wellbore, the drillbit removed and a
rotary coring bit is attached in its place. Similar to a drillbit, the rotary coring bit consists
of solid metal with diamonds or tungsten for cutting at the reservoir rock; but unlike a
drillbit, a rotary coring bit has a hollow center.
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8.5 Sketch coring bits.
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Fig. Conventional core barrel
Fig. Diamond core barrel

August 3, 2022
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Fig. Core Barrel Detail
Fig. Wireline core barrel

8.6 Describe core bit stabilization.
A major factor in drill bit selection is the type of formation to be drilled.
The effectiveness of a drill bit varies by formation type.
There are three types of formations: soft, medium and hard.
A soft formation includes unconsolidated sands, clays, soft limestone's,
red beds and shale.
Medium formations include dolomites, limestone's, and hard shale.
Hard formations include hard shale, calcites, mudstones, cherty lime
stones and hard and abrasive formations.
When we collection the core sample we need bit stabilization. Bit
stabilization depends upon the factors.
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8.7 Describe preservation process of core sample.
Core Handling Process
• Prepare adequate number of boxes, have rags.
• Set up “rig floor” boxes to receive core.
• Supervise core layout to ensure correct orientation and order.
• Wipe core clean with clean dry rags.
• Fit core. Space rubble between ends of core. Put rubble in sample bag and
mark depths.
• Strap core, uncovered interval understood to be at bottom unless known
otherwise.
• Mark core with reference lines and depths, using marker pens.
• Describe the core and shows.
• Box core and mark boxes.
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The Importance of Coring
Coring provides the only valid representation of the formation. It’s the
only means of direct measurement. All other methods such as well logs
require interpretation. While conventional well logs play an important
part in reservoir identification, only coring can ensure reliable
correlation of those logs to the actual subsurface conditions. And for
the most advanced analysis, only core samples can yield critical data
such as porosities, permeability's, and saturations.
August 3, 2022
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Any Questions
August 3, 2022 21

THANKS TO ALL
August 3, 2022 22

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