Well logging records measurements made in boreholes to characterize underground formations. Key logs described include gamma ray, which measures natural radioactivity to identify shale; spontaneous potential, which indicates lithology; caliper, which measures borehole size; resistivity, which distinguishes water and hydrocarbon zones; and neutron, which determines porosity. Mud logging continuously monitors drilling mud and cuttings for gas readings. Well testing evaluates reservoir properties through daily tests and drill stem tests to determine flow rates and commercial potential.

2. TOPIC:
WELLLOG& WELLTesting
Assigned by:
Sir Qamarudin khokhar
Sir Ali Ghulam Sahito
Presented by:
GhulamAbbas Abbasi

3. What is well Logging
 Well log is a continuous record of measurement made in bore hole
respond to variation in some physical properties of rocks through which
the bore hole is drilled.
 The record of the measurements, typically a long strip of paper,
is also called a log.
 continuous measurement of rock properties along the borehole made in
bore.

5. Gamma Ray Log
The gamma ray log is a record of a formations radioactivity.
GR Log is a method of measuring the naturally occurring gamma radiation to
characterized the rock or sediments in the bore hole or drilled hole.
 The radiation emanates from naturally occurring uranium ,thorium and potassium.
 The simple gamma ray log gives the radioactivity of the three elements combined
unlike the spectral gamma ray log.
 Amongst the sediments ,shales have by far the strongest radiation.
 It is the reason that the simple gamma ray log has been called the ‘shale log’.

6. Gamma Ray Log
 Radioactivity of shales and clays.
 In petroleum borehole logging the commonest natural radioactivity (by volume) is
found in shale's (clays).
 A high gamma ray value frequently means shale.
 A typical shale analyzed by a spectral gamma ray tool shows that each of the three
elements U,TH,K is contributing and an analysis of shale's in general shows the
relative contribution of each element to the overall radioactivity

7. Gamma Ray Log
 GR log reflects shale or clay content.
 Clean formations have low radioactivity level.
 Correlation between wells,
 Determination of bed boundaries,
 Evaluation of shale content within a formation,
 Mineral analysis,
 Depth control for log tie-ins, side-wall coring,
or perforating.
 GR log can be run in both open and cased hole.
 Low radioactivity is plotted to the left.
 High radioactivity s plotted to the right.

8. SP LOG
 The spontaneous potential (SP) curve records the naturally occurring
electrical potential (voltage) produced by the interaction of formation
connate water, conductive drilling fluid, and shale
 The SP curve reflects a difference in the electrical potential between a
movable electrode in the borehole and a fixed reference electrode at the
surface
 Though the SP is used primarily as a lithology indicator and as a
correlation tool, it has other uses as well:
 permeability indicator,
 shale volume indicator
 porosity indicator, and
 measurement of Rw (hence formation water salinity)

9. SP LOG
 Primary Usage of SP Log
 Differentiate shaly from non shaly Formation
 Detect the permeable beds.
 Locate bed boundaries for correlation.
 Determine the value of formation water resistivity(Rw).
 Plotted in 1st track on linear scale graph.
 Horizontal scale value ranges between -80 to 20MV.
 Can not be recorded in hole filled with non conductive mud.
 Sp is positive/reverse if the mud filtrate is more saline than formation water.
 Sp is negative/normal if the formation water is more saline than the mud
filtrate.
 Permeable beds typically deflect the sp curve to left.
 The leftmost deflections indicate clean sands or carbonates.

10. Caliper log(Cali)
 A caliper log is a well logging tool that provides a continuous measurement
of the size & shape of borehole along its depth.
 Caliper tool is a mechanical device with four arms, which expend to touch
all sides of the well(borehole).
 In case of mud cake the diameter of hole will decrease.
 In case of washout the diameter of hole will increase.
 It is also used for measurement of the well caving protection.
 It is useful in QC and calculation of cement volume for casing.

13. Resistivity log
 Resistivity:-
 Resistance to flow of electric current.
 Logs measure and record the resistance offered by the rocks surrounding the borehole
to the passage of an electric current
 It is a method of well logging that works by characterizing the rock or sediment in a
borehole by measuring its electric resistivity.
 Resistivity is the inverse of conductivity,
 The ability to conduct electric current depends upon:
 The Volume of water,
 The Temperature of the formation,
 The Salinity of the formation


14. Resistivity log
 The Usage:
 Resistivity logs are electric logs
which are used to:
 Determine Hydrocarbon versus
 Water-bearing zones,
 Indicate Permeable zones,
 Determine Resistivity Porosity.
 High resistivity indicates the Hydrocarbons
 Low resistivity indicates the Water.

15. Types of Resistivity log
 MSFL: Micro spherically focus log
Log used to read invaded zone resistivity.
 LLS: Shallow/Medium matero log
Log used to read transitional zone resistivity.
 LLD: Deep lateral log
Log used to read un invaded zone resistivity.

16. Neutron Porosity Log
 The log
 The neutron log provides a continuous
record of a formation’s reaction to fast
neutron bombardment.
 It is quoted in term of neutron porosity
units.
 The Neutron Log is primarily used to evaluate
formation porosity.
 It is used to detect gas in certain situations,
exploiting the lower hydrogen density, or hydrogen
index.
 Low porosity and low density indicate the Gas factor.

17.  The high speed atomic particles (neutron) as the tool lowered in the well or
borehole.
 High speed neutron collide with two types of atoms in the rocks
surrounding the well.
 High speed neutron collides with large rock atom it remains bounce with
high speed & no loss of energy.
 High speed neutron collides with hydrogen atom (small atom) some
energy remains absorbed by small atoms , & bounce slow speed.
 Hence slow speed moving neutron indicates the gas factor.

19. Mud Logging
 Collection of different mud and gas parameters.
 Many sensors are being used for the parameters of mud and gas.
 Sensors
Temperature
Density
conductivity
 The different sensors sense and record in the computers present in Mud
logging Unit OR data Unit.

20. Function of mud logging unit
 MUD PARAMETERS:
 Mud weight in & out
 Mud Temperature in & out
 Conductivity in & out
 Drilling Parameters:
 Hook Position (Depth Sensor)
 Hook Load (to measure the weight on bit) “WOB”
 Torque
 Stand-pipe pressure

24.  Gas parameters:
 Total gas, H2S and CO2
 Hydrocarbons components,
(C1, C2, C3, iC4, nC4, iC5, nC5)

25. Well Testing
 Well testing is the technique & method for evolution of well conditions and
reservoir characteristics.
 Well test highlights the hydrocarbons properties.
 It indicates the characteristics of the underground reservoir where
hydrocarbons are trapped.
 It helps to identify the capacity of reservoir producing the hydrocarbons,
such as
Natural gas,
Oil & Condensate(mixture).

26.  There are basic well test type.
 i) Daily test
 i) DST
 i) Daily Test
 The daily test also termed as the ‘Flow Test’
 This test is used to obtain the individual well rates separator divides
the flow from the well into streams of the individual product
typically OIL,GAS ,WATER and Condensate.

27. DRILL STEM TEST
 Dst is an procedure test for isolating and testing the Pressure,
permeability, & Productive capacity of the formation.
 Its important for the measurement of Pressure & best way to obtaining the
information about formation fluids (oil gas & water).
 Used to determine the fluids present and flow rate, Also used to determine
the nature of reservoir.
 The main objective of DST is to evaluate the commercial zone (Potential
zone) by perforation.
 It can be performed in open (without casing) & cased hole(Casing).