Toxic metals have the ability to disrupt the structure and function of a number of subcellular organelles.

WELL LOGGING
By
LYOIDAH KICONCO
)
GEOLOGIST
(
BSc., MSc., MSc., Dip.Mngt

Course Title: Principles and Application of well logs
Objectives:
At the end of this course, the students should be able to understand
the basics of borehole geophysics, theory of measurements,
interpretations and applications of the different types of wire line logs.
Students should also know how to calculate the petrophysical
parameters required for formation evaluation )source and reservoir
rocks(.
References
:
Asquith, G. and Krygwski, D. )2004(: Basic well log analysis” The American Association of Petroleum
Geologists, Tulsa, Oklahoma
.
Rider, M.H. )1996(:”The geological interpretation of well logs” 2nd edition, Blackie and Son Limited,
London, UK
.
Schlumberger )1987(: “Principles and application of well logs“ Schlumberger Ltd., France
.
Web Site: www.brookes.ac.uk/geology/peg/short course
www.chee.uh.edu/petroleum/PETR6304
INTRODUCTION

 What is a “Log”.
 What is well logging.
 Well logs; the necessity.
 Objectives of wire line logs.
 Data acquisition
 Data recording
 Types of boreholes and well logs.
 Logging companies.
 Principal uses of wire line logs.
OUTLINE

 A log is a record of a voyage, like a ship’s log or
travelling.
 A well log is a record of the voyage of a
measuring instrument into a well bore.
 The instrument itself is sometimes called a log,
but it really is a logging tool.
 The log is a paper or digital recording of the
measurement s made by the logging tool, versus
depth.
What is a log

Well Logging
 Well logging is a technique used in oil and gas
industry to measure rock and fluid properties to
find hydrocarbon zones in the geological
formations within the earth’s crust.
 The logging procedure consists of lowering a
logging tool on the end of a wireline into an oil
well to measure the rock and fluid properties.
 An interpretation of these measurements is
then made to locate and quantify potential
depth zones containing oil and gas
(hydrocarbons).

Well Logging
 Logging is usually performed as the logging
tools are pulled out of the hole.
 Data is recorded and the printed record is
called a “ well log” and may be transmitted
digitally to office locations.
 Well logging is performed at various intervals
during the drilling of the well and when the total
depth is drilled.

Well Logging
 Refers to down hole measurements made
through instrumentation that is lowered into the
well at the end of the wireline cable.
 The wireline consists of an outer wire rope and
inner group of wires.
 The outer rope provides strength for lowering
and lifting heavy instruments and the inner
wiring provides for transmission of power to
down hole equipment and for data telemetry
uphole to the recording equipment (DATA
acquisition system-DAS).

Well Logging
 Done after a given section of the hole has been
drilled.

Well logs- the necessity
 These measurements are necessary because
geological sampling during drilling )cutting
sampling( leaves a very imprecise record of the
formations encountered.
 Entire formation samples can be brought to the
surface by mechanical coring, but this is both
slow and expensive.
 The results of coring, of course, are unequivocal.
Logging is precise, but equivocal, in that it needs
interpretation to bring a log to the level of
geological or petrophysical experience.
 However, logs fill the gap between ‘cuttings’ and
cores, with experience, calibration and
computers, they can almost replace cores, as they
certainly contain enough information.

Objectives of wire line logging
1-Lithology identification
2-Determination of reservoir characteristics )e.g. porosity,
saturation, permeability(.
3-Discrimination between source and non source rocks
4-Identification the fluid type in the pore space of reservoir
rock ) gas, oil, water(
5-Identification of productive zones.
6-Determination the depth and thickness of productive zones.
7-Locating reservoir fluid contacts.
8-Well to well correlation for determining the lateral extension
of subsurface geologic cross sections.
9-Determination formation dip and hole angle and size.

 Conventional Wireline
 Involves lowering of instruments down hole
attached to a calibrated cable which also
carries power supply to the tool. Its lowered into
the hole then pulled up providing a continuous
record of the rock characteristics the device
was designed to detect.
 A number of logs a run simultaneously to
minimise costs
DATA
ACQUISITION

DATA
ACQUISITION
 Logging tools
 Logging tools were
developed to measure the
electrical, acoustic,
electromagnetic, and other
properties of rocks and
their contained fluids.

Horozontal Drilling )HD(
 Involves pushing tools downhole since it is not
possible to transport conventional wireline devices into
horizontal or highly deviated wells (TLC Tough
Logging Conditions)
 Beneficial in marginal fields, thin reservoirs, thin
hydrocarbon columns. They expose the drainhole to a
much more larger reservoir area and minimise water
or gas coning by reducing drawdown pressures
 They intersect far more fissures in fractured reservoirs
than conventional boreholes
DATA
ACQUISITION

 Since wireline tools will not “fall” in highly deviated
and horizontal wells, they must be pushed down the
borehole to reach the target.
 This is achieved through drill pipe conveyed or
coiled tubing techniques
DATA
ACQUISITION

Drill pipe conveyed logging
 Conventional WL device are attached to the end of the
drill pipe and pushed to the intervals of interest. A
swivel head is used to join the device to the drill pipe
to allow preferential tool orientation. Power is supplied
through a side entry sub and down the drill where it
connects to the logging tool.
DATA
ACQUISITION

Coiled Tubing )CT( techniques
 May also be used to convey WL tools downhole
 1.5’ tubing in diameter is coiled around a reel. The
logging device is attached to the end of the tuning
which is fed into the well by a rotating reel.
 A wireline cable passing through the tubing supplies
the power to the logging tool.
DATA
ACQUISITION

Coiled Tubing )CT( techniques
DATA
ACQUISITION

Measurement While Drilling )MWD(
 Sensors are incorporated into the drill collars
 MWD provide accurate control on well depth,
inclination and azimuth.
 MWD also record some parameters like Resistivity
and Gamma Radiation
DATA
ACQUISITION

MWD tool and data transmission system
DATA
ACQUISITION

Logging While Drilling )MWD(
 Include more advanced tools to provide accurate,
quantitative measurements of resistivity
(Compensated Dual Resistivity/CDR), spectral
gamma ray, formation density and neutron porosity
(Compensated Density Neutron CDN)
DATA
ACQUISITION

MWD and LWD data may be transmitted directly to the surface or
stored in memory chips downhole
Advantages of MWD/LWD include
 Savings in terms of rig time
 Provision of real time data helping in optimising drilling
operations: early detection of pressure changes, casing point
selection and continuous directional information
Disadvantages of MWD/LWD
 They are limited to gamma ray, density, porosity and resistivity
logs
 Except for the GR they lack accuracy and high resolution of WL
measurements
 MWD/LWD services are not always cheaper than WL
DATA
ACQUISITION

 Presented graphically alongside a
depth scale
 API grid is the standard in the
Petroleum Industry
 One track to the left of the depth
column and two to the right
 Three types of grids are used;
 Linear
 Logarithmic
 Split grid
DATA RECORDING

Types of boreholes
 According to Casing operation
- Cased holes
- Open holes
 According to conductivity of the borehole
- Conductive (water base drilling mud)
- Non-conductive boreholes (oil base mud, air
drilled or cased holes)

Types of well logs
Wireline logs
(Electrical, Radioactive, Sonic and
Acoustic, Radioactive or nuclear,
Mechanical, Thermal and Magnetic logs)
Formation Testers
(Repeated Formation Tester, Drill Stem
Tests)

Some Logging Companies
 Schlumberger
 Gearhart
 Dresser Atlas
 Welex
 Haliburton
 Weatherford
 Others

Important Dates
•1927-1931: Doll, Schlumberger brothers - France, 1st resistivity, SP
• 1935 – Dipmeter
•late 1940's - Gamma-ray, neutron
•1950's - Focused resistivity tools, induction tools
•1960's - Digital recording, full waveform sonic (3D velocity)
•1970's - Borehole televiewer, VSP, Slimline sondes, integrated circuitry
•1980's - Borehole radar, EM propagation, cross-hole tomography, deep
logs

Principal uses of open hole wireline logs

Toxic metals have the ability to disrupt the structure and function of a number of subcellular organelles.

Figure shown represents the first well logging
record by Henri Doll in 1927

Schlumberger Logging
Trucks in the past

Toxic metals have the ability to disrupt the structure and function of a number of subcellular organelles.

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