PETROLEUM DEVELOPMENT GEOLOGY WELLSITE GEOL

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Wellsite geology is hybrid of
appllied geology on oil and gas well
drilling, its study rock cuttings and
wireline logs from oil and gas wells
to determine what rock formations
are being drilled into and how the
drilling should proceed.
Wellsite Geologist is geologist in
charge on data acquisition from oil
and gas well drilling operation.
They are required to monitor vital
operations during the course of the
well, make sure that the well
program are carried out perform
formation evaluation activities to
ensure the well is drilled and
evaluated in the most safe, efficient
manner, and cost-effective. They
also liaise with drilling engineers,
petroleum engineers and mud
logging geologist during the course
of projects.

JOB PORPOSES

JOB SPIRIT

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COMPANY MAN
WELLSITE GEOLOGIST
DRILLING ENGINEER
TOOLPUSHER & RIG CREW
MUDLOGGING CREW
MUD & CHEMICAL ENGINEER & CREW
CEMENTING ENGINEER & CREW
WIRELOGGING ENGINEER & CREW
TESTING ENGINEER & CREW
OTHER SERVICES ENGINEERS & CREW
SUPPORTING CREW


COMPANY MAN

GEOLOGIST

DRLG ENG.

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TOOL PUSHER
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1.

Supervision of “Formation Evaluation”
contractors (Mud Logging Geologists,
MWD Logging Engineers, Wireline
Logging Engineers, Coring and Well
Testing Personnel)

2.

Logistics concerning the formation
evaluation contractors and their

equipment

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All safety aspects for the well and
personnel during these evaluation
operations

4.

Quality control of all evaluation results
and logs prior to accepting the data or
logs from those contractors

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Providing relevant correlation and well
data to those contractors during their
operations

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Checking all reports and logs from the
evaluation contractors prior to sending
them to oil company offices


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Monitoring and supervising the

collecting, processing and dispatching
of formation evaluation samples

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Safe-guarding the collection, storage
and transmission of information and
reports at the wellsite

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Wellsite interpretation of the formation
evaluation data

10. Checking and occasionally approving
and signing of service reports and
invoices of the formation evaluation
contractors
11. Keeping the drilling superintendent
and operations geologist fully
informed of all formation evaluation
operations




Wellsite Geologist should be
completely familiar with all
aspects of the drilling
prognosis. Particular attention

should be paid to any sections
which may require geological
decisions.
1. Determination of Primary and
Secondary Objectives
2. Determination of Casing Points
3. Detection of Overpressured
Intervals
4. Detection of Lost Circulation
Zones


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Correlation and Detection of Marker Horizons
Determination of Geologic Basement or Economic Basement
Selection of Logging Run Intervals
A complete set of correlation logs and reports should be compiled
Near by well’s mudlogs, lithlogs and wireline logs should be used
as sources of information


REGIONAL GEOLOGY PREPARATION
FOR WELLSITE GEOLOGIST
to anticipate if it should deviate from the prognosis

• Nature and depth of basement within the
basin
• Geologic age of the section
• Depositional environments and expected
lithologies
• Tectonic setting within the basin
• Formation pressure anomalies
• Hydrocarbon occurrences within the basin
• Basin correlations


Wireline Logging Unit
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VSP å Used to “look ahead”, formation top confirmation
RFT å Fluid sampling, Pressure determination, Oil/Water/Gas
gradients
Resistivity å Water Saturation, Porosity, Hydrocarbon evaluation
Density & Neutron å Lithology confirmation, Correlation, Porosity,
Overpressure detection, Gas/Oil contacts
Sonic å Porosity, Mechanical properties, Overpressure
Dipmeters å Structure, Well trajectory, Facies analysis,
Sedimentology
Sidewall Cores å Biostratigraphy, Geochemistry, Lithology

confirmation, Hydrocarbon evaluation

Mud-Logging Unit
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Cuttings å Geochemistry, Lithology, Correlation, Density, Calcimetry,
Hydrocarbons, Shale Factor (C.E.C.), Hole Stability, Bit Condition
Hydrocarbons å Total gas, Chromatograph, Gas Ratios, Connection
gases, Trip gases, Oil shows
Gases å CO2, H2S
Engineering å Dxc, Torque, Drill Rate, Formation Pressures


MWD/FEMWD unit data
• Directional å Borehole Trajectory (MWD), Dogleg
Severity
• Gamma Ray å Lithology Determination, Shale
Content,
• Resistivity å Correlation, Hydrocarbon Evaluation,
Pressure Indication, Sw Estimations
• Density å Lithology, Correlation, Pressure Indication,
Gas/Oil Contact
Others
• Coring å Biostratigraphy, Reservoir analysis,
Porosity, Permeability

To ensure satisfactory results, the Wellsite
Geologist will be responsible for:

Ü Safety aspects during logging operations
Ü Organizing personnel and equipment
logistics
Ü Logging Quality Control and Data
accuracy
Ü Carry out quick look log interpretation and
reporting to operation geologist.


îExistence and depth of known markers.
îTop and bottom of each reservoir interval
îGross & net thickness for each reservoir
interval
îType of hydrocarbon and hydrocarbon/water
contacts
îAverage and range of calculated porosity
and water saturation values for each interval
îRw in the clean, water-bearing formations
îPropose well test intervals




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THE TEAM å MUDLOGGING CREW:
• MUDLOGGING GEOLOGIST (MUDLOGGER)

• PRESSURE ENGINEER / DATA ENGINEER
• SAMPLE CATCHER

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MUDLOGGING GEOLOGIST å
– CUTTING & CORE DESCRIPTION, HYDROCARBON SHOW,
POROSITY ETC.

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PRESSURE ENGINEER & DATA å
– RECORD, MONITOR & ANALYSE THE DRILLING PARAMETERS
SUCH AS ROP, RPM, WOB, TORQUE,
– MUD DATA: MUD TANK LEVEL (MUD LOOS & GAIN), MUD
WEIGHT IN/OUT, TEMPERATURE IN/OUT
– MUD PUMP DATA : CAPACITY, EFICIENCY, VOLUME IN ETC.

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SAMPLE CATCHER å
– COLLECT AND PREPARE SAMPLE FOR MUDLOGGING
GEOLOGIST





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DRY SAMPLE
– obtained from the washed samples collected from the 80-mesh
sieve. A heat source is used for drying purposes.
– Several precautions when drying samples are:
• DO NOT oven dry oil-based mud samples
• Do not over-dry samples, because they will burn (the burning can be
mistaken for oil staining)
• Clay samples should not be oven dried - only air dried

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WET SAMPLE
– collected at the shale shaker. Normally the drilling fluid is not
rinsed off.

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GEOCHEMICAL SAMPLE
– These samples require special treatment.
– A bacteriocide (i.e. Zepharin Chloride) is necessary to prevent the
growth of bacteria which can form additional gas. The samples are
normally sealed at the wellsite, and shipped separately.


Each lithology should be accurately described, and
that observations recorded in the following order:
a. Rock Type

g. Sorting

b. Classification

h. Luster

c. Color

i. Cementation/Matrix

d. Hardness/Induration

j. Visual Porosity

e. Grain Size

k. Accessories/Inclusions

f. Grain Shape

l. Oil Show Indications

Usually major oil company has own cutting description manual and its
standar legend.


COMPARISON CHARTS FOR VISUAL ESTIMATION OF
PERCENTAGE COMPOSITION