petrophysical data and open hole logging...

Introduction to Petrophysical Data and Open Hole Logging Basics

PETROPHYSICAL DATA AND OPEN HOLE LOGGING

BASICS

LEARNING OBJECTIVES

By the end of this lesson, you will be able to:

Understand the role of Petrophysics and why it is critical to theoil and gas business

Understand the relationship of Petrophysics to Geology,Geophysics, and Reservoir Engineering

Complete basic calculation of oil volume in a reservoir andexplain which petrophysical parameters are required

Recognize the difference in the Static (Geologic) Model and theDynamic (Reservoir Simulation) Model

Identify key parameters of the Earth Model and what a “normal”pressure gradient is in psi/ft and ppg

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WHAT IS PETROPHYSICS?

Petrophysics is derived from the Greek word petra meaning "rock" and physis meaning "nature"

As defined by an SPE Reprint, petrophysics is “… the study of the physical and chemical properties of rocks and their contained fluids. Petrophysics uses rock properties and relationships among these rock properties to identify and evaluate hydrocarbon reservoirs, source rocks, seals and aquifers”

Gus Archie is the known as the “Father of Petrophysics”

Petrophysics plays a fundamental role in description, characterization and evaluation of rock-fluid packages

WHY PETROPHYSICS IS FUNDAMENTAL

Petrophysics is a science… but it is also a practice.


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Petrophysics consists of:Geology Reservoir EngineeringMechanical EngineeringDrillingGeophysics


Petrophysics

Geophysics Geology

ReservoirEngineering



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GIVE ME A FEW “GLUE” EXAMPLES…

Attic hydrocarbons Produces out of the Gething sandstone Fine-grained sandstone Contains approximately 3 percent potassium feldspar

A zone that looked like silty shale was first drilled through. As drilling continued, the drilling fluid was carefully engineered

and resulted in an exceptionally prolific wet gas reservoir. The life of the field was extended by 30 years because it

consisted of attic hydrocarbons.

Reservoir compartmentalization On the inshore blocks of Angola Series of anastomosing channels which cut across from each other Each bounding surface of the channels serve as a vertical or lateral permeability

barrier It was assumed that the entire package was hydrocarbon bearing

Pressure tests, repeat formation tests or drill stem tests were run Did not produce uniformly Pressure and gas-oil ratios were variable

Different reservoirs were identified using core and rock typing Core and log data were integrated to determine continuity and

connectivity.

WHAT IS A PETROPHYSICIST?

A petrophysicist is a petrophysical engineer

A petrophysicist is responsible for planning, acquiring and interpreting borehole data.

Data sources includemudlogs and openholeand cased hole well logs.


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Stage or Phase1. Rank Exploration2. Field Discovery3. Field Development4. Secondary Recovery5. Tertiary Recovery6. Field Maintenance7. Field Abandonment8. Remediation

THE PETROPHYSICS CONTINUUM

1

2

3

4

5

6

7

8K

NO

WL

ED

GE

IN

CR

EA

SE

PR

OB

LE

MS

IN

CR

EA

SE

Key Learning Points

Petrophysics Applies at All

Levels!

PETROPHYSICAL DATA SOURCES

Reservoir characterization requires competent integration of data from many sources!

Cuttings Hydrocarbon Analysis Cores Logs Fluid/Pressure Tests



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THE PETROPHYSICAL SCENE – MULTIPLE SCALES

Phase Activity Formation Evaluation Method

1. Exploration Define Structure Seismic, Gravity, Magnetics

2. Drilling Drill Well Mud Logging, Coring, MWD, LWD

3. Logging Log Well Open-hole Logs

4. Primary Evaluation Log Analysis and TestingSidewall Cores. VSP, Wireline FT, DST

5. Analysis Core & Fluid Analysis Laboratory Studies

6. FeedbackRefinement of Seismic Model Time/Depth Calibration

Integrated Field Study Log/Core Calibration

7. Exploitation Producing Hydrocarbons Material Balance Analysis

8. Secondary Recovery

Production Logging Production Log analysis

Assisted Lifting Flood Efficiency Analysis

Water or Gas Injection Micro-rock Property Analysis

9. Abandonment Economic Decisions

Phase Activity Formation Evaluation Method

1. Exploration Define Structure Seismic, Gravity, Magnetics

2. Drilling Drill Well Mud Logging, Coring, MWD, LWD

3. Logging Log Well Open-hole Logs

4. Primary Evaluation Log Analysis and TestingSidewall Cores. VSP, Wireline FT, DST

5. Analysis Core & Fluid Analysis Laboratory Studies

6. FeedbackRefinement of Seismic Model Time/Depth Calibration

Integrated Field Study Log/Core Calibration

7. Exploitation Producing Hydrocarbons Material Balance Analysis

8. Secondary Recovery

Production Logging Production Log analysis

Assisted Lifting Flood Efficiency Analysis

Water or Gas Injection Micro-rock Property Analysis

9. Abandonment Economic Decisions

PETROPHYSICS RELATED ACTIVITIES

Highlighted in yellow are most critical petrophysical phases

Introduction to Petrophysical Data and Open Hole Logging Basics ═════════════════════════════════════════════════════════════════════════

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Oil Vol = A*h*(N/G)*porosity*(1-Sw) where: Area A = 1000 sq. ft. Thickness, h = 100 ft Net to Gross, N/G = 60% What is the oil volume “in place” in this “subsurface reservoir”

Oil Vol = __ bbls? And, what inputs are from petrophysical data?

HCVOL= A*h* (N/G)*por*(1-Sw) where: A = 1000 sq. ft., h = 100 ft, N/G = 60%, Por = 20%, Sw = 10% HCVOL = 1000 x 100 x .6 x .2 x .9 = 10800 ft3

cu ft x .1781 bbl/ft3 HCVOL= 1923 bbl oil Oil Vol = 1923 bbls.

THE HYDROCARBON VOLUME AND PETROPHYSICAL DATA

Porosity = 20% Water Saturation, Sw = 10%

Solution

Hint:1 cu. Ft. =

0.1781 bbls

KEY PARAMETERS IN EARTH MODEL

In order to use logs and cores to understand the Earth; corrections are needed for:

Pressure Water Salinity Temperature Water Density Borehole/Formation

Environment



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EARTH MODEL: TEMPERATURE AND PRESSURE GRADIENTS

Both temperature and pressure increase in a predictable way with

depth into the subsurface.

EARTH MODEL: TEMPERATURE AND PRESSURE GRADIENTS

Geothermal Gradient Gradual increase of temperature with increasing depth

(e.g., 1ºF/100ft)

Petrophysical Effects Influences on logs Activity level of ions in subsurface waters

increase with depth Drilling mud properties can change with

depth Certain wireline tools are effective only

within certain temperature ranges

Influences all facets of well design


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EARTH MODEL: PRESSURE GRADIENTS

Overburden Pressure –gradual increase of pressure with increasing depth in the earth's crust (e.g., 1.1psi/ft) OP = FP + GP

Petrophysical Effects Fundamental control on

phi-k (porosity-permeability)

Significant influence on well design

Influences logs Certain wireline tools are

effective only within certain pressure rangesHydrostatic Pressure –

gradual increase of pressure in a fluid column: 0.43 psi/ft (fresh water) 0.465 psi/ft (“normal

pressured” salt water) 0.35 psi/ft for (oil) 0.08psi/ft for gas

EARTH MODEL: PRESSURE GRADIENTS



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Important inputs for many petrophysical applications include:

Formation Temperature Formation Pressure Fluid Densities

These corrected parameters are used for: Log Analysis Completion Planning Producibility Estimates

TEMPERATURE AND PRESSURE GRADIENT SUMMARY

WHERE DOES PETROPHYSICS FIT IN RESERVOIR ANALYSIS?

The task for reservoir scientists (geologists, petrophysicists, engineers) is to locate hydrocarbon reservoirs and evaluate the oil and gas recoverable volumes.

Requires detailed description, characterization of reservoir rocks and associated seals/aquifers

Data Sources Seismic Data – 2D, 3D and 4D Geological Interpretation of Facies and Rock Types Petrophysical Data – Logs, Cores, Test Data Production Data Fluid Properties Data


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PETROPHYSICS INTEGRAL TO RESERVOIR ANALYSIS

1. Seismic analysis

2. Define container (trap size)

3. Petrophysical characteristics

4. Geologic modeling (and rock typing)

5. Mapping, volumetric determination

6. Model validation

7. Interwell modeling

Key Learning Points

Integrating petrophysics occurs in all

steps!

PETROPHYSICS – AN IMPORTANT PIECE

Petrophysical answers are indirect

Also true of static and dynamic reservoir models

When appropriate subsurface data is gathered, the results are valid and lead to good business solutions

There is never a “unique” solution but integration of all data narrows down the solutions to a set of “valid” ones.

BUT, Only a Piece

GeologyEngineering

Petrophysics Geophysics



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HOW DOES PETROPHYSICS INTEGRATE?

Static model(Geologic model)

Dynamic model(Reservoir Simulation model)

(Borehole) Seismic

Core data

Mudlog data

LWD Wireline Logs

Reservoir monitoring

Open hole logs Resistivity Nuclear Acoustic Other

Cased hole logs Nuclear Production logs Other

Field studies

Corrections: Invasion Layering Deviation

Interpretation modelsincl. QC & Uncertainty

Static model(Geologic model)

Dynamic model(Reservoir Simulation model)

LEARNING OBJECTIVES

Understand the role of Petrophysics and why it is critical to theoil and gas business

Understand the relationship of Petrophysics to Geology,Geophysics, and Reservoir Engineering

Complete basic calculation of oil volume in a reservoir andexplain which petrophysical parameters are required

Recognize the difference in the Static (Geologic) Model and theDynamic (Reservoir Simulation) Model

Identify key parameters of the Earth Model and what a “normal”pressure gradient is in psi/ft and ppg


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