Introduction to Petroleum Engineering - Lecture 13 Final- Formation Evaluation - Well Logging

8/14/2019 Introduction to Petroleum Engineering - Lecture 13 Final- Formation Evaluation - Well Logging

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BEng (Hons) Petroleum Engineering

Course:

Introduction To Petroleum Engineering

Instructor

Dr. Tarek Darwich


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Course Outlines: What is Petroleum Engineering?

The Life Cycle of Oil and Gas projects,

Origin, formation and accumulation of Petroleum,

Oil & Gas Exploration,

Appraisal of Oil & Gas Discoveries,

Development of Oil & Gas Discoveries,

Producing Oil & Gas Fields, Transportation of Oil & Gas,

The Petroleum Industry & the Environment,

Petroleum Economics.

I ntroduction to Petroleum Engineer ing

Year 2012 - 2013


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Formation Evaluation


Year 2012 - 2013

Formation evaluation is the analysis and interpretation of core data, logdata, well test data, in terms of the nature of the formation andthe fluids content.

The objectives of Formation Evaluation are: To derive lithology and other information on formation characteristics for use in

future exploration, appraisal and development.

To ascertain if commercially producible hydrocarbons are present

Main parameters evaluated

Lithology Rock properties (porosity and permeability)

Fluids types and saturation


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Formation Evaluation in the Exploration Phase


Year 2012 - 2013

In the exploration phase, emphasis is put on welldata with limited information about interwellregions.

Well data results are characterised by largeuncertainties.

Well data include:

Mud logging

Core data (routine and special core analysis)

Well logging (wireline and while drilling Downhole pressure data and fluid sampling

Formation testing


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Well Logging


Year 2012 - 2013

It can be either open-hole or cased-hole logging.

Open-hole logging is performed:

Before setting casing or liner

Several tools can be run together.


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Open-hole Logging Tools


Year 2012 - 2013

Gamma Ray

Lithology identification and correlation

Conductivity/Resistivity

Measures formation resistivity to identify fluid content

Density

Measures porosity and identifies lithology

Neutron

Measures porosity and identifies lithology

Locate gas and fluid contacts

Sonic

Measures acoustic velocity for porosity and identifies lithology

Borehole Seismic

- Recovers Seismic data


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Year 2012 - 2013

Fluid Sampling

Retrieves fluid samples under reservoir conditions

Estimates permeability

Rock sampling

Provides side wall cores


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Well Logging Unit


Year 2012 - 2013


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Year 2012 - 2013


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Well Logs


Year 2012 - 2013
http://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=202UW_hQ_npIPM&tbnid=kAbacfcvnOMguM:&ved=0CAUQjRw&url=http%3A%2F%2Flogdigi.com%2Fclient%2Findex.php%3FcPath%3D2&ei=etkdUY69BOGj0QWh-4DYBg&bvm=bv.42553238,d.d2k&psig=AFQjCNHjKRkBpCotmNz6sjlkocSvKlqDMQ&ust=1360997108449009


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Openhole Log Evaluation


Year 2012 - 2013


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Year 2012 - 2013


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Year 2012 - 2013


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Clastic and Carbonate Rocks


Year 2012 - 2013


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Clastic and Carbonate Rocks

Relative Abundance


Year 2012 - 2013

Mudstone

(Siltstone

and shale;clastic)

~75%

Sandstone

and conglomerate

(clastic)

~11%Limestone and

Dolomite

(carbonate)

~14%


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Rock Matrix and Open Space


Year 2012 - 2013


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Porosity


Year 2012 - 2013

Porosity is defined as the fraction of the rock that is occupied by voids(pores).

Porosity can be measured through core holes and/or openhole wireline logs.


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Porosity Log Types


Year 2012 - 2013

Three main log types: Bulk Density, Sonic and Neutron.

These logs do not measure porosity directly.

To accurately calculate porosity, the analyst must know: Formation Lithology

and fluids in the pore space.

The three porosity logs:

Respond differently to different matrix composition

Respond differently to presence of gas or light oils

Combinations of logs can

Imply composition of matrix

Indicate the type of Hydrocarbon in pores.


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Permeability


Year 2012 - 2013

Permeability is a property of the porous medium and is a measure of thecapacity of the medium to transmit fluids.

It may be also defined as the measure of the fluid conductivity of theparticular material.

Permeability can be determined from Core analysis

Well Test Data

Log Data (Magnetic Resonance Imaging MRI)

D L


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Darcys Law


Year 2012 - 2013

Where Q is the fluid flow rate,

K is the permeability of the rock the fluid is flowing through,

U is the viscosity of the fluid

A is the cross sectional area

L is the distance over which the fluid is flowing Delta P is the pressure drop

Darcys Law


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Fluid Saturation


Year 2012 - 2013

The saturation of any given fluid in a pore space is the ratio of the volume ofthat fluid to the total volume of the pore space.

Irreducible water saturation is the minimum water saturation obtainable in arock

Water is usually the wettingfluid in oil and gas reservoirs.

Water-wet reservoir Oil-wet reservoir


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Initial Fluids Saturation


Year 2012 - 2013

Pores are initially saturated with water (Sw=1.0)

Hydrocarbons (oil and/or gas) migrate up-dip into a trap due to havingdensity less than water density (gravity force)

Hydrocarbons are distributed such gravity and capillary forces are inequilibrium.

Minimum initial water saturation remains in hydrocarbon zone even afteraccumulation occurs.

When a reservoir is drilled, some of the fluids near the wellbore are pushedaway and the zone is invaded by the drilling fluids.

If hydrocarbons were present, the water saturation after invasion will behigher than the original water saturation.


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Fluids Saturation Changes


Year 2012 - 2013

A shallow resistivity log will see the invaded zone water saturation. A deeperresistivity log will see the original formation water saturation as long asinvasion was not too deep.

Production of oil and gas will change the fluids saturation. The amount of

change varies with the driving mechanism (Solution-gas drive, gas expansiondrive, water drive, .)

Reservoir monitoring (by running special cased-hole logging) is used toassess the changes of water saturation over time.

Changes in the position of the fluids contacts may lead to a work-over of thewell to restrict the perforated interval to reduce water and/or gas production.


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Fluids Saturation Measurements


Year 2012 - 2013

Direct Measurements:

Core Analysis

Indirect Measurements:

Well log analysis (conductivity/resistivity logs)

Capillary pressure measurements

Core measurements may be affected by flushing of cores by filtrate fromdrilling fluids.

Core measurements may also be impacted by changes in pressure and

temperatures as core sample is brought from reservoir conditions to surfaceconditions.

Reservoir monitoring (by running special cased-hole logging) is used toassess the changes of water saturation over time.

-


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Maximum Water Saturation for Oil & Gas Production


Year 2012 - 2013


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Fluids Saturation and Resistivities


Year 2012 - 2013


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Fluids Saturation and Resistivities


Year 2012 - 2013


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Examples of Log Data in a Discovery Well


Year 2012 - 2013


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Example of Log Data in a Discovery Well


Documents

Introduction to Petroleum Engineering - Lecture 13 Final- Formation Evaluation - Well Logging