Геологія видобутку нафти і газу (Oil & gas production geology)

Oil & Gas Production Geology – 01 Overview
Геологія видобутку нафти і газу – 01 короткий опис

Вольфганг Нахтманн
Wolfgang Nachtmann — RAG — Wien
wolfgang.nachtmann@rag-austria.at

Content of Lecture
Зміст лекції

Oil & Gas Reservoirs – from uncontrolled
eruptions to an optimum production
strategy – geological and reservoir-
relevant parameters and methods to
develop oil & gas fields

Oil & Gas Production Geology – 01 Overview | 2011 | 2

Petroleum – a Basic Element Sine Qua Non
Нафта – обов‘язкові вимоги

In the twentieth century, oil, supplemented by natural gas, toppled King
Coal from his throne as the power source for the industrial world.
Oil also became the basis of the great postwar suburbanization movement
that transformed both the contemporary landscape and our modern way of
life. Today, we are so dependent on oil, and oil is so embedded in our daily
doings, that we hardly stop to comprehend its pervasive significance. It is oil
that makes possible where we live, how we live, how we commute to work,
how we travel—even where we conduct our courtships. It is the lifeblood of
suburban communities.
Oil (and natural gas) are the essential components in the fertilizer on which
world agriculture depends; oil makes it possible to transport food to the
totally non-self-sufficient megacities of the world.
Oil also provides the plastics and chemicals that are the bricks and mortar of
contemporary civilization, a civilization that would collapse if the world's oil
wells suddenly went dry.
Prologue to The Prize by Daniel Yergin, 1991


What is Petroleum
Що таке нафта і газ

Glossary of Petroleum Industry Common Terms & Symbols

PETROLEUM
A generic name for hydrocarbons, including crude oil,
natural gas liquids, natural gas and their products.

Petroleum is crude oil, a naturally occurring liquid that can be
distilled or refined to make fuels, lubricating oils, asphalt, and other
valuable products. Used in a broad sense, petroleum also refers to
natural gas and solid asphalt, …


The Value Chain of Petroleum Industry – Three Legs
Ланцюг вартості у нафтогазовій індустрії – три етапи

The oil industry can be divided into three major components: upstream,
midstream and downstream.

The upstream industry includes exploration and production activities,
hence is also referred as the exploration and production (E&P) sector.

The midstream industry processes, stores, markets and transports
commodities including crude oil, natural gas, natural gas liquids (NGLs)
like ethane propane and butane and sulphur.

The downstream industry includes oil refineries, petrochemical plants,
petroleum products distributors, retail outlets and natural gas distribution
companies.

In general, both, internationally and domestically, the oil and gas sector
is characterized by the existence of "integrated" companies, which are
present in all these three sectors.

Upstream: Exploration and Produktion (E & P)
Апстрім: Розвідка та видобуток (E & P)
Upstream sector, the first part of the oil and gas industry, deals with exploration and
production of oil and gas. Oil exploration takes place at oil wells in four stages:

• the first stage is drilling, act of boring a hole through which oil or gas may be
produced if encountered in commercial quantities.
• the second stage is completion, process in which the well is enabled to produce
oil or gas.
• the third stage is production, production time of oil and gas.
• the final stage is abandonment, where the well no longer produces or produces
so poorly that it is a liability to its owner and is abandoned.

An oil field is a region with an abundance of oil wells extracting petroleum (oil) from
below ground. Because the oil reservoirs typically extend over large(r) areas, full
exploitation entails multiple wells scattered across the area.
There are more than 40,000 oil and gas fields of all sizes in the world (BP statistical
Review,2006) and the largest discovered conventional oil field is the Ghawar Field
(75-83 billion bbl) in Saudi Arabia.

In tandem with the stagnated reserves, the production of oil has also been sluggish
over the last decade, as a matter of fact during the last ten years oil production has
increased by only 1.6%.

The World Consumes one Cubicmile of Oil per Year
Світ споживає одну кубічну милю нафти на рік

1 cubic mile of oil contains as
much energy as we would get
from 52 new nuclear power plants
working for the next 50 years


Development of Worldwide Oil & Gas Reserves
Світова розробка резервів нафти і газу

Distribution of proved oil & gas reserves in 1988, 1998 and 2008
Percentage

Öl

Gas

BP Statistical Review of World Energy 2009

Oil Reserves-to-Production (R/P) Ratios
Співвідношення резервів нафти до видобутку (R/P)

BP Statistical Review of World Energy 2010

R/P Model
Модель R/P
Data base:
2007 Reserves 1283 Mrd bbl
2007 Production 29,8 Mrd bbl / a
30
R/P 41,6 years

R/P Model-Assumption:
World Annual Oil Production (bln bbls)

25 stable production on 2007 level until
complete exhaustion of reserves
20

15

10

5

0
2007 2017 2027 2037 2047 2057 2067 2077 2087 2097


R/P Model Versus More Realistic Expectations
R/P модель у порівнянні з більш реалістичними очікуваннями

Data base:
2007 Reserves 1283 Mrd bbl
2007 Production 29,8 Mrd bbl / a
R/P 41,6 years
30
R/P Model-Assumption:
stable production on 2007 level until
World Annual Oil Production (bln bbls)

25 complete exhaustion of reserves
Assumption ignores that:
20 production from known fields won‘t
stay stable – an annual decline of
3% appears realistic
15
New reserves will be added from
exploration and field developments
10

5

0
2007 2017 2027 2037 2047 2057 2067 2077 2087 2097


Reserves Additions: New Discoveries versus Existing Fields
Доповнення резервів: нові поклади у порівнянні з існуючими родовищами


Reservoir Management – Key to More Production from Old Fields
Менеджмент пластів – методи збільшення видобутку з нафтових родовищ


The Production Geologist – Member of a Multidiscipline Work Force
Геолог з видобутку – представник багатопрофільної робочої сили

A production geologist, in general,
• works in a subsurface team
• is responsible for understanding the
geological framework of the reservoir
• supports to understand how geology
influences fluid flow within a producing
reservoir and creates „dead end pockets”
that could eventually trap hydrocarbons (the
bigger ones of these pockets may be worth
targeting with new wells)
• takes a leading role in planning such wells
• typically uses computer software for a good
part of his work


The Subsurface Team
Надра, команда


Reservoir Description – Data (Sources)
Опис пласта – дані (джерела)

Reservoir description is the base for a most effective and efficient reservoir
management. Here, the production geologist plays a key role and will use
a variety of data (sources), including:
• mud logging data
• core data
• sedimentology and petrography reports, studies
• outcrop analogs / modern depositional environments
• a broad spectrum of wireline log and logging-while-drilling (LWD) data
• production log data
• well test data
• fluid samples
• production data
• seismic data

Production Geologist Static Model of Reservoir
Reservoir Engineer Dynamic Model + Simulation of Flows
Common Target: maximization of production from an oil or gas field


Subsurface Techniques Over Time
Техніки розробки надр, основні етапи


Terminology Used in Appraising Oil & Gas Pools
Термінологія, що використовується при аналізі нафтогазових покладів


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Oil & Gas Production Geology – 02 Basic Principles
Геологія видобутку нафти і газу – 02 основні принципи


Petroleum System Puzzle
Паззл нафтогазової системи

MIGRATION
PATHS

GEOLOGICAL MIGRATION
SITUATION RESERVOIR

SOURCE
ROCK TRAP
TRAP OVER
SEAL
TIME

MATURITY
OF SOURCE
ROCK

Oil & Gas Production Geology – 02 Basic Principles | 2011 | 2

The Petroleum System – Elements and Processes
Нафтогазова система – елементи та процеси


Petroleum System Definition
Визначення нафтогазової системи
The essential elements and processes and all genetically-related hydrocarbons that occur in
petroleum shows, and accumulations whose provenance is a single pod of active source rock.

Elements
Processes
Source Rock
Migration Route Generation
Reservoir Rock Migration
Seal Rock Accumulation
Trap Preservation

Елементи Процеси
Материнська порода Формування
Шлях міграції Міграція
Пластова порода Накопичення
Непрониклива порода Збереження
Пастка

Oil & Gas Production Geology – 02 Basic Principles | 2011 | 4 Source: JMA 2000

Schematic Cross Section through a Petroleum System
Схематична поперечна секція через нафтогазову систему

Predicting the location, type, and quality of hydrocarbon systems is critical to successful oil and
gas development. Technology, such as seismic imaging and computer modeling, has improved the
process in recent decades.
http://www.learner.org/courses/envsci/unit/text.php?unit=10&secNum=4


Trap Type 1 – Anticlinale
Тип пастки 1 - антикліналь

http://www3.uakron.edu/geology/Foos/Energy/poil3.html

Trap Type 2 – Fault
Тип пастки 2 – структурна пастка


Trap Type 3 – Pinch Out
Тип пастки 3 – пастка виклинювання


Trap Type 4 – Stratigraphic
Тип пастки 4 - стратиграфічна


HC-Trap Types in the Vienna Basin 1
Типи пастки вуглеводнів у Віденському басейні 1


HC-Trap Types in the Vienna Basin 2
Типи пастки вуглеводнів у Віденському басейні 2


View at a Petroleum System
Вигляд на нафтогазову систему

Source and Seal

Reservoir
Monterey Fmt. – Gaviota Beach, Ca.

E & P Cycle
Цикл розвідки та вибодутку (Р та В)

Discovery

Prospect-
Appraisal
Definition
& Planning

E & P Cycle
Seismic, Field-
Gravimetry EXPLORATION Development

PRODUKTION
Basin-Analysis, Reservoir
(Play) Concept(s) Management
Regional Geology,
Data (Expl. History),
Analogies


E & P Cycle
Цикл розвідки та вибодутку (Р та В)

Відкриття

Визначення
Аналіз &
перспективи
планування

E & P Цикл
Сейсміка, Розробка
гравіметрія РОЗВІДКА родовища

ВИДОБУТОК
Аналіз басейну,
Пласт
(комплексу)
концепція(ї) Менеджмент
Регіональна геологія,
дані (іст. розвідка),
аналогії


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Oil & Gas Production Geology – 03 Reservoir Description
Геологія видобутку нафти і газу – 03 опис пласта


Sedimentary Rocks
Осадові породи

Practically, all rock-elements of a petroleum system are
sediments. So do, of course, almost all reservoir rocks.

Clastic (siliciclastic) rocks (80-85% of the stratigraphic
record)
Carbonate sediments and rocks (10-15% of the
stratigraphic record)
Organic (carbonaceous) sediments and rocks
Evaporites
Volcaniclastic sediments and rocks

Oil & Gas Production Geology – 03 Reservoir Description | 2011 | 2

Integrated Study (Scale/Disciplines) – Micro- to Basin Scale
Інтегроване дослідження (масштаб/алгоритм) – масштаб від мікро- до басейну

Courtesy: Uli Bieg, RAG


Environments of Clastic Deposition
Середовище теригенних відкладів


Preliminary depositional model
Початкова літологічна модель

„River“ dominated delta



Log correlation – Digitalization of available data and storage in Petrel
Кореляція каротажу – електроний вигляд наявних даних та записів у Петрель


Idealized Succession – Flood-dominated river delta
Ідеалізований варіант – дельта річки, с переважанням течії

Trigger mechanism

River
mouth
Outburst of
ephemeral sediment laden floods
Un-confined
Confined

flow
flow

Masterbedding
planes Mouthbar



Synthetic Deposition model
Синтетична модель залягання

jet flow


A model of Subaqueous Slope Channel and Deep-Water Fan
Модель підводного похилого каналу та глибоководний конус виносу


Deep water Fan Shapes
Глибоководні конусні виноси

(SCHOLLNBERGER et al 1974)


Appraisal and Development of a Reservoir
Аналіз та розробка пласта

A sheet-like turbidite reservoir will need only a few wells to appraise and develop it.
Channelized turbidite reservoirs will require several wells for appraisal and development – due to this
fact they may be less profitable.


Introduction – Deep-Water Depositional Models
Вступ – глибоководні літологічні моделі

Submarine Transport and Depositional Processes

Foredeep Basin

Inner Axial Outer

Wedge-Top Basinal
Basins Turbidite
elt System
st-B
ru
Th
ld-
Fo

Courtesy: Anne Bernhardt, SPODDS modified from Mutti et al., 2003

Submarine Depositional Processes – Turbidity currents and debris flows
Підводні літологічні процеси – турбідитний та уламковий потік

Sediment gravity flows:
Subaqueous flows that are driven down slope by gravity acting on particles

Debris Flow Deposit Turbidite

Tc

Tb

Ta

Courtesy: Anne Bernhardt, SPODDS


Lithofacies – Debris Flow Deposits
Літофації – відклади уламкових потоків


Lithofacies – Debris Flow Deposits
Літофації – відклади уламкових потоків

2 cm 2 cm 2 cm


Lithofacies – Turbidity current deposits
Літофації – відклади турбідитних потоків


Core of a Good Quality Reservoir Rock
Керн породи якісного пласту


Sandstone Reservoir – No Porosity
Пласт пісковика – ніякої пористості

Pore space filled with Calcite-cement

= no room for oil/gas

Carbonate Rocks
Карбонатні породи

Carbonate sand usually consists either of (fragmented)
skeletal remains or non-skeletal grains (e.g., molluscs,
corals, forams, algae, bacteria, and many others)
Most organisms initially form unconsolidated carbonate
sediments
Coral reefs and microbial mats (e.g., stromatolites) are
examples of more solid carbonate structures

Carbonate mud (micrite) is commonly the product
either of chemical precipitation or algal/bacterial
activity (e.g., ooids, onkoids, pisoids)

Dunham classification of carbonate rocks:
Texturally-based subdivision (cf. clastics): mudstone,
wackestone, packstone, grainstone, rudstone
Organically bound framework during formation: boundstone

Tropical Carbonate Platforms: Facies Belts
Тропічні карбонатні платформи: фаціальні зони


Franconian Jurassic – Examples for Porosities in Carbonates
Франконський ярус, Юра – приклади пористості у карбонатах
Kalk-Stbr.-Ittling Dolomit-Stbr.-Bernhof

Courtesy: Roman Koch, GZ Nordbayern

Fractured Carbonate Rock
Роздроблена карбонатна порода


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Oil & Gas Production Geology – 04 Reservoir Parameters
Геологія видобутку нафти і газу – 04 параметри пласта


Key Reservoir Description Needs
Основні характеристики пласта

Oil & Gas Production Geology – 04 Reservoir Parameters | 2011 | 2

Example of a Structure Map
Приклад структурної карти


Reservoir Distribution
Розповсюдження пласта


Trap – a Matter of Reservoir Discontinuity Reasons
Пастка – через уривчастість пласта

Oil & Gas Production Geology – 04 Reservoir Parameters | 2011 | 5 Source: McMoRan, 2010

Reservoir Thickness and Barriers
Потужність пласта та ізоляція

Gross pay
total thickness of the reservoir unit
Net pay
the fraction of the reservoir that has
porosity above a minimum threshold (this
is the sum of the productive zones)

Reservoir barriers
Reservoirs are heterogeneous in both vertical and horizontal dimension at all
scales. This is due to Stratigraphic facies changes, faults, variation in
diagenetic features such as cementation or dissolution, etc. A huge body of
data is needed to adequately characterize most reservoirs. Most often
reservoir barriers are revealed by the pressure history of neighboring wells.


Definitions: from Reservoir to Net Pay
Визначення: від пласта до ефективної нафтонасиченої потужності


Porosity model for a shaly sand reservoir (from Al-Ruwaili et al.1 © 2004 SPE)
Модель пористості для сланцевого піскового пласта (з Al-Ruwaili et al.1 © 2004
SPE)


Field Development after a Discovery Well
Розробка родовища після свердловини, що відкрила родовище


Initial Field Evaluation
Початкова оцінка родовища


Full Field Development
Повна розробка родовища


Terminology of Reservoir Related Parameters 1/2
Визначення параметрів, стосовно пласта 1/2


Terminology of Reservoir Related Parameters 2/2
Визначення параметрів, стосовно пласта 2/2


Terminology of Fluid Contacts in Reservoirs
Визначення контактів флюідів у пласті


Pressure Gradients while Drilling through Different Media
Градієнти тиску під час буріння при різних умовах

Pressure gradients encountered while drilling depend on the penetrated media


Hydrocarbon Column
Висота покладу вуглеводнів


Reserves Estimation in a Field Over Time
Оцінка резервів родовища упродовж часу


Effect of Fluid Contacts on Volumetric Maps
Вплив контакту флюідів на волюметричні карти

Typical isopach maps of reservoirs when the fluid contact is above the sand base


Isopach Maps – Inner and Outer OWC
Карта рівної товщини – внутрішній та зовнішній водонафтовий контакт

Isopachs when the fluid contact is below the sand base


Anticlinal Traps and Spill Point
Антиклинальні пастки та точка максимальної насиченості пласта

Where are spill points of these
structures?
Is any of the structures filled?
Are there not yet drilled prospects
on this map?
What is the faults‘ role?


Porosity
Пористість

Porosity


Porosity


Total versus Effective Porosity
Повна та ефективна пористість


Types of Porosity
Типи пористості


Methods of Measuring Porosity
Методи виміру пористості


Porosity Measurement from Core
Вимір пористості з керну


Porosity from Logs
Пористість з каротажу


Characteristics of Logs
Параметри каротажу


Rock Types and Their Porosities
Типи пород та їх пористість


Reservoir Rock versus Trap Rock
Пластова порода та пасткова порода

Oil & Gas Production Geology – 04 Reservoir Parameters | 2011 | 31 www.priweb.org/.../reservoir/reservoir.html

Characteristics of Porosity
Параметри пористості

Effective porosity vs. total porosity Types:
Primary porosity
Secondary porosity
Porosity in Clastic rocks vs Carbonate rocks
Relationship between porosity and permeability

Depositional aspects: What is good porosity?
Composition 0-5% - Negligible
Sorting 5-10% - Poor
Rounding 10-15% - Fair
Grain size 15-20% - Good
Packing >20% - Very good
Diagenesis: Practical cut off for oil
Dewatering Sandstone ~8%
Compaction Limestone ~5%
Cementation For gas the cut off is lower

Porosity in Carbonates
Пористість у карбонатах

Depositional porosity is a function
of rock texture, grain sorting and
shape. Sorting and shape in turn
are related to bottom agitation at
the depositional site. Where
currents and waves are
particularly active, lime mud is
winnowed from carbonate sands.
In contrast, lime muds tend to
collect in less agitated
environments or where trapped by
organisms, and after the sediment
dewaters little or no porosity is
retained. Many of the world's
larger carbonate reservoirs have
porosities that are largely
depositional in origin.

Oil & Gas Production Geology – 04 Reservoir Parameters | 2011 | 33 http://strata.geol.sc.edu/thinsections/diagenesis.html

Relationship Between Carbonate Diagenesis and Porosity
Відношення між карбонатним диагенезом та пористістю

The relationship between porosity and diagenesis is complex and
variable. The major diagenetic processes affecting porosity are
dissolution, cementation and dolomitization.
Each process requires a permeable host rock and a mechanism to
flush chemically active waters through the rock. The water movement
is controlled regionally by the hydrostatic head, structure and rock
fabric.
Dissolution creates and enhances porosity. Commonly, however,
dissolution of carbonate grains is accompanied by calcite cementation
in adjacent primary pores. The end product in such a case is tightly
cemented carbonate sand with well-developed moldic porosity and
low associated permeability.
Cementation is an extremely important diagenetic process because it
reduces porosity. The degree of cementation varies from thin cement
coatings around the grains that partially fill the pores and alter
permeability patterns to calcite spar that completely fill the pores.

Permeability
Проникливість

Permeability

“Permeable” is “Porous,” but “Porous” May Not Be “Permeable”


Permeability


Permeability

This is the key parameter in determining reservoir quality. Many rocks (e.g.
shales, chalk) have high porosity, but very low permeability. Determined from
Darcy's law.
Main controls on permeability are:
• Grain size (determines the size of the pore throats)
• Pore connectivity

What is good
Effective permeability: When multiple
permeability?
fluids are present they interfere with each
other. So that the effective permeability of
the moving fluid is much lower than if a <1 millidarcy - Poor
single fluid is present. In a typical reservoir 1-10 md - Fair
at least water and oil are present, 10-100 md - Good
frequently water, oil, and gas share the 100-1000 md - Very good
pore space.


Permeability is a Function of:
Проникливість є функією:


Porosity – Permeability Correlation
Кореляція пористості та проникливості


Increase/Reduction of Porosities and Permeabilities
Підвищення/зменшення пористості та проникливості

Processes that reduce porosity and permeability:
• Compaction
• Cementation
• Heavy hydrocarbon residue

Processes that enhance porosity and permeability:
• Dissolution
• Fracturing
• Dolomitization

Carbonate rocks are often subjected to early cementation, so reservoir
quality depends very strongly on dissolution, fracturing and dolomitization.
Most carbonate reservoirs are due to secondary porosity.
Reefs sometimes preserve primary porosity.


Capillary Pressure
Капілярний тиск


Fluid Distribution within a Reservoir
Розповсюдження флюідів всередині пласта


Reservoir Quality
Якість пласта


Capillary Pressure Curves
Криві капілярного тиску


Reservoir Engineering aspects
the Production Geologist should
be aware of


Reservoir Engineering Tasks
Завдання технології розробки


Building a Reservoir Description
Структура опису пласта


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Oil & Gas Production Geology – 04 Reservoir Fluids
Геологія видобутку нафти і газу – 04 пластові флюіди


Hydrocarbon Content – Production Data
Об'єм ВВ – виробничі дані

Assessment and Adaption of volumetric
reserves by production history

„dynamic methods“ for oil & gas
reservoirs

Oil & Gas Production Geology – 05 Reservoir Fluids | 2011 | 2

Dynamics
Динаміка

Production (Exploitation) is governed by Reservoir
Fluid(s) and their Drive Mechanism

The relations are provided by

Material Balance
Simulation


Calculation of Volumes
Розрахунок/параметри об‘єму

at standard conditions
Oil: 1,01325 [bar(a)] 15 [°C]
Gas: 1,01325 [bar(a)] 0 [°C]

Transformation from reservoir to surface via
„Formation Volume Faktor“ B;

B = V Reservoir / V Standard conditions

Bo, Bg from PVT analysis in labs or from correlation


PVT Correlation for Oil
PVT кореляція для нафти

Standing
Lasater
Vasquez and Beggs
Petrosky
Beggs and Robinson for oil-viskosity

Evaluated Data:
Bubble Point Pressure Pb [psia oder bara]
Solution GOR Rs [scf/STB oder Sm3/m3]
Formation Volume Factor Oil Bo [RB/STB oder Rm3/m3]
(saturated oil)
Oil-Viskosity µo [centiPoise]


Formation Volume Factor (FVF), B for Oil
Фактор формування об‘ємів, B для нафти

Two Phases:
• P > gas dissolution pressure Pb
Bo increases with pressure reduction
• P < gas dissolution pressure Pb
Bo decreases with pressure reduction

2 Phases FVF, BT
Bo

Pb PReservoir
1

Formation Volume Factor (FVF), B for Gas
Фактор формування об‘ємів, B для газу

One Phase

The Volume develops disproportional
to the Pressure

Bg ~ 1 / PReservoir

Correction necessary since natural gas is not an
„ideal“ gas


Gas Reservoir
Газовий пласт

Natural gas is a „real“ gas
Deviations from the ideal p.V/T = constant. Behavior
described by the z-factor, „real gas favtor“

Z-Factor depends on

• gas composition (approximated via density ρ)
• pressure
• temperature


Z – Real Gas Factor
Z – фактор реального газу

Gas reservoir:
z-“real gas factor“ for natural gas, ρ = 0.565 (Luft =1)

1,2

1,1

1
z [-]
110 [°C]
0,9 90 [°C]
70 [°C]
50 [°C]
0,8 30 [°C]
10 [°C]

0,7
0 100 200 300 400 500
Pressure [bar]

Dynamic Hydrocarbon Calculation
Динамічне визначення об‘єму ВВ

Method for „dynamic“
HC-volume definition:
Winj
Np Gp Wp

P
Oil volume (OIP), N
Gas volume (SGIP, GIP), G

„Tank“ for MB,
Aquifer simulation cell

Untypical Oil-Water Contact Configurations
Нетипове розташування контакту води з нафтою


Drive Mechanisms in Reservoirs
Механізми імпульсу в пластах

Expansion drive (Expansion of Fluids)
Volumetric gas reservoir
Oil reservoir without gas cap
Water drive
Natural water drive by aquifer expansion
Compaction
Compaction of reservoir by overburden
Water injection
Pressure maintenance in reservoir by water
injection
Gas(Re)injection
Pressure maintenance in reservoir gas
injection


Example(s) for Oil Reservoirs
Приклад(и) нафтових пластів

Pressure Oil field
[bar]
200
Oil expansion
150
Int. Gas, Gas cap
100
Water drive
50

0
0 1000 2000 3000 4000 5000
Oil Production [m³ or t]


Graph for Gas Equation
Графік для газового рівняння

P/z [bar] Scheme for a graphic material balance
200

150
„displacement“
100

„depletion drive“
50
overpressured
0 reservoir
0 100 200 300 400
G
500
Gp Mio [Nm³]


Example of a Graphic Material Balance
Приклад графічного балансу матеріалів

P/z [bar]
200
Pi/zi
150 Well 2
Well 3
100 Well 4

Result:
50
„depletion drive“ without
water, G = 490 Mio [Nm³]
0
0 100 200 300 400 0
500 G
Gp Mio [Nm³]


Scheme for Well Test
Схема випробування свердловини

Fluid
(O, G, W)
HC prone
Formation
Pressure
Rate
(Volume,
Time)


Well Test – 1. Flow Period
Випробування свердловини – 1. робоча фаза

Procedure for OHT and CHT:

Rate
1. Flow period

Time
t1

Pressure

Time

Well Test – 1. Pressure Build Up
Випробування свердловини – 1. зміна тиску


Rate

Time
t1 ∆ t1

Pressure 1. Pressure build up

Time

Well Test – 2. Flow Period
Випробування свердловини – 2. робоча фаза


Rate
2. Flow period

Time
t1 ∆ t1 t2

Pressure

Time

Well Test – 2. Pressure Build Up
Випробування свердловини – 2. зміна тиску


Rate

Time
t1 ∆ t1 t2 ∆ t2
2. Pressure build up
Pressure

Time

Well Test – Pressure Build Up Interpretation 1/7
Випробування свердловини – аналіз результатів зміни тиску 1/7

Diagnostic - Plot
Log p 1. Pressure build up
2.5

1.5

0.5

-0.5
Log t
-1.5 -0.5 0.5 1.5 2.5



Diagnostic - Plot
Log p 1. Pressure Build Up
2.5

1.5

0.5 derivative

-0.5
-1.5 -0.5 0.5 1.5 2.5


Diagnostic - Plot
Log p 1. Pressure build up
2.5

1.5

0.5

-0.5
-1.5 -0.5 0.5 1.5 2.5


Nach Horner:

pressure
160

2.5 140

1.5

0.5
120

-0.5
-1.5 -0.5 0.5 1.5 2.5
(t+dt)/dt
100
0.0 0.2 0.4 0.6 0.8 1.0



Nach Horner:
pressure
160

140

120

(t+dt)/dt
100
0.0 0.2 0.4 0.6 0.8 1.0



Nach Horner:

pressure
160
permeability, k 1

140
k1 ~ k2
permeability, k 2
120

(t+dt)/dt
100
0.0 0.2 0.4 0.6 0.8 1.0


Nach Horner:

pressure
160 P* ... Reservoir pressure

140

120 2m m
Inclination 2m:1m ... Fault
(t+dt)/dt
100
0.0 0.2 0.4 0.6 0.8 1.0

Initial Saturation
Початкова насиченість

Capillary pressure measurement at core samples

via:
• porous Diaphragma
• centrifuge
• mercury capillary pressure measurement


Saturation Distribution 1/2
Розподілення насиченості 1/2

Result of capillary pressure measurement
[bar]
Pc
300 k = 2000 [mD]

k = 20 [mD] equivalent to
height of HC
200 column

100 h = Pc /(ρw - ρo)g
ρ

0
0 20 40 60 80 100
Water saturation, Sw [%]

Saturation Distribution 2/2
Розподілення насиченості 2/2

h[m] Irreducible water
40

k = 2000 [mD]
30
k = 20 [mD]

20

10
capillary water
0
Free Water Table
-10
0 20 40 60 80 100
Water saturation, Sw [%]

Fluid Distribution within a Reservoir
Розподілення флюідів всередині пласта


Producing Behavior of an Oil Column
Робочій режим/характер нафтового стовпа


Value of Information
Отримання інформації

Value of Information

Tests:
• influx (gas, oil, water and their ratios)
• pressure (initial, reduced; limited reservoir; tight)
• rate (initial rates, production behavior; permeabilities)

Capillary pressure measurements:
• saturations (control of volumetrics)
• permeabilities


Definition of Recovery Factor (RF)
Визначення фактору витягання з нафтового пласта

the Recovery Factor RF is a product of:
ED ….. Displacement Efficiency
EV……. Vertical Sweep Efficiency
EA ……. Areal Sweep Efficiency

RF = ED * EV * EA


Displacement Efficiency ED
Коефіціент витіснення ED

depends on saturation ratios

initially Soi (initial oil saturation), Swi (initial water saturation)
and

at production end Sor (residual oil saturation)

Soi = (1 – Swi)

ED = (Soi - Sor) / Soi z.B.: Swi = 0.3 ( Soi = 0.7), Sor =
0.3

ED = (0.7 – 0.3 ) / 0.3 = 0.571429


Sweep Patterns
Витіснення


Vertical Sweep Efficiency EV
Ефективність вертикального витіснення з пласта EV

depends on:
heterogeneity in the reservoir (permeability profile)
dip of reservoir layer(s)
mobility ratio of displaced fluid (oil) and displacing fluid
(water or gas)
Density difference between displaced (oil) and
displacing fluid (water or gas)


Areal Sweep Efficiency EA
Ефективність витіснення за площею EA

depends on:
Heterogeneity of the reservoir
Mobility ratio between displaced fluid (oil) and fluid to
be displaced (water or gas)
Pattern of production and injection wells


Factors Influencing why Oil is Left Behind in Oil Fields
Фактори впливу на залишки нафти позаду пласта


Attic Oil
Нафта продуктивного пласта над стовпом горизонтальної свердловини


When Drilling Becomes Uneconomic
Коли буріння стає нерентабельним


Maturity Pie Chart of an Oil Field
Секторна діаграма зрілості нафтового родовища


ves
Re ser
r06–
hapte
hC
wit
tinue
Con


Oil & Gas Production Geology – 06 Reserves Assessment
Геологія видобутку нафти і газу – 06 підрахунок запасів

Patos Marinza Heavy Oil Field, Albania


Reserves versus Resources – the BIG Difference
Резерви та ресурси – ВЕЛИКА різниця

Resources are always much
higher than Reserves.
In a classification of geological
resources (mineral commodities,
coal, oil, gas) we usually
differentiate between reserves that
can be produced economically
today with existing technology and
at given prices, and potential
respectively prospective resources
which can only be produced with
improved technologies and at
higher prices in the future.

Oil & Gas Production Geology – 06 Reserves Assessment | 2011 | 2

Resources Classification System
Система класифікації ресурсів


Gas in Place (GIIP) and Ultimate Recovery (UR)
Геологічні запаси та максимальне витягання

GIIP gas initially in place (m³)

GIIP = A x h x Ф x (1 – Sw) x Bgi
A area (m²)
h net pay (m)
Ф porosity (%)
Sw water saturation (%)
Bgi formation volume factor

UR ultimate recovery (m³)

UR = GIIP x RF
RF recovery factor (%)

Reserves = UR - Production

Reserves Classification Terms
Умови класифікації резервів

Proved
„Very Likely“ – reserves exhibiting a low degree of
uncertainty (~ 90 % confidence level)

Probable
„Likely“ – reserves exhibiting low to moderate degree of
uncertainty

Possible
Potential – reserves exhibiting moderate to high degree of
uncertainty


Why are Reserves Important?
Чому резерви важливі?

Proved
Generally only category reportable to regulatory agencies
Generally only category used by lenders

Probable
Combined with proved, often the basis for field development
plans and commitments (Business Planning!)

Possible
Identifies upside potential and areas for further investigation
and data collection.


Evaluation Methods
Методи оцінки

Volumetric Approach (Early Life, Performance Not
Indicative, Complex Reservoirs, Always an Essential
Baseline)
Map, Calculate OIP, Recovery Factor
Analogy
Reservoir Simulation

Performance Approach ( More Mature Fields, Performance Trends
Established, Limited Additional Development, Volumetrics Still Informative)
Decline Analysis
Material Balance
Reservoir Simulation
Analogy


Геологія видобутку нафти і газу (Oil & gas production geology)

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