Панова Александра Викторовна
МП Адаптация курса лекций «физические основы разработки нефтяных месторождений и методов повышения нефтеотдачи» к условиям современных образовательных стандартов
Physical foundations of oil fields development and enhanced oil recovery methods
Tyumen, 2014
U
DK
622.276.6(075.8)
BBK 33.36 я 73
Korotenko V.A., Kryakvin A.B., Grachyov S.I., Khayrullin Am. At., Khayrullin Az. Am.
Physical foundations of oil fields development and enhanced oil recovery methods: Textbook – Tyumen: TSOGU, 2013, p.159.
In the manual there are observed the main methods of oil field development and enhanced oil recovery methods. The basis of the used methods, technologies of field development, the applied dynamic models in addition to the geological characteristics of the reservoir structures are the physical laws. Understanding of the physical processes occurring in the formations determines the choice of rational technology for development and appropriate choice of methods of enhanced oil recovery.
The manual is recommended to the bachelors, students, masters and postgraduate students of the specialty "Oil and gas industry".
Reviewers:
Professor of the Department of development and operation of oil deposits of the Russian State Oil and Gas University. of I.M. Gubkin, N.N. Mikhailov, Doctor of Technical Sciences.
The Head of the Department of algebra and mathematical logic, Tyumen State University, V.N. Kutrunov, Doctor of Physical-mathematical Sciences, Professor.
Introduction
The development of oil fields is called the scientifically grounded process of extraction of mineral resources, containing hydrocarbons. This process is based on the creation and management of filtration flows of fluids (oil, water and gas) in the reservoir to the bottom of producing wells to develop fully oil and gas reserves. The development of oil and gas fields is based on the achievements of such sciences as underground hydromechanics, physics of oil and gas reservoir, geophysics, mathematics.
As oil and gas reserves production, so to increase the production rates there are applied enhanced oil recovery methods, based on physical interactions between formation fluids and reservoir rock; injected reagents and hydrocarbons.
Darcy’s law of filtration was opened 1856, but only in the 20th century there were developed the foundations of physics and mechanics of porous and fractured media and processes of oil and gas extraction from such media. The basis of modern theory and practice of oil and gas fields development were established and worked out by Masket M, Leverett, Gubkin I.M., Krylov A.P., Leibenzon L.S., Muravyev I.M., Khristianovich S.A., Charny N. A., ShchelkachevV.N., Mirzadzhanzade A.H., Borisov Y.P., Zheltov Y.P.,Barenblatt G.I., Nikolaevskiy V.N., Telkov A.P., Medvedskiy P.I., Surguchev M.L.,Lysenko V.D., and others.
In the middle of the 20th century there were solved a number of problems associated with the fields development by means of natural and mixed modes. At that period of time geophysical and hydrodynamic well survey started to develop actively. There were new models of oil strata with fractured and fractured-porous reservoirs. To design and control the development processes there were used the exact and approximate mathematical tasks solving of underground hydromechanics. During recent years numerical methods and computer simulation are widely used.
In the end of 50-60sin the result of the initial formation pressure decrease the primary method of stimulation of formation was the water injection, performing two functions: 1) reservoir pressure maintenance (increase) (RPM); 2) oil displacement to the bottom of producing wells. At the same time the geological characteristics of the developed deposits structure were taken into account. It was one of the first methods of oil recovery increase. Then, hydrodynamic methods of stimulation have been used.
Moreover, aqueous solutions of chemicals have been used for bed stimulation as well as fresh water injection. Thermal methods have been started to use widely to develop the deposits containing the high-viscosity oil.
During the second and subsequent stages of field development, there are the flows of collaborative filtration in the reservoir: oil+gas, oil+water, oil+gas+water. So, there is multi-phase, multi-component filtration in the reservoir that in its turn makes it difficult to increase hydrocarbon production and requires the implementation of oil recovery increase methods, taking into account the conditions of collaborative filtration.
The majority of old unique oil fields, providing earlier the bulk of the produced oil, are exhausted now. Production facilities of new fields or new reservoirs of old, depleted ones have low pool-reservoir properties (PRP), heterogeneity and sophisticated geological structure. To extract oil and to choose appropriate technologies it is necessary to take into consideration all the physical and chemical processes that have a significant impact on the production of difficult- to- recover reserves.
The manual outlines the known methods of oil fields development and methods of oil recovery increase, the usage of which depends on the physical processes happening in the formation. Oil field development is inextricably linked with the methods of oil recovery increase, so it was logical to combine them in one manual.
The first Chapter describes the main geological and physical concepts, definitions, used in the other chapters. The second Chapter covers the development of oil fields by means of natural modes and types of reservoir energy. Special attention is paid to the manifestation causes of elastic deformation energy.
The third Chapter outlines the systems of oil field development with stimulation of formation, technological development indicators and main types of flooding. The fourth Chapter discusses the development models of oil fields, special attention is given to the models, describing filtration in reservoirs with sophisticated geological structure. The fifth Chapter provides the basic project documents for the development of oil fields, the problems arising during the operation and development of sophisticated deposits are under the view here. The sixth Chapter is devoted to the review of the geological structure and methods of high-viscosity oil fields development.
The seventh Chapter deals with methods of oil recovery increase and their connection with the regulation of oil field development. The eighth Chapter gives information about physical - chemical methods of stimulation. Chapter nine is about hydrodynamic methods of oil recovery increase. It is emphasized that not all non-stationary flooding is cyclic. Chapter ten is dedicated to gas and water-gas methods of oil recovery increase. The eleventh Chapter discusses thermal, thermic methods of oil recovery increase, used for the production of high-viscosity oil reserves. Chapter twelve is devoted to the features of well operation process after hydraulic fracturing, wells with horizontal end and acoustic methods of stimulation to the bottom-hole formation zone.
Annex 1 provides additional information about filtration by means of stationary filtration modes that allow to understand physical characteristics of the processes, occurring in the formation. The pressure disturbances radii of the deposits that are rich in low-viscosity and high-viscosity oils are under the view. In Annex 2 there are observed some peculiarities of hydraulic fracturing in reservoirs with sophisticated geological structure. Annex 3 gives the classification of oils composition, there is given the concept of effective temperature that is necessary to know to use thermal oil recovery increase methods. Also, there is represented the method of initial pressure gradient determination.
The manual does not describe the methods of oil fields development control, which are detailed in the works [3,7,13], and are offered for students ' individual studying.
PART 1. THE DEVELOPMENT OF OIL FIELDS.
CHAPTER 1. THE CONCEPTS AND PARAMETERS, DETERMINING THE PROCESSES OF HYDROCARBON PRODUCTION.
The basic geological notions.
A deposit is called natural local accumulation of oil in one or more hydro-dynamically associated reservoirs.
Afield is a system of oil deposits, dedicated to one or more traps, located on the same local area. A field can be single - or multilayer.
The deposits are divided into single-phase and two-phase. Single-phase deposits are the deposits containing one phase in reservoir conditions.
Gas deposits (GD) contain light hydrocarbons (C-C4) in gaseous form. In gas-condensate deposits (GCD) as well as light hydrocarbons there are heavy hydrocarbons (С5+- С8 ) that are in gaseous form in reservoir conditions, while in the normal conditions (on the surface) have the form of hydrocarbon liquid- condensate. Oil deposits contain heavier hydrocarbons С9-С15 in liquid state. Lighter hydrocarbons are dissolved in oil and, therefore, in reservoir conditions are in liquid phase. In addition, there are dissolved asphaltenes, resins, paraffins and other chemical compounds in oil.
Two-phase deposits are the deposits, containing two phases in reservoir conditions. They include oil and gas deposits, gas, gas-condensate-oil deposits. In two-phase deposits lighter hydrocarbons are in gaseous state, heavier are in liquid state. Condensate is partially dissolved in oil and partially in gas. The conventional boundary of liquid and gas phases is called gas-oil contact. Fig.1.1.
Fig. 1.1.Oil deposit.
There are two phases at the same time in two-phase deposits (reservoir) - gaseous (gas) and liquid (oil) –there is no impermeable boundary between them, this is a single hydrodynamic system. Oil extraction leads to the redistribution of pressure in gas cap, the formation of two-phase filtration, the change of gas-oil contact position, internal and external gas-pool outlines.
Geological peculiarities of reservoir structure are characterized by the following factors:
Compartmentalization coefficient:
,
Where ni - a number of interlayers in i - well, N – a number of the wells.
Sandiness coefficient:
,
Where hief –interlayer net thickhess in i - well, Hi – gross pay thickness of drilled in by i -well, N – a number of wells.