книги / Разработка нефтяных и газовых месторождений. Ч. 1

7.PROJECT ENGINEERING DOCUMENT CONTENT

7.1.Geology

General Information

Preparation of engineering document should be started from studying geographical and administrative location of the field, climatic conditions available regional infrastructure.

Geological Structure

This Section shall provide lithologic-and-stratigraphic characteristic of the entire penetrated section from the surface, including types of accumulations, their sizes, hydrocarbon phase and other.

All characteristics are obtained by integrated interpretation of seismic survey, GPS geological survey, geophysical survey, drilling, core and other data.

Such characteristics shall be represented in report in the textual and graphic forms (cross-sections, maps, profiles, layouts and diagrams).

Geological and Physical Reservoir Characteristics

Geological-and-physical characteristics of reservoirs (porosity, permeability, fluid saturation, fluid content, reservoir properties threshold values and other) are determined Based on the core analysis data. Parameters to be taken for engineering shall be substantiated considering laboratory, geophysical, hydrodynamic surveys.

Physicochemical properties of oil, gas and water (viscosity, density, chemical composition, relationship between oil properties and pressure, associated component content – iodine, boron, bromine and other, potential wax precipitation and other) are determined based on the laboratory analysis of surface and subsurface samples of fluids.

Digital 3D Geological Model Development

At this stage, all available data about field geology, including a priori data, should be correlated and formalized.

In-place Reserves

This Section shall provide data about the amount of in-place and recoverable reserves and categories of reserves for all estimation targets.

7.2. Engineering Design

Engineering design part of project document shall contain substantiation of field development engineering solutions and engineering parameters.

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The main tasks of this Section are:

–Field research data analysis;

–Development analysis;

–Selection of development targets;

–Selection of development cases;

–Selection of working agents;

–Selection of enhanced oil recovery and formation stimulation methods;

–Selection of method of computation of engineering parameters;

–Selection of engineering monitoring system; and

–Selection of engineering control methods.

Field Research Data Analysis

This Section deals with analyzing reservoir and well productivity characteristics, and Selection of their value to be taken for computing engineering parameters.

Development Analysis

Development Analysis is the most significant stage of design. Conclusions to be made at this stage shall be the basis for making all project solutions. It is necessary to analyze:

–Well stock structure;

–Well performance;

–Deviation of actual indicators from target indicators;

–Reservoir pressure dynamics for each zone;

–Reservoir temperature change;

–Recovery of reserves form reservoirs and zones;

–Effectiveness of measures for enhancing reservoir performance; and

–Effectiveness of applied development system.

Selection of Development Targets

In the majority of cases, hydrocarbon fields are multipay fields. Often they have many domes which contain hydrocarbons in various phases (oil, gas and condensate). Each reservoir is characterized by its own thermodynamic conditions. Reservoirs differ by material constitution (terrigenous, carbonate and other), by productivity (low productive, high productive and so on), by void types (porous, fractured, fractured-cavernous-porous and so on), by wettability (hydrophobic and hydrophilic) and by other important characteristics. Reservoir saturating oils can significantly differ by viscosity. And, there are different reservoir drives.

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Development of each oil reservoir will be most efficient, in terms of oil recovery factor, only if it is developed with its unique development system (well spacing, injection pressure, well operation processes, formation stimulation methods and so on).

In cases when combination of several productive formations (reservoirs) causes no unevenness of reserves recovery, or reservoirs are the single hydrodynamic system, they can be combined in one production target.

Selection of Development Cases

For each reservoir it is necessary to consider several development cases which differ in reservoir drive, well spacing, application of enhanced oil recovery methods, working agents, well design, brining into design capacity and so on.

The recommended development case shall be selected based on integral consideration of engineering characteristics and economical parameters of development.

Selection of Working Agents

Working agent shall be selected based on the analysis of laboratory studies, test injections and accumulated experience in this area.

This part shall provide the basic data and information about agents, potential complications, problems which can occur in their application (process, environment and other), and mechanical availability for application of agents (well string state, behind-the-casing cement and other). It is also necessary to describe ways of waste water disposal.

Selection of Enhanced Oil Recovery and Formation Stimulation Methods

Application of various enhanced oil recovery methods and methods of stimulating production makes it possible to enhance effectiveness of the development system.

Effectiveness of the methods applied in the given field should be determined by field-geologic analysis. Statistic analysis makes it possible to identify advantages of each method and the most probable effectiveness, as well as most favorable and least favorable conditions for their application. And the most efficient methods should be selected based on the analysis data.

Selection of Methods of Engineering Parameter Computation

The methods of computation of engineering parameters shall be specified based on the particular geological and physical conditions of development. Selection of the computation method depends on stage of development, knowledge about

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the reservoir, fluid and reservoir properties, and applied or planned to be applied production technology.

At present, the basic method of computation is a 3D multi-phase mathematical modeling. In some instances, when a field is insufficiently studied, it is allowed to use methodologies based on the simpler models: analogy-statistic, stratified models and so on.

Development Monitoring

Project engineering document shall provide a research program to be developed under the effective guidelines, and such research program shall establish for each well the type, frequency, research object (reservoir) and resources. There can be two programs: mandatory and special. The mandatory research program evenly covers the entire area of the development target, the entire stock of observation and monitor wells. This program shall envisage measuring reservoir and bottomhole pressure, fluid flow rates, gas-oil factors, water cut, well productivity, surface and subsurface fluid sampling, evaluation of technical state of wells.

Development Control

This Section shall provide recommendations on application of control methods for bringing engineering characteristics of development in compliance with those specified and approved in project engineering document, without introducing any changes in the development system.

7.3. Geological-and-Engineering (Hydrodynamic) Model

Geological-and-engineering model should combine the geological and engineering part. The geological model is a static part, i.e. it contains data which undergo no changes in the process of modeling. The engineering part contains well data and their change gives the ground for the model transformation to dynamic model, i.e. the processes in development target, are modeled.

The state-of-the-art methods of earth interior investigation do not make it possible to obtain accurate data about geological structure and distribution of porosity and permeability within the reservoir volume. In this connection, all models require preliminary adjusting (adaptation) before application.

Model adaptation means adjustment of geological characteristics on the basis of correlating the analysis data with actual data of well operation.

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7.4. Engineering Part

The project solutions on reservoir engineering shall be taken considering technical capabilities (technical state of wells, availability of water supply sources, state-of-the-art machinery and so on).

Analysis of Technical State of Wells

Technical state of wells shall be the basis for making a decision on conducting well works aimed at improving development.

Technical reasons which restrict opportunity to use wells:

–Casing leak;

–Behind-the-casing flows (because of breakdown of cement sheath or breakdown of cohesion of cement with rock or casing; and

–Well failure (fall of tools or pumping equipment).

Technical state of well shall be analyzed on the basis of special geophysical surveys, temperature logging and flow metering.

Selection of Lift Method

Lift methods are subdivided into flowing well operation and artificial lift well operation. In order to find out whether flowing well operation is possible or not, it is necessary to calculate maximum well flowing pressure, and forecast the duration of flowing well operation. Artificial lift well operation is more costeffective, as it requires additional well equipment, but, at the same time, it makes it possible to enhance rate of withdrawal due to increasing underbalance. As a rule, flowing well operation takes place in the first years of production, and then, as water encroachment increases and reservoir pressure decreases, wells are brought onto artificial lift. But it is necessary to substantiate the conditions for transferring from flowing operation to artificial lift operation.

Production rates, oil and fluid production, well commissioning by years and water cutting of well production shall be determined for each lift method, and optimal bottomhole pressure and potential maximum decrease of bottomhole pressure shall be substantiated.

Methods of Mitigation Response in Well Operation

Oil production in the field is conducted under the particular conditions which depend on geological and physical properties of rocks, physicochemical properties of fluids, climatic conditions and other.

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The above conditions can cause the following problems in well operation:

–Wax and asphaltic resinous components deposition in boreholes;

–Mineral salt deposition;

–Water or gas breakdown;

–Sand sloughing;

–Hydrate formation and other.

It is necessary to predict probability of this or that problem in well operation, and develop the most effective preventive measures.

Water Supply Source

If a field requires development by maintaining reservoir pressure with water injection, it is necessary to determine the possible water supply sources.

Corrosion Protection

Water contains dissolved oxygen, mechanical impurities, bacteria, hydrogen sulfide and other aggressive elements.

It is necessary to study the potential sources of corrosion, probability and propose solutions on corrosion prevention.

Well Design and Drilling Engineering Requirements

Well is the basic member of the development system. Well production capacities depend on well construction quality, and drilling costs depend on well design. Each reservoir is characterized by its own geological and physical properties of rocks. In addition, climatic conditions can greatly differ. Wells of various types differ in design and hole making technologies (exploration, injection and production wells). Based on the expected well flow rate, the respective downhole equipment should be selected considering well diameter.

Well design features and well drilling technologies should be provided in project engineering document.

Basic Pattern of Field Facilities

It is necessary to specify the equipment and facilities (number of satellites, group pumping stations, oil gathering and treatment stations and so on), the required length of external oil pipeline, roads, power transmission lines and other, as well as capital expenditures and operating expenses required for field infrastructure development.

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Conservation of Environment and Mineral Resources

A variety of sources of atmospheric emissions and oil field wastes contaminating environment are formed at various stages of hydrocarbon production, treatment and transportation. Atmosphere, water bodies, ground and soils are contaminated in the process oil production mainly in case of emergency situation, loss of sealing of process equipment (wells, units of the oil gathering and treatment system and so on) and piping. Directly and indirectly, all contamination sources affect atmosphere, water bodies, soil, animal and vegetal life, and natural complexes.

The most important task in hydrocarbon field development is to conserve the environment.

In accordance with the effective laws, resolutions and regulations, project engineering documents shall specify the basic organizational and technical measures for ensuring people safety, conservation of mineral resources and environment from potential harmful impacts associated with the given hydrocarbon field operation. All the above measures must be accompanied with instructions of responsible organizations and persons, as well as regular control of their implementation considering the requirements of Rostekhnadzor.

7.5. Economics

Economic appraisal makes it possible to determine cost effectiveness of each development case under consideration by analyzing the ratio of financial expenditure to return from implementation of such development cases.

The basic index for selecting one development case from all development cases is Net Present Value (NPV). The development case characterized by maximum NPV for design project life shall be the best one.

8. GAS RESERVOIR ENGINEERING

Gas, gas condensate and oil-and-gas reservoir engineering is characterized by specific features caused by difference in properties of light hydrocarbons and oils. The main differences are:

–Properties of light hydrocarbons (< С5) greatly depend on thermobaric conditions in reservoir and their change;

–High elastic capacity of gas; and

–High filterability of gas.

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8.1. Oil-and-Gas Reservoir Engineering

The main specific feature of oil-and-gas reservoir is «additional» reservoir pressure margin associated with gas cap. But, it can be used to the full extent for oil displacement only if permeability of reservoir rocks is very high, oil viscosity is low, formation dip is large, and oil recovery from reservoir is low. Under other conditions gas-oil displacement is of extremely unstable nature (gas cone and lateral coning) and it causes unacceptable decrease of oil recovery factor, especially if development is under comparatively high pressure gradients.

The basic principle of oil-and-gas reservoir development is to minimize as much as possible the cross impact of gas cap and oil leg, and to enhance the role of water in oil displacement. It is implemented by developing with immobile gas-oil contact (edge water flooding and gas withdrawal in proportion to reservoir pressure decrease) by applying barrier water flooding (water injection in gas-oil contact zone with adequately proportioned simultaneous gas and oil recovery).

8.2. Oil-and-Gas Condensate Reservoir Engineering

The development conditions of oil-and-gas condensate reservoirs are the most complex as condensate flowing under reservoir pressure decrease is easily «lost». Displacement of fat reservoir gas by dry gas injected in gas cap minimizes such unfavorable effect. For this purpose, the same reservoir gas, after treatment at cycling plant, is used, sometimes in combination with water injection.

8.3. Gas and Gas Condensate Reservoir Engineering

Gas and gas condensate reservoir engineering is complicated with violation of linear filtration rule in well bore zones, flow curvature, two-phase filtration (gas condensate mixtures), reservoir destruction near well bore.

At the same time, there are conditions which are conductive to simplifying gas reservoir engineering: high gas mobility and high gas recovery factors.

The gas field development project engineering documents additionally include the special chapter «Consumer Characteristic. Gas Recovery form Reservoir.» This Chapter mainly deals with issues related to ensuring reliability of gas supply to consumers, backing up production wells (for emergency use if some high flow rate wells break down), gas transportation and storage.

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9. RESERVOIR ENGINEERING MANAGEMENT

IN OOO LUKOIL-PERM

9.1. Organizational Structure of OOO PermNIPIneft Engineering Organization

In Russia, project engineering documentation (PED) is developed by specialized organizations: industry scientific research and design institutes (PermNIPIneft, TatNIPIneft, Gyprovostokneft, TomskNIPIneft, VNIIneft and other).

These organizations were founded in infancy of oil industry for scientific maintenance of oil production and providing oil producers with project engineering documentation. Scientific research and design institutes (NIPI) in oil industry are the powerful scientific centers in the regions of their location. They are integrated enterprises covering the entire cycle of scientific maintenance of oil production from prospecting and exploration projects to development projects.

For developing project engineering documentation, all NIPI has special structural divisions (illustrated by the example of OOO PermNIPIneft):

–Exploration geology department: analysis of data obtained by prospecting and exploration operations, generation of scientific concept for further prospecting;

–Reserves estimation department: geological modeling and field reserves estimation;

–Petroleum reservoir engineering department: geological and engineering field modeling and project engineering documentation development;

–Petroleum reservoir engineering monitoring department: day-to-day analysis of development, and generation of recommendation on improving development systems by geological and technical actions;

–Oil production equipment and technology department: selection of the most effective lift method, downhole equipment and formation stimulation methods;

–Well drilling equipment and technology department: selection of the most effective well design and well construction technology for particular conditions;

–Economic assessment department: analysis of economic effectiveness of various field development cases;

–Field infrastructure development operating procedure department: laboratory research of corrosion processes on oil field equipment; generation of recommendations on water treatment for reservoir pressure maintenance and so on;

–Field research laboratory: interpretation and analysis of hydrodynamic data;

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–Rock research laboratory: research of geological and physical properties of rocks by core analyzing under laboratory conditions;

–Fluid research laboratory: laboratory research of physicochemical properties of oil, gas and condensate;

–Hydrogeology laboratory: research of physicochemical properties of surface and subsurface water; and porosity and permeability of water-containing reservoir rocks;

–Geophysical survey data interpretation laboratory: determination of rock properties on the basis of logs;

–Environment laboratory: environmental study in field area, generation of recommendations on environment monitoring system;

–Engineering division includes a great number of departments which deal with various issues of field infrastructure development, such as: power supply, road construction, construction of industrial and non-industrial buildings and installations, plumbing systems, in-field oil gathering and treatment systems, telemechanics and other, i.e. all issues related to surface development and oil transportation.

For developing project engineering documentation, all above structural divisions perform work in their domains. Final correlation of all sections and generation of documentation takes place in the Petroleum Reservoir Engineering Department, i.e. it produces the final product. The Department also follows-up the documentation at all stages of expert examination and defense, including at the final stage of consideration – at the meeting of Central Development Commission (CDC).

9.2. Project Documentation Development and Approval Procedure

OOO LUKOIL-PERM acts as initiator of PED development. The experts of the company prepare Terms of Referеnce, which provides the tasks to be solved by PED developing.

Design organization develops a schedule based on such Terms of Reference. Developed documentation undergoes the acceptance procedure of the Customer, which includes expert examination and defense at the Scientific and Technical Council of OOO LUKOIL-PERM. Then, subsoil user submits the developed documentation to the RF Ministry of Natural Resources that conducts the state expert review. If expert opinion is favorable, the developed documentation is presented at the CDC meeting, and the subsoil user and designers defense the

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