RU2176311C2 - Method of development of gas condensate-oil deposit - Google Patents

Abstract

FIELD: development of hydrocarbon deposits complicated with presence of zones with different rock permeabilities. SUBSTANCE: method includes tapping of producing section with central vertical and peripheral inclined wells. They have parts located within continuous formation along its strike. Wells are to be perforated. Producing section is tapped by wells according to regular geometric pattern and from one derrick substructure. Peripheral inclined wells are drilled at preset zenith angle. It provides for getting of bottom-hole to designed depth in foot of continuous producing formation to corners of regular hexagon. In three wells located through 120 deg along occurrence of continuous formation, in direction of its maximum saturation with hydrocarbons, gently sloping areas are drilled with wells from roof to foot of formation, and they are provided with strainers. Perforation of wells is made in two stages. At the first stage, subject to perforation are intervals in all wells in zone of discontinuous formations. At the second stage, continuous formations in vertical well and in inclined wells having no sloping areas are perforated. EFFECT: increased well production rate and hydrocarbon recovery factor from producing formation, reduced expenditures for well drilling and for field equipment. 5 dwg

Description

 The invention relates to the development of hydrocarbon deposits, and in particular to methods for developing hydrocarbon deposits complicated by the presence of zones with different permeability of rocks, and may find application in the development of gas condensate and gas condensate-oil fields.

 The known method of cluster drilling, used in the extraction of hydrocarbons [1]. Its essence lies in the fact that several inclined wells with certain zenith angles pass from one drilling base. The method of cluster drilling, despite some technological complications, is very effective, because can significantly reduce the time spent on dismantling, transportation and installation of drilling equipment and, accordingly, reduce the cost of drilling operations.

 There is a method of increasing the opening surface of the reservoir and expanding the drainage zone during the development of oil and gas deposits by sinking horizontal sections of wells in the reservoir [2]. Despite certain technological difficulties in drilling horizontal wells, the method makes it possible to increase the production rate of the wells and the coefficient of hydrocarbon recovery from the formation without increasing the amount of drilling work, which reduces the cost of produced hydrocarbons.

 It is known that in order to increase the yield of useful components, in particular from gas condensate-oil fields, due to the specifics of their geological structure, the procedure for opening productive formations and putting wells into operation is essential [3]. The task is to, at the initial stage of field development, achieve maximum hydrocarbon output from discontinuous formations with low permeability. This explains the fact that the currently used methods for developing hydrocarbon deposits, as a rule, differ in the order of perforation of the sections of the productive stratum and commissioning of wells.

 It is well known that hydrocarbon deposits can significantly differ from each other in the composition and properties of hydrocarbons, geological structure, conditions of occurrence of productive formations, their permeability, etc. For this reason, universal methods for placing production wells in the field under development have not yet been created. Wells are drilled along a standard dichotomous, square, rectangular or other grid, and they also use 5-, 7-, 9-point cells for this purpose [4]. Naturally, in each case, a geometrical grid or cell is selected for well placement, which, taking into account the above factors, ensures maximum hydrocarbon yield with minimal financial and labor costs for developing the field.

A known method of developing an oil reservoir [5]. Its essence is as follows. Drill vertical wells, placing them on a geometric grid, which is two regular, deployed relative to each other at 30 ^o hexagons with producing wells on the sides, in the corners and in the center of the hexagons. Additional wells pass, revealing the discontinuous part of the formation, and place them within the internal hexagon, symmetrically to the external. The layers are opened in two stages: at the first, the discontinuous part of the section is opened in the wells located on the sides of the external hexagon and in producing additional wells, and at the second, in the wells on the sides of the external hexagon, the entire productive section is opened.

 The main disadvantages of the method are the complexity of the geometrical drilling network, the large volume of drilling operations and the associated significant time spent on installation, dismantling and transportation of the derricks. This increases capital investment in field development.

 There is also a method of developing an oil reservoir [6]. According to the specified method, the oil reservoir is drilled with 5-point cells. The cell contains producing vertical wells located in the corners of the square. This wells have horizontal sections in the reservoir. A vertical injection well is drilled in the center of the square.

 The disadvantage of this method is that there is a high probability that an injection well enters the zone of low permeability of the formation, which reduces the flow rate of the wells and oil recovery.

 The closest technical solution for the same purpose as the proposed invention is a method for the development of oil deposits according to the clause of the Russian Federation N 2112868 [7]. The essence of the method is as follows. The oil and gas reservoir is drilled with producing and injection well systems consisting of one vertical and at least two pseudo-horizontal shafts. Downhole systems have a strike along the strike. In this case, a gas condensate cap is opened with vertical wells, and oil rims are opened with pseudo-horizontal ones.

The main disadvantages of the prototype under paragraph. RF N 2112868 are:
- limited scope (mainly for elongated deposits, folded by continuous layers),
- a significant amount of drilling due to the large number of injection wells.

 The task was set - using a simple grid of opening the field with a limited number of wells, to ensure the development of a gas condensate-oil field with a high value of well production and hydrocarbon recovery from productive formations, as well as reducing the cost of drilling wells and equipping the field.

The problem is solved as follows. A well bush consisting of one central vertical and six peripheral deviated wells is drilled from one drilling base. All wells are producing. The angle of inclination of the peripheral wells to the horizon is set so as to ensure that their bottom at the design depth in the bottom of the continuous formation gets into the corners of the regular hexagon. In three inclined wells located at an angle of 120 ^o relative to each other, in a continuous formation from its roof and to the sole along the strike of the formation in the direction of greatest hydrocarbon saturation, sloping sections are drilled, which are equipped with filters after sinking. The opening of productive formations is carried out in two stages: on the first - in all wells, intervals intersecting discontinuous formations are perforated, on the second - in a vertical well and in wells without gently sloping sections, an interval located in a continuous formation is perforated.

Further, the invention is illustrated by drawings, which depict:
- in FIG. 1 is an isometric image of a wellbore in a hexagonal pattern with a central well;
- in FIG. 2 is a horizontal projection of a cluster of wells in a hexagonal pattern with a central well,
- in FIG. 3 is a diagram of the intersection of continuous and discontinuous productive formations of a vertical and deviated well and an inclined well with a sloping section;
- in FIG. 4 - development plan of the North - Vasyugan gas condensate field, compiled by Tomskgaz OJSC;
- in FIG. 5 - development plan of the North - Vasyugan gas condensate field, compiled by "TyumenNIIGiprogaz".

The implementation of the proposed method is shown by the example of the development of a part of the Myldzhinsky gas condensate-oil field in the Tomsk region. A wellbore consisting of one central vertical 2 and six peripheral inclined 3 wells is drilled from one drilling base 1 (FIGS. 1, 2). All wells are producing. The zenith angle of inclined wells 3 is in the range of 22 - 24 ^o , which ensures that the bottom of the wells in the bottom of the continuous formation at a depth of 2200 - 2400 m gets into the corners of a regular hexagon at a distance of about 1000 m from the bottom of a vertical well located in the center of the hexagon. Thus, a continuous layer is opened by a vertical well at an angle of 90 ^o , and three inclined wells through 120 ^o - at a given angle of 66 - 68 ^o to the horizon. The remaining three deviated wells, also located at 120 ^o , intersect the continuous formation along its strike by sloping sections 4 (Fig. 3). The angle of inclination of these sections of the wells is selected based on the thickness of the continuous formation in such a way that their path passes within the continuous formation from its roof and to the bottom at a distance of 250 - 500 m from the angle of the hexagon. At the same time, these areas are directed towards the highest formation saturation with hydrocarbons. In the process of casing these wells, sections 4 are equipped with filters.

 Perforation of wells is carried out in two stages: at the first stage, sections located in discontinuous formations 5 are perforated in all wells; at the second stage, as reservoir pressure decreases, sections of vertical and three deviated wells that do not have inclined sections in a continuous formation 6 are perforated (Fig. . 3).

 At present, Tomskgaz is launching a project to develop the North Vasyugan gas condensate field, which is also based on the proposed method (Fig. 4). It is planned to drill 3 well clusters at the field with a total of 21 wells. Capital investments for drilling amount to $ 40 million with a total capital cost of $ 75 million. This project has undoubted advantages over the project developed by the Tyumen Research Institute of Hyprogas, the basis of which is the use of 3 - and 5-point cells with a square and rectangular grid of vertical wells (Fig. 5). The TyumenNIIGiprogaz project provides for the drilling of 10 cells with a total of 44 wells. Capital investments for drilling amount to 80 million US dollars with a total capital investment of 235 million US dollars.

 This shows the technical, technological and economic advantages of the proposed method for the development of gas condensate and gas condensate-oil fields.

Thus, the proposed method allows you to:
- increase the flow rate of wells and the recovery rate of hydrocarbons from reservoirs;
- reduce the number of production wells;
- reduce the time spent on installation and dismantling and transportation of the oil rig;
- to reduce the costs of the binding of wells and arrangement of the field;
- improve the ecological situation in the fishing area.

Sources of information
1. Handbook of a drilling engineer. T. 2. / Ed. IN AND. Mitsevich and N.A. Sidorova.- M .: Nedra, 1973.

 2. A. M. Grigoryan. Opening of strata with multilateral and horizontal wells.- M .: Nedra, 1969.

 3. Yu. V. Zheltov et al. Development and operation of oil and gas condensate fields. - M.: Nedra, 1979.

 4. V.D. Lysenko. Oilfield development. Theory and Practice.- M .: Nedra, 1996.

 5. RF patent N 2012792, E 21 V 43/30, 43/20. A method of developing an oil reservoir. B.I. N 9.1994 g.

 6. US patent N 4727937, NKI 166 - 245. A method of developing an oil reservoir, 1986

 7. RF patent N 2112868, E 21 B 43/16, 43/00. A method of developing oil and gas deposits. B.I. N 16, 1998

Claims (1)

A method of developing a gas condensate oil field, including opening a productive section with wells with a central vertical well and peripheral deviated wells having sections located within a continuous formation along its strike, and perforating wells, characterized in that the producing section is opened with wells on a regular geometric grid and with one drilling base, and the peripheral inclined wells pass with a given zenith angle, ensuring that their face is projected depth at the bottom of the continuous productive formation in the corners of a regular hexagon, and in the three wells arranged at 120 ^o, along the strike of the continuous layer in the direction of its greatest hydrocarbon saturation drilled gently sloping portions of the roof and to the foot of the reservoir and equipped with their filters and wells perforation produced in stages in two stages: at the first stage, intervals are perforated in all wells in the zone of discontinuous formations, at the second stage - a continuous formation in a vertical well and deviated wells that do not have gently sloping areas.

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