RU2760112C1 - Method for developing oil deposits with low-permeability reservoirs - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to the oil industry, namely to the development of oil deposits with low-permeability reservoirs. To implement the method for developing oil deposits with low-permeability reservoirs, previously on the territory mapped by seismic operations using the method of the general depth point of the territory, the elements of occurrence are determined - the arch, the strike line and the angle of incidence of the structure. A prospecting well is drilled at the top of a seismic uplift, after calculating the economically viable specific oil reserves for one horizontal design well, the specific area of the reservoir is determined, which provides one horizontal well with recoverable reserves. A square cell is built with an area equal to the area of the reservoir, providing recoverable reserves for one horizontal well. A grid with square cells is built with an area equal to the area of the deposit, providing recoverable reserves for one horizontal well; directional and horizontal wells are arranged. First, directional wells are drilled closest to the exploration well, then horizontal wells are drilled in the center of square cells formed by directional wells. The horizontal wellbores are placed in a perpendicular-cross direction to each other with the condition that the entry and bottom points of the horizontal wells correspond to the intersection points of the diagonals within one square cell. The bottom of the exploration well is aligned on the structure with the developed grid so that the exploration well is in the center of a square cell with horizontal wells, then by rotating around the vertical axis that passes through the location of the exploration well, the grid is oriented so that the horizontal wells are directed at an angle of 90° and 180° to the stretch line of the structure. The well pattern is completed by positioning the bottom of the directional wells to the contour of the oil-water contact.

EFFECT: invention provides an increase in the efficiency of the development of oil deposits with low-permeability reservoirs.

1 cl, 1 dwg

Description

The invention relates to the oil industry, namely to the development of oil deposits with low-permeability reservoirs.

The known method of cluster drilling of oil deposits based on horizontal and vertical wells (see Erokhin V. P., Shchavelev N. L., Naumov V. I., Fadeev E. A. Experience and problems of construction of horizontal wells. Oil industry, No. 9 , 1997, pp. 32-35). According to this method, the drilling of an oil reservoir is carried out according to an areal scheme, production wells are constructed with horizontal boreholes, and injection wells with vertical boreholes. In this case, well clusters are placed at the locations of injection wells.

The disadvantage of this method is that the density of the well pattern is not much different from the options with vertical wells, the required number of wells is significant. The number of well pads is equal to the number of injection wells, that is, the number of such pads is large. Consequently, the costs of their construction, as well as the corresponding infrastructure, are significant. Therefore, the environmental impacts are also significant.

Also known is a method of developing an oil reservoir with multilateral wells (patent RU No. 2330156, IPC Е21В 43/16, publ. 27.07.2008), including drilling parallel production and injection horizontal wells, followed by multiple hydraulic fracturing of the formation, pumping a working agent in injection wells and product selection from production wells. At the same time, it is envisaged to drill at least one production and one injection horizontal wells in layers with a permeability of no more than 2 mD and a distance between horizontal wellbores of at least 50 m. Production wells are located in the maximum oil-saturated thicknesses. The angle between the maximum principal formation stress and the direction of the horizontal wellbores of production and injection wells ranges from 30 ° to 60 °. The number N of stages of multiple hydraulic fracturing is selected based on the condition N = 1 + L / 100, where L is the length of the horizontal wellbore, and is rounded to a larger integer. The total number of horizontal wells is drilled in quantity, based on the calculation that the specific initial geological reserves of oil per one horizontal well are at least 50 thousand tons.

The disadvantages of this technology are the high risks of rapid flooding of horizontal wells in more permeable layers and loss of recoverable reserves, the cost of drilling directional wells to extract the remaining pillars of oil. Also, the disadvantage is the low information content in the vertical section due to the lack of wells that have penetrated the entire oil-saturated section of the reservoir.

The closest is the method of developing an oil field (patent RU No. 2087687, IPC Е21В 43/16, publ. 20.08.1997), including the selection of sites for the placement of the infill wells according to the maps of distribution of hydrocarbon reserves, calculation of economically viable specific oil reserves, assessment the profitability of drilling each well and drilling additional production and injection wells. According to the method, the sequential construction of maps of initial recoverable reserves, active recoverable reserves, undrained oil reserves and current oil-saturated thicknesses is carried out, then on the last map, the areas of placement of the infill wells are outlined, limited by the value of the current oil-saturated thickness, not less than the value of the maximum profitable drilling thickness, and additional wells drilled at points in delineated areas where the amount of undrained reserves ensures profitable well operation.

The disadvantage of this method is a low rate of withdrawal with an oil recovery factor as a result of the fact that the sealing stock of wells is drilled in contoured areas with an oil-saturated reservoir thickness not less than the marginal cost-effective, subjecting reserves to conservation in the oil zone of areas, reservoirs with a thickness less profitable, thereby reducing oil recovery ...

The technical tasks are to increase the efficiency of the development of oil deposits with low-permeability reservoirs, to maintain high rates of extraction of reserves of low-permeability reservoirs due to the optimal location of horizontal wells along the area of the oil-containing formation.

Technical problems are solved by the method of developing oil deposits with low-permeability reservoirs, including the calculation of economically viable specific oil reserves per one horizontal design well.

What is new is that preliminarily, on the territory mapped by the seismic survey using the method of the general depth point, the occurrence elements are determined - the arch, the strike line and the dip angle of the structure, a prospecting well is drilled at the top of the seismic uplift, after calculating the economically viable specific oil reserves per one horizontal design well, they determine specific area of the reservoir, providing recoverable reserves for one horizontal well, build a square cell with an area equal to the area of the reservoir, providing recoverable reserves for one horizontal well, then build a grid with square cells with an area equal to the area of the reservoir, providing recoverable reserves for one horizontal well, have directional and horizontal wells, while first drilling directional wells closest to the exploration well, then horizontal wells in the center of square cells formed by directional wells, with horizontal wellbores are placed in the perpendicular-cross direction to each other with the condition that the entry and bottomhole points of horizontal wells correspond to the intersection points of the diagonals within one square cell; wells, then by rotation around the vertical axis, which passes through the location of the prospecting well, orient the grid so that the boreholes of the horizontal wells are directed at an angle of 90 ° and 180 ° to the strike line of the structure; contact.

FIG. depicts a grid layout with equilateral square cells with horizontal wells in the center of the square cells.

The method of developing oil deposits with low-permeability reservoirs is as follows.

Preliminarily, on the territory mapped by seismic works by the method of the common depth point - CDP (for example, in 2D, 3D, 4D, etc. structure), the occurrence elements are determined - the arch, the strike line and the angle of incidence of the structure. Next, a prospecting (or exploratory) well is drilled at the crest of a seismic uplift. The economically viable specific oil reserves are calculated for one horizontal design well. After calculating the economically viable specific oil reserves for one horizontal design well, the specific area of the reservoir is determined, which provides one horizontal well with recoverable reserves.

A square cell is built with an area equal to the area of the deposit, providing recoverable reserves for one horizontal well. Next, a grid (stencil) with square cells (see Fig.) Is built with an area equal to the area of the reservoir, providing recoverable reserves for one horizontal well. The length of the sides of the square cell is determined by the density of the grid relative to the profitable reserves per one horizontal (production) well.

Directional and horizontal wells are placed on the grid, while first the directional wells closest to the exploration well are drilled, then horizontal wells are drilled in the center of square cells formed by directional wells (the drilling sequence will remain in this order).

Moreover, the horizontal wellbores are placed in the perpendicular-cross direction to each other with the condition that the entry and bottom points of the horizontal wells correspond to the intersection points of the diagonals within one square cell. The bottom of the exploration well is combined on the structure with the developed grid so that the exploration well is located in the center of a square cell with horizontal wells. The horizontal wellbore length is a straight line connecting two points of adjacent cells. The length of the horizontal wellbore is also dependent on the grid density and uniformly changes up or down as the grid changes. The center of the grid (stencil) is the location of the exploration well. Then the grid is rotated by rotation around the vertical axis, which passes through the location of the exploration well, the grid is oriented so that the horizontal wellbores are directed at an angle of 90 ° and 180 ° to the strike line of the structure. The well pattern is completed by positioning the bottom of the directional wells to the contour of the oil-water contact, i.e. the location of the boreholes of directional wells is limited by the contour of the oil-water contact.

This arrangement of boreholes of directional and horizontal wells is optimal, it allows maintaining high rates of extraction of reserves of low-permeability reservoirs.

An example of practical application.

Preliminarily, on the CDP mapped by seismic works in a 2D structure (other examples of practical application were carried out in a 3D, 4D, etc. structure) of the territory, the elements of occurrence were determined - the arch, the strike line and the angle of incidence of the structure. An exploratory well was drilled. We calculated the economically viable specific oil reserves per one horizontal design well. The economically viable specific oil reserves per one horizontal design well amounted to 20 thousand tons, the area of the reservoir per one horizontal well was 160 thousand square meters. We built a square cell with an area of 160 thousand square meters, equal to the area of the deposit, providing recoverable reserves for one horizontal well. Next, we built a grid with equilateral square cells.

First, the design bottom holes of the directional wells were placed, then the horizontal wells (see Fig.) In the center of the square cells formed by the directional wells. Moreover, the boreholes of the horizontal wells were directed in a perpendicular-cross direction to each other with the condition that the entry and bottom-hole points of the horizontal wells correspond to the intersection points of the diagonals within one square cell. Those. first the bottom of directional wells No. 1,2,3, then the bottom of the horizontal well No. 4gs. And so on: directional wells No. 26,29,30 and horizontal well No. 31gs, then directional wells No. 33,34.4 and horizontal wells No. 36gs, 32gs, then directional wells No. 5,6 , 8 and horizontal wells No. 7gs 44gs, then directional wells No. 9,10,13 and horizontal No. 12gs, then directional wells No. 14,16,17 and horizontal well No. 15gs, then directional wells No. 18,21,22 and horizontal well # 19gs, 20gs, 23gs, 28gs, then # 24.25 and # 27gs and so on (first directional wells, then horizontal wells inside an imaginary square).

Then, the bottom of the exploration well on the structure was combined with the developed grid so that the exploration well was located in the center of the cell with horizontal wells. Then, by rotating around the vertical axis, which passes through the location of the prospecting well, the grid was oriented so that the horizontal wellbores were directed at an angle of 90 ° and 180 ° to the strike line of the structure, the well grid was finished by positioning the bottom of the directional wells to the contour of the oil-water contact. The resulting grid with the location of the target wells is limited in horizontal space by a closed structure equal in absolute elevation to the conditional oil-water contact - OWC for the oil reservoir (i.e., the grid ends in directional wells to the OWC contour).

The proposed method of developing oil deposits with low-permeability reservoirs increases the efficiency of developing oil deposits with low-permeable reservoirs, ensures the maintenance of high rates of extraction of reserves of low-permeability reservoirs due to the optimal location of horizontal wells along the area of the oil-containing formation.

Claims (1)

A method of developing oil deposits with low-permeability reservoirs, including the calculation of economically viable specific oil reserves per one horizontal design well, characterized in that the elements of occurrence are determined on the territory mapped by seismic operations using the method of the total depth point - the arch, the strike line and the angle of the structure dip, are drilled a prospecting well at the top of a seismic uplift, after calculating the economically viable specific oil reserves for one horizontal design well, the specific area of the deposit is determined, providing one horizontal well with recoverable reserves, a square cell is built with an area equal to the area of the deposit that provides one horizontal well with recoverable reserves, then a grid is built with square cells with an area equal to the area of the reservoir, providing recoverable reserves for one horizontal well, directional and horizontal wells are located, while at the same time, nak is drilled first directional wells closest to the prospecting well, then horizontal wells in the center of square cells formed by directional wells, and the horizontal wells are positioned in the perpendicular-cross direction to each other with the condition that the entry and bottomhole points of horizontal wells correspond to the intersection points of the diagonals inside one square cell, align the bottom of the exploration well on the structure with the developed grid so that the exploration well is in the center of the square cell with horizontal wells, then rotate around the vertical axis that passes through the location of the exploration well, orient the grid so that the horizontal wellbores were directed at an angle of 90 ° and 180 ° to the strike line of the structure, the grid of wells ends with the location of the bottom of directional wells to the contour of the oil-water contact.

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