RU2595106C1 - Method of developing deposit with fractured reservoirs - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to oil industry and, in particular, to development of carbonate reservoirs with fracture-cavity type hollow space within roof part of structure in presence of roof caldera. Method comprises determining deposit sections with roof caldera, characterised by distribution of radial cracks and annular impermeable crack with decreasing downward along section of their opening. Determining zones of crack propagation of different types and cavity zone at said section. Determining direction of movement of regional flow of liquid on fracturing zones. In cavity zones placing production wells with exposure of all reservoirs of caldera at section. Injection wells are located in northern part inside caldera at distance of not less than 100 m to nearest producer well at equal distance between adjacent cracks with opening and pumping of displacement agent into lower reservoir. Displacement agent is injected into injection wells. Product is extracted through production wells.

EFFECT: technical result is increased oil flow rate of production wells and final oil recovery factor due to increased recovery of oil deposits in carbonate fractured-cavity reservoirs.

1 cl, 2 dwg

Description

The proposed method relates to the oil industry, in particular to the field of development of carbonate reservoirs with a fissure-cavernous type of void space within the arch part of the structure in the presence of the arch caldera.

A known method of developing an oil reservoir (patent RU No. 2513962, IPC ЕВВ 43/20, publ. 04/20/2014, bull. No. 11), including determining the direction of fracturing of the reservoir, drilling the reservoir with vertical and / or directional and multilateral wells in a square grid and the formation of five-point development elements by drilling in the center and at the corners of the elements of vertical and / or directionally directed injection wells and drilling between the central and corner wells in the development element of a multilateral well production well with round ennym end of the barrel. The injection of the working agent is carried out through the injection well and the selection of products through production wells. When watering producing wells, watering intervals are determined and waterlogged intervals are isolated. In this method, before drilling the deposits, areas with total oil-saturated thicknesses of more than 6 m in carbonate reservoirs and / or areas with effective oil-saturated thicknesses of not less than 2 m in the oil zone and not less than 4 m in the water-oil zone in terrigenous reservoirs, in these areas before drilling multilateral wells produce a refinement of the direction of fracture of the reservoir, multilateral wells are made in the form of a semi-ellipse, the major axis of which is directed at an angle of 30-60 ° to the direction of fracture at wearing the semi-minor axis to the semi-major axis of the ellipse is 0.1-0.8, while the trunks of multilateral wells are ascending with a minimum distance in the lower part to the oil-water contact of 4 m for carbonate reservoirs and 2 m for terrigenous reservoirs, in the upper part with a minimum 1 m to the top of the reservoir.

The disadvantage of this method is that when placing injection wells, the location of fracture zones is not taken into account when the main flows pass through the cracks, as a result of which the risk of premature flooding of production wells increases.

A known method of developing an oil field (patent RU No. 2277630, IPC ЕВВ 43/14, ЕВВ 43/20, ЕВВ 43/30, publ. 06/10/2006, bull. No. 16), including drilling injection and production wells, injection of fluid, selection products. In this method, wells are drilled with the study of elevations and depressions, determining the direction of movement of the natural flow of formation water as the direction of this stream from the rise to the depression, and determining the formation permeability anisotropies created by this stream. In this case, the contour and near-side injection wells are placed in accordance with the direction of movement of the natural formation water flow - and the external oil circuit from the side of the natural flow of produced water, additionally place the contour rows of injection wells subpendicular to the direction of the natural flow of formation water, horizontal production wells are drilled subperpendicular to the direction formation water flow.

The disadvantages of this method are the low coefficient of oil recovery, high water cut of the product and incomplete coverage by water flooding of oil reservoirs during the development of fractured-cavern type reservoirs due to the irrational placement of production and injection wells relative to the fracturing and cavity zones.

The closest in technical essence to the proposed is a method for the development of fractured reservoirs (patent RU No. 2526082, IPC ЕВВ 43/20, publ. 08/20/2014, bull. No. 23), including the determination of fracturing or decompression lines of the reservoir, the construction of production and injection wells with taking into account the fracturing of the reservoir, injection of the displacing agent into injection wells, and oil extraction through production wells. In this method, a site is selected for development with oil-saturated thicknesses of more than 10 m, preventing rapid watering of the produced oil, the location of decompression nodes — intersections of decompression lines — is determined, production vertical wells are drilled along an uneven grid with penetration into decompression nodes, and injection wells are located in compacted carbonate reservoirs with minimal and medium fracture between several decompression units at approximately equal distance from them.

The disadvantage of this method is the low efficiency of the injection when the injection wells are located between the decompression nodes in the dense part of the formation in the region where there are no zones of fracture and cavity. When placing production wells in decompression units, the risk of rapid flooding increases.

The technical task of the proposed method is to increase the oil recovery coefficient and the efficiency of the development of oil deposits in reservoirs with a fissure-cavernous type of void space due to the rational placement of production and injection wells, taking into account the location of fracturing zones.

The technical problem is solved by a development method, including determining fracture zones, constructing production and injection wells taking into account the fracture of the reservoir along an uneven grid, pumping the displacing agent into injection wells and selecting products through production wells.

What is new is that areas of the reservoir with a vault caldera, characterized by the propagation of radial cracks and an annular impenetrable crack, with openness decreasing down the section, are determined, the propagation zones of cracks of various types and cavity zones in this section are determined, and the directions of the regional fluid flow along the zones are determined fractures, producing wells are located in the cavern zones with the opening of all the caldera collectors along the section, and injection wells are located in ernoy portion inside caldera at least 100 m to the nearest production well at the same distance between nearest cracks with opening and injection of the displacing agent in the lower header.

In FIG. 1 shows a diagram of the implementation of the proposed development method (top view - north up).

In FIG. 2 shows a diagram of an implementation of the proposed development method in longitudinal section.

The inventive method is carried out in the following sequence.

The oil reservoir area within the vault caldera 1 (structure formed by an annular discharge, the lowered block of which is located inside the ring) (Fig. 1) with fractured cavernous carbonate reservoirs is drilled with vertical producing wells 2-7 outside of fracture zones 8, 9, in all areas collectors 10-13 (Fig. 2). At the first stage, development is carried out at a natural water pressure mode until the flow rate is reduced by half. After that, the injection well 14 is drilled (Fig. 1, 2) with its placement in the northern part of the caldera 1, from the direction of the regional fluid flow 15 (Fig. 1), since the total vector of the direction of movement of the regional fluid flow has a southerly direction, while the injection well 14 (Fig. 2) is located in the zone of presence of only the lower cavernous formation at a distance of at least 100 m from the nearest producing well outside the fracture zones. When the agent is pumped into the lowest cavernous reservoir 10 (Fig. 2), the oil will be displaced from the cavern zones first into radial 8 and ring 9 fractures and, filling them, will increase reservoir pressure, displace oil from the lower 10 and increase the oil saturation of the upper 11-13 layers. Since the volume of cracks is small, their openness decreases down the section due to their structure characteristic of the vault caldera, and the annular crack 9 (Fig. 1), which created the caldera, is an impenetrable barrier, the conducting system will be filled faster than the same segment with the pore permeability organization. Thus, selection will be faster compensated. Further injection will increase the reservoir pressure in the entire element of the reservoir within the vault caldera 1, limited by an annular crack 9.

Concrete example

The implementation of this method, we consider the example of the site, characteristic of the deposits of the Bashkirian stage, characterized by a fractured cavernous type of reservoir.

On the site of the oil deposits within the vault caldera 1 (Fig. 1) with the presence of annular 9 and radial 8 cracks, an element of development is organized, including production 2-7 and injection 14 wells, placed on an uneven grid. Production wells 2-7 were drilled in the zones of presence of all reservoirs 10-13 at a distance of 50-100 m from fracture zones 8, 9 (Fig. 2). The average daily oil production rate for producing wells 2–7 amounted to 5 tons / day. At the first stage, a reservoir was developed at a natural water pressure mode until the flow rate was halved to 2.5 tons / day, while the reservoir pressure decreased from 11.5 to 5 MPa. We drilled an injection well 14 (Fig. 1, 2) with its placement in the northern part of the caldera 1, from the direction of the regional fluid flow 15 (Fig. 1), because the total vector of the regional liquid flow direction is southward, with the injection well 14 (Fig. 2) located in the zone of presence of only the lower cavernous formation 10 at the same distance between the nearest fractures 8, 9. When the agent is injected into the lowest cavernous reservoir 10 ( Fig. 2) the oil is displaced from the cavernous zones first into radial 8 and annular 9 fractures and, filling them, increases reservoir pressure, displaces oil from lower 10 and increases oil saturation of the upper 11-13 layers. Since the volume of cracks is small, their openness decreases down the section due to their structure characteristic of the vault caldera, and the annular crack 9 (Fig. 1), which created the caldera, is an impenetrable barrier, the conducting system fills faster than the same segment with pore organization permeability. In this way, selection is compensated faster. As a result of the organization of injection by the development element within the vault caldera 1, the reservoir pressure increased to 10 MPa, the oil flow rate from production wells 2-7 increased from 2.5 to 4 tons / day.

The proposed development method allows to increase the coverage of oil reserves in carbonate fractured-cavern reservoirs, to increase the oil production rate of producing wells, to increase the final oil recovery coefficient.

Claims (1)

A method for developing a reservoir with fractured reservoirs, including determining fracture zones, constructing production and injection wells taking into account the fracturing of the reservoir according to an uneven grid, pumping a displacing agent into injection wells and selecting products through production wells, characterized in that sections of the reservoir with a vault caldera characterized by the propagation of radial cracks and an annular impenetrable crack, with their openness decreasing down the section, determine the distribution zones transects of cracks of various types and cavernous zones in this section, determine the direction of movement of the regional fluid flow through fracture zones, producing wells are located in cavern zones with the opening of all caldera reservoirs along the section, and injection wells are located in the northern part of the caldera at a distance of at least 100 m to the nearest producing well at the same distance between the nearest fractures with opening and injection of the displacing agent into the lower reservoir.

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