RU2060365C1 - Method for developing flooded oil deposit in stratum of monolithic structure - Google Patents

Abstract

FIELD: development of oil deposit in monolithic stratum. SUBSTANCE: method includes pumping in working agent through injection wells in unsteady mode and oil extraction through producing wells. Distribution of current oil saturated beds is determined and current value of oil saturation gas pressure is detected at late stage of deposit development. Wells flooded to a level close to limiting one located in edge areas with lowered values of current oil saturated beds are developed at regular intervals. Wells located in ares with increased values of current oil saturated beds are developed under conditions of high-speed liquid extraction and bottom pressure below current value of gas saturation of oil. Once flooding close to limiting one has been achieved in wells located in the area of increased current oil saturated beds and edge area, one may reveal intervals with failed to be extracted oil deposits in opencast collieries of this wells. Isolation of perforated area is carried out in wells with the intervals like this followed by perforation of intervals comprising loss of oil production, and these wells are developed at high-speed modes. Individual producing wells with open intermediate beds including oil failed in being displaced after achieving limiting flooding are changed over for injection of working agent with selective perforation opposite intermediate beds identical to intermediate beds comprising oil in opencast collieries of adjacent developed wells. EFFECT: increased oil production. 2 cl

Description

 The invention relates to the oil industry and can be used to develop a flooded oil reservoir in a monolithic reservoir.

A known method for the development of oil deposits, including the injection of a working agent through injection wells and the selection of oil through production wells [1]
The method does not allow to produce oil with a high oil recovery coefficient.

The closest to the invention in technical essence and the achieved result is a method of developing an oil reservoir, including the injection of a working agent through injection wells in an unsteady mode and the selection of oil through production [2]
The known method allows to extract an increased amount of oil from the reservoir due to unsteady effects and changes in the direction of flow of the displacing agent in the reservoir. However, it does not provide extraction of oil from all the numerous interlayers of a diverse permeable monolithic formation. Separate layers are not developed. The main reason for this is the flow around these cut intervals around the injected water. Thus, in the flooded volume of the reservoir are interbeds containing oil that was not extruded due to insufficient intensity of exposure.

 The purpose of the invention is the increase in oil recovery of the deposit due to a more complete involvement in the development process of undeveloped oil-containing interlayers located in the flooded volume of the monolithic formation, by increasing the intensity and efficiency of exposure to them from producing and injection wells.

 This goal is achieved by the fact that in the method of developing an irrigated oil reservoir in a monolithic reservoir, which includes injecting a working agent through injection wells in an unsteady mode and taking oil through production wells, at a late stage of reservoir development, the distribution of current oil-saturated thicknesses is determined and the current value of oil saturation pressure is determined gas. Wells with water cut close to the limit, located in the marginal zones with reduced values of the current oil-saturated thicknesses, are operated periodically. Wells located in areas with increased values of current oil saturated thicknesses are operated under conditions of forced withdrawal of liquid and bottomhole pressures below the current pressure of oil saturation with gas. Upon reaching water cut close to the limit, wells located in areas with increased values of oil-saturated thicknesses and the marginal zone reveal intervals with undeveloped oil reserves. In the well with such intervals, the perforation zone is isolated, followed by the perforation of the intervals containing under-extracted oil, and these wells are operated in forced modes. In order to increase the impact on interbeds with undeveloped reserves, individual producing wells in which interbeds with underfilled oil were opened after reaching the maximum water cut were transferred under injection of a working agent during selective perforation against interbeds identical to interbeds containing crude oil in sections of neighboring producing wells.

 The essence of the invention lies in the fact that at a late stage of developing a reservoir in a monolithic reservoir, the targeting of current oil reserves (oil-saturated thicknesses above the upper flooded layer in the context of the monolithic reservoir), as well as intervals in the flooded volume containing unplaced oil, and based on knowledge places of concentration and the nature of the distribution of residual oil reserves to ensure their production due to the intensification of the impact on these reserves from producing and injection wells.

PRI me R. The oil reservoir (self-development block) has the following characteristics: dimensions 4x4 km, reservoir thickness 40 m, the permeability of the reservoir varies from tens of millidarsi to 2 darsi. The stratum is dissected by intercalations of clay that are not sustained along strike. The dissection coefficient 7. The viscosity of oil in reservoir conditions 1.2 cP, water 0.5 cP. The pressure of oil saturation with gas 13 MPa. Current water cut 95%
The deposit (self-development block) has been in operation for 25 years. 75 production and 42 injection wells were drilled. Water is pumped through 21 injection wells, and formation fluids are collected through 63 production wells. Injection wells operate in an unsteady mode, changing the pressure gradients and the direction of flow of the displacing agent in the oil-containing formation.

 At the late stage of reservoir development, with the development of about 70% of recoverable oil reserves in wells, the current oil-saturated thicknesses were determined, according to which the nature of the distribution of current oil-saturated thicknesses was established. According to these data, a zone with increased thicknesses (h≥5 m) and an edge zone with thicknesses less than 1.5 m were outlined.

 In the zone of increased concentration of current oil reserves, i.e. of current thicknesses, there are 16 highly flooded production wells, which switched to forced operation with bottomhole pressures 20% lower than the current values of oil saturation pressure with gas (11.0 MPa). There are 27 highly flooded wells in the marginal zone. They were transferred to periodic operation in antiphase with the operation of injection wells.

 Wells were identified in the block, in the water-filled section of which several oil-containing intervals were noted. Highly waterlogged wells with a water-flooded middle part and the presence of oil-containing intervals in the bedrock and in the bottom sole are noted. Wells with oil-saturated intervals localized only in the near-bed part of the formation, as well as wells with alternating flooded and oil-containing interlayers, were noted.

 In accordance with the sequence of work, regulated by the proposed method, in the water cut of one of the wells N 1, which reached the maximum water cut (99%) and the presence of a layer with crude oil 4 m thick (2576-2580 m), the perforation interval was filled through which the well it was flooded (2560-2563 m), then the interval containing oil (2577-2579 m) was perforated and the well was put into operation.

 In the other extremely waterlogged well, located 600 m from the above marked well N 1, the initial perforation zone was filled, the interval of the analogue put into operation in well N 1 was perforated, and water was pumped.

 Carrying out operations similar to those carried out in well No. 1 is planned in all producing wells of the block 2 years after the wells reach the central zone of maximum water cut of the products.

 Implementation of the proposed method will increase the recovery factor by 1.5-2% relative to the rate provided by the prototype.

Claims (2)

 1. A method of developing a water-cut oil reservoir in a monolithic reservoir, including pumping a working agent through injection wells in an unsteady mode and taking oil through production wells, characterized in that at a late stage of reservoir development, the distribution of current oil-saturated thicknesses is detected and the current value of the oil non-saturation pressure is determined gas, while wells with water cut close to the limit, located in the marginal zones with reduced values of the current oil-saturated thicknesses, the operator wells periodically, wells located in areas with increased values of current oil-saturated thicknesses are operated under conditions of forced withdrawal of liquid and bottomhole pressures below the current value of oil saturation pressure with gas, when wells reach water cuts that are close to the limit, located in areas with increased values of current oil-saturated thicknesses and intervals with undeveloped oil reserves in the sections of these wells are identified in the boundary zone, and in the wells with such intervals, isolation of the perforation with subsequent perforation intervals containing nedoizvlechennuyu oil, and operate well at these forced modes.  2. The method according to claim 1, characterized in that the individual production wells, in which the interlayers were opened with underexposed oil after reaching the maximum water cut, are transferred under injection of the working agent during selective perforation against interlayers identical to the interlayers containing oil in sections of adjacent producing wells .