RU2090744C1 - Method of development of oil deposit - Google Patents

Abstract

FIELD: development of oil deposits by water-flooding the formations. SUBSTANCE: for withdrawal of oil, oil formation is perforated only at its roof, and for water injection, formation is perforated at its foot. Piston mode of oil displacement upward by water is ensured by application of respective surfactants and selection of hydrodynamic conditions of water injection and oil withdrawal. EFFECT: higher efficiency. 1 dwg

Description

 The present invention relates to the development of oil fields through production wells during flooding.

 It is known that the most effective and common way to increase oil recovery is water flooding of the oil reservoir (Sh.K. Gimatudinov, I. I. Dunyushkin, etc. Development and operation of oil, gas and gas condensate fields. M. Nedra, 1998, p. 77). In this case, various waterflooding systems are used: in-circuit, block, area, selective, focal. The main disadvantage of waterflooding of the oil reservoir is that in this case the extracted oil is quickly watered and a large amount of water is extracted with the oil. The water cut of oil reaches 90%. It is necessary to incur large expenses for pumping and extracting water from the reservoir, for separating oil from water at oil treatment points. In order to maintain reservoir pressure during waterflooding, as much water is pumped into it as much fluid is extracted.

 The process of oil displacement from the reservoir by injected water is affected by the capillary phenomenon and hydrodynamic conditions. Insufficient accounting of these factors leads to uneven oil-water contact and accelerated water breakthrough to the oil producing well.

 In addition, usually during oil production using flooding do not pay attention to the points of oil extraction and water injection. Casing is perforated over the entire height of the oil reservoir, i.e. at the same time, fluid is taken from the lower and upper parts of the reservoir.

 Known closest to the proposed invention a method of developing an oil field, implemented in ed. St. N 1615338 A1 c. E 21 B 43/00, 1990. Here, water is also injected throughout the entire thickness of the oil reservoir; the effect of separation of liquids (oil-water) of different densities is not used.

 The aim of this proposal is to reduce the ingress of water injected for waterflooding from an oil reservoir into an oil well. This goal is achieved using the method of waterflooding of the oil reservoir, characterized in that the siege column is perforated only at the roof of the oil reservoir, and water for flooding is pumped only into the lower part of the reservoir by selecting chemical additives (surfactants) to the injected water and selecting the hydrodynamic injection mode provide gravity piston mode of oil displacement from the reservoir. In this case, the displacement of oil by water begins from the lower part of the formation and gradually the displacement reaches the upper part of the roof of the formation. Since the casing is perforated only at the formation, water used for water flooding can enter the oil well only at the very end of the formation’s operation. This moment of well operation will be characterized by a sharp increase in oil cut, at which it is no longer practical to operate the well. The quality of oil displacement from the reservoir can be checked by re-enabling such a well after a certain downtime. In this case, if the leading movement of water occurred in the reservoir, when the extraction of fluid from the reservoir and the injection of water into the reservoir ceased, the separation of oil and water will occur, and at the beginning of the restart of the well, anhydrous oil will again come into operation.

 With this method of developing an oil field, the amount of water extracted from the oil decreases sharply, the volume of water pumped into the reservoir decreases, and the cost of dewatering the produced oil at the points of its preparation decreases.

 The implementation scheme of the proposed method for developing an oil field is shown in the figure.

 Oil reservoir 1 was opened by oil producing a) and pumping water b) wells. The production well has a casing 2, which is isolated by a cement ring. At the top of the formation, the casing and cement ring have a perforation 4. The heating well has a production string 5, a packer 6 and perforation 7 at the bottom of the oil reservoir.

 The method is implemented as follows.

 Oil reservoir 1 is drilled by a network of producing a) and injection b) wells using existing technology. The oil reservoir is opened for oil extraction by perforation 4 of the casing string 2 and cement ring 3 at the roof of the oil reservoir 1. The injection well b) equipped with a production string 5 for supplying water is isolated from the annulus 6 by a packer 6, and the casing and cement are used to exit the water the ring of the injection well is perforated at the sole 7 of the oil reservoir.

 This ensures the selection of oil from the upper part during the injection of water into the lower part of the oil reservoir. The oil production rate is determined by the ability and properties of the oil, and water is pumped in an amount equal to the amount of oil withdrawn. At the same time, surfactants are added to the water, which reduce the capillary penetration of water into the reservoir. These conditions ensure that oil is displaced from the water reservoir in the piston mode from bottom to top, which allows anhydrous oil to be extracted from the reservoir until the oil-water interface reaches the level of perforation in the producing well. After the oil-water interface reaches the height of the level of oil withdrawal from the reservoir and the water cut of the specified value is reached, liquid withdrawal from the reservoir and water injection into the reservoir are stopped and time is given for the ascent of oil that has lagged behind the oil-water interface. After a certain downtime, fluid recovery from the reservoir and water injection into the reservoir resumes again. In the case of anhydrous oil recovery, well operation continues until re-watering of the oil.

 This method of developing an oil field allows you to produce anhydrous oil, dramatically reduces the cost of oil production, reduces the cost of oil produced, increases the profit of oil companies. The effectiveness of using the method increases in more powerful (thicker) layers.

Claims (1)

 A method of developing an oil field, including opening a perforation of an oil formation in production and injection wells, pumping water into the oil formation through an injection well, and taking oil through a production well, characterized in that the oil formation in the injection well is opened at the bottom and water is pumped in, and in the production a well is opened at the roof and oil is sampled.