RU2084617C1 - Method for development of oil pool - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: method is applied to development of pool with substantial nonuniformity of reservoir. According to method, oil is taken from pool through producing wells, and working agent is injected through injection wells. For isolation of absorption zones, pumped into injection well are two portions of degassed oil with viscosity higher than viscosity of crude oil and heated to temperature at which its viscosity is close to viscosity of water in pool conditions. Pressure of injecting first portion is preset at 15-25% lower than pressure of injecting working agent. Between injecting portions of degassed oil, water is pumped being prior to it heated to temperature of degassed oil heating temperature. Volume of injected second portion is 30-70% of volume of first injected portion. Amount of injected water is 15-30% of total volume of degassed oil being pumped. EFFECT: high efficiency.

Description

 The invention relates to the oil industry and can be used in the development of oil deposits with significant reservoir heterogeneity.

There is a known method of developing an oil reservoir, in which oil injection is alternated with injection periods through injection wells, and oil is continuously withdrawn prior to watering production wells, and oil is pumped between water injection, while oil is extracted through production wells during oil injection periods through injection wells [1]
The disadvantage of this method is the low oil recovery, resulting from the rapid displacement of the oil zone formed near the injection wells.

Closest to the invention in technical essence is a method of developing an oil reservoir, including the selection of oil through production wells and pumping a working agent and degassed oil through injection wells, using degassed oil with a viscosity higher than the viscosity of the oil in the developed reservoir [2]
The disadvantage of this method is the low oil recovery occurring due to the small amount of degassed oil near the injection well and insufficient alignment of the injectivity profile of the injection wells.

 The aim of the invention is to increase oil recovery deposits by creating long-term isolation of highly permeable layers and more complete alignment of the injectivity profile of injection wells.

 This goal is achieved by the fact that in the method of developing an oil deposit, including the selection of oil through production wells, injection through the injection wells of a working agent and preheated degassed oil with a viscosity higher than the viscosity of the oil in the developed reservoir, according to the invention, the degassed oil is heated to a temperature at which it the viscosity is close to the viscosity of water under reservoir conditions, and is pumped in two portions at the injection pressure of the first portion less than 15-25% of the working agent injection pressure, I am waiting for the portions of the degassed oil injection to pump water heated to the heating temperature of the degassed oil, while the injection volume of the second portion of degassed oil is 30-70% of the injection volume of the first portion, and the water injection volume is 15-30% of the total degassed oil injection volume.

 To align the injection profile in injection wells, the use of degassed oil makes it possible to isolate highly permeable layers with the creation of hydrophobic zones. When developing a reservoir, a working agent bypasses these zones and enters adjacent non-washed oil-saturated zones, displacing oil from them. The use of highly viscous degassed oil allows you to create a tampon zone that is difficult to destroy by an unheated working agent. To pump highly viscous degassed oil into the reservoir, it is heated. In this case, heating to a viscosity comparable to the viscosity of the formation water promotes deep penetration, and subsequent cooling in the reservoir conditions - reliable fixation of the insulating material in the washed zone of the formation.

 The injection of heated water between the injection portions of the heated degassed oil promotes the deeper advancement of the first portion of oil, and the subsequent injection of the second portion of the heated degassed oil contributes to the displacement of the heated water into adjacent highly permeable regions, their washing and filling with the second portion of the injected oil.

 The reduced injection pressure of the first portion of the heated degassed oil contributes to a more complete filling of high permeability layers without affecting low permeability layers, that is, a more complete alignment of the injectivity profile of the well.

 The ratio of the volumes of injected portions of heated degassed oil and heated water is defined as the most optimal, leading to the achievement of the greatest result in oil recovery during the development of the deposit after insulation work.

 During development, the injected volume of viscous degassed oil gradually moves along the washed high-permeability layer, forcing the working agent to displace the oil from adjacent low-permeability zones. When approaching a production well, viscous degassed oil creates additional isolation of water inflows and increases coverage by the influence of the formation zone near the production well.

Example 1. An oil reservoir is developed with the following characteristics: a depth of 1227 m, a carbonate reservoir, permeability of 220 mD, a porosity of 17%, an average saturated thickness of 9.3 m, a deposit area of 1,0247 ha, an initial mark of BHK 1066, a GOC of 1,027.5 m, an initial reservoir pressure 13 MPa, initial reservoir temperature 30 ^o C, oil density at surface conditions 0.894 g / cm ³ , oil viscosity at reservoir conditions 12.4 MPa • s, sulfur content 2.9% paraffin content 4.5% gas saturation 21 m ³ / t, saturation pressure 7.75 MPa.

 Oil is taken from the reservoir through 560 producing wells and the working agent is pumped with water through 200 injection wells.

An injection well with an initial injection rate of 350 m ³ / day at a wellhead pressure of 10.5 MPa is perforated in the interval of the productive formation by 5.2 m. The operating interval is 2 m, highly permeable intervals 1.5 m, and the depression radius 8 m.

The required volume of injection of highly viscous degassed oil is
V = π • R ² • h • m • K • K _{draw oh}
where R is the radius of depression (repression), m;
h the interval of the reservoir, subject to the limitation of injectivity, m;
m porosity;
K _{vt is} the displacement factor;
K _oh coverage ratio. V 3.14 • 8 ² • 1.5 • 0.2 • 0.75 • 0.7 32 m ³
Degassed oil with a viscosity of 125 MPa • s at 27.4 ^° C, produced in another field, is heated to 90-100 ^° C, while its viscosity decreases to 1 MPa • s. The viscosity of produced water at 30 ^o C is 0.8 MPa • s. 16 m ^{3 of the} first portion of heated degassed oil is pumped into the bottomhole zone of the well at a pressure of 8.5 MPa (80% of the working agent injection pressure). The first portion is pushed with 6 m ^{3 of} water heated to 90-100 ^° C, then 8 m ^{3 of} heated to 90-100 ^° C is pumped with degassed oil and pushed with heated water at a pressure of 10.5 MPa at the wellhead. After that, they switch to the injection of the working agent in the usual mode of reservoir development.

Example 2. Perform as example 1, but the injection pressure of the first portion of the heated degassed water is set to 9.0 MPa, the injection volume of the first portion of degassed oil is 24.6 m ^{3 of the} second 7.4 m ³ , the water injection volume is 4.8 m ³ .

Example 3. Perform, as example 1, but the injection pressure of the first portion of the heated degassed oil is set at 7.9 MPa, the injection volume of the first portion of degassed oil is 18.8 m ³ , the second 13.2 m ³ , the volume of water injection is 9.6 m ³ .

 The application of the method allows to increase the coverage of the formation by exposure and increase oil recovery by 2-3%

Claims (1)

 A method for developing an oil deposit, including oil extraction through production wells, injection of a working agent through injection wells and preheated degassed oil with a viscosity higher than the oil viscosity in the developed reservoir, characterized in that the degassed oil is heated to a temperature at which its viscosity is close to the water viscosity in reservoir conditions, and injected in two portions at an injection pressure of the first portion less than 15 25% of the injection pressure of the working agent, between the injection portions of degassed oil injected water heated to the heating temperature of degassed oil, the volume of pumping a second portion of the degassed oil is 30 to 70% of the injection of the first portion, and the amount of water injection 15 30% of the total pumping degassed petroleum.