RU2112136C1 - Process developing inhomogeneous oil pool - Google Patents

Abstract

FIELD: oil production. SUBSTANCE: while developing oil pool by flooding aqueous solution of partially hydrolyzed polyacrylamide and clay suspension in equivalent volumes are injected in turn through injection hole. Water in the amount of 5-10% of volume of pumped aqueous solution of partially hydrolyzed polyacrylamide is pumped between these volumes. Technological curing in the course of 8-60 h is then performed. Next pumping of working agent is conducted under increased pressure corresponding to take-in characteristics of well before treatment. Oil is removed through production wells. EFFECT: improved efficiency of process.

Description

 The invention relates to the oil industry and can be used in the development of a heterogeneous oil reservoir by flooding.

 A known method of developing a heterogeneous oil reservoir, including flooding, sequentially alternating injection into the flooded reservoir of an aqueous solution of partially hydrolyzed polyacrylamide and clay slurry and subsequent injection of the displacing agent [1].

 The disadvantage of this method is the low efficiency of isolation due to incomplete deposition of clay particles.

The closest in technical essence to the proposed method is a method of developing a heterogeneous oil reservoir, which includes sequentially alternating injection into an flooded reservoir of an aqueous solution of partially hydrolyzed polycarylamide with a molecular weight of (0.9 - 14) • 10 ⁶ and a degree of hydrolysis of 5 - 30% and a clay suspension followed by injection of the displacing agent and the selection of oil [2].

 When implementing the known method, a more complete precipitation of clay particles occurs in large pores of the formation, however, the effectiveness of the method remains low due to the small depth of processing of the bottomhole zone. In this regard, the oil recovery of the reservoir remains at a low level.

 The invention solves the problem of increasing oil recovery due to deeper treatment of the bottom-hole zone of wells.

 The problem is solved in that in a method for developing a heterogeneous oil formation, including water flooding, sequentially alternating injection of an aqueous solution of partially hydrolyzed polyacrylamide and a clay suspension into a flooded formation followed by injection of a displacing agent and selection of oil, according to the invention, the ratio of injection volumes of an aqueous solution of partially hydrolyzed polyacrylamide and clay suspensions are set equivalent between the injection of an aqueous solution of a partial hydrolyzed polyacrylate IDA and injection of a clay suspension pump water in a volume of 5-10% of the injection volume of an aqueous solution of partially hydrolyzed polyacrylamide, after the clay suspension is pumped, technological exposure is carried out for 8-60 hours, and the displacing agent is injected with an increased pressure corresponding to the injectivity of the well before treatment .

The essential features of the invention are:
1. Water flooding.

 2. The sequentially alternating injection into the flooded layer of an aqueous solution of partially hydrolyzed polyacrylamide and clay slurry.

 3. Subsequent injection of the displacing agent.

 4. The selection of oil.

 5. The establishment of an equivalent ratio of injection volumes of an aqueous solution of partially hydrolyzed polyacrylamide and clay slurry.

 6. Water injection between the injection of an aqueous solution of hydrolyzed polyacrylamide and a clay suspension.

 7. The injection volume of water is 2-10% of the injection volume of an aqueous solution of partially hydrolyzed polyacrylamide.

 8. Carrying out technological exposure after injection of clay slurry.

 9. The duration of technological exposure 8 - 60 hours

 10. Injection of a displacing agent with increased pressure corresponding to the injectivity of the well prior to treatment.

 Signs 1 to 4 are common with the prototype, signs 5 to 10 are essential distinguishing features of the invention.

 The task of increasing the oil recovery of the flooded oil reservoir is achieved by introducing polyacrylamide and clay into the washed, highly permeable zones, blocking these zones and subsequently pumping a displacing agent, which will bypass the clogged zones along the non-washed oil-saturated zones and displace oil from them to the producing wells.

 The use of an equivalent (equal) ratio of the injection volumes of an aqueous solution of partially hydrolyzed polyacrylamide and clay slurry contributes to an increase in the penetration depth of plugging agents, the use of buffer injection of water in a volume of 5 - 10% of the volume of an aqueous solution of partially hydrolyzed polyacrylamide. In this case, the components do not react until the desired depth is reached, but begin to react with the deposition of clay during technological exposure. A deep and strong mudding of highly permeable formation zones is achieved. High strength plugging allows you to increase the injection pressure of the displacing agent without fear of destruction of the tampon.

 As a result, the displacing agent under high pressure penetrates into the pores with the smallest size and displaces oil from there. Oil recovery increases.

 The method is as follows.

 After flooding, a 0.001-0.05% aqueous solution of partially hydrolyzed polyacrylamide is pumped into the injection well in a sequentially alternating mode, water in a volume of 5-10% of the injection volume of an aqueous solution of partially hydrolyzed polyacrylamide, a clay suspension in a volume equal to partially aqueous volume hydrolyzed polyacrylamide. Technological exposure is carried out for 8 - 60 hours and a displacing agent (water) is pumped with a pressure that ensures injectivity of the well before treatment.

Example 1. Develop an oil reservoir with the following characteristics: the size of the reservoir 25 x 10 km, the permeability of low permeability zones 10 mD, highly permeable - 100 mD, porosity 11%, oil saturation 72%, saturation pressure 4.4 MPa, gas factor 11.9 m ³ / t, oil density 860 kg / m ³ , oil viscosity 11.9 mPa • s, sulfur 2.5%, asphaltenes 5.6%, paraffins 3.8%, reservoir temperature 35 ^o C, reservoir thickness 15 m, depth reservoir 1100 m, reservoir pressure 11 MPa. The deposit is developed by water flooding, while oil is taken through production wells and water is pumped as a working agent through injection wells. After 20 years of development, the water cut of the extracted products reached 65 0 70%. For processing, choose an injection well located near production wells with maximum water cut of the produced products. The injectivity of the well 500 m ³ / day. 150 m ^{3 of a} 0.05% aqueous solution of partially hydrolyzed polyacrylamide, 11 m ^{3 of} water, 150 m ^{3 of a} clay suspension with a density of 1050 kg / m ^{3 are} pumped into the formation through an injection well. Injection pressure 12 MPa at the wellhead. Technological exposure is carried out for 48 hours, after which the water injection is resumed as a working agent under pressure at the mouth of 15 MPa, which ensures a well injectivity of 500 m ³ / day (injection pressure before treatment was 9 MPa). Continue the process of developing deposits. After 1.5 months, a decrease in water cut of produced products in producing wells by 45% was noted while maintaining their flow rate.

Example 2. Perform as example 1. Through an injection well with an injection rate of 450 m ³ / day, 100 m ^{3 of a} 0.07% aqueous solution of partially hydrolyzed polyacrylamide, 5 m ^{3 of} water, 100 m ^{3 of a} clay suspension with a density of 1020 kg / m ³ . Technological exposure is carried out for 8 hours, after which the injection of formation water as a working agent is resumed under a pressure of 14.5 MPa at the wellhead, which ensures a well injectivity of 450 m ³ / day (injection pressure before treatment was 9 MPa). After 1 month, a decrease in water cut of produced products in producing wells by 35% was noted while maintaining their flow rate.

Example 3. Perform as example 1. Through an injection well with an injection rate of 600 m ³ / day, 200 m ^{3 of a} 0.1% aqueous solution of partially hydrolyzed polyacrylamide, 20 m ^{3 of} water, 200 m ^{3 of a} clay suspension with a density of 1080 kg / m ³ . Technological exposure is carried out for 60 hours, after which water injection as a working agent is resumed under pressure at the mouth of 15.5 MPa, which ensures a well injectivity of 600 m ³ / day (injection pressure before treatment was 8.5 MPa). After 1.5 months, a decrease in water cut of produced products in producing wells by 50% is noted while maintaining their flow rate.

 The application of the proposed method will reduce the water cut of the extracted products and increase oil recovery by 2 - 3%.

Claims (1)

 A method for developing a heterogeneous oil reservoir, including flooding, sequentially alternating injection of an aqueous solution of partially hydrolyzed polyacrylamide and a clay suspension into a flooded formation, followed by injection of a displacing agent and selection of oil, characterized in that the ratio of injection volumes of an aqueous solution of partially hydrolyzed polyacrylamide and clay suspension sets the equivalent between the injection of an aqueous solution of partially hydrolyzed polyacrylamide and the injection of clay slurry Oil refineries pump water in a volume of 2-10% of the injection volume of an aqueous solution of partially hydrolyzed polyacrylamide, after the clay suspension is pumped, technological exposure is carried out for 8-60 hours, and the displacing agent is injected with increased pressure, corresponding to the injectivity of the wells before treatment.