RU2286446C1 - Acid well bottom zone treatment method - Google Patents

Abstract

FIELD: oil industry, particularly to isolate thief zones in injection wells or water inflow zones in production wells drilled in carbonate reservoirs.

SUBSTANCE: method involves cyclically injecting hydrochloric acid solution, sulfur-containing aqueous mixture in well bottom zone and removing reaction products from well bottom zone. Desulfurization by-product obtained during sour oil preparation is used as above mixture. The by-product is 3-6% sulfur suspension in water. Above suspension is preliminarily injected through well to provide 0.8-1.0 MPa pressure increase in comparison with initial injection pressure. During cyclic hydrochloric acid solution injection 13-15% hydrochloric acid solution is forced with oil, wherein the solution has pressure of 1-2 MPa and taken in amount of 0.4-0.5 m³ per 1 meter of productive reservoir depth. Then 1.5-2.5 hour technological time delay is executed and oil in well is substituted for 13-15% hydrochloric acid solution. 13-15% hydrochloric acid solution under 1-2 MPa pressure and taken in amount of 0.9-1.1 m³ per 1 m of productive reservoir depth is injected and 3.5-4.5 hour technological time delay is executed. Then 13-15% hydrochloric acid solution is injected in hydro-impulse regime in 5-7 cycles. Each cycle includes injection operation lasting for 0.8-1.2 min, 4-6 min time-delay and solution holding under 1-2 MPa pressure. Then well is flushed with oil and reaction products are removed from the well by swabbing operation.

EFFECT: increased efficiency of highly-permeable zone isolation in carbonate reservoir.

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Description

The invention relates to the oil industry and may find application in the isolation of absorption zones in injection wells or water inflows in producing wells, under conditions of developing carbonate reservoirs.

A known composition for isolating water inflow in oil wells, containing, in parts by weight: synthetic plasticized isoprene rubber (SPIC) 100, kerosene or nefras-solvent heavy oil 900-4900, technical sulfur 1-4, zinc oxide 1-4, diethyldithiocarbate sodium (DEDTA) 1-4, captax-2-mercaptobenzthiazole 1-4. SPIC is dissolved in kerosene or nephras. Sulfur, zinc oxide, DEDTA and Captax are added to the resulting solution. Thoroughly mixed until a homogeneous state. Brief description of the composition: improved performance by expanding the temperature range of its use and lowering the initial viscosity (RF Patent / No. 2068075, publ. 20.10.96).

The known composition is not effective enough to isolate water inflows in carbonate reservoirs.

The closest to the proposed invention in technical essence is a method of treating a well in carbonate reservoirs, which includes cyclic injection of hydrochloric acid into the formation, followed by selling it with a reagent solution, which forms poorly soluble or insoluble in acid compounds with a carbonate reservoir, which use 2-5% aqueous solutions of oxygen-containing sulfur compounds; or sodium bisulfate, or sodium or potassium pyrosulfate, or ammonium, followed by their removal from the formation, the latter being pumped in the amount necessary for encrusting a larger zone of carbonate reservoirs than in the previous cycle (RF Patent No. 2052086, publ. 10.01.96 - prototype )

The known method allows you to isolate highly permeable zones, however, the effectiveness of the method is low due to the low degree of mudding of cracks in the carbonate reservoir of the bottomhole zone of the well.

The invention solves the problem of increasing the efficiency of isolation of highly permeable zones in a carbonate reservoir.

The problem is solved in that in the method of acid treatment of the bottom-hole zone of the well, which includes cyclic pumping into the bottom-hole zone of a solution of hydrochloric acid, an aqueous mixture containing sulfur, and removal of reaction products from the bottom-hole zone, a by-product of desulfurization from a sour oil preparation unit is used as said mixture in the form of a 3-6% suspension of sulfur in water, the suspension is previously pumped through the well to increase the pressure by 0.8-1.0 MPa from the initial discharge pressure, and when cyclic the first injection of hydrochloric acid solution are selling oil 13-15% hydrochloric acid solution at a pressure of 1-2 MPa at the rate of 0.4-0.5 m ^{3 /} m. productive formation, technological exposure for 1.5-2.5 hours, replacement of oil in the well with a 13-15% hydrochloric acid solution, injection of a 13-15% hydrochloric acid solution at a pressure of 1-2 MPa at the rate of 0 , 9-1.1 m ^{3 /} l.m. reservoir, technological exposure for 3.5-4.5 hours, hydro-pulse injection of a 13-15% hydrochloric acid solution for 5-7 cycles in a cycle mode of 0.8-1.2 min; injection - 4-6 min exposure at a pressure of 1-2 MPa, after which the well is washed with oil, and the reaction products are removed from the bottom-hole zone by swabbing.

SUMMARY OF THE INVENTION

Repeated exposure of hydrochloric acid to productive formations represented by carbonate rocks creates highly permeable zones in the form of fistulous dissolution channels extending to great depths. When developing productive formations while maintaining reservoir pressure by water injection, dissolution channels are ways of premature water breakthrough, as a result of which some reserves remain undeveloped. Existing methods for isolating highly permeable zones solve the problem partially or temporarily. Proper alignment of the inflow profile or throttle response is not achieved. The proposed invention solves the problem of increasing the efficiency of isolation of highly permeable zones in the carbonate reservoir. The problem is solved as follows.

When isolating highly permeable zones of the bottom-hole zone of the well, a 3-6% suspension of sulfur in water is pumped through the well to increase the injection pressure by 0.8-1.0 MPa from the initial injection pressure, then a 13-15% hydrochloric acid solution is injected at a pressure of 1-2 MPa at the rate of 0.4-0.5 m ³ hydrochloric acid per meter productive formation. The hydrochloric acid solution is forced through with oil. Perform technological exposure for 1.5-2.5 hours. Replace the oil in the well with a 13-15% hydrochloric acid solution and pump a 13-15% hydrochloric acid solution at a pressure of 1-2 MPa at a rate of 0.9-1.1 m ^{3 /} pm. productive formation. Perform technological exposure for 3.5-4.5 hours. Then, a 13-15% hydrochloric acid solution is pumped in 5-7 cycles in a cycle mode of 0.8-1.2 minutes; injection is 4-6 minutes holding at a pressure of 1-2 MPa. The well is washed with oil. The well is mastered by swabbing to remove reaction products from the bottom-hole zone.

Sulfur is used as a sulfur compound as a by-product of desulfurization, which is formed during the preliminary preparation of sour oil at the sour oil preparation unit. The sulfur used is neutral with hydrochloric acid. The sulfur composition is “native” to reservoir fluids. By particle size, sulfur meets the injection requirements, as mined from the same reservoir.

Sulfur slurry injection allows reliable isolation of highly permeable zones of the reservoir.

Pulse injection of a hydrochloric acid solution with holding under pressure allows the acid solution to penetrate into the low-permeability zones of the rock and increase the permeability of the low-permeability zones. As a result, the permeability of high- and low-permeability zones of the productive formation is leveled, the coverage of the formation by exposure increases, and oil recovery from the reservoir increases.

Concrete example

The bottom-hole zone of an oil producing well is processed at a depth of 1251 m. The reservoir is perforated in the interval from 1195 to 1214 m. The bottom-hole zone reservoir is carbonate pore-fractured. The well was decommissioned at a current fluid rate of 6.2 m ³ / day and a water cut of produced products of 50%. There is no annular circulation of formation fluid. There are zones washed by pumped water in the range of 1212-1214 m and 1206-1207.5 m.

Stop the well. A 6% suspension of sulfur in water is pumped through the tubing string into the well to increase the injection pressure by 1.0 MPa from the initial injection pressure, then a 14% hydrochloric acid solution is pumped at a pressure of 2 MPa based on a 0.5 m ³ hydrochloric acid solution on the metro productive formation. The hydrochloric acid solution is forced through with oil. Perform technological exposure for 2 hours. The oil is replaced in the well with a 14% hydrochloric acid solution and a 14% hydrochloric acid solution is pumped at a pressure of 2 MPa at the rate of 1 m ^{3 /} l.m. productive formation. Perform technological exposure for 4 hours. Then, a hydroimpulse injection of a 14% hydrochloric acid solution is carried out for 6 cycles in a cycle mode of 1 min; injection - 5 min exposure at a pressure of 2 MPa. The well is washed with oil. The well is mastered by swabbing to remove reaction products from the bottom-hole zone.

As a result of processing, the water cut of the produced products decreased to 25% while maintaining the flow rate of the well. When performing traditional treatments of the bottom-hole zone of the well under similar conditions, the water cut of the produced products was 35-40% with a decrease in well production.

The application of the proposed method will improve the efficiency of the method and reduce the water content of the produced products.

Claims (1)

A method of acidic treatment of the bottomhole zone of a well, comprising cyclic injection into the bottomhole zone of a solution of hydrochloric acid, an aqueous mixture containing sulfur, and removal of reaction products from the bottomhole zone, characterized in that a by-product of desulfurization from a sour oil preparation unit in the form of 3-6% suspension of sulfur in water, preliminary carry out the injection of the specified suspension through the well to increase the pressure by 0.8-1.0 MPa from the initial discharge pressure, and with cyclic filling chke hydrochloric acid solution are prodavku oil 13-15% aqueous hydrochloric acid solution at a pressure of 1-2 MPa, the rate of 0.4-0.5 m ³ /p.m producing formation process was held for 1.5-2 5 hours, replacing the oil in the well with a 13-15% solution of hydrochloric acid, injecting a 13-15% solution of hydrochloric acid at a pressure of 1-2 MPa at the rate of 0.9-1.1 m ^{3 /} lm productive formation, technological exposure for 3.5-4.5 hours, hydro-pulse injection of a 13-15% hydrochloric acid solution for 5-7 cycles in a cycle mode of 0.8-1.2 min; injection - 4-6 min exposure at pressure 1-2 MPa, after its oil wells produce washing and removal from the well bottom zone of the reaction products produced by swabbing.