SU1710698A1 - Method of water isolation in carbonate and carbonized formations - Google Patents

Abstract

The invention relates to the oil industry and can be used to isolate water in carbonate or carbonated formations. The aim of the invention is to increase the efficiency of isolating carbonate or carbonized reservoirs and to avoid re-opening of the reservoir. The goal is achieved in that the method of isolating water in a well involves pumping a cement slurry into the formation and flushing the wellbore after cementing, with 3-10% and 20-27% aluminochloride being sequentially pumped into the formation before pumping the cement suspension . A solution of aluminochloride of increased concentration is pumped in an amount of 0.5 m per meter of thickness of the formation being treated, and the washing of the wellbore is carried out no later than 30 minutes after injection of cement mortar into the formation. The method makes it possible to reduce the consumption of cement slurry by an average of 52-56 tons per well in highly absorbent formations due to the formation of a waterproofing screen after the reaction of the aluminum chloride solution with limestone, and to eliminate additional demolition operations, reducing the time required by 4 days. In addition, the success of the work carried out increased by 20-30%. Ztabl.

Description

The invention relates to the oil industry and will find application in the isolation of water in carbonate or carbonized formations.

There is a method for isolating the inflow of water into production wells, including the sequential injection of a hypanoerosil mixture and aluminum chloride crosslinking reagent into the formation. This method is not sufficiently effective due to the fact that the blocking material is not formed in the entire volume of the mixture, and, in addition, the interaction of the reactants is accompanied by release of free water.

The closest in technical essence to the present invention is a method for isolating formation water in wells, including pumping cement mortar and washing the well after cementing.

The disadvantage of this method is that when isolating carbonate reservoirs, which are fractured porous formations of thick thickness, high cement consumption is required. So. For example, in the fields of Tatarstan, up to 60 tons of cement slurry is required per borehole on average, and the success of the work performed is low. Such technology requires re-opening of the formation with perforations, which is fraught with the danger of the productive formation communicating with the aquifer due to the integrity of the cement stone behind the column. In addition, the re-opening and subsequent restoration of reservoir properties of the reservoir itself is time-consuming, associated with tripping operations.

The purpose of the invention is to increase the efficiency of isolation of carbonate or carbonized reservoirs, as well as the elimination of the reopening of the productive Glast.

The goal is achieved by the fact that in the described method, which includes pumping cement slurry into the reservoir and flushing the wellbore after cementing, before pumping the cement slurry, 3-10% and 20-2T% alumina chloride solutions are subsequently injected into the formation, and a solution of aluminum chloride of increased concentration is pumped in the amount of 0.5 m per 1 m of the thickness of the formation being treated, and the washing of the wellbore is carried out no later than 30 minutes after the injection of cement mortar into the formation.

A comparison of the proposed solution with the known one shows that the use of aluminum chloride to obtain a water insulating screen in the reservoir is known, but in combination with hydrolyzed

polyacrylonitrile and aerosilnoe additive.

In the proposed method, the aluminum chloride is pumped in the form of two rims of aqueous solutions with different concentrations in combination with cement mortar.

Due to the use of different concentrations of aluminum chloride in the proposed method, they simultaneously perform two functions: a gelling agent (the first rim) and a cement solution hardening accelerator (the second rim).

The essence of the invention is as follows.

When injected into carbonate rocks, the rims of acidic and lumochloride with a concentration of 3–10% form a highly viscous gel in the pores of the formation. The waterproofing properties of the gel obtained by aluminum chloride in the acidic form are 4-5 times higher than the gel obtained by solutions of aluminum chloride and aluminum chloride in the basic form. Subsequent cement injection

solution prevents the formation of a gel formed from the formation at high pressure drops, and the 20-27% solution of aluminum chloride injected in front of the cement minimizes the setting time of the cement slurry, which allows rinsing the wells almost immediately after cementing. the solution from the bottomhole formation zone, and therefore exclude both the output of the aluminum chloride solution forming the gel, and the re-opening operation. It should also be noted that the use of acidic aluminum chloride in comparison with aluminum chloride prevents the loss of strength and the occurrence of porosity and fracturing in the cement stone.

Injecting a small rim of fresh water after the aluminum chloride solution of 20-27% concentration is necessary to prevent direct contact of the cement mortar with aluminum chloride as it moves through the tubing.

Thus, the proposed method has significant differences as compared with the known ones, which consist in a strictly unambiguous order of the supply of reagents, due to the previously unknown features of the interaction of acid aluminum chloride with the carbonate component of the rock and cement.

Under field conditions, the method is carried out as follows.

After determining the water flow paths, the filling pipes are lowered into the well, the lower end of which is installed in the perforated interval of the casing. Depending on the injectivity of the formation and the expected pressure on the production string, the lower end of the filling pipes is equipped with a packer or a funnel. Consistently pumped into the aquifer aluminum chloride 3-10% concentration at the rate of 5-10 per 1 m thickness of the reservoir. Moreover, the larger screen size is created, the more concentrated the solution of aluminum chloride within the specified concentration range is taken. Next, complete the rim of a 20-27% aqueous solution of aluminum chloride at a rate of 0.5 m per meter of formation thickness. Then follows the rim (buffer) of fresh water in a volume of 1 m and cement mortar. Cement mortar take in the amount of 4-8 tons.

After cementing, the wellbore zone of the well is immediately rinsed with fresh water in order to remove residual cement. After flushing the well, the shoe of the casting pipes is raised 150 m above the production filter and the well is left to wait for the cement to harden for 24 hours.

The effectiveness of the proposed method is determined under laboratory conditions. When testing, the following materials are used: acid aluminum chloride of the general formula (AL2 (OH) CIs - is a production waste obtained by washing the reaction mass from the spent catalyst complex during the alkylation of benzene with propylene (aluminum chloride is a yellow or gray liquid, the content of the main substance in terms of A1Cl3 is 17-27% by weight; cement and fresh water.

The study of the water insulating properties of the proposed isolation method is carried out on a 25 cm long, 2.7 cm diameter loose tubular reservoir model filled with ground limestone with a fraction of 0.15-0.25 mm of biogenic origin, lifted from a depth of 1445-1447 m wells.

Testing the recommended isolation method made it possible to simulate the injection of working fluids into the reservoir and to continuously monitor their flow rate according to the well-reservoir and reservoir-well schemes. The blocking effect g was taken as a criterion for evaluating the effectiveness of the tested method in comparison with the known method, which was determined on the basis of the data obtained during testing by calculation using the Darcy formula

“Ko-Ki - KGGde where Kft is the coefficient of permeability to blockage of the reservoir model,

K - coefficient of permeability after blockage of the reservoir model

When testing the proposed method, initially ... the limit of aluminum chloride concentrations for the first Fringe, designed to form a waterproofing screen in the pores of the reservoir on contact with carbonate rock, is determined.

Aluminum chloride solutions were used with ten different concentrations, wt.%: 27; 20; 15; ten; 7; five; four; 3; 2.8; 2.1.

The test results are presented in table 1 ..

Given in Table. The results of laboratory studies show that the optimal concentration range of aluminum chloride is in the range of 3-10%, since when the concentration of aluminum chloride is less than 3%, the clogging effect is sharp

decreases, and at a concentration of more than 10%, an increase in permeability due to the dissolution of lime is observed.

In the second stage of testing, the

limits of concentrations of the alumina chloride solution for the second rim. For this, the setting time of the cement mortar on contact with the aluminum chloride solution was determined. Moreover, the tests started with a concentration of aluminum chloride of at least 15%, based on the condition that no gelation took place in the bottomhole zone of the reservoir, since in this case the permeability of this zone and, accordingly, the production well flow rate decreases. The maximum concentration during testing is 27%, which corresponds to the limiting content of aluminum chloride in the waste used. Besides

In addition, a further increase in the concentration of aluminum chloride and, accordingly, a reduction in the setting time of the cement slurry is impractical.

The test results are given in

5 tab. 2

From the data table. 2 it also follows that the optimum concentration range of aluminum chloride for the second rim is 20-27%, since, when the concentration of aluminum chloride solution is less than 20%, the end of curing of the cement mortar on contact with aluminum chloride is 8 hours or more, which does not allow for washing bottomhole zone. immediately after centration.

The main results obtained during the testing of the proposed and known methods, with the sums of the volumes of working solutions are given in Table. 3

0

The blocking effect of the proposed method is 78-99% versus 54% by a known method.

Technical and economic advantages

5 of the proposed method are as follows. The use of the proposed method as compared with the known, allows to save a cement slurry with an average of 52-56 tons per well due to

0 formation of a waterproofing screen during the interaction of the aluminum chloride solution in the pores and cracks with limestone; Eliminate additional tripping operations associated with the rotary opening of the productive formation. A perforator after carrying out the insulation works by cementing and subsequent treatment of the formation, as a result, the time required is reduced by 4 days. In addition, the success of the work carried out increased by 20-30%.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A method for isolating water in carbonate or carbonized formations, comprising pumping a cement slurry into the formation and washing the wellbore after cementing, characterized in that, in order to increase the efficiency of the isolation process and avoid reopening the formation after treatment, before injection additionally, 3-10% and 20-27% solutions of aluminum chloride are pumped into the reservoir, the cement slurry is additionally injected into the reservoir, and the aluminum chloride solution of elevated concentration is pumped into the amount of 0.5 m per 1 m thickness of the treated formation, and the wellbore is washed no later than 30 minutes after injection of cement mortar into the reservoir. Table 1 Table 2