SU1663182A1 - Method of water influx shutoff in borehole - Google Patents

Abstract

The invention relates to an oil producing industry. The goal is to increase the insulation efficiency by reducing the mechanical and oxidative degradation of polyacrylamide. N ₁ N - dimethylformamide ratios of 1 wt.h. dimethylformamide and 0.35 - 0.55 wt.h. water. The polymer in this state exists indefinitely and does not undergo mechanical or oxidative degradation. The prepared solution has a viscosity of 0.02-0.1 Pa ^. which allows it to be injected into the formation. After the polymer solution is injected into the well, an aqueous solution of potassium bichromate is injected. When insulated with an aqueous solution of polyacrylamide with the addition of dimethylformamide, mechanical and oxidative degradation of the polymer is eliminated, resulting in an increase in the viscosity and strength of the polymer, and consequently, its insulating properties. 1 il.

Description

The invention relates to the oil industry, in particular, to methods for isolating water inflow into production wells for adjusting the injectivity profile of injection wells.

The aim of the invention is to increase the efficiency of isolating the flow of water into the well by reducing the mechanical and oxidative degradation of polycrylamide (PAA).

The method of isolating the water inflow into the well includes sequential injection of an aqueous solution of polyacrylamide and a crosslinking agent into the well, with NN-dimethylformamide (DMF), in an amount of 1 May h DM FA KJL35-0.55 wt.h. . water

The method is carried out as follows.

Prepare a solution of polyacrylamide (PAA) in a mixture of water and DMF, taken in a ratio of 0.35-0.55 1, by mechanical movement for 30 minutes. This forms a solution with a partially dissolved polymer. The state of the polymer in this solution is intermediate between the suspension and solution. The polymer in such a solution has a supramolecular structure, that structure consisting of macromolecules. This structure is stabilized by N.N-dimethylformamide, the polymer in this state exists indefinitely and does not undergo both mechanical and oxidative degradation.

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0.02-0.1 Pa s, which allows pumping it into the reservoir.

After the polymer solution is pumped into the well, an aqueous solution of potassium bichromate is injected.

When the PAA solution comes into contact with the formation water and the crosslinker solution, the polymer is crosslinked, consisting in the transformation of the supramolecular structure of the polymer into a three-dimensional network structure, which has rubber-like properties and a high blocking effect. It should also be noted that the proposed method allows the use of PAA solutions with a concentration of more than 1% (up to 5%) for aodoisolation. Injecting such solutions is not difficult, as they are low viscosity and fluid. The use of solutions with a high content of PAA also contributes to an increase in the strength of the cross-linked polymer.

The method of water insulation using an aqueous solution of PAA with DMF additive eliminates the mechanical and oxidative degradation of the polymer and makes it possible to use highly concentrated solutions of PAA, as a result of which the viscosity and strength of the polymer and, consequently, the water insulating properties increase.

The method has been tested in laboratory laboratories as follows. As a model, a core with a length of 0.5 m and an internal diameter of 1.5 cm, filled with sand with a particle size of 0.1-0.36 mm, was used. Oil from the oil-saturated core is displaced with reservoir water to the maximum water content of the outgoing fluid samples from the core and the initial water permeability of the core is determined (for example, in ml / 5 min) at an overpressure of 0.5 MPa. Then an aqueous solution of PAA with the addition of DMF in the amount of two pore volumes is pumped into the core. Before pumping, the solution is subjected to mechanical and oxidative effects by vigorous stirring using a mechanical stirrer with a rotation frequency of 1500 rpm for 0.5 h.

Following the PAA solution, an aqueous solution of a binder is injected, for example, potassium bichromate (BHC). After 24 h, the reservoir water is pumped and the final water permeability of the core is determined at the same excess pressure, the relative decrease in the initial core permeability of water K0 ™ is calculated according to the formula Cotn Kk / Kk, where Kki Kk is the initial and final water permeability of the core.

PRI me R 1. To a solution containing 7.8 g of fresh water and 22 g of DMF (0.35: 1 ratio), 0.6 g (2%) of PAA is added and vigorously stirred for 0.5 h with a speed of 1500 rpm. The resulting solution is pumped into the core, then pumped with 30 ml of a 0.1% aqueous solution of potassium dichromate. Stand 24 hours and pass formation water through a core at an overpressure of 0.5 MPa. The water is not filtered through the core (Cottage).

Example 2. Analogously to example 1, the core is impregnated with a treated solution containing 1.5 g (5%) of PAA, 10 g of fresh water and 18.5 g of DMF (water-DMF ratio of 0.55: 1), then pumped 30 ml 0, 3% potassium dichromate solution.

The reservoir water through the core is not filtered (Kotn °°)

Example 3. Analogously to example 1, the core is impregnated with a treated solution containing 0.8 g (2.7%) of PAA, 0.3 g of water and 20, 9 g of DMF (0.4: 1 ratio), then 30 ml of 0 is pumped, 2% potassium dichromate solution. Water through the core is not filtered (Cot of).

Example 4. Analogously to example 1, the treated solution is injected, containing 0.5 g (1.7%) of PAA, 5.9 g of water and 23.6 g of DMF (ratio 0.25: 1) and 30 ml of 0.2% - potassium dichromate solution.

The PAA in the solution is in the form of dispersed particles, a solution with the supramolecular structure of the polymer is not formed.

Water flows through the core (Cotn 35).

Example 5. Analogously to example 1, a solution containing 1.6 g (5.3%) of PAA, 10.65 g of water and 17.75 g of DMF is pumped in (ratio 0.6: 1). The solution does not have fluidity, it can not be pumped to the core.

The use of the proposed method will improve the quality of insulation works to limit the water inflow into oil wells and to adjust the injectivity profile of difficult-to-homogeneous oil and gas deposits, which leads to an increase in the duration of the effect and an increase in oil production (with a simultaneous decrease in water production) for each well -operation.

Claims (1)

Invention Formula The method of isolating the inflow-water into the well, including sequential injection into the well of an aqueous solution of polyacrylamide and a cross-linking agent, is characterized in that, in order to increase the isolation efficiency by reducing the mechanical and oxidative degradation of polyacrylamide, pre-enter t NN-dimethylformamide in the ratio of 1 wt.h. dimethylformamide to 0.35-0.55 wt.h. water.  The composition contains, in addition to the binder, the antioxidant sodium hyposulfite (0.2%).