SU1731943A1 - Oil field development control method - Google Patents

Abstract

The method of regulating the development of oil fields. SUMMARY OF THE INVENTION: An aqueous solution of polyacrylamide and an aqueous dispersion of bentonite clay are injected into the formation as a mixture. The mixture contains 0.5-10% bentonite clay and 0.05-0.5% polyacrylamide with a ratio of not more than 20. After the mixture is injected, hydrochloric acid and water are injected into the formation. Improving the efficiency of the process is provided by the formation in the porous medium of clay associates with polyacrylamide with high regulatory ability with respect to the injected water. As a result of the implementation of the method, the oil recovery coefficient of the reservoir increases, the development of the deposits is improved. 1 tab. SO with

Description

The invention relates to the oil and gas industry, in particular, to methods for regulating the development of fields by water flooding and isolating the water inflow of oil and gas wells in order to increase the oil and gas output of the formation.

There is a method of controlling the development of deposits by pumping an aqueous solution of polyacrylamide. However, this method is ineffective in fields with fissured or highly permeable rock (over 2 microns), i.e. polyacrylamide molecules do not effectively resist the flow of water in such a porous medium, even at high concentrations in solution (0.3-0.5%).

There is a method of controlling development, including alternately pumping 0.05-0.1% aqueous solution of polyacrylamide and 1-6% aqueous dispersion of bentonite clay. However, it is not effective enough, because associates of clay particles formed due to their adsorption on a polyacrylamide molecule when mixed in a porous medium of an aqueous solution of polyacrylamide with an aqueous suspension of clay, have a low regulatory ability due to their low strength with respect to the flow of water.

The purpose of the invention is to increase the efficiency of the method due to the formation in the porous medium of clay associates with polyacrylamide with high regulatory

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ability with respect to the injected water.

This goal is achieved by pumping an aqueous solution of polyacrylamide and an aqueous dispersion of bentonite clay as a mixture containing 0.5-10% bentonite clay and 0.05-0.5% polyacrylamide at a ratio of not more than 20, and before pumping water into hydrochloric acid is injected into the formation.

The essence of the method lies in the fact that the injected mixture of bentonite clay and polyacrylamide in water with a ratio of not more than 20 is kinetically stable (does not stratify) and, as in the known method, low-strength clay associates with polyacrylamide are formed. However, when they are mixed with acid, for example, hydrochloric acid, which is injected into the dispersion of clay in an aqueous solution of polyacrylamide, strong associates are formed, which at polymer concentrations above 0.1% and clays above 3% are highly viscous and rubber-like gels. The hardening of the clay dispersion in the polymer solution in the presence of acid is due to the suppression of the negative charge of both the clay surface and the polyacrylamide molecule. They transfer to weakly dissociated aluminum-silicon acids and acrylic acid units in the polyacrylamide molecule, which form strong associates among themselves due to the hydrogen bond. As a result, the clay particles are firmly held on the polyacrylamide molecule due to the hydrogen bond with both the acrylate and acrylamide parts. polyacrylamide molecules. As a result, at low concentrations of clay and polyacrylamide, acidic clay associates in polyacrylamide are larger in size and strength than their neutral associates in the known method, this leads to a better redistribution of the injected water from the high-permeable part, usually the water-saturated part of the formation. As a consequence, the effectiveness of the method is higher than that of the known.

The invention is illustrated by the following examples. At the same time, the efficiency of the methods is evaluated by the regulating ability (PC) of the injected chemical reagents to change the volume filtration rate of water through high and low permeable layers.

The experiments were carried out on a reservoir model that is not uniform in permeability according to the following procedure.

The reservoir model is represented by two parallel tubes (cores) of bulk sand 17.3 cm long and with a diameter

2.5 cm with a common inlet and separate outlet, saturated with water with a total salt content of 4.1%, determine the permeability of each core to water. She is

for a highly permeable core, 25–52 µm2, and for a low permeability, 0.24–0.71 µm2. Then the water in each core is displaced (by three core volumes with an oil of viscosity of 8.2 mPa – s at 20 ° C. They are fed into the model with a common inlet and pumped water with a total salt content of 0.034% to the maximum water content of liquid samples coming from their highly permeable core. At the same time, the volumes of liquid coming from high (VB) and low permeable (VH) cores are determined. per unit of time, and according to him calculate the regulating ability of water by the formula

WG2. 0 KU VH.

Then, according to this method, 1 pore volume of the model of the tested dispersion of 0.25-10% bentonite clay in 0.025-0.5% aqueous 5 solution of polyacrylamide (PAA) is sequentially pumped and RSD, 1 pore volume of the hydrochloric acid model (RSN is evaluated) and 4 pore volumes of water and

PCB is determined.

To assess the effect of hydrochloric acid, this method was used to control the experiment, and 4 volumes of water pores were pumped over the dispersion of clay in an aqueous solution of PAA (without pumping hydrochloric acid before water).

In the prototype method, a pore volume of an aqueous solution of PAA and an aqueous dispersion of clay, and then 4 pore volumes of water, is pumped into the formation model in two cycles of 0.5 pore volume. In this case, the consumption of PAA and clay in these experiments is the same with their consumption in compared experiments on

0

five

0

this way. Calculate PC after

injection of the last fringe of clay (RSP) and

after water (RSV).

The method is more effective for regulating the development, the smaller the PCb.

The characteristics of permeability models and the results of the experiments are given in the table, from which it is clear that this method is several times more efficient than the prototype method (cf. experiment 2 from 6.3 to 7).

At the same time, in most experiments, the reservoir model is highly nonuniform in permeability, and water with residual oil saturation does not move along low-permeability

core. Hence PCi is °°. The use of a dispersion of 0.25% clay in a 0.025% PAA solution showed no control effect (PCB °° in experiment 1). However, doubling their content in the aqueous dispersion is effective (see experiment 8), i.e. the water moves along the low-permeability core. Therefore, the lower concentration of clay in the composition taken 0.5%, and polyacrylamide 0.05%. An increase in their content in the composition, respectively, to 2.5 and 0.1%, leads to the shutdown of the highly permeable core, and the water moves only along the low permeable core (see experiment 3), and an increase in their content to 10–0.5% - to complete reservoir water isolation of the reservoir model, i.e. water at a certain pressure gradient (AP) does not move through either high or low permeable cores. Hence, for the upper limit of the clay content in the composition we take 10%, APAA-0.5%.

In field practice, this method can be used to regulate the development of a field by pumping a composition with a clay content of up to 2.5% and polymer up to 0.1% through injection wells, and for isolating water inflow into production wells, flows between reservoirs and other technical measures associated with high pressure gradients — by injecting a composition with a high content of clay and polyacrylamide to reduce the injectivity

injection pressure and then hydrochloric acid and water.

Claims (1)

Using this method will improve the quality of isolation work to limit the flow between reservoirs and the water inflow into oil wells and can be used to regulate the development of fields during flooding, which will lead to an increase in oil production (with a simultaneous decrease in water production) for each well operation. DETAILED DESCRIPTION OF THE INVENTION Method for controlling the development of oil fields, including injection into the reservoir of an aqueous solution of polyacrylamide, aqueous dispersion of bentonite clay and water, characterized in that, in order to increase its efficiency due to the formation of clay associates with polyacrylamide with high regulatory ability to the injected water, an aqueous solution of polyacrylamide and an aqueous dispersion of bentonite clay is injected as a mixture containing 0.5-10% bentonite clay and 0.05-0.5% polyacrylamide and their mass ratio is not more than 20, and hydrochloric acid is pumped into the formation before water is injected into the formation. Characteristics of reservoir models for permeability and regulating ability (PC) of various clay and fluid dispersions in these models