RU2597593C1 - Method for balancing injection well water-intake capacity profile and restriction of water influx to production wells - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to oil industry, in particular, to methods of limiting water influx in production wells and balancing injection well water-intake capacity profile. Using the presented method in oil industry will allow to eliminate limitations on the use of polymer gel-forming compositions at deposits with mineralized water, increase their efficiency. In method for balancing of injection well water-intake capacity profile and restriction of water influx to production wells, which involves pumping to the formation of an aqueous solution of polyacrylamide and a cross-linking agent, where the said solution is prepared on the formation water with subsequent introduction of sodium hydroxide up to pH 8.0, sodium bicarbonate in the amount of 2.48 wt%, additionally introduced chelating agent - disodium dihydrogen ethylenediaminetetraacetate in the amount of 0.1-5.0 wt%, then polyacrylamide in the amount of 0.2-3.5 wt%, chrome acetate in the amount of 0.47 wt%.

EFFECT: technical result is the increase of technological effectiveness of using polymer compositions, and the formed gel in less susceptible to degradation.

1 cl, 2 tbl

Description

The invention relates to the oil industry, in particular to methods for leveling the injectivity profile of injection and limiting water inflow in production wells. It can be used for wells with any geometry.

The problem of isolation and limitation of water inflow remains very relevant. Today, there are countless methods to limit water in productive formations - from relatively simple to complex and costly.

The most cost-effective are chemical methods that affect the water-saturated intervals of the oil-saturated reservoir and preserve the permeability to oil. The effectiveness of the technology used depends on the methods of its implementation and the correctly selected grouting material.

World and domestic experience shows that, for leveling the injectivity profile of water injection wells and limiting the movement of water in highly permeable washed formations, highly effective formulations based on aqueous solutions of gelling agents are highly effective. Under surface conditions, these are low-viscosity solutions that can selectively filter into the flooded intervals of highly permeable formations, creating artificial gel-like screens that resist the movement of injected water.

Gelling solutions can be pumped into production wells to limit associated water and to injection wells to redistribute flows. Traditional application scheme: an aqueous solution of gelling agents is injected into the formation and left alone to form a gel in the pore space of the treated zone.

A known method of isolating water inflows using alkaline silica gels based on aqueous solutions of alkali metal silicates. The gelation regulator is the rock, reservoir temperature and hydrochloric acid (RU 2065442, CL 20.08.96).

The disadvantage of this method is the obligatory presence of large volumes of fresh water. The preparation of the injected compositions, the injection of the pre-injection site and the injection of the composition into the reservoir must always be carried out using fresh water, which is not always possible in the field.

A known method of developing an oil field by injecting into the oil reservoir a gelling composition based on aluminum and urea salts (RU No. 2120544, 10.20.1998.).

The disadvantage of this method is the low strength characteristics of the gel, which reduces the effectiveness of the insulation as a whole. In addition, such reagents are recommended at elevated reservoir temperatures, which limits their scope.

The most effective are methods involving the injection into the formation of compositions based on water-soluble synthetic polymers.

So, there is a known method of developing an oil reservoir, based on the injection of an aqueous solution of an anionic polymer and salts of a polyvalent cation (RU 2167281, 08/04/1999).

A known composition, including the injection of polyacrylamide and trivalent chromium (RU 2186393, 07.24.2000).

The disadvantage of the methods is the low efficiency of the technology, since the injection of solutions is carried out without taking into account the complex of technological properties of polymers: gelation time and initial shear gradient. The optimal volume of the injected compositions is not calculated, which leads to the creation of an insufficient volume of the gel screen and a decrease in the efficiency of the technology as a whole.

The most effective methods are polymer flooding, in which a preliminary study of the physical characteristics and calculation of the required volumes of injected compositions is carried out.

There is a method of choosing a gel-forming composition to enhance oil recovery and waterproofing works (RU 2496818, 12/30/2011).

It is positive that the method is carried out taking into account the characteristics of the formation and a particular well, the injection of gelling solutions is carried out on the basis of predefined properties of the polymers: dynamic viscosity, gel time, static shear stress and calculation of the initial pressure gradient. This allows you to correctly select the concentration of the polymer and the crosslinker in the solution, the injection time and the volume of the polymer composition.

The disadvantage of this method is that the quality of the polymer dissolution water is not taken into account, which in some cases leads to a decrease in the strength of the resulting gel and its premature destruction, which makes it impossible to create a long-term barrier to water filtration.

Closest to the claimed solution is a method of using modified polymer compositions to enhance oil recovery, including the injection into the formation of an aqueous solution of polyacrylamide and chromium acetate, the solution being prepared in produced water with the addition of caustic soda to pH 8.0 and additional sodium carbonic acid in an amount 2.48 wt.% And a dosage of polyacrylamide in an amount of 1.33 wt.% And chromium acetate in an amount of 0.47 wt.% (RU 2352771, 04.20.2009).

The disadvantage of the above method is not a wide scope, limited by the mineralization of dissolution water.

The objective of the invention is to remove the restrictions on the use of saline water for the preparation and injection of gel-forming solutions, the creation in reservoir conditions of a time-stable gel-forming rim with a high level of hydrodynamic resistances.

The problem is solved by the proposed method, which includes injecting into the formation an aqueous solution of polyacrylamide and chromium acetate, the specified solution being prepared on formation water with the sequential introduction of caustic soda to pH = 8.0, sodium carbonate in an amount of 2.48 wt.%, Characterized in that in addition, complexon-trilon B is added to water in an amount of 0.1-5.0 wt.%, polyacrylamide in an amount of 0.2-3.5 wt.%, and chromium acetate in an amount of 0.47 wt.%.

A distinctive feature of the proposed method from the prototype is the introduction into water of dissolution of Trilon B complexone, as well as other quantitative content of polyacrylamide in the solution.

The optimal composition of the injected polymer composition is determined taking into account the kinetics of dissolution, gelation in specific reservoir conditions and determining the stability of the polymer gel over time.

In the case of processing highly permeable formations, the insulating composition may additionally contain various mineral fillers up to 10.0 wt.%.

The following reagents are used to prepare the composition according to the claimed method: PAA DP9-8177 (TU 2458-001-82330939-2008), chromium acetate (TU 2499-001-50635131-00), sodium hydroxide (GOST 2263-79), sodium carbonic acid (GOST 2156-76), Trilon B (GOST 10652-73).

In the preparation of polymer compositions by the present method can be used polyacrylamides or mixtures thereof, physicochemical properties comparable with the investigated DP9-8177.

Formation water is usually used to dissolve polymers in the field, so the degree of mineralization of the water is of great importance. The most critical factor is the content of salts of divalent cations (hardness).

High rigidity minimizes the ability of polymer molecules to repel, unfold, which reduces the effectiveness of its use, the proper increase in the viscosity of the working solution does not occur. The time of dissolution and structuring of the polymer increases, which leads to additional energy costs and to long downtime of the wells. The gel formed under such conditions is less stable and more susceptible to blurring and destruction.

Trilon B (disodium salt of ethylenediaminetetraacetic acid) forms stable water-soluble complexes with most cations. Adding this complexon shields, reduces the negative impact of hardness salts on polymer molecules, reducing the overall dependence of the technology on water mineralization. In addition, it is a very affordable and non-deficient reagent.

To confirm the feasibility of the invention in laboratory conditions, studies were conducted to determine the dissolution and gelation of the polymer with a long-term assessment of the stability of the polymer gel.

Testing was carried out according to generally accepted methods.

The destruction of the gel was evaluated visually. Observations were carried out during the year.

Preparation of working solutions was carried out by sequential introduction of alkali into mineralized water to pH = 8.0, soda, complexon, polymer and chromium acetate.

The polymer dissolution time was fixed from the moment the polymer was introduced into water until it was completely dissolved. The gelation time was determined from the moment the polymer solution was mixed with chromium acetate (crosslinker) to the loss of gel mobility. The polymer was dissolved in the reservoir waters of the Ivinsky and Ulyanovsk deposits, the gel stability was determined at the reservoir temperature of these deposits - 24 +/- 1 ° С.

The results of the analysis of water are presented in table 1.

The research results are presented in table 2.

An analysis of laboratory studies allows us to conclude that polymer solutions prepared on mineralized waters, previously prepared and containing complexon binding hardness salts, have better technological characteristics in comparison with the prototype. The destruction of the polymer gel is slowed down, the gels are more stable over time.

An increase in the polymer content in the solution leads to an increase in the viscosity of the solution, which eliminates the use of standard equipment, and a decrease below the claimed amount of polymer reduces the efficiency of the technology as a whole.

The amount of complexon introduced, Trilon B, is determined experimentally and depends on the type and composition of the formation water of a particular field. For example, for the Ivinskoye field with water salinity - 220 g / l, compositions 5–7 can be recommended (Table 2). For the Ulyanovsk field with water salinity of 160 g / l, the compositions are 12-14 (Table 2).

The polymer compositions according to the claimed method are more technologically advanced - the dissolution and gelation time of the composition is reduced, and the formed gel is less susceptible to degradation, more stable.

The application of the proposed method in the oil industry will remove the restrictions on the use of polymer gelling compositions in fields with mineralized waters (Volga region, Kazakhstan, etc.) and increase the efficiency of reservoir development in general. The polymer composition according to the proposed method can be used in wells of any geometry.

Claims (1)

A method for aligning the injection response profile and limiting water inflow in producing wells, including injecting an aqueous solution of polyacrylamide and a crosslinker into the formation, the solution being prepared in produced water with successive injection of caustic soda to pH = 8.0, acidic sodium carbonate in an amount of 2.48 wt. %, characterized in that in addition to water, complexon-trilon B is added in an amount of 0.1-5.0 wt.%, polyacrylamide in an amount of 0.2-3.5 wt.% and chromium acetate in an amount of 0.47 wt. .%.