RU2508446C1 - Method of development of heterogeneous-layer oil deposits - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: proposed method comprises injection of working agent via injection wells, extraction of oil via production wells, injection of sealing agent based on sodium silicate and acid into injection or production wells, holding the welds for a day and making them operate. Prior to injecting said sealing agent into bed, water-slug is injected in amount inhibiting the mixing of bed water with sealing agent till its gelation but not smaller than one volume of tubing. Holding is performed after injection of said agent into the bed. Sealing agent is composed by gel-like compound of the following composition, wt %: sodium silicate - 3-8, sulfonic acid - 0.38-1.5, chromium acetate - 0.35-0.9, monoethanol-amine - 0.35-0.9.

EFFECT: higher efficiency of sealing.

2 ex, 1 dwg

Description

The invention relates to the oil and gas industry, in particular to methods for producing oil from heterogeneous flooded formations at a late stage of oil field development.

A known method for the selective isolation of the influx of formation water into oil wells, involving the injection of water-soluble polymers of acrylic series [Kleshenko II, Grigoryev AV, Telkov AP Insulation work during completion and operation of wells. - M. Nedra, p.31]. The mechanism of isolation of formation water is based on the interaction of acrylic polymers with multivalent salts of formation water or the adsorption of polymers on the rock. However, this method is applicable only for the isolation of highly saline water of calcium chloride type.

A known method of limiting the flow of water into the well, including the sequential injection of an aqueous solution of sodium silicate and hardener - [SU, No. 1423726, ЕВВ 33/12, 1988]. In this case, an aqueous solution of sodium silicate reacts with a hardener - a solution of hydrochloric acid, which results in the formation of a highly viscous gel, which then turns into a solid substance - silica sol, clogging the pores.

The disadvantages of this method include the fact that during the injection process premature and uneven mixing of the injected solutions occurs, with the formation of a blocking screen near the injection line and even in the wellbore. As a result, the composition does not reach its destination and wide coverage of flooded zones of the formation is not achieved.

The closest analogue of the invention is a method for developing stratified heterogeneous oil fields (RF, No. 2128768, ЕВВ 43/22, 1999), used in the treatment of bottom-hole zones of production or injection wells in order to isolate water inflows into production wells and to align the injectivity profile of injection wells as well as during isolation of annular overflows in wells and during the liquidation of old wells. According to the method, an insulating agent is pumped through injection wells, oil is taken through production wells. When watering producing wells, an isolating agent based on sodium silicate and hydrochloric acid is pumped into the wells. The well is maintained during the day and put into operation.

The disadvantage of this method is the low insulation efficiency, short gelation time, low strength (30Pa) and the danger of precipitation of silicic acid salts when the gel-forming composition meets highly mineralized formation waters.

The invention solves the technical problem of increasing the efficiency of insulation by increasing the gelation time, increasing the strength of the gel.

The problem is solved in that in a method for developing stratified heterogeneous oil fields, which includes injecting a working agent through injection wells, taking oil through production wells, injecting an insulating agent based on sodium silicate and acid, flooding the producing wells with an insulating agent, holding the wells in during the day and putting them into operation, according to the invention, first, before pumping the insulating agent into the formation, a rim of fresh water is pumped in volume, ensuring which does not mix formation water with an insulating agent until the time of gelation, but not less than one volume of tubing, the exposure is carried out after the agent is pushed into the formation, and a gelling composition in the following composition is used as an insulating agent, wt.%:

Sodium silicate 3-8 Sulfamic acid 0.38-1.5 Chromium acetate 0.35-0.9 Monoethanolamine 1.5-2.5 Water rest

Thus, the proposed method differs from the analogue of the novelty of the composition and the method of pumping the composition into the reservoir. The additional introduction of chromium acetate to the acid-gel-forming system (sodium silicate + sulfamic acid) leads to further hardening of the system. This occurs due to the formation of complexes between negatively charged silicate ions and the trivalent chromium cation in three-dimensional form. Thus, the gel is formed due to hydrogen bonds with silicic acid, hardened by spatial silicate acetate complexes.

In addition, the difference from the prototype and the novelty of the method is the injection method, which consists in preliminary pumping fresh water rims into the reservoir to displace mineralized formation water, in order to prevent precipitation during the reaction of metal salts with silicate ions according to the scheme:

Na ₂ Si ₃ O ₇ + CaCl ₂ = CaSi ₃ O ₇ | + 2NaCl

Na ₂ Si ₃ O ₇ + MgCl ₂ = MgSi ₃ O ₇ | + 2NaCl

The volume of the rim of fresh water is selected so that during pushing into the reservoir an insulating agent, due to the formation of “tongues”, the composition would not mix with mineralized formation water until the gelation period expires. For this, the volume of fresh water rim takes at least one volume of tubing, the larger this volume, the better the obtained insulation effect.

To determine the optimal ratio of reagents, experiments were carried out with different ratios of components.

Powdered sodium silicate was used, dried on a spray dryer of the Dubitel OJSC plant with a 2.95 module. Sulfamic acid (SAK) was applied at a 15% concentration with a density of 1.083 g / cm ³

Chromium acetate (AX) was used as a 10% solution with a density of 1.039 g / cm ³ .

Monoethanolamine (MEA) was taken in commercial undiluted form.

The studies were mainly conducted with insulating agents containing 5-7% sodium silicate, in which sufficient gel strength (1000-7000 Pa) was obtained with the required gelation time (10-20 hours).

According to the data of the laboratory work, graphs were plotted against the time of gelation onset and the strength of the gel obtained on the concentration of sulfamic acid (SAA) Figure 1.

As can be seen from the figure, with an increase in the content of sulfamic acid in the solution, the strength of the insulating agent increases and the start time of gelation decreases, therefore, to obtain sufficiently strong gels with the required gelation time, it is necessary to choose the optimal concentration of sulfamic acid, which is from 0.8% to 1 6% of the mass.

When the content of NAO more than 1.6% of the mass. sharply reduced gelation time, although the strength is high. With a decrease in the amount of NAO less than 0.8, the gel formation is slow, but the strength characteristics decrease.

As can be seen from the figure, in comparison with the prototype of the inventive composition, the gel time increases by 2.28 times, and the strength increases by 230 times.

Thus, the technical task in the claimed invention is considered solved.

An example implementation of the proposed method on a production well. The depth of the well is 3500 m, the tubing is lowered to 3250 m, the thickness of the reservoir is 2.5 m.

Preparing 25 m ^{3 of a} water-insulating agent of the following composition: 6.4% sodium silicate, 0.7% chromium acetate, 1.064% NAO, 2.5% MEA and 89, 366% water.

Initially, 25 m ^{3 of} fresh water is supplied to the tubing. Following fresh water, 25 m ^{3 of an} insulating agent (2.5 volumes of tubing) is pumped. Then, 10 m ^{3 of} squeezing fluid (which uses fresh water) is supplied to the tubing and the entire previous volume of fluids is forced into the reservoir. The well is left for a day to solidify the gel, then proceed to the development process.

An example implementation of the proposed method on an injection well. The depth of the well is 3000 m, the discharge pipes are lowered to 2900 m, the thickness of the receiving formation is 1.5 m.

Prepares 15 m ³ water-insulating agent containing 6.7% of the mass. sodium silicate, 0.82% of the mass. chromium acetate, 0.85% sulfamic acid and 1.50% monoethanolamine and 90.13% water.

Initially, 20 m ^{3 of} fresh water rims (two volumes of pipes) are initially fed into the discharge pipes, followed by 15 m ^{3 of an} insulating agent. All this mixture is squeezed into the reservoir by squeezing liquid (fresh water) in the volume of injection pipes of 10 m ³ . The well is left for “setting” for 24 hours, then work on pumping water resumes.

The application of the proposed method will allow you to successfully develop heterogeneous permeability, waterlogged deposits while increasing the coefficient of oil recovery and reducing water cut of the product.

Claims (1)

A method of developing layer-by-layer heterogeneous oil fields, including pumping a working agent through injection wells, taking oil through production wells, injecting an insulating agent based on sodium silicate and acid into the injection or production wells during flooding, holding the wells for 24 hours and putting them into operation work, characterized in that previously, before injection of the insulating agent into the formation, a rim of fresh water is pumped in a volume that ensures that the formation water does not mix with the isolation with the expanding agent until the time of its gelation, but not less than one volume of tubing, the exposure is carried out after the agent is pushed into the formation, and a gelling composition of the following composition is used as an insulating agent, wt.%:
Sodium silicate 3-8 Sulfamic acid 0.38-1.5 Chromium acetate 0.35-0.9 Monoethanolamine 1.5-2.5 Water Rest