RU2262584C2 - Formation permeability control method - Google Patents

Abstract

FIELD: oil production industry, particularly to restrict water influx into oil and gas wells and to level off injectivity profile in injection wells.

SUBSTANCE: method involves injecting dividing plug, working agent, and then dividing plug again in formation through injection or production well; forcing the injected reagents into well. Working agent is liquid zeolite production residue, namely mother zeolite solution and aqueous strong acid solution. Mother zeolite solution is fed as separate plug or mother zeolite solution and aqueous strong acid solution are injected simultaneously or serially. Sweet water is used as the dividing plug. Waste water is utilized for injected reagents forcing.

EFFECT: increased efficiency of permeability reduction in watered highly porous reservoir.

3 ex, 1 tbl

Description

The invention relates to the oil industry, in particular to methods for limiting water inflow into oil and gas wells and alignment of the injectivity profile in injection wells.

A known method of plugging a flooded formation, which consists in injecting into the formation through a well an emulsifying rim, a gel-forming rim, and again an emulsion-forming rim (RF patent No. 2094601, E 21 B 43/22, 10.27.1997). The composition does not have a sufficiently high clogging ability of the flooded reservoir.

The closest in technical essence to the claimed method is a method for controlling the permeability of the formation, carried out by injection into the formation through an injection or production well emulsion-forming and gel-forming rims, while the emulsion-forming rim is pumped before and after the gel-forming at a volume ratio of from 1: 1: 1 to 1: 2: 1, a solution of a surfactant in oil is used as an emulsifying solution, and a mixture of zeolite dissolved in alumina chloride is used as a gelling solution, and an aqueous solution of hydrochloric acid (RF patent 2148160, Е 21 В 43/22, 43/32, 04/27/2000, Bull. No. 12).

The disadvantage of this method is the low technological and economic efficiency.

The objective of the invention is to increase the efficiency of reducing the permeability of an irrigated high-permeability reservoir, as well as increasing the profitability of oil production by using cheap reagents and simplifying the technology for preparing the plugging composition.

This task is achieved by the fact that in the method of regulating the permeability of the formation, including injecting into the formation through an injection or production well a separating rim, a working agent, then again separating the rim and forcing the injected reagents, according to the invention, use liquid waste from the production of zeolites - mother a solution of zeolites and an aqueous solution of a strong acid, moreover, the mother liquor of zeolites is pumped into a separate rim or pumped simultaneously or sequentially atochny solution zeolite with an aqueous solution of a strong acid as a separating slug use fresh water as well as the punching liquid is wastewater.

The mother liquor from NaX type zeolite crystallization is a waste product. It is obtained at the stage of maturation of zeolite crystals. It is an aqueous solution with a density of 1030-1065 kg / m ³ . The average chemical composition of the mother liquor in terms of oxides, g / l:

Na ₂ O - 30-45

Al ₂ O ₃ - 3.0-6.0

SiO ₂ - 20-30

Mechanical impurities - zeolite crystals, not more than 5 wt.%. The solution has an alkaline reaction, the pH of the solution is in the range of 12.0-13.0.

As an aqueous solution of a strong acid, for example, an aqueous solution of hydrofluoric acid can be used, which is a clear liquid with a basic substance content of 18-20 wt.%, Corresponding to TU 2122-555-092209438-01 or hydrochloric acid, GOST 857-88, in the form of a 15% aqueous solution.

Fresh water according to GOST 2874-82, the mass fraction of calcium ions up to 40 g / m ³ , magnesium ions - up to 10 g / m ³ , density - 1000 kg / m ^{3 is} used as a separating rim.

Water with a density of 1105-1118 kg / m, a mass fraction of calcium ions of more than 400 g / m ³ , magnesium ions of more than 200 g / m ³ , and a pH of 7-8 are used as waste water.

The chemical essence of the proposed method lies in the fact that the mother liquor of zeolites of the above composition, when interacting with mineralized formation water containing calcium and magnesium cations, forms insoluble silicates in the flooded formations:

Na ₂ O + SiO ₂ + Ca ²⁺ → CaSiO ₃ + 2Na ⁺ .

At the same time, with aqueous solutions of strong acids, the mother liquor of zeolites forms a dense gel as a result of the liberation of silicic acid, one molecule of which can hold up to 300 water molecules.

So, for example, an aqueous solution of hydrochloric acid interacts with silicon oxide of the mother liquor of zeolites with the formation of silicic acid by the reaction:

2HCl + SiO ₂ → H ₂ SiO ₃ ,

while an aqueous solution of hydrofluoric acid liberates silicic acid when reacted with sodium oxide of the mother liquor of zeolites:

H ₂ SiF ₆ + Na ₂ O → H ₂ SiO ₃ .

In both cases, the closure substance is silicic acid, capable of polymerization and sol formation (gelation).

Thus, the high effect of blocking the aquifers according to the proposed method is provided by the formation of an insoluble sediment during the interaction of the mother liquor of zeolites and produced water or sediment and a dense gel upon contact of the mother liquor of zeolites with formation water and an aqueous solution of strong acid, or a dense gel when injected together layer of the mother liquor of zeolites and aqueous solutions of strong acids (HCl, H ₂ SiF ₆ , etc.).

The effectiveness of the proposed method was evaluated by reducing the permeability of the reservoir model when filtering the working agent. A bulk core of quartz sand 300 mm long and 50 mm in diameter was used as a reservoir model. The initial core permeability of 0.68-2.51 μm ^{2 was} selected by changing the sand fractions in the range of 0.05-1.20 mm. Saturation and determination of permeability were carried out by filtering wastewater with a density of 1105-1118 kg / m ³ . The pressure drop remained constant.

The isolation effect was calculated as follows:

Comparative data on the blocking ability of the artificial model of the proposed and known methods are shown in the table.

Example 1. The bulk core was saturated with waste water with a density of 1118 kg / m ³ , its initial permeability was determined, then it was pumped into it between dividing rims - fresh water, 40 ml of the mother liquor of zeolites and squeezed with waste water. The volumetric ratios of the dividing rim before and after and the mother liquor of zeolites were 1: 1: 2. Filtration was stopped for 24 hours to react, then permeability was determined and the effect of isolation was calculated. It amounted to 93.0%.

Example 2. The core was saturated with waste water with a density of 1110 kg / m ³ , its initial permeability was determined, then between the separating rims - fresh water, the mother liquor of zeolites and an aqueous solution of hydrofluoric acid were sequentially pumped, with a volume ratio of 1: 2. After the reagents were pressed through wastewater, the core was left for 24 hours to react. The high isolation effect (97.5%) is due to the formation of a clogging screen, firstly, as a result of the interaction of the mother liquor of zeolites and formation water with the formation of insoluble silicates, and secondly, by the interaction of the mother liquor of zeolites and an aqueous solution of hydrofluoric acid with the formation of silicic gel acid and, thirdly, the interaction of an aqueous solution of hydrofluoric acid and produced water with the release of water-insoluble hydrofluoric sodium.

Example 3. In an artificial core saturated with waste water, after determining its initial permeability, between the dividing rims - fresh water, the working agent was filtered, with a volume ratio of 1: 2, consisting of 20 ml of the mother liquor of zeolites and 20 ml of 15% hydrochloric acid and squeezed through water with a density of 1105 kg / m ³ . The filtration was stopped for 24 hours for gelation of the mother liquor of zeolites under the influence of an aqueous solution of hydrochloric acid. The insulation effect was 95.3%, while by the known method it is possible to achieve an insulation effect of not higher than 64.8% (see table, example 4), which is 28.2-32.7% lower than the proposed method.

The proposed method for regulating the permeability of the reservoir is carried out by conventional technological methods and technical means used in the construction, repair and operation of production wells.

The technology of the method of regulating the permeability of the formation with the aim of limiting water inflow into oil and leveling the injectivity profile in injection wells is notable for its simplicity. For this, after preparatory work, a working agent is pumped through the separating rims into the well (mother liquor of zeolites, or separately mother liquor of zeolites and a solution of strong acid, or a mixture of mother liquor of zeolites and a solution of strong acid). Next, the composition is pushed from the wellbore into the reservoir with sewage and technological exposure is carried out for 16-24 hours.

In practice, the method is implemented, for example, as follows.

The object of isolation is an injection well, in which the terrigenous reservoir DP is perforated. The effective oil-saturated thickness of the formation is 5.2 m. The permeability of the formation varies from 0.17 to 0.9 μm ² . The density of the injected water is 1105 kg / m ³ . The injectivity of the reservoir with a pressure of injection of water of 10 MPa is 320 m ³ / day. Technological efficiency is determined by 5 surrounding oil wells. The water cut of oil production varies from 85 to 95%, the average daily oil production rate from 1.2 to 5.5 tons / day.

Before and after pumping the working agent, a separation rim was pressed through - fresh water in a volume of 24 m ³ . The working agent is 48 m ^{3 of the} mother liquor of zeolites. Technological exposure for 24 hours. As a result of the implementation of the proposed method in the surrounding oil wells, the water cut of the produced oil decreased by 30-70%.

The known method is tested in a pilot area operated by 1 injection and 4 surrounding production wells, in which the D1 formation is perforated. The effective oil-saturated thickness is 5.7 m. The density of the injected water is 1118 kg / m ³ . The injectivity of the well at a pressure of 9.5 MPa 320 m ³ / day. The permeability of the formation of 0.18-0.24 microns ² . The water cut of the production of surrounding producing wells is 93-96%, the average daily oil production rate is 3.2-6.4 m ³ / day. According to the known method, before and after the gel-forming composition, an emulsifying rim was applied in a volume of 24 m ³ (0.5 m ^{3 of} neonol AF ₉ -6 and 23.5 m ^{3 of} oil). The gel-forming composition included 2 t of zeolite in 24 m ^{3 of} 22% alumina and 20 m ^{3 of a} solution of 8% hydrochloric acid. The well was stopped for response for 72 hours.

The decrease in water cut in production wells amounted to from 10 to 50%.

Thus, the proposed method in comparison with the known one allows to increase the technological efficiency of oil production in the form of reducing its water cut, simplifies the technology and improves the environmental friendliness of the preparation of separating and clogging rims at the wellhead, since it does not require the preparation of a surfactant emulsion in oil and the dissolution of solid zeolite in aluminum chloride and hydrochloric acid (according to the prototype), and also allows with great economic effect of approximately 130 thousand rubles. only from the cost of chemicals needed for one permeability control operation, utilize zeolite production wastes and at the same time eliminate one of the possible environmental pollution factors in the area of the zeolite manufacturing plant.

Table Laboratory data on the efficiency of plugging an artificial reservoir model by proposed and known methods Example No. Volumetric relationships of injected agents The effect of isolation,% separation rim working agent separation rim stock solution of zeolites aq. strong acid solution stock solution of zeolites + aq. strong acid solution (1: 1) prototype 1 1 2 - - - 1 93.0 2 1 1 2 - - 1 97.5 3 1 - - 2 - 1 95.3 4 1 - - - 1 1 64.8

Claims (1)

A method for controlling the permeability of a formation, including injecting into the formation through an injection or production well a separating rim, a working agent, then again separating the rims and forcing the injected reagents, characterized in that liquid waste from the production of zeolites — mother liquor of zeolites and an aqueous solution of strong acids, moreover, they either inject the mother liquor of zeolites with a separate rim or pump simultaneously or sequentially the mother liquor of zeolites and an aqueous solution creates a strong acid as the separating rim using fresh water, and for punching of uploaded reagents used wastewater.