RU2447258C1 - Method to insulate absorption zone in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method to insulate an absorption zone in a well includes portion preparation of plugging compositions based on acetone-formaldehyde resin and liquid glass that harden in presence of structure formers, their pumping into a well and placement in an absorption zone. During preparation of two separate portions of plugging compositions, a gel powder and a structure former for liquid glass are added into a portion from acetone-formaldehyde resin, a structure former for acetone-formaldehyde resin is added into a portion of liquid glass, and structure formers are represented by accordingly a phosphogypsum and a 15% aqueous solution of caustic soda, besides, pumping and movement of plugging composition portions in the well is carried out by two contactless flows, and mixing of flows is carried out upstream the absorption zone at the ratio of 1:1 with the following ratio of components, wt parts: the first flow: acetone-formaldehyde resin 120, gel powder 25, phosphogypsum 40, the second flow: liquid glass 105, 15% aqueous solution of caustic soda 30.

EFFECT: increased efficiency of repair insulation works under conditions of high absorption due to prevention of hydraulic insulation screen washout in process of its formation.

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Description

The proposal relates to the oil industry, in particular to methods of isolating the absorption zone in the well, and can be used for repair and insulation work in conditions of large absorption.

There is a method of isolating the water inflow and the absorption zone by simultaneously and separately injecting two streams into the flooded part of the formation: one stream is hypane, water glass, water, the other is an aqueous solution of hydrochloric acid 0.44-4.0% (Patent RU No. 1774689, IPC ЕВВ 33/138, publ. BI No. 1, 1996). After mixing the streams, an aqueous acid solution is additionally pumped into the well.

The main disadvantage of this method is the duration of the curing of the well for the hardening of the plugging mixture (at least 48-72 hours), as a result of which the waterproofing screen is eroded in the intensively absorbing zone of the formation directly during its formation.

The closest in technical essence to the claimed method is a method of isolating the formation absorption zone by sequentially pumping portions of sodium liquid glass, a suspension of gypsum chemical based on water, liquid sodium glass and a suspension of chemical gypsum mixed with formaldehyde resin and an acid hardener (Patent RU No. 2391489, IPC Е21В 33/13, С09К 8/502, С09К 8/508, publ. BI No. 16, 06/10/2010). The disadvantages of the method include:

- sedimentation deposition of phosphogypsum from an aqueous suspension and its adhesion to the metal surfaces of oilfield equipment, as a result of which there are technological difficulties when pumping an aqueous suspension into a well, and the quality and reliability of the insulating screen due to a lack of phosphogypsum when it is bonded to liquid glass is reduced;

- a long structuring time (at least 48 hours) of the plugging mixture, which negatively affects the success of waterproofing works in conditions of intense absorption.

The technical task of the proposal is to increase the efficiency of repair and insulation works in conditions of large absorption by preventing complications during repair and insulation works by eliminating the deposition of phosphogypsum, as well as reducing the time of well repair.

The problem is solved by a method of isolating the absorption zone in the well, including batch preparation, injection into the well and placement in the absorption zone of a cementing hardening based on acetone-formaldehyde resin and liquid glass that hardens in the presence of structure formers.

What is new is that in the preparation of two separate portions of the grouting composition, clay powder and a structurant for liquid glass are introduced into a portion of acetone-formaldehyde resin; sodium, and the injection and movement of portions of the cement composition in the well is carried out by two contactless flows, and the mixing of the flows is carried out in front of the absorption zone in a ratio of 1: 1 in the following ratio of components, parts by weight:

first thread:

acetone formaldehyde resin - 120 clay powder - 25 phosphogypsum - 40

second thread:

liquid glass -105 15% aqueous sodium hydroxide solution - thirty

To implement the method using acetone-formaldehyde resin according to TU 2228-006-48090685-2002; clay powder according to TU 390147001-105-93 with rev. No. 1-3; grade A phosphogypsum according to TU 2141-677-00209438-2004, liquid sodium glass in accordance with GOST 13078-81 (liquid glass), caustic soda in accordance with GOST 2263-79.

The essence of the invention is to isolate the absorption zone in the well during repair and insulation works by forming a plugging mass formed in it when the components of the proposed grouting composition are mixed.

In the preparation of the components of the first portion, the clay powder is mixed with acetone-formaldehyde resin, and a uniform suspension is formed. When phosphogypsum is added and the suspension is mixed, sedimentation of phosphogypsum does not occur, and it does not adhere to the metal surfaces of oilfield equipment when injected into the well because it is suspended in a clay suspension of resin with thixotropic properties. To prepare the second portion, liquid glass and a 15% aqueous solution of sodium hydroxide are mixed, and a homogeneous solution is formed. Injection and movement of portions of the cement composition in the well is carried out by two contactless flows, for example, one stream is pumped through the annulus, and the other through the tubing string.

When mixing the components of the two streams in front of the absorption zone, phosphogypsum reacts with liquid glass, which leads to a thickening of the grouting composition, and a 15% aqueous solution of caustic soda reacts with acetone-formaldehyde resin, resulting in a dense grouting mass in the absorption zone.

In laboratory conditions, the optimal ratio of the components of the grouting composition was established, while focusing on the beginning of structuring 30 minutes after mixing the components of the grouting composition so that when it enters the absorption zone, the composition quickly forms a waterproofing screen and does not erode. Since the basis of the grouting composition is acetone-formaldehyde resin, first of all, the necessary amount and concentration of the structure-forming agent - sodium hydroxide solution per 120 mass parts were determined. acetone-formaldehyde resin (100 ml), the determination results are presented in table 1.

The start time of structuring was determined as follows. In a 250-ml glass beaker, the calculated amount of grouting components was mixed, and the time after which the meniscus of the liquid ceased to shift was taken as the time for structuring to begin.

According to the results (Table 1), 30 mass parts were selected. 15% sodium hydroxide solution per 120 parts by weight acetone-formaldehyde resin with a structuring start time of 30 minutes, sufficient to form a waterproofing screen and block the absorption zone with further compaction of the grouting mass for several hours to the state of the stone.

Table 1 The results of determining the amount and concentration of caustic solution per 120 mass. including acetone-formaldehyde resin The amount of an aqueous solution of caustic soda, mass. hours The time to start structuring acetone-formaldehyde resin with an aqueous solution of sodium hydroxide of various concentrations, min 10% fifteen% twenty% 10% fifteen% twenty% twenty twenty twenty one hundred 60 twenty thirty thirty thirty 70 thirty fifteen 40 40 40 fifty twenty 10

Next, the required amount of clay powder, phosphogypsum and water glass was determined per 120 mass. including acetone-formaldehyde resin, the test results are presented in table.2.

The amount of phosphogypsum and water glass was selected according to the optimal time for the beginning of the structuring of the composition (30 min) and the sedimentation stability of the cement slurry. As can be seen from the data in table 2, a decrease in the amount of clay powder is less than 25 mass. hours and phosphogypsum less than 40 mass. including leads to its deposition, and the increase in clay powder in the stream up to 30 mass. hours and phosphogypsum up to 50 mass. including leads to non-fluidity grouting mortar after mixing. In a composition containing 120 mass. including acetone-formaldehyde resin, 25 mass. including clay powder, 40 mass. including phosphogypsum and 105 mass. including liquid glass, the deposition of phosphogypsum does not occur, the time to start structuring the cement composition is 30 minutes The results of model tests confirmed that this composition is optimal for creating a durable waterproofing screen in the absorption zone.

Testing the water-insulating ability of the composition according to the proposed method and prototype was carried out on reservoir models 30 cm long and 2.7 cm inner diameter, filled with quartz sand of a fraction of 0.2-0.3 mm, which allows modeling the injection of reagents into the reservoir. The reservoir model was saturated with reservoir water, after which the grouting composition with the ratio of components according to the proposed method was pumped and left to react. The amount of injected composition was equal to the pore volume of the reservoir model. After 24 hours, water was pumped in and breakthrough pressure was determined. The results of model tests are presented in table 2, according to which it is obvious that the water-insulating ability of the composition according to the proposed method is not inferior to the prototype, even when exposure to structuring for 24 hours, in contrast to 48 hours for the prototype.

An example of a specific implementation of the method.

The work was carried out in an oil well with a production casing with a diameter of 146 mm and a current bottom of 1785 m. At a depth of 1328 m, a violation of the integrity of the production casing with a specific injection rate of 6.1 m ³ / (h · MPa) was revealed. When implementing the method, a tubing string with a diameter of 73 mm was lowered to a depth of 1325 m. A mixture of 12 tons of acetone-formaldehyde resin was prepared; 2.5 tons of clay powder and 4 tons of phosphogypsum. For this, a mixture of clay powder and phosphogypsum was packaged in a cement mixing unit and the mixture was shut on acetone-formaldehyde resin, similar to the preparation of a cement mortar. The finished mixture of acetone-formaldehyde resin, clay powder and phosphogypsum was pumped into the averaging tank. 10.5 tons of water glass and 3 tons of a 15% aqueous solution of caustic soda were mixed in the measuring tanks of two cementing units of the CA-32im type. Then, portions of the cement composition in the form of two contactless flows were simultaneously separately injected into the well, a mixture of acetone-formaldehyde resin, clay powder and phosphogypsum (the first stream) through the annulus, and 10.5 tons of water glass and 3 tons of 15% aqueous sodium hydroxide solution ( second flow) - along the tubing string, and the flow rate of the first pump unit was maintained 20% higher than the flow rate of the second pump unit. At the exit from the tubing, 2 streams are mixed, and a ready-made cement slurry is pumped into the interval of violation of the integrity of the production string. The grouting composition was pushed into the violation interval by pumping technological fluid — produced water — into the well. Then, the tubing was lifted to a depth of 1100 m and the well was left for the time of structuring the composition for 24 hours. The well was compressed with a pressure of 20 MPa for 30 minutes and the results of pressure testing showed that the production string was tight.

Using the proposed method will improve the efficiency of repair and insulation works in conditions of large absorption by preventing complications during repair and insulation works by eliminating the deposition of phosphogypsum. Due to the reduction in the time of structuring the grouting composition, the time for work and the repair of the well is reduced by 5-15%. Due to the rapid curing, the waterproofing screen does not erode during its formation, which increases the efficiency of work by 20-30%.

table 2 Testing results of grouting composition Grouting composition Structure structuring time The exposure time in the reservoir model, h Breakthrough Pressure, MPa / m The first stream, parts by weight Sedimentation stability after mixing the components of the first stream The second stream, mass. hours Acetono formaldehyde resin Clay powder Phosphogypsum Liquid sodium glass 15% aqueous sodium hydroxide solution Start, min End h 120 fifteen twenty phosphogypsum settles 120 thirty 120 23 - 120 twenty thirty phosphogypsum settles 110 thirty 90 eighteen 120 25 40 fluid uniform. solution 105 thirty thirty 10 24 6.0 120 thirty fifty non-fluid solution 90 thirty 10 3 - - The composition of the prototype ^∗ 48 5,0 ^∗ The composition of the prototype reproduced and tested by the applicant.

Claims (1)

A method of isolating the absorption zone in the well, including batch preparation, injection into the well and placement in the absorption zone of grouting compositions based on acetone-formaldehyde resin and liquid glass hardening in the presence of structure formers, characterized in that when preparing two separate portions of grouting compositions, they are introduced into a portion of acetone-formaldehyde resin clay powder and a binder for liquid glass; a binder for an acetone-formaldehyde resin is introduced into a portion of liquid glass , which are used respectively phosphogypsum and a 15% aqueous solution of caustic soda, and the injection and movement of portions of the grouting compositions in the well is carried out by two contactless flows, and the flows are mixed in front of the absorption zone in a ratio of 1: 1 in the following ratio of components, wt. hours:
first thread: acetone formaldehyde resin 120 clay powder 25 phosphogypsum 40 second thread: liquid glass 105 15% aqueous sodium hydroxide solution thirty