RU2560037C1 - Method for limiting water influx in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for limiting water influx in well includes injection of water-soluble polymer and salts to the reservoir. Gel-forming compound is prepared preliminary by successive solving of components in 100 weight fractions of fresh water at temperature of 18-25°C in the following order: 0.01-2.0 weight fractions of potassium chloride, 0.1-0.6 weight fractions of sodium thiosulfate, 0.4-0.6 weight fractions of water-soluble acrylamide polymer with molecular weight of 5.9·10⁶ and degree of anionicity of 1.9, 0.1-0.12 weight fractions of sodium bichromate. Gel-forming compound is injected to water-bearing reservoir within 2-5 cycles with volume of 5-20 m³ each and consumption rate of 100-200 l/min. At that fresh water for each cycle is brought to pH=3.4-5.6 by adding 5-15 l of inhibited hydrochloric acid. Then gel-forming compound is injected into the well with cross-binding of the first cycle but not before completed injection of gel-forming compound during the last cycle.

EFFECT: improved efficiency of water inflow limitation in water-flooded reservoirs and increased duration of the effect upon repair.

3 ex, 1 tbl

Description

The proposal relates to the oil industry, in particular to methods of limiting water inflow in flooded reservoirs and leveling the injectivity profile of injection wells using water-soluble polymers.

A known method of isolating the absorption zones when drilling wells (application RU No. 2001129405, IPC ЕВВ 33/138, publ. 08/20/2003, bull. No. 23). The method uses a composition that contains a finely divided water-swelling polymer (particle diameter less than 0.1 mm) "Aquament", which swells quickly when in contact with water, as well as a water-soluble polymer, a crosslinker and a filler in the following ratio, wt. %:

water-swelling polymer "Aquament" 1-5 filler 0-5 water soluble polymer 0.1-4 stapler 0.001-0.5 fresh water rest

The pre-swellable polymer is closed in inert solvents, which are used as anhydrous hydrocarbon products: diesel fuel, gasoline, kerosene, polyhydric alcohols (glycerin, polyglycols), which can be used as a carrier fluid and a separation buffer from water when injected into the absorption zone .

The main disadvantage of this method is that upon contact with water, the water-swellable polymer swells quickly, and the water-soluble polymer dissolves, and a viscous polymer mass forms, which cannot penetrate deep into cracks and pores, but remains in the zone of contact with water.

Closest to the technical nature of the claimed proposal is a method of developing a heterogeneous formation (patent RU No. 2167281, IPC EV 43/22, publ. 05.20.2001, bull. No. 14). The method includes injecting into the formation a water-soluble polymer, a salt of a polyvalent cation and a dispersion of gel particles that swell 100-5000 times. As a water-soluble polymer using polyacrylamides, polysaccharides, polymethacrylamides and cellulose derivatives with a concentration of 0.1-1.0 wt. % the salts of polyvalent cations are acetates, nitrilotriacetates, tartrates, citrates, ammonium chromate and dichromate, alkali metal chromates and dichromates, chromium and potassium alum with a solution concentration of 0.001-0.5 wt. %

The main disadvantage of this method is the low mechanical strength of the gel from which the waterproofing screen is formed. This is due to the high degree of swelling of the dispersed phase - gel particles (up to 5000 times), therefore, after 4-5 months there is a syneresis, which leads to a reduction in the technological effect of the application of the method and will need to be repaired.

The technical objectives of the proposal are to increase the efficiency of restricting water inflow in flooded reservoirs and to increase the duration of the effect of repair work.

Technical problems are solved by the method of limiting water inflow in the well, including the injection of water-soluble polymer and salts into the formation.

It is new that a gel-forming composition is preliminarily prepared by alternately dissolving the components in fresh water with a temperature of 18-25 ° C in the following order: potassium chloride, sodium thiosulfate, a water-soluble acrylamide polymer with a molecular weight of 5.9 · 10 ⁶ and an anionic degree of 1.9, sodium dichromate and pump it into the flooded reservoir in 2-5 cycles with a volume of 5-20 m ³ each and with a flow rate of 100-200 l / min in the following ratio of components, wt. hours:

water-soluble acrylamide polymer with a molecular weight of 5.9 · 10 ⁶ and a degree of anionicity of 1.9 0.4-0.6 potassium chloride 0.01-2.0 sodium thiosulfate 0.1-0.6 sodium dichromate 0,1-0,12 fresh water one hundred,

moreover, the fresh water of each cycle is adjusted to pH = 3.4-5.6 by adding 5-15 l of inhibited hydrochloric acid, then the gelling composition is pumped into the well taking into account the crosslinking of the first cycle, not earlier than the end of the injection of the gelling composition of the last cycle.

Reagents used in the proposal:

- a water-soluble polymer of acrylamide with a molecular weight of 5.9 · 10 ⁶ and a degree of anionicity of 1.9 (hereinafter water-soluble polymer);

- potassium chloride according to GOST 4568-95;

- sodium thiosulfate according to GOST 244-76;

- sodium dichromate according to GOST 2651-78;

- inhibited hydrochloric acid according to TU 2458-264-05765670-99;

- fresh water with a density of 1000 kg / m ³ .

A water-soluble polymer is a white powder that dissolves well in water with the formation of a viscous solution, obtained by copolymerization of acrylamide and alkali metal acrylate without crosslinking. It is intended for use in technological operations to increase oil recovery and leveling the injectivity profile of injection wells.

The essence of the proposal is to limit water inflow in the well during repair and insulation works by forming a water-proof screen from the gel-forming composition in the water inflow zone. To prepare the gelling composition, fresh water is required with a temperature of 18-25 ° C (hot water is delivered in the winter season) and a pH in the range of 3.4-5.6, which is achieved by adding inhibited hydrochloric acid. At pH <3.4, gelation is accelerated, and gelation time is reduced, at pH> 5.6, gelation is slowed down, and gelation time is increased, so the pH range from 3.4 to 5.6 is chosen as optimal for crosslinking the composition from 4 to 20 hours The fresh water temperature of 18-25 ° C provides complete dissolution of the components of the composition. Further, the components of the composition are alternately added to water with a pH of 3.4 to 5.6, and each subsequent one is added only after dissolving the previous one in the following sequence: potassium chloride, sodium thiosulfate, and a water-soluble polymer. Sodium dichromate is added last, after which everything is mixed. The resulting composition must be pumped into the well in 2-5 cycles with a flow rate of 100-200 l / min. From fieldwork experience it was found that the total volume of the gel-forming composition depends on the power and injectivity of the flooded intervals of the formation and ranges from 10 to 80 m ³ , and the volume of each cycle is from 5 to 20 m ³ with a period of crosslinking of the gel-forming composition from 3 to 20 h. The crosslinking period of each subsequent cycle is 3-8 hours shorter than the previous one, while the injection is carried out taking into account the beginning of crosslinking of the gelling composition of the first cycle - not earlier than the end of the injection of the gelling composition of the last cycle into the well. The stitching period of the first cycle is the longest, and the last is the shortest. A pH in the range of 3.4-5.6 is achieved by adding inhibited hydrochloric acid in an amount of 5 to 15 L per cycle of the gel-forming composition. Changing the ratio of the components of the composition, get the necessary time for crosslinking the gelling composition - from 4 to 20 hours

After crosslinking the gel-forming composition in reservoir conditions, a strong cross-linked polymer system is formed, which does not dissolve and does not collapse in reservoir conditions under the influence of formation water and temperature, which will increase the duration of the effect of repair work.

In laboratory conditions, a gel-forming composition is prepared as follows. 200 ml of fresh water (100 parts by weight) are poured into a 300 ml beaker. For the preparation of a gelling composition, fresh water is used with pH = 7.5 and a density of 1000 kg / m ³ . The pH of the water is reduced to pH = 5.31 by adding 0.1 ml of 24% inhibited hydrochloric acid.

Then, while continuously stirring the contents of the beaker on a paddle mixer, 4 g of potassium chloride (2 parts by weight) are added to the water and stirring is continued until it is completely dissolved (about 3 minutes). With further continuous stirring, 1.2 g of sodium thiosulfate (0.6 parts by weight) are added to the contents of the beaker and stirring is continued until it is completely dissolved (about 5 minutes). Then, while continuously stirring the contents of the beaker into the solution, preventing the formation of lumps, slowly add 1.2 g of a water-soluble polymer (0.6 parts by weight) and mix the mixture until the water-soluble polymer is completely dissolved (about 20 minutes) at a speed of 500 rpm . Immediately before the start of testing, 0.24 g of sodium dichromate (0.12 parts by weight) is added to the prepared solution of a water-soluble polymer with stirring and continuous mixing is continued until the sodium dichromate is completely dissolved (about 3 min). In this case, the beginning of crosslinking occurs after 3 hours and the end after 4 hours (experiment No. 1, table). The remaining experiments are carried out similarly. The results of laboratory tests are presented in the table. By changing the ratio of the components, the crosslinking time of the gelling composition can be adjusted within 4-20 hours

Experiments Nos. 2 and 10 are excluded from the claimed range, since the crosslinking time of the gel-forming composition does not provide the optimal injection time into the well - 3-20 hours. Based on the test results, the compositions that were included in the claimed range of the ratio of components, wt. hours:

water-soluble acrylamide polymer with a molecular weight of 5.9 · 10 ⁶ and a degree of anionicity of 1.9 0.4-0.6 potassium chloride 0.01-2.0 sodium thiosulfate 0.1-0.6 sodium dichromate 0,1-0,12 fresh water one hundred

The implementation of the proposed method is presented in 3 examples.

Example 1. Water was limited in a well with a current bottom of 1837 m and a perforation interval of 1727.3-1732.0 m. The tubing was lowered to a depth of 1700 m. 10 m ^{3 of} gel-forming composition was prepared and pumped into a flooded formation in 2 cycle with a flow rate of 100 l / min.

1st cycle with a volume of 5 m ³ - 5 m ^{3 of} fresh water with a temperature of 22 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 3.40 by adding 5.1 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 30 kg of potassium chloride (0.6 wt.) Were successively dissolved in water in a mixing-averaging installation, then 10 kg of sodium thiosulfate (0.2 wt.) Were added and dissolved, then 20 kg of a water-soluble polymer ( 0.4 parts by weight). Then, with constant stirring of the resulting solution, 5 kg (0.1 parts by weight) of sodium dichromate was added to it. Stirring was continued for 10-20 minutes. The planned time for crosslinking the gel-forming composition is 11 hours (experiment No. 7, table).

2nd cycle with a volume of 5 m ³ - 5 m ^{3 of} fresh water with a temperature of 18 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 3.47 by adding 5 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 50 kg of potassium chloride (1 parts by weight), 20 kg of sodium thiosulfate (0.4 parts by weight), 25 kg of a water-soluble polymer (0.5 parts by weight) were successively dissolved in water in a mixing-averaging unit. ), 5.5 kg of sodium dichromate (0.11 wt. H.). The planned time for crosslinking the gel-forming composition is 7 hours (experiment No. 5, table).

The composition of the second cycle of the waterproofing composition was selected and prepared so as to pump it into the well earlier than the crosslinking of the gel-forming composition of the first cycle begins.

After pumping the entire gelling composition, the tubing was raised by 200 m in order to exclude their sticking and the well was left to respond for 24 hours.

Then the well was mastered and put into operation. As a result of the work, the water cut of the well decreased by 25%, the additional oil production was 2.2 tons per day.

Example 2. The proposed method was used to isolate a waterlogged layer in a well with a current bottom of 1877.8 m and a perforation interval that revealed a productive horizon in the range of 1860-1877.8 m. The tubing was lowered to a depth of 1840 m. The volume of the gelling composition was 40 m ³ . A gelling composition was prepared and pumped into the flooded formation in 3 cycles with a flow rate of 150 l / min.

1st cycle with a volume of 15 m ³ - 15 m ^{3 of} fresh water with a temperature of 23 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 5.60 by adding 10 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 1.5 kg of potassium chloride (0.01 parts by weight) were successively dissolved in water in a mixing-averaging unit, then 15 kg of sodium thiosulfate (0.1 parts by weight) was added and dissolved, then 60 kg of water-soluble polymer (0.4 parts by weight). Then, with constant stirring of the resulting solution, 15 kg (0.1 parts by weight) of sodium dichromate were added to it. Stirring was continued for 10-20 minutes. The planned crosslinking time of the gel-forming composition is 20 hours (experiment No. 11, table).

2nd cycle with a volume of 15 m ³ - 15 m ^{3 of} fresh water with a temperature of 23 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 5.31 by adding 10 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 60 kg of potassium chloride (0.4 wt.), 30 kg of sodium thiosulfate (0.2 wt.), 60 kg of a water-soluble polymer (0.4 wt. hours), 15 kg of sodium dichromate (0.1 wt. hours). The planned crosslinking time of the gel-forming composition is 13 hours (experiment No. 8, table).

3rd cycle with a volume of 10 m ³ - 10 m ^{3 of} fresh water with a temperature of 23 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 4.82 by adding 8 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 100 kg of potassium chloride (1 parts by weight), 50 kg of sodium thiosulfate (0.5 parts by weight), 40 kg of a water-soluble polymer (0.4 parts by weight) were successively dissolved in water in a mixing-averaging unit. ), 10 kg of sodium dichromate (0.1 wt. H.). The planned time for crosslinking the gel-forming composition is 8 hours (experiment No. 4, table).

The preparation of the gelling composition was planned so that the last cycle was prepared and pumped into the well earlier than the crosslinking of the first cycle of the gelling composition began.

After pumping the entire gelling composition, the tubing was raised by 200 m in order to exclude their sticking and the well was left to respond for 24 hours. Then the well was mastered and put into operation. As a result of the work, the water cut of the well decreased by 20%, the additional oil production was 2 tons per day, the well continues to work without repair for more than 24 months.

Example 3. The method was used for waterproofing work in a well with an artificial bottom of 1787 m and a perforation interval of 1164-1167 m. The tubing was lowered to a depth of 1140 m. The volume of the gel-forming composition was 80 m ³ . A gelling composition was prepared and pumped into the flooded formation in 5 cycles at a flow rate of 200 l / min.

1st cycle with a volume of 20 m ³ - 20 m ^{3 of} fresh water with a temperature of 20 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 5.60 by adding 15 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 2 kg of potassium chloride (0.01 mass parts) were successively dissolved in water in a mixing-averaging unit, then 20 kg of sodium thiosulfate (0.1 mass parts) were added and dissolved, then 80 kg of a water-soluble polymer ( 0.4 parts by weight). Then, with constant stirring of the resulting solution, 20 kg (0.1 parts by weight) of sodium dichromate were added to it. Stirring was continued for 10-20 minutes. The planned crosslinking time of the gel-forming composition is 20 hours (experiment No. 11, table).

2nd cycle with a volume of 20 m ³ - 20 m ^{3 of} fresh water with a temperature of 20 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 5.31 by adding 13 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 80 kg of potassium chloride (0.4 wt.), 40 kg of sodium thiosulfate (0.2 wt.), 80 kg of a water-soluble polymer (0.4 wt. hours), 20 kg of sodium dichromate (0.1 wt. hours). The planned crosslinking time of the gel-forming composition is 13 hours (experiment No. 8, table).

3rd cycle with a volume of 15 m ³ - 15 m ^{3 of} fresh water with a temperature of 20 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 3.40 by adding 15 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 90 kg of potassium chloride (0.6 wt.), 30 kg of sodium thiosulfate (0.2 wt.), 60 kg of a water-soluble polymer (0.4 wt. hours), 15 kg of sodium dichromate (0.1 wt. hours). The planned crosslinking time of the gel-forming composition is 10 hours (experiment No. 7, table).

4th cycle with a volume of 15 m ³ - 15 m ^{3 of} fresh water with a temperature of 20 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 3.47 by adding 12 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 150 kg of potassium chloride (1 parts by weight), 75 kg of sodium thiosulfate (0.5 parts by weight), 60 kg of a water-soluble polymer (0.4 parts by weight) were successively dissolved in water in a mixing-averaging unit. ), 16.5 kg of sodium dichromate (0.11 wt. H.). The planned time for crosslinking the gel-forming composition is 7 hours (experiment No. 5, table).

5th cycle with a volume of 10 m ³ - 10 m ^{3 of} fresh water with a temperature of 25 ° C was collected in a pre-washed mixing and averaging unit of the UOP-20 type. The pH of the water was adjusted to 5.31 by adding 7 L of inhibited hydrochloric acid to the water, followed by stirring. With constant stirring, 200 kg of potassium chloride (2 parts by weight), 60 kg of sodium thiosulfate (0.6 parts by weight), 60 kg of a water-soluble polymer (0.6 parts by weight) were successively dissolved in water in a mixing-averaging unit. ), 12 kg of sodium dichromate (0.12 wt. H.). The planned crosslinking time of the gel-forming composition is 4 hours (experiment No. 1, table).

The preparation of the gelling composition was planned so that the last cycle of the gelling composition was prepared and pumped into the well earlier than the crosslinking of its first cycle began. They sold the gel-forming composition into the reservoir by pumping technological fluid into the tubing in a volume that provided reselling in the reservoir by 0.2-0.5 m ³ . After pumping the entire gelling composition, the tubing was raised by 200 m to prevent sticking and the well was left to react for 36 hours. As a result of the work, the water cut of the well decreased by 30%, additional oil production was 2 tons per day, the well continues to work without repair for more than 18 months.

Thus, the proposed method provides an increase in the efficiency of limiting water inflow in flooded reservoirs and an increase in the duration of the effect of repair work.

Claims (1)

A method of limiting water inflow in a well, including the injection of a water-soluble polymer and salts into the formation, characterized in that the gel-forming composition is preliminarily prepared by alternately dissolving the components in fresh water at a temperature of 18-25 ° C in the following order: potassium chloride, sodium thiosulfate, water-soluble acrylamide polymer having a molecular weight of 5.9 × 10 ⁶ and a degree of anionicity 1.9, sodium bichromate and it is pumped into the water cut in 2-5 cycles volume every 5-20 m ³ and at a rate of 100-200 l / min at the following ratio of the components in, parts by weight .:
water soluble molecular acrylamide polymer mass of 5.9 · 10 ⁶ and a degree of anionicity of 1.9 0.4-0.6 potassium chloride 0.01-2.0 sodium thiosulfate 0.1-0.6 sodium dichromate 0,1-0,12 fresh water one hundred,
moreover, the fresh water of each cycle is adjusted to pH = 3.4-5.6, adding 5-15 l of inhibited hydrochloric acid, then the gelling composition is pumped into the well taking into account the crosslinking of the first cycle, not earlier than the end of the injection of the gelling composition of the last cycle.