RU2188930C2 - Method of shutoff of water inflow to well - Google Patents

Abstract

FIELD: oil and gas producing industry, particularly, methods of shutoff of water inflows to oil and gas wells, elimination of annular spaced crossflows and lost circulation in well drilling, alignment of flood front in injection wells. SUBSTANCE: method includes injection of suspension of water-soluble polymer in organic fluid into well bottom-hole formation zone, forcing of said suspension into formation by water, and allowing it to stand for definite time. Suspension concentration amounts up tp 21-50%. Polymer is used in the form of polyacrylamide and/or its derivatives, polyvinyl alcohol and/or its derivatives, carboxymethyl cellulose and/or its derivatives. High pressure is built up and dwelling is effected under said pressure. Injected into well is 0.5-4.0 cu.m of suspension of water-soluble polymer in organic fluid per each running meter of formation effective thickness. Organic fluid is used in the form of pure oil, distillate, kerosene, gas oil, hexane, gasoline, condensate, diesel fuel. Pressure under which suspension of water-soluble polymer in organic fluid is injected amounts at wellhead up to 1.0-40.0 MPa. Displacing fluid is used in the form of water with pH 4-12. Dwelling under pressure is continued for 3-72 h. EFFECT: improved water-shutoff properties of water-soluble polymers in elimination of water inrushes to producing wells and annular space crossflows and limited injectivity of injection wells within wide range of temperatures. 6 cl, 3 tbl

Description

 The invention relates to the oil and gas industry, in particular to methods for isolating water inflow in oil and gas wells, eliminating annular flows, eliminating absorption during well drilling, and can also be used to level the waterflood front in injection wells.

 One of the main methods for extracting oil from formations in the late stages of field development is to force it out by water being pumped under pressure into the formation through injection wells. In the process of oil displacement, there is a change in the filtration characteristics of the reservoirs, which lead to breakthroughs of water and behind-the-casing flows, as a result of which the oil production rate decreases and the water cut of the product increases.

 When waterproofing work in the well, various compositions are used that close the water flow, but also block the passage of oil to the bottom of the well. Therefore, after carrying out such work, a long period of well development is necessary, often even with repeated perforation, which, in turn, due to high pressures in the bottomhole formation zone, can lead to leakage and the resumption of water inflow at low oil flow rates.

 The closest in technical essence to the claimed one is a method of isolating water inflow into a well, including injecting a suspension of a water-soluble polymer in an organic fluid into the bottomhole zone of the well, pumping it into the formation with water, and holding in time (see auth. St. USSR 1501597, Е 21 В 43 / 22, publ. 10/23/1991 prototype).

 The technical result of the invention is to improve the water-insulating ability of water-soluble polymers during the elimination of water breakthroughs in production wells, the elimination of casing flows and the limitation of the injectivity of injection wells in a wide temperature range.

 The problem is solved in that the method of isolating water inflow in the well includes injecting a suspension of a water-soluble polymer in an organic fluid into the bottomhole zone of the well, pumping it into the formation with water and holding for a while, while the concentration of the suspension is 21-50 wt.%, Polyacrylamide is used as the polymer and / or its derivatives, polyvinyl alcohol and / or its derivatives, carboxymethyl cellulose and / or its derivatives, create increased pressure and exposure under this pressure.

0.5-4.0 m ³ suspension of a water-soluble polymer in an organic fluid is pumped into the well for each running meter of effective formation power.

 Anhydrous oil, distillate, kerosene, gas oil, hexane, gasoline, condensate, diesel fuel are used as an organic liquid.

 The injection pressure of a suspension of a water-soluble polymer in an organic fluid at the wellhead is 1.0-40.0 MPa.

 As a squeezing liquid, water with a pH of 4-12 is used.

 The exposure time under pressure is 3-72 hours

 The concentration limits of the suspension and its volume are selected depending on the type of complication in the well, porosity, permeability of the formation, flow rate and degree of water cut, type and composition of the formation water and the effective thickness of the formation.

 Before using in the well, the required volume of the suspension of water-soluble polymer, the amount and type of polymer are selected. This composition is thoroughly mixed in averaging tank and pumped into the reservoir. The following can serve as an organic liquid: unstable gasoline, diesel fuel, hexane, oil, etc.

 The suspension of a water-soluble polymer in the reservoir is sold with water with a pH of 4-12 and is kept under pressure for 3-72 hours. At this time, the organic fluid is replaced by water, during the interaction with which the polymer swells and increases in volume, turning into a dense rubbery mass, and blocks access to water from the zone of violation to the bottom of the well. When the polymer suspension enters the oil-bearing part of the formation, polymer swelling does not occur, because due to its lower permeability than in the disturbance zone, oil is replaced by water much more slowly and during development of the well this part of the polymer is removed from the bottom-hole zone of the formation by the reverse fluid flow.

 It is these concentrations of water-soluble polymer, the volume of the suspension and the injection regimes that ensure the implementation of the technical result.

Case Studies
To determine the plugging ability of the proposed composition, laboratory studies were conducted. The research methodology was as follows.

Through bulk models of various permeability 1000; 2000; 3000 μm ² pumped a suspension of a water-soluble polymer with a concentration of 21%; 25%; 40% 50% and 55%. Diesel was used as the organic liquid for the preparation of the suspension.

After the suspension of suspensions of water-soluble polymers (polyacrylamide with a molecular weight of 2 × 10 ⁶ , carboxymethyl cellulose of the KMTs-85/700 brand and polyvinyl alcohol) was pumped, the mixture was held in water for 5 h in time, water was pumped until the reaction products were completely displaced, and the maximum displacement pressure was determined.

In the table. Figure 1 presents data on the pressure of the displacement of suspensions of polyacrylamide with a molecular weight of 2 • 10 ⁶ different concentrations from bulk models, MPa.

 Table 2 presents data on the pressure of displacement of CMC 85/700 suspensions of different concentrations from bulk models, MPa.

 In the table. 3 presents data on the pressure of displacement of suspensions of polyvinyl alcohol of various concentrations from bulk models, MPa.

 An analysis of the results of laboratory work (Tables 1, 2, 3) shows that the use of suspensions of polyacrylamide, carboxymethyl cellulose and polyvinyl alcohol in an organic liquid increases the waterproofing ability of the proposed composition.

Example 10
To verify the effectiveness of this composition under field conditions, the 3404 well of the Ermakovskoye field was treated. The perforation interval is 5 m, the annular flow from the underlying water reservoir, the injection rate of 500 m ³ / day at a pressure of 4.0 MPa.

To eliminate the annular flow, 100 kg of polyacrylamide with a molecular weight of 2 • 10 ⁶ were prepared. Then the prepared composition was mixed in 5 m ^{3 of} anhydrous oil and pumped into the reservoir. Selling was carried out with industrial water with a pH of 6.5 in a volume of 6.0 m ³ at a pressure of 2.0 MPa. After treatment, the well was left to react for a period of 6 hours, after which pressure testing was carried out at a pressure of 8.0 MPa. The well is tight, the annular flow is eliminated.

Example 11
To limit water inflow, well 24157 of the Samotlor field was treated. Perforation interval 10 m, total production rate 120 m ³ / day, water cut 98%, oil production rate 2 t / day. A suspension of polyacrylamide with a molecular weight of 2 • 10 ^{6 was} pumped into the well, of which anhydrous oil in 10 m ³ , polyacrylamide 100 kg. Selling was carried out with water with a pH of 8.0 in a volume of 20.0 m ³ at a pressure of 5.5 MPa. At the end of the sale, the pressure rose to 10.0 MPa. After the well was put into operation, the total production rate was 40 m ³ / day, the water cut was 81%, and the oil production rate was 6.3 tons / day.

Claims (6)

 1. A method of isolating water inflow in a well, including injecting a suspension of a water-soluble polymer in an organic fluid into the bottomhole zone of a well, pumping water into a formation and holding for a while, characterized in that the concentration of the suspension is 21-50 wt. %, polyacrylamide and / or its derivatives, polyvinyl alcohol and / or its derivatives, carboxymethyl cellulose and / or its derivatives are used as a polymer to create increased pressure and holding under this pressure. 2. The method according to p. 1, characterized in that 0.5-4.0 m ^{3 of a} suspension of a water-soluble polymer in an organic fluid is pumped into the well for each linear meter of the effective formation power.  3. The method according to p. 1, characterized in that anhydrous oil, distillate, kerosene, gas oil, hexane, gasoline, condensate, diesel fuel are used as the organic liquid.  4. The method according to p. 1, characterized in that the injection pressure of a suspension of a water-soluble polymer in an organic fluid at the wellhead is 1.0-40.0 MPa.  5. The method according to p. 1, characterized in that as the squeezing liquid is used water with a pH of 4-12.  6. The method according to p. 1, characterized in that the exposure time under pressure is 3-72 hours

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