RU2144608C1 - Method for blocking of absorbing beds in well - Google Patents

Abstract

FIELD: mining industry. SUBSTANCE: this relates to methods of preparing wells to overhaul repair by blocking of absorbing zones in well. According to method, injected into well are buffer, blocking and pressure-forcing liquids. Used in function of blocking liquid are at least two compounds which in process of mixing create viscous structure possessing high adhesive and convertible properties, for example, compound No.1 includes following components, mas.%: copolymer of styrene with maleic anhydride treated by sodium hydroxide, 15-20; water, the balance. Compound No.2 includes following components, mas.%: acetic acid, 4-5; water, the balance. Compounds are made separately and injected into well successively. Application of method ensures higher efficiency of blocking of absorbing well beds due to enhancing structural-mechanical and adhesive properties of blocking compounds. EFFECT: higher efficiency.

Description

 The present invention relates to the mining industry, in particular to methods for preparing wells for overhaul by blocking the absorption zones in the well.

 There is a method of blocking absorbing formations, which consists in injecting a blocking micellar solution into the bottomhole formation zone (PZP) before killing a well (see USSR patent N 2047745, class E 21 B 43/2, 1988).

 The disadvantage of this method is the relatively low efficiency of blocking the formation and subsequent development of wells.

The closest in technical essence and the achieved result to the proposed method is a method of blocking the absorbing formations, which consists in the fact that before injecting the killing fluid into the well, a buffer liquid for gas displacement and blocking composition are sequentially pumped (see ac USSR N 1828912, class E 21 B 33 / 138,1993). Moreover, as a blocking composition using chalk suspension, consisting of the following components,%:
Chalk - 57-62
VZhS flotoreagent - 8-12
Water - Else
This composition is designed for the formation of chalk crust on the surface of the rock to prevent absorption. After carrying out repair work on the well, the chalky crust is destroyed by hydrochloric acid treatment of the bottomhole zone.

 The disadvantage of this method is the low efficiency of killing, since the flotation reagent VZhS does not lead to a significant improvement in the structural and mechanical properties of the blocking fluid, such as viscosity, stability, thermal stability.

 The instability of the blocking composition does not allow work (circulation, flushing the well) directly in the perforation interval, since the filtration of the liquid in the PPP increases.

 The aim of the invention is to increase the efficiency of the method of blocking the absorbing layers of the wells by increasing the structural-mechanical and adhesive properties of the blocking composition.

 The proposed method is especially effective at abnormally low reservoir pressures and in the late stages of field development, when the known compositions do not exclude the absorption of kill fluids in large quantities.

The method is achieved by the fact that buffer, blocking and filling liquids are pumped into the well, and at least two compositions are used as a blocking liquid, which form a viscous structure in the mixing process that has high adhesive and reversible properties, for example
composition N 1, wt.%:
Sodium hydroxide treated styrene copolymer with maleic anhydride - 15-20
Water - Else
composition N 2, wt.%:
Acetic acid - 4-5
Water - Else
moreover, the compositions are prepared separately and pumped into the well sequentially.

 Water-soluble polymers used in the proposed method are obtained by copolymerization of styrene with maleic anhydride, followed by treatment of the high molecular weight compound with sodium hydroxide.

 During the interaction of the polymer with weak acids, a water-insoluble, highly viscous stable mass is formed, which has high adhesion to the rock of the well.

 This property of the polymer is used when killing wells to temporarily block a highly permeable reservoir by forming an impermeable, polymer film that reduces the filtration of fluid into the formation, especially in the case of an API.

When you add a hot solution of hydroxides, such as sodium, potassium, etc. (T = 40-45 ^o C), the polymer mass is destroyed and goes into a liquid state.

The method is as follows. For underground repair operations, before killing, 5-8 m ^{3 of} buffer fluid is pumped sequentially into the well to displace the gas and prevent the blocking fluid from degassing, 2-3 m ^{3 of} composition N 1 (acetic acid solution with a mass fraction of 4-5%), 1.5- 2 m ^{3 of} composition N 2 (15-20% water-soluble polymer) and push them into the perforation interval with an invert emulsion or saline solution. Moving along the wellbore and penetrating into the porous medium, compositions N 1 and N 2 mix with each other and form a highly viscous mass with high structural and mechanical properties, which forms a polymer film that is not permeable to muffling fluid. After this, the necessary repairs are carried out.

 After completion of the repair work, the PZP is released by a hot solution of sodium hydroxide with a mass fraction of 15-17%. In this case, the highly viscous mass is destroyed and goes into a liquid state.

 When developing a well on a torch and putting it into operation after repair work, the well immediately enters a stable mode of operation.

 Based on the foregoing, we believe that the proposed method of blocking the perforation interval in a well satisfies the requirement of the criteria of "novelty" and "inventive step", since the use of such a combination of features to achieve the goal is not previously known. It allows you to get a polymer film on the wellbore with a high indicator of structural and mechanical properties, which leads to a decrease in the filtration of the fluid into the formation and reliably blocks it, which is especially important when killing wells in the conditions of oil production.

 It should be noted that a decrease in the concentration of reagents (lower limit) leads to an increase in the filtration of fluids into the formation, an increase in the absorbed volumes of the fluid, and the time for completion of the well after repair. With an increase in the concentration of components in the solution of the above values (upper limit), the highly viscous mass becomes technologically unsuitable due to the difficulties encountered when pushing it into the perforation interval.

 The following are specific examples of the implementation of the method with packer and packerless layout of the operation of wells.

Well N 3162
1. The design and technical condition of the wells.

 1.1. Electric column: d = 168 mm-1257 m - cement to the mouth.

 1.2. Artificial slaughter - 1248 m, current slaughter according to PIP 1238 m.

 1.3. Perforation intervals: 1195-1233 m.

 1.4. Tubing d = 114 mm lowered to a depth of 1152 m.

 1.5. The mouth is equipped with AF type AFK-6-100 / 100-210XL.

1.6. The well was stopped in 97 g. Parameters to a stop:
P _y = 4.15 MPa, T _y = 17 ^o C, Q = 110 thousand m ³ / day (01.1997),
M = 16 g / l (12.1997). P _PL = 4.7 MPa, P _ST = 4.3 MPa, GVK 1240 m, K _p = 35%.

 1.7. Previous work: hydrophobization.

 2. The work plan.

2.1. Prepared and delivered to the well 5% solution of acetic acid in a volume of 3 m ³ ; water-soluble polymer (mass fraction of 15%) in an amount of 2 tons; 40 m ³ invert emulsion solution (IER) with a density of 0.98 g / cm ³ .

 2.2. We prepared a working platform for the placement of special equipment around the wellhead in a radius of 25-30 m.

 2.3. We mounted the filling and return lines, arranged special equipment according to the standard scheme.

 2.4. Two TsA-320 tied up the pipe space of the well through a tee. They tested the injection line at 7.5 MPa.

2.5. We pumped 6-7 m ³ IER into the tubing to displace the gas from the tubing and reduce the pressure and fill the annulus. Then they started to inject 0.2 m ^{3 of} industrial water, a solution of acetic acid in a volume of 3 m ³ .

2.6. The second TsA-320 pumped 4 m ^{3 of a} solution of a water-soluble polymer (mass fraction of 15%), 0.2 m ^{3 of} industrial water and pushed the solutions into the perforation interval of 3 m ³ IER. The annulus was closed when the acetic acid solution approached the tubing shoe and the solution was pushed into the reservoir with 5 m ³ IER. During the injection process, the maximum pressure was 5.5 MPa.

 2.7. They closed the well and monitored changes in pipe and annular pressures for 11-12 hours.

 2.8. Before further work was carried out, according to the main plan, the IER well was circulated for at least two cycles.

Well N 12261
1. The design and technical condition of the well.

 1.1. Conductor - 245 mm-546 m, cement to the mouth.

 1.2. Electric column 168 mm-1252.5 m, cement to the mouth, pressed at 130 atm.

 1.3. Tubing 114 m lowered to a depth of 1239 m.

 1.4. Artificial Slaughter - 1239 m.

 1.5. Perforation intervals: 1200-1216 m; 1226-1237 m.

 1.6. Packer 2PYAG installed at a depth of 994-996 m.

 1.7. FA type AFK-6-100 / 100 - 210 HL.

1.8. Well operation parameters before stopping:
P _g = 4.1 MPa; T = +12 ^o C; Q = 440 thousand m ³ / day; mineralization - 18 g / l; GVK - 1245 m. P _pl = 4.7 MPa, K _p = 31%.

 2. The work plan.

 2.1. We prepared a site for the placement of special equipment, special equipment and containers for the delivery of kill fluids.

2.2. 35 m ^{3 of} ESI with a density of 1000 kg / m ³ , 1.5 m ^{3 of} water-soluble polymer (mass fraction of 19%), 1.8 m ³ of acetic acid solution (mass fraction of 4%) were delivered to the well.

 2.3. Collected discharge, flare and return lines. The pressure line was pressure tested at one and a half times working pressure of 70 atm.

 2.5. Conducted preparatory work to determine the tightness of the packer, for this vented the pressure in the annulus. If the annular pressure drops to 0, while the pipe pressure does not change, the packer is tight.

2.7. Jamming was carried out according to the scheme. Bleed to 0 and filled the annulus of the IER in a volume of 7 m ³ . 5-7 m ³ BMP were pumped into the tubing to displace gas and reduce wellhead pressure, then pumping unit N 1 0.2 m ^{3 of} technical water, a solution of acetic acid in a volume of 1.8 m ³ and aggregate N 2 1.5 were pumped sequentially m ³ water-soluble polymer and 0.2 m ³ industrial water. The injected solutions were sold in the perforation interval of 9 m ³ IER. The maximum pressure of the liquid was 6 MPa.

2.8. After observing the pipe and annular space, the gas cap was vented and IER wells were added to the volume of 1 m ³ .

During repair work, in particular flushing of the face, destruction of excess cement bridge, etc., a steady circulation of fluid was observed in the well. The amount of absorbed kill fluid for the entire repair period of these wells was 8-10 m ³ , which is 5-6 times lower than average. During the development of the wells, they entered the operating mode within three days.

 Thus, the use of the proposed method for blocking the absorbing formations in the well by increasing the structural-mechanical and adhesive properties of the blocking fluid allows maintaining the permeability of the productive reservoir at the same level and shortening the time of well development and output after a major overhaul.

Claims (1)

A method of blocking absorbing formations in a well, comprising injecting buffer, blocking and filling liquids into the well, characterized in that at least two compositions are used as blocking liquid, which form a structure during mixing that has high adhesion and reversible properties, for example
composition 1, wt.%:
Maleic anhydride styrene copolymer treated with sodium hydroxide - 15 - 20
Water - Else
composition 2, wt.%:
Acetic acid - 4 - 5
Water - Else
moreover, the compositions are prepared separately and pumped into the well sequentially.