RU2580534C1 - Method for repair and insulation works in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil and gas industry, in particular, to methods of sealing defects of production string, liquidation of leakiness of cement sheath in tight formations and restrict water influx in well. Method provides repair insulation works in well and includes injection into the zone of isolation of water shutoff composition consisting of silicon dioxide hydrosol of density 1196-1220 kg/m and sodium chloride solution of density 1012-1030 kg/m, which are mixed on the surface and is pumped into the fault in the following ratio of components, vol. parts: silicon dioxide hydrosol 200-400, gelling agent 100, when specific injectivity of isolated interval is more than 0.8 m³/(h·MPa) sequential injection of water shutoff composition is made followed by buffer of fresh water, and formation of mineralised water with density of 1180-1190 kg/m³ with the following ratio of components in vol. parts: silicon dioxide hydrosol 200-400, gelling agent 100, formation mineralized water 100.

EFFECT: technical result consists in improvement of efficiency of remedial cementing works in well due to increase quality of repair works.

1 cl, 2 tbl

Description

The invention relates to the oil and gas industry, in particular to methods for sealing violations of the production string, eliminating leakage of the cement ring in low-permeable formations and limiting water inflow in the well.

A known method of repair and insulation work in the well (AS No. 933948, IPC E21B 33/138, publ. 06/07/1982, bull. No. 21), including the injection of a viscoelastic plugging solution in the following ratio, wt.%:

2% polyacrylamide solution 49.3-97.3 technical formalin 1.2-2.7 5% solution of KMTS-600 1.5-49.5.

The disadvantage of this method is that in a cement slurry use a 2% aqueous solution of polyacrylamide and a 5% solution of CMC-600, which have a high viscosity. Such a solution is only suitable for pumping into highly permeable and fractured reservoirs. Long gelation time for 1-20 days. leads to more expensive repair work, which also relates to the disadvantages of the known method.

Closest to this proposal is a method of repair and insulation work in the well (patent RU No. 2525079, IPC E21B 33/138, publ. 08/10/2014, bull. No. 22), including the injection into the insulation zone of a water-insulating composition consisting of a silicon-containing polymer (water glass) and gelling agent. A 0.03-0.05% solution of DP9-8177 polyacrylamide is preliminarily prepared, it is added to water glass and mixed until a homogeneous mixture is obtained, then the resulting mixture and gelation regulator are pumped sequentially, separating them with fresh water buffer, in the following reagent ratio , vol.%:

liquid glass 20-50 0.03-0.05% solution of DP9-8177 polyacrylamide 10-15 gelling regulator 40-65,

as a gelation regulator use a 10-20% solution of calcium chloride technical or 10-20% solution of POLYPACS-30 LF (polyaluminium chloride).

The disadvantage of this method is that the mixture is not completely mixed in the well, therefore, the plugging mass will form only at the boundary of mixing of these components, and this is not enough for reliable sealing of production casing and long-term overlap of cracks in the cement ring, through which water enters the well.

The technical task of the proposal is to increase the efficiency of the method of repair-insulation work (RIR) in the well by improving the quality of repair work.

The technical problem is solved by the method of repair and insulation work in the well, including pumping into the isolation zone a water-proofing composition consisting of an inorganic silicon-containing polymer and a gelling agent.

New is that in the waterproofing composition as an inorganic silicon-containing polymer, a silicon dioxide hydrosol with a density of 1196-1220 kg / m ^{3 is used} , and a solution of sodium chloride with a density of 1012-1030 kg / m ^{3 is} used as a gelling agent, which is mixed on the surface and pumped into violation interval for the following ratios of components, vol.h .:

silica hydrosol 200-400 gelling agent one hundred,

when the specific injectivity of the insulated interval is more than 0.8 m ³ / (h · MPa), a water-insulating composition, a buffer of fresh water and produced mineralized water with a density of 1180-1190 kg / m ^{3 are} sequentially pumped with the following ratios of components, vol.h .:

silica hydrosol 200-400 gelling agent one hundred formation mineralized water one hundred.

Silicon dioxide hydrosol is an opalescent yellowish solution with a mass concentration of silicon dioxide in the range of 29-31%, a silicate module in the range of 4.1-9.4, a pH in the range of 9-10.5, and a kinematic viscosity of not more than 10 mm ² / with a density in the range of 1196-1220 kg / m ³ .

Sodium chloride in accordance with GOST Ρ 51574-2000 edible salt. Technical conditions

The essence of the proposed method is as follows. The injectivity of the isolated interval is determined. Immediately before pumping into the well, a waterproofing composition consisting of a silica hydrosol and a gelling agent is prepared and pumped into the well.

A waterproofing composition for sealing violations of the production string at a specific injectivity of the insulated interval of 0.1-0.5 m ³ / (h · MPa) or eliminating leakage of the cement ring at 0.5-0.8 m ³ / (h · MPa) is prepared in a clean, steamed measuring device of the cementing unit, where the calculated amount of the silica hydrosol is collected. The operation of the cementing unit “on itself” creates a circulation of a silica hydrosol according to the pump-mernik-pump scheme, and then a calculated amount of sodium chloride is gradually introduced into the circulating hydrosol of silica in small portions, the waterproofing composition is mixed for 10-15 minutes and pumped into the violation interval . The gel formation time depends on the ratio of the components of the waterproofing composition and ranges from 2 to 6 hours

A waterproofing composition to eliminate the leakage of the cement ring and limit water inflow with a specific injectivity of the insulated interval of more than 0.8 m ³ / (h · MPa) is prepared similarly to the above. To prevent erosion of the waterproofing composition, to obtain a denser gel and waterproofing screen that is resistant to pressure drops, a buffer of fresh water in the amount of 0.2-0.3 m and 100 rpm is pumped into the violation interval after pumping the waterproofing composition. mineralized formation water with a density of 1180-1190 kg / m ³ .

The required volume of the waterproofing composition, depending on the specific injectivity of the isolated interval, is established from field experience and is shown in table 1 (based on one well).

In order to establish the optimal ratio of the components of the water-insulating composition for sealing violations of the production string at a specific injectivity of the insulated interval of 0.1-0.5 m ³ / (h · MPa), eliminate leakage of the cement ring at 0.5-0.8 m ³ / ( h · MPa), as well as to limit water inflow and eliminate leakage of the cement ring with a specific injectivity of the insulated interval> 0.8 m ³ / (h · MPa), the gelation time of the composition and its water insulating ability were determined. The waterproofing ability of the proposed method and the closest analogue was tested on reservoir models with a length of 30 cm and an inner diameter of 2.7 cm, filled with quartz sand fraction 0.2-0.3 mm, which allows you to simulate the injection of reagents into the reservoir. The reservoir model was saturated with fresh water, after which the water-insulating composition was pumped according to the proposed method and the closest analogue and left to react. The amount of injected composition was equal to the pore volume of the reservoir model. After 12 hours, 24 hours and 6 months, water was pumped in and the breakthrough pressure of the water was determined. The average results of model tests of the water-insulating ability of the proposed method and the closest analogue are presented in table. 2.

According to the results of model tests, the best insulating ability of the waterproofing composition according to the proposed method was established in comparison with the closest analogue, which is determined by the values of the water breakthrough pressure in the models after 12 hours, 24 hours and 6 months. Taking into account the gelation time, the optimal range of the ratio of the components of the water-insulating composition (No. 2-5, 7-9) was selected, vol.h .:

silicon dioxide hydrosol with a density of 1196-1220 kg / m ³ 200-400 sodium chloride with a density of 1012-1030 kg / m ³ one hundred.

To eliminate the leakage of the cement ring and limit water inflow with a specific injectivity of the insulated interval of more than 0.8 m ³ / (h · MPa), after pumping the waterproofing composition, an additional buffer of fresh water is pumped in a volume of 0.2-0.3 m ³ and 100 vol. hours mineralized formation water with a density of 1180-1190 kg / m ³ . Gelling in this case occurs when the water-insulating composition and saline formation water with a density of 1180-1190 kg / m ³ come into contact, and the breakthrough pressure of the obtained gel is already 12 hours higher than the breakthrough pressure of the gel obtained by the closest analogue after 24 hours, which indicates better waterproofing ability of the waterproofing composition according to the proposed method and, therefore, to improve the quality of repair work.

Thus, the proposed method provides an increase in the efficiency of sealing violations of production casing, leakage of the cement ring and limitation of water inflow in low-permeable formations by improving the quality of repair work, which is determined by the reliability of the sealing and the increase in the time between overhauls of the well.

Claims (1)

A method of repair-insulating work in a well, comprising injecting into the isolation zone a water-proofing composition consisting of an inorganic silicon-containing polymer and a gelling agent, characterized in that a silicon dioxide hydrosol with a density of 1196-1220 kg / m ^{3 is} used as the inorganic silicon-containing polymer, and as a gelling agent, a solution of sodium chloride with a density of 1012-1030 kg / m ^{3 is used} , which is mixed before injection and pumped into the violation interval at a specific injection rate ty of the isolated interval of 0.1-0.8 m ³ / (h · MPa) with the following ratios of components, vol.h .:
silica hydrosol 200-400 gelling agent one hundred,
when the specific injectivity of the insulated interval is more than 0.8 m ³ / (h · MPa), a water-insulating composition, a buffer of fresh water and produced mineralized water with a density of 1180-1190 kg / m ^{3 are} sequentially pumped with the following ratios of components, vol.h .:
silica hydrosol 200-400 gelling agent one hundred formation mineralized water one hundred.