RU2406818C1 - Method of protection against sand phenomena in oil wells - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: in method of protection against sand phenomena in oil wells, which involves subsequent pumping to the formation through production well of gaseous agent, solution of urethane pre-polymer in acetone, water with the above solution pushed to the formation, there performed is the above pumping of gaseous agent during not less than one 1 hour at pressure exceeding formation pressure by 1.1-1.9 times, water pumping - in volume of 0.5-2 parts of the volume of the polymer solution at its concentration of 10-40%, and after the above solution is pumped, gaseous agent is also pumped till the pumping pressure is stabilised.

EFFECT: increasing efficiency of reduction of sand phenomena in oil wells at maintaining the productivity.

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Description

The invention relates to the field of oil production and can be used to reduce the removal of sand from oil and gas condensate wells.

The development of oil reservoirs is often accompanied by complications associated with the destruction of the oil reservoir and, as a result, with the appearance of sand in the produced products. The removal of sand at the wellhead leads to the destruction of technological equipment and the emergence of the need for costs for its repair and replacement. To combat this phenomenon, it is possible to use downhole filters. However, the cost of such filters is high, and they require periodic recovery [1. In wells equipped with pumps, the possibility of providing space for such filters is extremely limited, which causes additional difficulties in the repair and maintenance of these devices during operation.

Closest to the technical nature of the claimed method is a method of reducing sand in oil and gas wells by creating an in-situ filter. An in-situ filter is created by pumping a solution of urethane polymer in acetone into the well, followed by water displacement. [2].

The disadvantage of this method is its lack of effectiveness when used for oil wells in flooding conditions.

In oil reservoirs, the pore space is filled with oil and water. Upon contact of the polymer solution and water, the polymer is released in the pore space and the permeability of the oil reservoir is reduced in the bottomhole zone of the well. The consequence of this is a decrease in well productivity.

The aim of the invention is to increase the efficiency of reducing sand in oil wells while maintaining productivity.

This goal is achieved by the fact that in a method of controlling sand occurrences in oil wells, which includes sequential injection of a gaseous agent into the formation through a producing well, a solution of a urethane prepolymer in acetone, water with a solution being injected into the formation, the said gaseous agent is injected for at least 1 hours at a pressure exceeding the reservoir 1.1-1.9 times, water injection - in the amount of 0.5-2 hours from the volume of the polymer solution at its concentration of 10-40%, and after injection of the specified solution, additionally there is an injection of a gaseous agent to stabilize the injection pressure.

In the implementation of the inventive method, the strengthening of the bottom-hole zone of an oil formation well begins with the displacement of the formation fluid from the pore volume of the formation rock by a gaseous agent, and associated gas, nitrogen, air can be used as gas. Subsequent injection of a urethane polymer solution occurs without contact with the formation fluid. Subsequent - after injection of the specified solution - injection of the gaseous agent-gas rim leads to a uniform distribution of the polymer solution over the rock surface, evaporation of the solvent and curing due to contact with water vapor. The need for the number of gas rims is one more than the rims of the polymer solution due to the fact that the first gas rim frees up the pore space for the polymer solution, and the subsequent rim leads to effective spreading of the solution over the surface of the formation rock. Otherwise, the permeability of the rock, and consequently, the production rate, will decrease or stop altogether. To reduce the risks of reducing permeability, the number of rims of the polymer solution can be two or more, which allows you to adapt the technology to specific geological and field conditions.

The above gas pressure limits are justified by the fact that when the gas pressure is less than 1.2 from the reservoir pressure, there will be no effective displacement of fluid from the first volume of the formation rock. At a pressure 2 times greater than the reservoir, a violation of the uniformity of fixing the sections of the reservoir containing sand is possible.

Example 1

An oil well works with sand removal on the formation with a reservoir pressure of 90 atm and periodically after 3 months of work it stops to carry out repair work to remove the sand plug. To prevent the formation of sand plugs after the next removal of the sand plugs in the well, the proposed method was applied. To do this, gas-air was injected into the well for 4 hours at a pressure of 130 atm using the UNG-8/15 booster unit. Then, 7 m ^{3 of a} 15% solution of urethane prepolymer in acetone was pumped into the well. Then, gas-air was injected and the solution was pushed for 5 hours with gas at the same pressure. Then water was pumped with a rim volume of 7 m ³ , i.e. 1 of the volume of the specified solution. The well was put into operation. As a result of the measures, the well worked non-stop for 12 months.

Example 2

An oil (production) well works with sand removal on the formation with a reservoir pressure of 110 atm and periodically after 5 months of work it stops to carry out repair work to remove the sand plug. To prevent the formation of sand plugs after the next removal of the sand plugs in the well, the proposed method was applied. For this, air was injected into the well for 4 hours at a pressure of 130 atm using a UKM compressor-membrane installation. Then 4 m ^{3 of a} 12% solution of urethane prepolymer in acetone was pumped into the well. Then, an injection was carried out with a solution being sold for 5 hours with gas-air at the same pressure. Then, another 4 m ^{3 of the} 12% indicated solution was pumped and gas was pressed for 5 hours under the same conditions. Then, water was pumped in a volume of 6 m ³ , i.e. 1.5 volumes of solution. The well was put into operation. As a result of the activities, the well worked non-stop for 12 months and continues to work.

Information sources

1. RU No. 2158358, 09/03/1999, Sand filter.

2. RU No. 2285791, 09/21/2005, A method of controlling sand occurrences in oil and gas wells.

Claims (1)

A method of controlling sand occurrences in oil wells, comprising sequentially injecting a gaseous agent into a formation through a producing well, a solution of a urethane prepolymer in acetone, water and selling said solution into a formation, characterized in that said gaseous agent is injected for at least 1 hour at a pressure exceeding the reservoir 1.1-1.9 times, the injection of water in a volume of 0.5-2 hours from the volume of the polymer solution at a concentration of 10-40%, and after the injection of the specified solution, gas is additionally injected shaped injection agent to stabilize the pressure.