RU2435952C1 - Procedure for treatment of filtration zone of horizontal well with abnormally low reservoir pressure - Google Patents

Abstract

FIELD: gas and oil production. ^ SUBSTANCE: procedure consists in lowering production string - PS- into well to depth of beginning of filter in horizontal section of borehole and in lowering flexible pipe into PS. Liquid and gas are pumped into the well through this flexible pipe. According to the invention a level of well fluid is determined in the well before flexible pipe lowering. Upon flexible pipe lowering under the level of fluid and before its coming out from the PS gas in form of air-nitrogen mixture is pumped through the flexible pipe to complete replacement of well fluid with gas in the PS. Further, the flexible pipe is lowered to its coming out for not over one metre from the PS and the flexible pipe is lowered to bottomhole with interval-by-interval stops every 50-100 m. Liquid in form of water solution of surface-active substance - SAS with air-nitrogen mixture is pumped till mechanical impurities emerge on surface in each interval. ^ EFFECT: raised efficiency of treatment of filtration section of horizontal well borehole due to high evacuation of clay material. ^ 1 ex, 1 dwg

Description

The invention relates to the oil industry - the development of horizontal wells after drilling and further extraction from them of super-viscous oil by thermal methods.

A known method of processing and well development (RF Application No. 97103442, ЕВВ 43/22, publ. 03.20.1999), including the injection into the well of an aerated solution of surfactant in water and well development. Before the surfactant is injected into the well in water, it is aerated at a rate of 3.1-4.4 under reservoir conditions, and it is pumped into the bottomhole zone cyclically, alternating with the injection of unaerated fluid under pressure not lower than the difference between 1.3 -R _pl. where R _pl. - reservoir pressure.

Aeration of an aqueous solution of a surface-active substance (SAS) can reduce the hydrostatic pressure of a liquid column in the well, which speeds up the process of well development. The disadvantage of this method is that its use was proposed in vertical wells and aeration of the liquid column could be carried out not lower than the descent depth of the end sleeve of the tubing, which in turn worsens the removal of clay material from the drilling fluid over the entire thickness of the perforated formation .

The closest in technical essence to the proposed method is a method of causing gas inflow from a horizontal wellbore (RF Application No. 2229019, ЕВВ 43/00, publ. 05.20.2004), including the descent of flexible pipes (GT) into the tubing string before the bottom hole the horizontal part of the wellbore, after which through them the barrel is flushed alternately with water and inert gas is purged. After each flushing and purging, the flow of gas from the well is measured.

The disadvantage of this method is that its use is limited to gas wells, and the flexible pipe involved in this process delivers carbonated fluid in one interval, which leads to the formation of stagnant zones along the horizontal wellbore. This reduces the quality of processing, i.e. removal of clay particles of the drilling fluid from the filtration zone of the horizontal wellbore, which, ultimately, reduces the flow of fluid from the reservoir.

The technical objective of this proposal is to increase the efficiency of processing the filtration part of the horizontal wellbore with flushing fluid, which creates low hydrostatic pressure on the formation and provides high removal of clay material with aerated surfactant flushing solution.

The problem is solved by the method of processing the filtration zone of a horizontal well with an abnormally low reservoir pressure, including the descent into the well of a string of tubing to the depth of the start of the filter in the horizontal part of the barrel, the descent of a flexible pipe into the tubing string through which liquid and gas are injected into the well

What is new is that before lowering the flexible pipe, the level of the borehole fluid in the well is determined, after lowering the flexible pipe to the level of the fluid, before it leaves the tubing string, gas in the form of an air-nitrogen mixture is pumped through the flexible pipe until the well is completely replaced in the tubing string by gas, then the flexible pipe is lowered to the exit of no more than one meter from the tubing string, after which the flexible pipe is lowered to the bottom with interval stops after 50-100 m with the injection of liquid in the form of an aqueous solution of a surface-active substance (surfactant) with an air-nitrogen mixture until the end of the removal of mechanical impurities to the surface in each interval.

The drawing shows a horizontal well in the context of an oil reservoir.

The method is implemented as follows.

A tubing string 4 is lowered into the production casing 1 at the beginning of the filter zone 2 of the horizontal wellbore located in the reservoir 3, the wellhead is sealed with fittings equipped with a lubricator (not shown in the drawing). A flexible pipe (coiled tubing) goes down through a lubricator to a tubing string 4 to a depth of 60-70 m below a level 5 of the fluid located in the well, determined by an echo sounder (not shown), 6. A compressor is connected to the coiled tubing line 6 (not shown), and the air-nitrogen mixture is injected, the liquid is taken from the tubing line 4 until the liquid is completely replaced with gas, which is determined by the absence of liquid spill to the surface along the tubing string 4. Simultaneously with the start of the air-nitrogen mixture injection, the flexible pipe is launched until it comes out from tubing 4 to a length of one meter. With the exit of the flexible pipe from the tubing, a pump unit (not shown) is connected to the line, which injects an aqueous surfactant solution. Gradually increasing the productivity of the pump until a stable circulation of the flushing solution to the surface is achieved, by launching the flexible pipe with the interval tolerance stop (interval 50-100 m) and supplying working agents, the well is processed until the bottom. In the absence of mechanical impurities in the liquid poured onto the surface in the process, the processing intervals are sequentially changed in increments of 50-100 m to the bottom, after processing the last operating interval, the work is stopped and the flexible pipe 6 is removed to the surface.

An example of a specific implementation.

According to the proposed scheme, the filter zone of several horizontal wells was processed at the Ashalchinsky super-viscous oil field: No. 15010, 15011, 15018, 15019, 15078.

After well No. 15019 after drilling, development and processing of a horizontal wellbore were carried out in the following sequence:

- made the descent of tubing with a diameter of 89 mm to a depth of 192 m;

- through the tubing they launched a GT with a diameter of 38 mm to a depth of 100 m;

- by connecting a nitrogen compressor to the GT line, a liquid column was aerated in the tubing with simultaneous tolerance of the GT to a depth of 193 m;

- upon reaching a depth of 193 m, a pumping unit was connected to the GT line and with the simultaneous injection of flushing liquid with an initial flow rate of 2-3 m ³ / h (warm wastewater with the addition of a 0.3% solution of ML-81) and pumping the air-nitrogen mixture from the compressor with at intervals of 100 m, they allowed the gas turbine and processed the filtration part until the bottom of the horizontal well. Processing was performed at each interval until the termination of the removal of mechanical particles to the surface.

The proposed method allowed to increase the efficiency and manufacturability of the development of a horizontal well with an abnormally low reservoir pressure, and ensured the restoration of filtration characteristics in the bottomhole formation zone due to the complete removal of clay material by aerated carbonated aqueous surfactant solution.

Claims (1)

A method of processing the filtration zone of a horizontal well with an abnormally low reservoir pressure, including lowering the tubing string into the well to the depth of the beginning of the filter in the horizontal part of the barrel, lowering a flexible pipe into the tubing string through which fluid and gas are injected into the well, the fact that before lowering the flexible pipe determine the level of the borehole fluid in the well, after lowering the flexible pipe under the fluid level before it leaves the tubing string, gas is pumped through the flexible pipe in the form of gas mixture until the well is completely replaced in the tubing string with gas, then the flexible pipe is lowered to exit no more than one meter from the tubing string, after which the flexible pipe is lowered to the bottom with interval stops after 50-100 m with liquid injection in the form of an aqueous solution of surface active substance - surfactant with an air-nitrogen mixture until the end of the removal of mechanical impurities to the surface in each interval.

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