RU2630938C1 - Method for cleaning and treating bottomhole zone of horizontal well in bitumen deposit - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for cleaning and treating the bottomhole zone of the horizontal well in bitumen deposit includes lowering a coiled tubing string into the well and fixation of the descent depth, pumping of aerated flushing fluid through the coiled tubing string, cleaning of bottomhole zone from colmatage sediments by flushing, transporting and circulating thereof into chute container. At that, lowering of the coiled tubing string equipped with pear-shaped packing at the end is carried out into the well down to the depth of 50 m below the well head. A nitrogen compressor is started in the line of the coiled tubing string and aeration of the flushing fluid is carried out, with simultaneous relowering of the coiled tubing string to down to the depth of the initial part of the shank filter. After that pump unit is started with supply of flushing fluid to the line of the coiled tubing string. Then bottomhole zone is cleaned in four cycles by flushing with aerated fluid. Each cycle consists of moving the coiled tubing string at a rate of 1 m/s to the face with simultaneous flushing with aerated fluid. After reaching the bottom, the movement of the coiled tubing string is stopped. The well is flushed with aerated fluid for 30 minutes. Then the pump unit and the nitrogen compressor are switched off. A 30 minutes process pause is held. At that, the level of liquid in the well is marked with echo sounder. Further, the coiled tubing string is raised to a depth of 50 m below the well head. After that the above-described cycle is repeated three times. Then bottomhole formation zone is treated by injection of 8% hydrochloric acid in interval of horizontal part of wellbore from beginning of filter part of the shankl to bottom by 0.2 m³ for every 50 m followed by forcing hydrochloric acid into fresh water formation.

EFFECT: improved cleaning quality of the horizontal well bottomhole zone and increased cleaning efficiency of well bottomhole zone.

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Description

The invention relates to the oil industry and may find application in the treatment of the bottom-hole zone in horizontal wellbores drilled in bitumen deposits.

A known method of processing the bottom-hole zone of a horizontal well in bitumen deposits (patent RU No. 2520989, IPC E21B 43/27, publ. 06/27/2014, Bull. No. 18), including the descent into the machined interval of the hydraulic perforator with a single-acting pipe string with the nozzle upward, jet exposure through it with a hydrocarbon solvent, then an acid solution, holding technological exposure to the acid reaction, removing equipment from the well, swabbing and putting the well into operation. At the mouth of a horizontal well, before lowering into the well, the lower end of the pipe string is equipped from bottom to top: centralizer-nozzle, single-acting hydroperforator with upward direction of the nozzle, pulsed fluid pulsator, valve consisting of a seat and a housing with openings sealed by a saddle fixed by a shear pin relative to corps. The pipe string is lowered to the stop of the centralizer-pipe in the bottom of a horizontal well. Then, in two stages, in a pulsed mode, a jet is applied through the hydroperforator to the bottom-hole zone of the formation, first with a hydrocarbon solvent and then with hydrochloric acid. When two stages are implemented, the pipe string is moved from the bottom to the mouth with a constant speed for the length of the filter while pumping hydrocarbon solvent or hydrochloric acid horizontal well. At the end of the hydrochloric acid injection, a hydroperforator is placed at the end of the filter from the side of the wellhead. Then, at the wellhead, a plug is installed in the pipe string and it is pressed through the pipe string with the process fluid until the plug fits on the valve seat and the shear pin is destroyed by the overpressure in the pipe string. Next, technological exposure is carried out for 1 hour, while in the process of technological exposure the pipe string is pulled all the way to the bottom of the horizontal well. Then, in three cycles, alternately either 0.5 m ^{3 of} process fluid is pumped into the pipe string or into the annulus of the well. At the end of the exposure time, the reaction products are washed out by reverse circular circulation in a 1.5 times volume of the well.

The disadvantages of the method:

- firstly, the low efficiency of acid treatment of the bottom-hole zone of the horizontal part of the well due to the presence of muds in the bottom-hole zone;

- secondly, a complex implementation technology associated with several trips of the pipe string into the well using a hydraulic perforator, a pulsed fluid pulsator, as well as the simultaneous injection of a hydrocarbon solvent or hydrochloric acid;

- thirdly, the high duration of the method, due to the fact that all technological operations are performed on the pipe string;

- fourthly, uncontrolled depression on the reservoir due to swab development, which does not allow for smooth development of the well.

The closest in technical essence and the achieved result is a method of cleaning the bottom-hole zone of a horizontal well (patent RU No. 2165007, IPC E21B 43/25, publ. 04/10/2001, bull. No. 10), including pumping a cleaning agent and forcing it, creating in the wellbore depressions, removal of clogging deposits and their transportation to the day surface by circulation of the flushing agent. Additionally, a string of flexible pipes (GT) is lowered into the well and the depth of descent is recorded. As a cleaning agent, an inert gas is injected through the GT column under a pressure not exceeding the pressure of the production casing pressure, and a foaming liquid is pumped through the annulus, the portion volume of which is determined by calculation. Moreover, the punching is carried out with an inert gas until the pressure jump is fixed at the wellhead. Depression in the wellbore is created by reducing the pressure at the wellhead to a value determined by calculation. Moreover, the transportation of clogging deposits to the trough is carried out by circulating an additional portion of aerated flushing fluid supplied from the wellhead through the GT string. Then, with the annulus closed, the aerated flushing fluid is pushed with an inert gas into the cleaned interval of the reservoir under pressure not exceeding the pressure of the test casing. The GT column is dragged for the length of the cleaned interval and, with the annulus open, blow the bottom with an inert gas. The cycle length of the pipes is determined by the cyclicality of the process and, if necessary, the operations are repeated.

The disadvantages of the method:

- firstly, the low quality of cleaning (removal of the mud) of the bottomhole zone of the well by flushing with aerated fluid, since during the implementation of the method the aerated flushing fluid is pushed into the formation under pressure from the production casing pressure, which leads to the absorption of the flushed aerated fluid by the formation, creating an uncontrolled depression, while the pressure in the annulus is not controlled;

- secondly, the low cleaning efficiency of the bottom-hole zone of a horizontal well drilled in bitumen deposits, associated with the lack of acid treatment after removal of the mud from the bottom-hole zone of a horizontal well in order to increase the injectivity of the formation;

- thirdly, the long duration of cleaning the bottom-hole zone of a horizontal well from colmatant, associated with the interval cleaning of the bottom-hole zone of a horizontal well by flushing, and when the method is implemented, the cyclicity of the process and the cleaning intervals are determined by the established length of the GT column casing (each time the GT column is lowered to a certain interval horizontal trunk) with a gradual bringing the pipe string to the bottom.

The technical objectives of the invention are to improve the quality and efficiency of cleaning the bottom-hole zone of a horizontal well drilled in bitumen deposits, reducing the duration of cleaning the bottom-hole zone of a horizontal well from colmatant.

The tasks are solved by the method of cleaning and processing the bottom-hole zone of a horizontal well in bitumen deposits, including the descent of a string of flexible pipes - GT and fixing the depth of descent, pumping aerated flushing fluid through the GT string, cleaning the bottom-hole zone from clogging deposits by washing and transporting them to the groove capacity.

What is new is that the GT column, equipped with a pear-shaped nozzle at the end, is lowered into the well to a depth of 50 m below the wellhead, the nitrogen compressor is launched into the GT column line and the washing fluid in the well is aerated while the GT column is drained to the depth of the beginning of the filter part of the liner, after which the pump unit is started with the flushing fluid supplied to the GT line, then the bottom-hole zone of the well is cleaned by flushing with aerated fluid in four cycles, each the cycle consists of moving the GT column at a speed of 1 m / s to the bottom while flushing with aerated liquid; upon reaching the bottom, the GT column is stopped moving, the well is washed with aerated liquid for 30 minutes, then the pump unit and nitrogen compressor are turned off, and the technological pause is maintained for 30 minutes, while the fluid level in the well is beaten with an echo sounder, then the GT string is raised to a depth of 50 m below the wellhead, after which the above cycle is repeated three times, then the treatment is performed injection bottomhole formation zone 8% hydrochloric acid in the range of the horizontal portion of the barrel from the start of a filter of the liner to the face of 0.2 m ³ per 50 m followed prodavkoy hydrochloric acid in fresh water reservoir.

In FIG. 1 and 2 schematically depict a method of cleaning and processing the bottom-hole zone of a horizontal well in a bitumen deposit.

The method of cleaning and processing bottom-hole zone of a horizontal well in bitumen deposits is implemented as follows

In order to clean a horizontal well (hereinafter referred to as a well) 1 (see Fig. 1), drilled in a bitumen deposit, from the mud (mud cake, sludge, sand) at the wellhead 1, the lower end of the GT 2 column, for example, is equipped with a pear-shaped diameter of 38 mm nozzle 3 with a diameter of 55 mm and carry out the descent of the GT 2 column into the well 1 to a depth of 50 m below the wellhead 1 (level 1), fix the depth of the lowering of the GT 2 column in the well 1.

The nitrogen compressor 4 is launched into the line of the GT 2 column and the aeration of the liquid located in the well 1 is started, while the GT 2 column is allowed to reach the start depth of the filter part 5 (perforation holes) of the shank 6, for example, to a depth of 450 m (level 2).

Next, they start the pumping unit 7, which injects the flushing liquid, which is used as warm wastewater with a temperature of 40-50 ° C with the addition of 0.3% by volume of a solution of a surface-active substance (surfactant), for example ML-81, with nitrogen injection nitrogen compressor 4 on the column GT 2 continue.

Bottom-hole zone 8 of the well 1 is cleaned by washing with aerated liquid in four cycles.

Each cycle consists of moving the GT 2 column at a speed of 1 m / s to the bottom 9 (level 3, depth 1000 m) while flushing with aerated liquid. When the bottom 9 is reached, the pear-shaped nozzle 3 rests against the bottom 9, as evidenced by the increased load on the GT 2 column, the movement of the GT 2 column is stopped and the well 1 is washed with aerated liquid for 30 min with the removal of the mud (clay, mud, mechanical impurities) from the bottomhole zone 9 to the groove capacity 10 through the annulus 11.

During the washing process, the flow rate of the washing liquid by the pump unit 7 is 2 l / s = 2.0 · 10 ^-3 m ³ / s to prevent its absorption by the reservoir 12. The pump unit injection pressure is 4.0-6.0 MPa. The nitrogen flow rate is 10 m ³ / min = 0.166 m ³ / s. Nitrogen injection pressure is 6.0-8.0 MPa.

Also, during the washing process, the pressure in the annulus 11 should not exceed the pressure of liquid absorption by the reservoir 12. For example, the pressure of the absorption of the reservoir 11 is 2.0 MPa, then the pressure in the annulus 11 should not be higher than 2.0 MPa, which is controlled using a manometer 13. After 30 minutes of flushing, the injection is stopped (the pump unit 7 and the nitrogen compressor 4 are turned off) in order to exit the colmatant from the bottomhole zone into the groove tank 10.

Maintain a technological pause for 30 minutes. At this time, the liquid level in the well 1 is beaten off with the help of an echo sounder, for example, the level after the first cycle was 400 m. After that, the GT 2 column is raised to level 1, the depth of the lowering of the GT 2 column in well 1 is recorded and the second cycle is carried out.

When implementing the second cycle, the whole process is repeated anew, starting from the start of nitrogen compressor 4 in the line of the GT 2 column and ending with the leveling of the liquid in the well 1. For example, the liquid level in the well after the second cycle was 300 m. After that, the GT 2 column is raised to level 1 (see Fig. 1) and fix the depth of descent of the column GT 2 in the well 1 and carry out the third cycle.

When implementing the third cycle, the whole process is repeated anew, starting from the start of nitrogen compressor 4 in the line of the GT 2 column and ending with the leveling of the liquid level in well 1. For example, the liquid level in the well after the third cycle was 200 m. After that, the GT 2 column is raised to level 1, fix the depth of descent of the column GT 2 in the well 1 and carry out the fourth cycle.

When implementing the fourth cycle, the whole process is repeated anew, starting from starting the nitrogen compressor 4 in the line of the GT 2 column and ending with the leveling of the liquid in the well 1. For example, the liquid level in the well after the fourth cycle was 100 m. At the end of the fourth cycle, clean water, which is determined visually in the gutter tank 10, therefore, the cleaning of the bottom-hole zone 9 of the horizontal well 1 with aerated flushing fluid from clogging deposits is stopped.

An increase in the level in well 1 with each cycle (400 m, 300 m, 200 m, 100 m) indicates the presence of inflow from the reservoir.

The column GT 2 (see Fig. 2) with the nozzle 3 is moved to the beginning of the filter part 5 of the shank 6, i.e. to a depth of 450 m (level 2) of well 1.

The bottom-hole zone of formation 9 is processed by injection of 8% hydrochloric acid in the interval of the horizontal part 15 of well 1, 0.2 m ³ for every 50 m, followed by the sale of 8% hydrochloric acid into reservoir 12 with fresh water with a density of 1000 kg / m ³ .

For example, at a bottom of 1000 m, the length of the shank 6 from its beginning to the end is 1000 m-450 m = 650 m. Thus, the stepwise movement of the GT column by 50 m at a speed of 1 m / s: from an interval of 450 m; 500 m; 550 m; 600 m; 650 m; 750 m; 800 m; 850 m, 900 m; 950 m; 1000 m, in each of these intervals, 0.2 m ^{3 of} 8% hydrochloric acid is injected. Total 10 intervals: 10⋅0.2 m ³ = 2 m ³ . Thus, in the horizontal part of the well 1 during the stepwise movement of the column GT 2 pump 2 m ³ . Next, they sell the volume of 8% acid pumped into the horizontal part 14 of well 1 into the bottom-hole zone 9 of fresh water formation 12 in a volume of 2 m ³ .

Thus, the uniform treatment of the bottom-hole zone 9 with acid over the entire length of the horizontal part 14 of the well 1 is ensured, which increases the processing efficiency and allows to increase the injectivity of the injection horizontal well 1 by 2 times in comparison with the prototype.

The quality of cleaning from the mud in the bottomhole zone of a horizontal well is improved by first starting the compressor, which aerates the fluid in the well, and then the pumping unit for supplying flushing fluid, which allows you to create a smooth depression on the formation, while controlling how the volume of fluid at the outlet trough capacity, and pressure in the annulus with a manometer.

Pumping flushing fluid with a pump unit with a flow rate of 2 l / s minimizes the absorption of fluid by the reservoir. All this in comparison with the prototype allows for the smooth development of a horizontal well drilled in bitumen deposits without absorption of aerated fluid by the formation or with its minimal losses.

The efficiency of cleaning the bottom-hole zone of a horizontal well is increased due to the fact that after removing the mud from the bottom-hole zone of a horizontal well, acid treatment is performed, while the volume of injected acid is evenly distributed along the entire length of the horizontal well in order to increase the injectivity of the formation.

The duration of cleaning the bottom-hole zone of a horizontal well from colmatant is reduced, since the cleaning takes place cyclically, not intervally, as described in the prototype, but along the entire length of the horizontal part of the well, this reduces the time for tripping.

The proposed method of cleaning and processing the bottom-hole zone of a horizontal well in a bitumen deposit allows you to:

- improve the quality of cleaning the bottom-hole zone of a horizontal well drilled in bitumen deposits by washing with aerated flushing fluid in several cycles along the entire length of the horizontal part of the well;

- to increase the efficiency of cleaning the bottom-hole zone of the well due to the processing of the bottom-hole zone with hydrochloric acid;

- reduce the duration of cleaning the bottom-hole zone of a horizontal well from the mud.

Claims (1)

A method of cleaning and treating a bottomhole zone of a horizontal well in bitumen deposits, including lowering a string of flexible pipes - GT and fixing the depth of descent, pumping aerated flushing fluid through the GT string, flushing the bottomhole zone from the clogging deposits and transporting them to a gutter, different the fact that the lowering of the GT string, equipped with a pear-shaped nozzle at the end, is carried out into the well to a depth of 50 m below the wellhead, a nitrogen compressor is launched into the GT string and the aeration of the flushing fluid located in the well is carried out while the GT string is drained to the depth of the start of the filter portion of the liner, then the pump unit is started with the flushing fluid supplied to the GT line, then the bottom-hole zone of the well is cleaned by flushing with aerated fluid in four cycles, each cycle consists of moving the GT column at a speed of 1 m / s to the bottom while flushing with aerated liquid; upon reaching the bottom, the movement of the GT column is stopped, the aeroir well is washed bath fluid for 30 min, then turn off the pump unit and nitrogen compressor, maintain a technological pause for 30 min, beat off the liquid level in the well with an echo sounder, then raise the GT string to a depth of 50 m below the wellhead, after which the cycle described above repeated three times, then the bottom-hole zone of the formation is treated by injection of 8% hydrochloric acid in the interval of the horizontal part of the trunk from the beginning of the filter part of the liner to the bottom of 0.2 m ³ for every 50 m followed by the sale of hydrochloric acid into the reservoir with fresh water.

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