RU2134773C1 - Method of gas recovery from water-bearing bed - Google Patents

Abstract

FIELD: gas and oil production industry. SUBSTANCE: method is used in development of oil and gas deposits and also in recovery of mineral water from water-bearing beds and sea bottom for technical and medical purposes. According to method, gas and degassed water are taken through string of pump-compressor pipes with lifting of bed water up to well head by means of immersed pump. Lowered into well is second internal string of pump-compressor pipes. Secured in its lower part from external side coaxially is additional pump-compressor pipe with blind bottom at distance of 0.2-0.3 m from shoe of internal string. Degassed water is recovered continuously through internal string of pump-compressor pipes. Gas is taken through annular space between external and internal strings of pump-compressor pipes. Brine water is delivered into annular space between coaxially secured additional pump-compressor pipe and internal string of pump-compressor pipe at speed less than speed of emersion of gas bubbles. Application of aforesaid method ensures increased recovery of gas from well. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to the gas industry and can be used in the process of developing gas and oil fields, as well as in the extraction of mineral water from aquifers and the seabed for technical or therapeutic purposes.

 A known method of producing gas from an aquifer, involving the production of produced water from an aquifer at an increased rate of withdrawal [1].

 The disadvantage of this method is that for the delivery to consumers of gas extracted together with produced water from the wells, significant energy costs for its compression are required.

 A known method of producing gas from an aquifer, including the degassing of water in tubing after raising the reservoir water to the mouth by means of a downhole pump and returning the water to the aquifer when the downhole pump is turned off, with sequential separate extraction of gas and degassed water from the well when starting up in the operation of the deep pump, after which the cycle is repeated [2].

 The disadvantage of this method is that due to the periodic shutdown of the downhole pump for a certain time, the amount of produced water and gas extracted from the well is reduced, respectively. In addition, the known method can be applied under conditions that the static level of produced water is at a considerable depth below the wellhead.

 To increase gas extraction from a well in the known method of producing gas from an aquifer, which includes taking gas and degassed water through a tubing string while raising reservoir water from the wellhead using a downhole pump, a second inner tubing string is lowered into the well to a certain depth pipes, in the lower part of which, from the outside, an additional tubing with a blind bottom is coaxially fixed at a distance of 0.2 - 0.3 m from the shoe of the inner column, degasser selection bath water during the operation of the deep pump is produced continuously along the inner column of tubing, and gas through the annular space of the outer and inner tubing columns, while the formation water into the annulus between the coaxially fixed additional tubing and the inner tubing string -compressor labor is fed at a speed less than the rate of rise of gas bubbles.

 When the formation water is raised using a deep pump to the wellhead through the inner column, a downward flow of the selected fluid is established in the annulus of the additional pipe and the inner column. Since the hydrostatic pressure in the installation interval of the additional pipe is much lower than the reservoir pressure, the bulk of the dissolved gas at this depth is degassed from the reservoir water and is in the form of free gas bubbles.

 As a result of the movement of produced water in the annular space of the additional pipe and the inner column from a lower speed, the gas bubbles rise up, gas is separated, with its accumulation in the annular space between the outer and inner columns. Therefore, the pressure at which gas is supplied from the well to the pipeline depends on the installation interval of the additional pipe.

 The method of gas extraction from an aquifer is illustrated in the drawing and is carried out as follows.

 A well pump 2 is lowered into the well 1 filled with produced water on the tubing string 3. Then, the inner string of tubing 4 is lowered to a certain depth into the well at a certain depth, in the lower part of which an additional tube 5 with a dead bottom is fixed. After that, the wellhead is tied with a water line 6 with an adjustable fitting 7 and a gas line 8 with an adjustable shut-off valve 9. An annulus 10 is connected to a gas line 8, on which a shut-off valve 11 is installed.

 After starting the operation of the deep pump 2 using the adjustable nozzle 8 set the desired flow rate of degassed water. The shutoff valves 9 and 11 are adjusted to a certain pressure at which the liquid level in the annular space should be above the coaxially located pipe 5.

For example, in the Cenomanian well of the Urengoy field, an aquifer that has opened at a depth of 1110 - 1130 m with a production string with a diameter of 219 mm and a wall thickness of 10.2 mm is lowered into 1100 m by a depth pump on tubing with a diameter of 168 mm and 8.9 mm. The second lift column with a diameter of 73 mm is lowered to a depth of 55 m, in the lower part of which an additional 5-6 m pipe is fixed with a diameter of 127 mm with a wall thickness of 6.4 mm. The deaf bottom of the additional pipe is installed 0.2 m lower from the shoe of the inner column for free passage of formation water from the annulus to the inner column. In the range of location of the coaxially located pipe, the areas of annular free spaces between the pipes, taking into account the wall thicknesses, are:
- between 168 mm column and 127 mm additional pipe - 5119 mm ² ,
- between 73 mm column and 127 mm additional pipe 6054 mm ² ,
- inside 73 mm of the column - 3018 mm ² .

Since the average ascent rate of gas bubbles in the water is about 27 m / s, the fluid flow rate is set at a level not higher:
Q = 6054 • 2700 = 16345800 mm ³ / s = 1412.3 m ³ / day.

When the formation water moves from the bottom of the well to the upper end of the additional pipe, the pressure in the moving fluid stream decreases from the reservoir pressure of 7.0 MPa to 0.5 MPa, which will lead to almost complete degassing of the dissolved gas from the produced water. With an average dissolved gas content of 3 m ³ / m ³ in the Cenomanian water of the West Siberian megabasin, the gas production rate will reach up to 4.2 thousand m / day, with a wellhead gas pressure in the annulus of up to 0.5 MPa

The maximum gas saturation of formation water in oil and gas basins at a depth of 3-4 km reaches 8 m ³ / m ³ and higher. Therefore, when pumping large volumes of water from a well with an increased diameter of production casing, gas extraction will be comparable to the productivity of production gas wells in individual gas fields. If at the same time the second column of tubing is installed at a depth of 200 - 300 m, then the pressure of the extracted gas at the wellhead can reach 2.0 - 3.0 MPa.

 Most effectively, the invention can be used in oil and gas fields, where production wells, after flooding, are usually subject to liquidation. When applying the new method, the gas recovery coefficient will increase at the last stage of the development of gas, gas condensate and oil fields. With the intensive withdrawal of produced water from waterlogged wells together with dissolved gas, trapped and localized natural gas will be extracted from gas deposits.

 Using the proposed method, it is possible to efficiently extract, if necessary, dissolved gas from the sea and ocean depths, for example, hydrogen sulfide from the Black Sea.

Sources of information:
1. Application of France N 7724416, E 21 B 43/00, 1977.

 2. USSR author's certificate N 1553655, E 21 B 43/00, 1990.

Claims (1)

 A method of producing gas from an aquifer, including the extraction of gas and degassed water through a tubing string while raising reservoir water to the wellhead using a downhole pump, characterized in that the second inner tubing string is lowered to a certain depth into the well, the lower part of which, from the outside, an additional tubing with a blind bottom is coaxially fixed at a distance of 0.2 - 0.3 m from the shoe of the inner column, the selection of degassed water during operation of the depths A pump is produced continuously along the inner string of tubing, and gas is produced through the annulus of the outer and inner tubing strings, while formation water is fed into the annulus between the coaxially fixed additional tubing and the inner tubing string. at a speed less than the rate of rise of gas bubbles.