RU2067167C1 - Method for gas recovery from gas-condensate formation - Google Patents

Abstract

FIELD: development of, mainly, gas-condensate and oil and gas-condensate deposits. SUBSTANCE: method for gas recovery from gas-condensate formation consists in stopping of operating well and cleaning of the formation and its neighborhood from hydrocarbon fluid by injection into formation of gas passed from the well with high formation pressure which is preliminary treated to separate dropping fluid without pressure drop. Gas injected into formation dissolves liquid hydrocarbon phase. Part of liquid hydrocarbon phase which has not been dissolved in gas is displaced by the injected gas along the formation from the hole bottom. Gas is supplied to well after separation at its own pressure. After treatment, well is operated again. EFFECT: higher efficiency. 1 cl, 2 dwg, 2 tbl

Description

 The invention relates to the field of field development, mainly gas condensate and oil and gas condensate.

 Known methods of producing gas from the formation, including increasing the permeability of the bottom-hole zone in order to increase the flow rate of gas in the wells and reduce depression on the formation by acid rock treatments, hydraulic fracturing, and sandblasting the bottom-hole zone (F.A. Trebin, Yu.F. Makagon, K. S. Basniev, Natural Gas Production, M. Nedra, 1976, p. 250-269).

 The closest to the proposed technical essence and the achieved result is a method of producing gas from a gas condensate formation, which includes shutting down a working well, cleaning the bottom-hole zone of a well from hydrocarbon liquid by supplying a solvent to the well and then putting the well into operation, and the formation is cleaned by injection into carbon dioxide reservoir for two days (R.M. Ter-Sarkisov, A.V. Nikolaevsky, B.V. Makeev. Accumulation of retrograde condensate in the bottomhole zone and its influence on the productivity of wells of the Astrakhan gas condensate field. M. Gas industry, 1993, pp. 23-25).

 The disadvantages of this method are the significant dilution of natural gas with carbon dioxide and, as a result, an increase in capacity for subsequent purification of natural gas, the need to build pumping stations in an anti-corrosion version for injection into the well, a small volume of the treated zone of the formation, since the injection of carbon dioxide takes two days .

 The invention is aimed at increasing the efficiency of cleaning the reservoir in the vicinity of the well from hydrocarbon condensate and reducing its cost.

 This problem is solved by the fact that according to the claimed method of producing gas from a gas condensate formation, including shutting down a working well, cleaning the formation in the vicinity of the well of hydrocarbon liquid by supplying a dissolving agent to the well and then putting the well into operation, gas released from wells with high reservoir pressure, which is previously subjected to separation from the droplet fluid without reducing the pressure, then under its own pressure ie the formation.

 Figure 1 and 2 shows the implementation scheme of the method.

 The diagrams show two wells with a large 1 and less than 2 reservoir pressure, a gas separator 3, a field assembly point 4.

 The method is as follows. Well 2 is put into operation with the minimum permissible pressure at the wellhead and is operated until the gas flow rate is stabilized. After that, well 2 is closed, gas from well 1 is supplied to device 3, where droplet liquid (hydrocarbon condensate and water) is separated from it, and separation gas is supplied to well 2 under its own pressure. Hydrocarbon condensate and water from device 3 are supplied to the field assembly point 4 (FIG. 1).

 The transfer of gas from well 1 to well 2 is due to the difference in wellhead pressures in the wells. In turn, the weight of the gas column in the wellbore leads to the fact that a significant difference in pressure is achieved in the separator and on the bottom of the well. When the separation gas enters the formation, its temperature also rises. At the same time, it is known that with increasing pressure in hydrocarbon gas condensate systems in the retrograde region, they become solvents of heavy fractions of hydrocarbon condensate (Stepanova G. S. Phase transformations of hydrocarbon mixtures of gas condensate fields. M. Nedra, 1974). Thus, due to the increase in pressure, the separation gas entering the formation dissolves the liquid hydrocarbon phase. The part of the liquid hydrocarbon phase, which is not dissolved in the gas, is displaced by the injected gas through the reservoir from the bottom of the well.

 After cleaning the formation in the vicinity of the well 2 from hydrocarbon fluid, gas production resumes from it (FIG. 2). After a decrease in well productivity to technologically permissible limits, a repeated treatment of the formation with separation gas is carried out.

 Example.

 An example is calculated for the wells of the Karachaganak gas condensate field. The productive stratum of the field is more than 1,500 m. During the operation of the field, the reservoir pressure in a number of wells that open the upper horizons of the fields (I object) decreased by 10 MPa or more. The reservoir pressure in the wells of the lower horizon (II object) remained at the initial level.

 Calculations were performed for well 328 and well 146.

 Well 328 reveals the productive stratum of the II facility in the range of 4558-5105 m. The measured current reservoir pressure is 53.8 MPa (initial pressure 55.5 MPa).

 Well 146 reveals the productive stratum of object I in the interval 3880–4047 m. The measured current reservoir pressure is 42.8 MPa (initial pressure 51.9 MPa).

 Based on geological information, measurements of formation and wellhead pressures and temperatures for well 328 and well 146, a mathematical model of an unpressurized gas bypass from well 328 through a separator to well 146 was constructed. A gas-condensate mixture from well 328 enters a high-pressure separator, where a droplet is separated from gas liquid. After that, gas separation (hereinafter referred to as gas) under its own pressure is supplied to the well 146. From table. 1 it can be seen that the reservoir pressure in the borehole 328 is sufficient to overcome pressure losses in the borehole and onshore equipment and to create repressions on the reservoir, which ensure injection of gas into the reservoir under its own pressure in a wide range of gas flow rates and bottomhole pressures.

 After treating the formation in well 146 for two months with separation gas, it is put into operation. In the table. Figure 2 shows the calculated gas production rates for well 146 in two versions without treating the formation with separation gas and after treatment (production rates for both options were calculated with equal depressions per formation). From a comparison of the options, it follows that after processing the gas flow rate increases by more than two times. The greatest effect is achieved in the first six months, after which it is necessary to re-treat the formation with a separation gas. TTT1

Claims (1)

 A method of producing gas from a gas condensate formation, including shutting down a working well, cleaning the formation in the vicinity of the wellbore of hydrocarbon fluid by supplying a solvent to the well and then putting the well into operation, characterized in that gas is used as a dissolving agent from the well reservoir pressure, which is previously subjected to separation from the droplet fluid without reducing the pressure, then under its own pressure is injected into the reservoir.

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