RU2067171C1 - Method for study of producing formation in natural pressure gas-lift well operation - Google Patents

Abstract

FIELD: development of, mainly, gas-condensate and oil gas-condensate deposits, particularly gathering the initial information required for evaluation of efficiency of cycling process in the deposit. SUBSTANCE: invention consists in natural pressure passing of gas between wells exposing the objects of development with different formation pressures. Prior to supply of gas to injection well, dropping fluid is separated from it in the high-pressure separator. Separated gas is injected into formation allows modelling of all main processes involved in cycling process: dynamics of formation pressure, repression on the formation, water-oil-condensate saturation of reservoir, and required measurements of parameters of gas injection:pressure and temperature in well and in formation, and compositions of injected and produced gases and fluid. EFFECT: higher efficiency. 1 dwg

Description

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

 When developing gas condensate fields while maintaining reservoir pressure by recirculating the separated gas (cycling process), a preliminary assessment of the effectiveness of its implementation is carried out (Shmygla P.T. Development of gas and gas condensate fields, M. Nedra, 1967, p. 203, 206). To carry out such calculations, initial data on injectivity of injection wells, coverage of the formation by the displacement process, changes in oil and gas condensate saturation of the formation, dynamics of formation and bottomhole pressures, and production composition of production wells are necessary. For this purpose, both direct and indirect methods are used.

 The indirect methods are based on the use of research data from producing wells and reservoir properties of rock samples taken from a productive reservoir. The use of such data and experience in the development of deposits by using the cycling process allows us to assess the effectiveness of the cycling process in this field based on existing mathematical models.

 Direct methods include laboratory studies of the processes of displacing formation fluid with dry gas from rock samples taken from a productive reservoir.

 However, such an assessment of the effectiveness of the cycling process based on existing methods is very approximate, especially for deep-seated deposits with low permeability reservoirs, and should be tested during gas injection into the reservoir. For this purpose, a differential pressure of the reservoir between different development sites can be used for uncompressed gas bypass between the wells. The prototype of the claimed is a method of maintaining reservoir pressure in an oil reservoir, which consists of uncompressed injection of gas into an oil reservoir from underlying gas-bearing objects by creating inter-layer gas flows through wells drilled on the lower gas-bearing object (Aut. St. USSR N 1239276, class E 21 V 43 / 18, op. 1986).

 The disadvantage of this method is that it cannot be used if the development objects are spaced horizontally, injecting gas without separating droplet hydrocarbon condensate from it leads to its loss in the formation, it is difficult to control and regulate the injection process, conduct well research, and the presence of droplet fluid leads to an additional decrease in pressure when gas enters the reservoir.

 The purpose of the invention is to obtain reliable source information necessary for evaluating the effectiveness of the cycling process and calculations for its implementation, in a simple and reliable way.

 The goal is achieved by the fact that in the known method of maintaining reservoir pressure, including uncompressed injection of gas by creating inter-layer flows between the objects being developed, the gas is passed between two or more wells, the injected gas is further separated on the surface from the droplet hydrocarbon condensate and the volume of gas separated is measured gas is supplied through an injection well into the formation. In the process of injection, production rates and injectivity of injection wells, dynamics of changes in reservoir and wellhead pressure, flow rates of produced and injected gas, hydrocarbon fluid and water, compositions of produced and injected gas, pressure loss in the reservoir-well gas-gathering system are measured.

 As the gas moves along the wellbore, its entry into the formation increases the pressure and temperature of the gas. As a result of the increase in pressure and temperature of the gas with respect to their values at the wellhead, the gas becomes an unsaturated droplet of hydrocarbon condensate. Drop hydrocarbon condensate in the liquid phase in the reservoir begins to dissolve in the injected gas. Thus, the proposed method allows you to simulate the method of maintaining reservoir pressure by injecting the separated gas into the reservoir and obtain the initial information necessary for its implementation.

 The drawing shows a diagram of uncompressed gas bypass between wells.

 The method is as follows. A pair of wells 1, 2 (drawing) with different reservoir pressures is selected. High pressure well 1 high pressure gas source. In 2, the reservoir pressure should be lower by an amount sufficient to overcome pressure losses in tubing, surface equipment, the bottomhole zone of wells and create repression on the reservoir in 2, necessary for pumping gas into the reservoir. If necessary, reservoir pressure of 2 is further reduced by taking gas from it.

 Gas-hydrodynamic and gas condensate studies are preliminarily carried out in 2 (Instruction for a comprehensive study of gas reservoirs and gas condensate wells, M. 1980). Then the gas from 1 is fed into the device 3 (gas separator), where there is a separation of the droplet liquid from the gas. Next, the separated gas is supplied to 2, and the condensate to the gas and condensate collection point of the field 4.

 In order to dry the bottom-hole zone of the injection well from hydrocarbon fluid and to reduce pressure losses in it when the gas moves into the formation in the initial period, gas is pumped alternately with its extraction with increasing volumes of gas. Then the gas injection is carried out in full (until the hydrodynamic stability of work 1 is lost). If necessary, gas is injected alternately with stops to stabilize (lower) the bottomhole pressure.

 In the process of injection through the injection well, the dynamics of gas flow rate, wellhead and bottomhole pressure, wellhead and bottomhole temperature are measured. During the stop period, the dynamics of the bottomhole pressure decrease is measured. Using the injection of indicators, the oil and gas condensate saturation of the reservoir is determined by a known method (ed. St. USSR N 1514918, class E 21 B 47/00, op. 1989. During the period of gas extraction from the same injection well, the flow rate and component composition of gas and liquid, bottom-hole are measured pressure and temperature. In the process of gas injection and sampling, the gas injection and gas inflow profiles are measured over the productive opening interval using the methods of thermometry, noise metering, and debitometry. In nearby production wells, gas production rates are measured during the injection basics and liquids and determine their component composition, measure bottomhole and wellhead pressures and temperatures 5 (drawing).

 Using the proposed method for studying productive formations, based on the obtained initial data on the injectivity of injection wells, the coverage of the formation by the displacement process, changes in oil and gas condensate saturation, the dynamics of formation and bottomhole pressures, the composition of production of producing wells, the parameters of the calculated mathematical models of the cycling process can be clarified and its effectiveness evaluated using these models.

Claims (1)

 A method for studying productive formations during unpressurized operation, including uncompressed gas bypass between the development sites with pressure measurement at the wellhead, characterized in that the gas is passed between the wells with the separation of condensate in the high-pressure separator, and the gas bypass is carried out alternately with increasing selection volumes with subsequent injection of gas in full, while in the process of injection and selection measure the injectivity of the discharge and flow rates of nearby production wells, dynamics of changes in formation, bottomhole and wellhead pressure, flow rates and composition of injected and produced gas, hydrocarbon fluid and water, pressure loss in the reservoir-well gas-gathering system and, based on the measurement results, simulate a cycling process.