Reservoir Note Hydrocarbon Gas Eor Numerical Simulation Study

As one of the important methods to enhance oil recovery, gas injection has been paid more and more attention. Recently, the proportion of oil production through gas injection in EOR yield is rising rapidly. Hydrocarbon gas injection method was proposed as a measure to maintain reservoir pressure, because it will not be any effect with the reservoir rock, so will not pollute the reservoir, and the injection gas can be recycled, therefore, it can be used as a storage method for future needs. In addition, the injected gas can effectively eliminate the interfacial tension and capillary pressure and minimize the residual oil saturation. X reservoir has the characteristics such as severe heterogeneity, high volatility and rich gas source. Under the condition that water injection is hard and development result is far from satisfactory, the study on injecting associated gas drive has great significance. Based on the EOR theory of miscible gas injection and oil-gas reservoir numerical simulation technique, this paper took G20 well area as the test area, discussed the oil reservoir EOR by injecting associated gas using numerical simulation software. The works and achievements are as follows:1. The mechanisms of gas drive such as FCM, multi-contact miscible flooding and immiscible flooding, the effect factors on the result of gas injection and screen criterions of hydrocarbon gas flooding reservoir were discussed deeply.2. Based on the fundamental theory of three-dimensional and three-phase multi-component model, the partial differential equation of flow in porous medium was derived and the corresponding difference equations was established, the resolution approach was given. At the same time, the phase equilibrium theory and the physical properties parameters calculation have been studied, which lays a good theoretical foundation for the use of compositional model.3. The phase behavior of fluid in G20 reservoir was matched which determined the features of oil reservoir and changes in components. Through slim tube experimental simulation, the MMP of injecting associated gas is 14.8MPa, which demonstrated that associated gas drive is suitable to this reservoir, and the result of gas injection is satisfactory.4. Four flooding methods of long core displacement experiments of high permeability core and low permeability core were discussed by numerical simulation respectively. The results show that, the oil well has least production after water flooding breakthrough; the oil well has large production after gas breakthrough by gas drive and WAG drive. For the high permeability cores, the displacement characteristics is the best by water and associated gas alternative drive, and the oil recovery enhanced by 27.81% than water flooding. For the low permeability cores, the displacement characteristics is the best by associated gas pulse injection drive, and the oil recovery enhanced by 31.65% than water flooding.5. The reserves and production history matching have been studied. By correcting the geological model and fluid physical parameters, the remaining oil distribution was determined. History matching show that, up to December 2009, due to injection and production uneven, the formation pressure decrease rapidly in the five development area, the average pressure close to the bubble point pressure. Particularly in District No.1, the most dissolved gas in crude oil emerge, and the difference between reservoir pressure and saturation pressure is small, the GOR will increase fleetly and the productivity will decrease rapidly once the pressure can't be maintained. So, the initial water flooding can't suitable to it. In order to utilize abundant gas resources, the feasibility study of injecting associated gas drive to this area is necessary.6. The reasonable developing technical indicators of associated gas injection drive in the injection and production well group have been demonstrated. The simulation results show that:â‘ maintaining reservoir pressure to 11 MPa, the displacement characteristics is the best by water and associated gas alternative drive, and the oil recovery enhanced by 6%-8% than water flooding. Once the formation pressure up to 15MPa above, the oil recovery by water and associated gas alternative drive enhanced by 8%-13% than water flooding;â‘¡there has 10 water and gas alternative slug by well group optimization, and the slug size is 0.01-0.02HCPV, which need 10 years to water and gas alternative by the interval of 6 month;â‘¢The water and gas alternative flooding should be implemented early as soon as possible;â‘£With the increase of injection gas composition's enriching degree, the development indicators become better and the oil recovery enhanced.