| The Toputai block of Tahe Oilfield is a carbonate fracture-cave reservoir with a depth of more than 5000m,a formation temperature of 130?,a reservoir pressure of 60-70 MPa,and a current recovery of 5.5%.Due to the lack of energy in the reservoir,the annual natural decline has reached 22%.The rapid decline of energy is the main reason for the decline.The efficiency of water injection in the early block is only 35.5%,and the better wells are mainly distributed near the oil-rich enrichment.However,the reservoirs in the secondary fault zone are poorly developed,the energy attenuation is fast,the water injection is difficult to maintain the pressure,and the production effect is poor.Based on the investigation of the reservoir and production history of the target block,this paper selects the typical well TP 101 as the target well,and according to the on-site gas-oil ratio self-matching live oil,the high-pressure physical property test of the target oil sample and the swelling test of CO2,natural gas and crude oil are carried out.The PVT software was used to fit and further analyze the swelling and viscosity reduction effect of different injection gases on crude oil in high temperature and high pressure environment.The minimum miscibility pressure of CO2/natural gas-target block crude oil was determined by thin tube experiment,and the improved mixed phase pressure model was used for prediction.The self-developed rotatable multi-slot-hole filling model and high-temperature and high-pressure indoor throughput equipment are used to carry out the throughput experiments on different wells and different injection gases,preferably injecting gas and injection-injection wells,and analyzing the mechanism of gas injection and throughput in carbonate fractured reservoirs.Through the numerical simulation study,the sensitivity analysis of gas injection time and well time was carried out,and the gas injection efficiency mechanism of fracture type weak energy oil well was analyzed in depth.The results show that the crude oil in the Topotai block has good swelling and viscosity reduction ability with CO2 and natural gas,which is beneficial to increase the productivity.Through the indoor thin tube experiment,it is determined that the minimum miscible pressure(MMP)of crude oil and CO2 in Toppu block is 30.1 MPa,and the MMP of natural gas is 47.6 MPa,which is less error with the prediction of improved miscible pressure model.The gas injection and puff test shows that the throughput is closely related to the type of injected gas and the injection well location.Natural gas is used as the injection.The gas effect is better than CO2.The effect of the well production under the bet is better than the horizontal injection and production increase.The numerical simulation results show that the prolonged gas injection time and the well time are beneficial to increase the oil production per well. |
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