The Feasibility Study Of Air Injection In C9 Low Permeability Reservoirs

In the C9 well area,the average permeability of the Xishanyao is 10 mD,which belongs to the low permeability reservoir and micro fracture development in the area.Since the beginning of 1993 water injection,after 20 years of development,the oil field has gone through the stage of production capacity construction,high and stable production stage,rapid decline phase,well pattern adjustment phase and comprehensive management stage.At present,many problems are exposed:oilfield injection production wells can not form an effective displacement system,water can not be injected,resulting in uneven distribution of pressure.In order to alleviate the contradiction between the injection production well and infill well pattern,but because the area of the micro crack growth,resulting in serious water breakthrough,a large number of production wells because of high water cut and shut in,the development status confronted with severe problems.Firstly,aiming at the above problems,the air injection feasibility study is proposed,analyze from the matching degree of reservoir fluid conditions and air injection selection criteria interlayer conditions to prevent gas channeling adaptability,formation dip adaptability,the mineral composition effect on the low temperature oxidation reaction.It is considered that this area are fit for air injection development.Secondly,numerical simulation to predict the potential of tapping the remaining oil.According to the geologic features of the blocks,we build up the 3D geological model.On the basis of geological model,the numerical mode which can fit the data of oil well production history has been set up.The remaining recoverable reserves and remaining oil distribution are obtained by numerical simulation.The distribution of residual oil shows that the oil saturation of J2X12-2 and J2x13-1 is higher,but the J2x13-2 and J2x14 layers have a higher degree of water flooding.Prediction of remaining recoverable reserves of 21.6×104t,with further tapping potential.Lastly,set up the air displacement numerical model and complete parameter optimization.The simulation results show that the air injection development is obviously better than that of water flooding;Because the construction of a small dip,gas injection position has an effect on the cumulative production;Gas-water injection alternating cycle has little effect on oil production;By optimization of gas injection,single well gas injection in 22000m3/d oil was the highest,that of single well gas injection best at about 22000m/d;The higher the oxygen content in the air,the greater the amount of oil production.In order to take into account the safety of production,while obtaining the maximum oil production,consider reducing oxygen to 10%production.The economic evaluation shows that when selecting the single well gasinjection in the 22000m/d development,the block can recover the cost in second years,air drive development can get a larger profit.