大牛地气田低孔低渗气藏合采时机分析

Analysis on Optimal Time of Commingled Production in the Low Permeability and Porosity Gas Reservoir

低孔低渗气藏多采用合采的方式开采,但合采会降低气藏采收率。为了确定最佳合采时机,提高合采时的采收率,针对大牛地气田各气层原始地层压力接近、低孔、低渗的特点,进行了长岩心并联试验,模拟气藏合层开采时的产气特征,通过绘制流压与采收率的关系曲线,对比了在不同合采时机下层间压力差和物性差异对最终采收率造成的影响。研究表明,具有此类特点的气藏的最佳合采时机为生产初期,在此时期能够取得较高的采收率;当存在层间压力差后再合采,高压层的物性越差,对采收率的影响越小,反之,高压层的物性越好或是与低压层的物性越接近,其对采收率的影响越严重。作者结合实际生产数据分析,证明了结论符合现场生产情况,具有较高的可靠性,可用于指导现场生产。

The commingled production was mostly used in the low permeability and porosity gas reservoirs.But it would reduce the recovery percent.In order to determine the optimal time and improve the recovery,aiming at Daniudi Gas Reservoir characteristics of pressure being close,low permeability and low porosity,long core parallel experiment was conducted to simulate the multilayer commingled production of the gas reservoirs,we painted curves of flow pressure and recovery ratio were plotted and the ultimate recoveries affected by different pressure and physical property were compared in the case of diverse time of multiple-zone commingled production.Finally the optimization time was determined.The experimental results indicate that the optimization time is the initial period of production.In this period high recovery can be obtained.When pressure difference is induced between layers,it would have a less impact on oil recovery with poor physical property of high-pressure layers.Contrarily it would have a greater impact on oil recovery.It is agreed with the field production and reliability is high.