海上特低渗碳酸盐岩油藏酸化效果分析

Acidification effect of offshore ultra-low permeability carbonate reservoir

针对海上某油田奥陶系潜山特低渗碳酸盐岩油藏,储层物性差,常规DST测试无产能,又难以实施人工压裂或酸压措施的问题,从油藏储集空间特点出发,提出利用酸化作业在储层中建立酸蚀人工裂缝、沟通天然微细裂缝和孔隙、改善储层渗流条件等措施,提高油井产能。经实施2口井酸化作业,酸化后日产油均达100 m3左右,且产油量稳定。分析酸化施工曲线以及试井曲线特征,选用"井筒储存+无限导流+均质油藏+无限大地层"的试井模型进行拟合,得到井筒及储层物性的各项参数,表明酸化作业能够有效沟通储层中的天然微细裂缝和孔隙,起到人工压裂或酸压措施同样的增产效果,是提高此类特低渗碳酸盐岩油藏产能的有效措施。

For the Ordovician buried-hill ultra-low permeability carbonate oil reservoir in an offshore oilfield,which is characterized by poor physical properties,the conventional DST reveals no production,and artificial fracturing or acid fracturing is infeasible.According to the characteristics of reservoir space,this paper put forward some measures such as acidizing the reservoir to create induced fractures,communicating natural micro-fractures and pores and improving reservoir seepage conditions,so as to improve the well productiv ity.The acidizing operation was carried out in 2 wells,revealing the stable daily oil production of 100 m^3.By analyzing the characteristics of acidizing curve and well test curve,and matching with the well test model of"wellbore storage+infinite conductivity+homogeneous reservoir+infinite thick layer",the parameters of wellbore and reservoir physical property were obtained.The results show that acidizing operation can effectively communicate the natural micro-fractures and pores in the reservoir,with the same effect as artificial fracturing or acid fracturing.Therefore,acidification is an effective measure to improve the productivity of such ultra-low permeability carbonate reservoirs.