一种计算致密砂岩油气藏有效孔喉下限的新方法——以苏里格气田盒8气藏为例

A New Method to Calculate the Lower Limit of Effective Pore Throat Threshold of Tight Sandstone Reservoirs:A Case Study of He-8 Gas Reservoir in Sulige Gas Field

鉴于压汞实验过程与油气充注成藏过程相类似,认为在密闭取心样品毛细管压力曲线上,与密闭取心样品含油气饱和度相等的进汞饱和度毛细管压力相对应的喉道半径为油气藏有效临界孔喉半径,具有代表性的密闭取心样品中最小的有效临界孔喉直径为油气藏有效孔喉下限。提出了一种准确、快捷计算致密砂岩油气藏有效孔喉下限的新方法,分析讨论了目前求取有效孔喉下限主要方法的优势及其局限性。以苏里格气田盒8气藏为例,采用密闭取心样品毛细管压力曲线法,求取的盒8气藏有效孔喉半径下限约为53.3 nm,由大于此喉道半径连通的孔隙体系才是勘探开发的主要对象。

Because the mercury injection process is similar to that of hydrocarbon charging and accumulation,it is considered that thethroat radius corresponding to the capillary pressure of mercury injection saturation which equals to hydrocarbon saturation of sealed-cor-ing samples should be the effective pore throat radius threshold on the capillary pressure curves of sealed-coring samples,and the mini-mum effective pore throat diameter threshold in representative sealed-coring samples is the lower limit of effective pore throat of the reser-voir.The paper proposes a new method to calculate the lower limit of the effective pore throat threhold of tight sandstone reservoirs accu-rately and rapidly.It also discusses and analyzes the advantages and limitations of the current methods.Taking He-8 reservoir of Sulige gasfield as an example and based on the method of capillary pressure curve of sealed-coring samples,the obtained effective pore throat thre-hold of He-8 reservoir is 53.3 nm.Therefore,it is concluded that the pore systems connected by the pore throat with the radius more than53.3 nm will be the main targets for exploration and development.