深层致密砂岩气藏有效储层的分类评价方法

Classification and Evaluation of Effective Reservoirs in Deep Tight Sandstone Gas Reservoirsin

深层致密砂岩有效储层的分类评价是致密砂岩气藏评价的重要环节。致密砂岩由于孔渗极低,且资料的品质难以保证,利用物性参数评价储层品质存在着一定的局限性。依据油气藏充注理论,结合储盖组合关系,利用研究区毛管压力资料,结合地层有效应力数据,建立了目的层的砂、泥孔喉半径计算模型,在此基础上利用聚类分析和正态统计方法,建立了有效储层的判别标准。研究认为,致密砂岩的有效储层与相邻盖层之间存在着较大的毛管压力差,即砂泥孔喉比大。研究区有效储层的砂泥孔喉比界限值随深度的增加而有增大的趋势,且储层质量越好,砂泥孔喉比越大。实际资料应用表明,利用砂泥岩孔喉半径比值能够有效地指示储层的有效性,通过与测试产量对比,所建立的储层分类划分标准能够对研究区有效储层进行分类划分。

Classification and evaluation of effective reservoirs in deep tight sandstone is an important step in tight sandstone oil and gas evaluation.Due to the extremely low porosity and permeability of tight sandstone and the difficulty in guaranteeing the quality of the data,there are some limitations in the evaluation of reservoir quality by physical property parameters.According to the theory of reservoir filling and the combination relationship between reservoir and cap,based on the capillary pressure data of the study area and the effective stress data of the stratum,the calculation model of pore throat radius of sand and mud in the target stratum is established.It is considered that there is a large capillary pressure difference between the effective reservoir of tight sandstone and the adjacent cap,that is,the ratio of sand to mud pore throat is large.The limit value of sand/mud pore throat ratio of effective reservoir in the study area tends to increase with the increase of depth,and the better the reservoir quality is,the bigger the sand/mud pore throat ratio is.The application of practical data shows that the ratio of pore throat radius of sand and mudstone can effectively indicate the effectiveness of the reservoir,and the established reservoir classification criteria can be used to classify the effective reservoir in the study area by comparing with the tested output.