致密砂岩储层油充注下限综合确定方法及其应用——以鄂尔多斯盆地马岭地区长8油藏为例

Comprehensive determining method of the lower limit of the oil-charging in tight sandstone reservoirs and its application:A case of Chang-8 oil reservoir in Maling area of Ordos Basin

致密砂岩储层束缚水饱和度高、束缚水膜厚度相对较厚,实验条件过于理想,使得计算孔喉半径下限不能代表真实储层孔喉半径下限,制约了致密油生产开发。利用高压压汞、核磁共振以及录井、试油等多种资料,求取储层条件下束缚水膜厚度,对比实验与储层条件的差异,综合确定致密砂岩储层条件下的充注下限,并结合生产资料对求取结果进行验证。结果表明:研究区储层束缚水膜厚度为9.88~95.98 nm,平均为58 nm,综合确定长8储层孔隙度下限为6.35%,渗透率下限为0.0491×10^-3μm^2,孔喉半径下限为0.077μm,求取结果与实际生产资料相吻合。该研究考虑了束缚水膜对储层充注下限的影响,对传统方法进行了修正,计算结果更加符合实际储层的充注条件,为致密油生产开发方案制定提供了可靠依据。

Tight sandstone reservoirs have rather high irreducible water saturation and relatively thick bound water film,and the experimental conditions are too ideal,which make the calculation of the lower limit of the pore throat radius not represent the lower limit of the real reservoir pore throat radius,thus the development and production of the tight oil is restricted.By means of the high pressure mercury injection,nuclear magnetic resonance,mud logging,oil testing data and so on,the water film thickness was managed to obtain under the conditions of the reservoirs,comparing the differences between the experimental and reservoir conditions,the oil-charging lower limit under the conditions of the tight sandstone reservoirs was comprehensively determined,and moreover the obtained results were verified with the help of the production data.The results show that the thickness of the reservoir water film in the study area is 9.88-95.98 nm,with the average of 58 nm,the comprehensively determined lower limit of the porosity of Reservoir Chang-8 is 6.35%,the lower limit of the permeability is 0.0491×10^-3μm ^2,and the lower limit of the pore throat is 0.077μm,the obtained results are consistent with the actual production data.The study results consider the influence of the bound water film on the lower limit of the reservoir filling,and modify the traditional method,the calculated results are more in line with the actual reservoir filling conditions,thus the reliable evidences have provided for the development and production plans of the tight oil.