低渗透储集层中油水层的地球化学综合判识——以济阳坳陷基山砂岩体为例

为了提高低渗透油藏油、水层识别的准确性，以济阳坳陷惠民凹陷基山砂岩体低渗透油藏为研究对象，探索以地球化学方法综合判识储集层流体性质的方法。以试油数据为参考，首先以热解定量方法初步评价，油层与油水同层、油水同层与水层的ST界限分别定为4．00mg／g及2．00mg／g；再以热解色谱定性方法将水层（或干层）与油层及油水同层明确区分；仍不能有效区分的油层及油水同层，则辅以热解参数表征的储集层变异系数进一步评价，变异系数高于0．3的为油水同层，低于0．3的为油层。具单一油源的多口井，可借助菲与二苯并噻吩（P／DBT）将油层及油水同层准确识别，P／DBT值大于12．5则为油层、小于等于12．5则为油水同层。对于相变较快，泥质薄层较多的低渗透油藏，利用热解参数S1／S2可评价储集层的真假隔层及油柱的纵向连通性。图4参17

Synthetic geochemical identification of oil or water layers in low permeability reservoirs: A case from Jishan sandbody, Jiyang Depression

Taking the low permeability reservoirs in the Jishan sandbody of Huimin Sag, Jiyang Depression as examples, together with limited data of well tests, the geochemical evaluation method for the reservoirs has been proposed as follows. Firstly, Rock-Eval provides hydrocarbon-content information to determine sketchily oil layers, water layers and oil-water layers, and the marginal values of ST are 4.00mg/g and 2.00mg/g respectively. Secondly, Pyro-GC is used as a supplementary tool to identify water layers. Thirdly, either variation coefficient calculated from the Rock-Eval data or P/DBT parameter from the GC-MS data is available to distinguish oil layers from oil-water layers. The variation coefficient values of oil-water layers are more than 0.3 and those of oil layers are less than 0. 3. The P/DBT ratios of oil-water layers are less than 12. 5 and those of oil layers are more than 12.5. The pyrolitic parameter S1/S2 can be used to distinguish genuine and sham barrier beds and evaluate the connectivity of oil columns for reservoirs with fast phase change and many muddy thin beds.