玛湖凹陷风城组页岩油地质工程甜点地震预测方法及应用

Seismic Prediction Method of Geological and Engineering Shale Oil Sweet Spots and Its Application in Fengcheng Formation of Mahu Sag

为了进一步加快准噶尔盆地玛湖凹陷下二叠统风城组页岩油勘探开发进程,寻找页岩油赋存的甜点区。在明确地质甜点以岩性为主控因素,工程甜点以脆性指数和水平主应力差为主控因素的基础上,建立了基于叠前同时反演的地质工程甜点地震预测方法。在地质甜点方面,通过岩心、实验、钻井、测井等资料,明确了页岩油甜点优势岩性为白云质粉砂岩,优选出优势岩性敏感弹性参数,利用叠前同时反演和岩相概率分析技术,预测白云质粉砂岩的分布范围;在工程甜点方面,将叠前同时反演获得的杨氏模量和泊松比,通过Rickman脆性指数法和组合弹簧模型分别得到研究区脆性指数体和地应力体。预测结果与钻井实测结果相吻合,证实了地质工程甜点预测的准确性,可供其他地区页岩油气勘探参考。

In order to further accelerate the exploration and development for shale oil in the Lower Permian Fengcheng formation in the Mahu sag,Junggar basin,sweet spots of shale oil should be identified.Considering that lithology is the main factor controlling geological sweet spots,and brittleness index and horizontal principal stress difference are the main factors controlling engineering sweet spots,seismic methods of predicting geological and engineering sweet spots were established on the basis of prestack simultaneous inversion.In terms of geological sweet spots,by using core,experiment,drilling and logging data,the dominant lithology for shale oil sweet spots was identified to be dolomitic siltstone,the elastic parameters sensitive to the dominant lithology were selected,and the distribution of dolomitic siltstone was predicted by using prestack isimultaneous nversion and lithofacies probability analysis techniques.In terms of engineering sweet spots,using the Young’s modulus and Poisson’s ratio obtained from prestack simultaneous inversion,cubes of brittleness index and insitu stress for the study area were obtained through the Rickman brittleness index method and a combined spring model.The predicted results are consistent with the actual drilling results,which confirms the accuracy of the prediction of geological and engineering sweet spots.The proposed methods can provide references for shale oil exploration and development in other areas.