用新思路评价冀中坳陷深县凹陷油气勘探风险

在冀中坳陷深县凹陷古近系沙河街组三段油气成藏规律和成藏主控因素识别的基础上,建立了油气勘探风险评价参数体系及油气井和干井空间属性特征库。用马氏距离、模糊数学等数据集成方法以及贝叶斯概率模型,结合钻探成果,分别建立了两种集成方法及二者结合的含油气概率预测模板,对凹陷内各点的含油气风险概率进行了预测,实现了全凹陷含油气风险概率可视化。预测结果揭示出深县凹陷低幅构造、深西断阶、深南及衡水断阶等低风险勘探目标,从而为下一步勘探部署提供了重要依据。然而由于方法本身的特点,预测结果存在一些差异。马氏距离和模糊综合预测模板的预测准确率分别为73.7%和79%,二者相结合法准确率达86%。由于模糊评判法综合利用了所有成藏地质信息,在很大程度上代表地质有利性,它指明的低风险范围较大,增加了勘探风险;而马氏距离方法只选取能区分油气井、干井的有效地质因素,指明的有利范围较小,预测目标更具体,但它缩小了有利区范围,可能会遗漏部分勘探潜力区。

Risk assessment for oil and gas exploration with new approaches in the Shenxian Sag of the Jizhong Depression

A parameter system for exploration risk assessment and a spatial attribute property set of oil & gas wells and dry holes was created based on study of oil accumulation patterns as well as their main controlling factors in the third member of Shahejie Formation in Shenxian sag of Bohai Bay Basin.In combination with the drilling data,templates for exploration risk assessment were established by using data integration methods,such as Mahalannobis distance method and Fuzzy mathematics method,and Bayes probability model.They were used to predict and visualize the risk probability of exploration for every point in the whole sag.The results revealed several low risk targets: Shenxian low amplitude structure,Shenxi,Hengshui and Shennan fault terrace.This work offered important information for further exploration in this area.However,disparity exists in the prediction results because of the limitations of these methods.The accuracy of the above former two methods is 73.7% and 79% respectively,and that of the integrated method is 86%.Since the Fuzzy assessment method employs all the information that represents favorable geological conditions,the low risk areas predicted with it is relatively large,hence increasing the exploration risk.On the contrary,Mahalannobis distance method only selects effective geological factors that can distinguish the oil & gas wells from dry holes,the favorable exploration area it predict is relatively small and the targets are more accurate.However,it may miss some potential exploration areas.