四川盆地东部卧龙河地区中二叠统茅口组白云岩岩石物理特征及分布预测

Petrophysics characteristics and distribution prediction of Middle Permian Maokou Formation dolomites in Wolonghe block,eastern Sichuan Basin

白云岩作为优质储层具有巨大的潜在经济价值,但在复杂构造背景下的白云岩地震预测方法尚不完善。为此,以四川盆地东部卧龙河地区中二叠统茅口组白云岩钻井岩心资料为基础,结合三维地震勘探资料研究该地区茅口组白云岩地质—地球物理特征规律,并基于岩石物理分析采用叠前同步反演有效预测了白云岩有利发育区。研究表明:①将纵波阻抗Z_p和V_p/V_s属性作为区分白云岩与灰岩的敏感属性,两者融合得到的白云岩指示因子(DIL)分布预测指示卧龙河构造中轴部及偏东的区域为该区茅口组白云岩的最有利发育区,预测结果与实际井情况吻合度高;②该区茅口组白云岩普遍发育于断裂两翼,越靠近断裂位置其厚度越大,且构造下盘白云岩厚度受地层倒转影响小于上盘部位。

Dolomite is a high-quality reservoir,and has great potential economic value,but its seismic prediction methods in the case of complex tectonic are not perfect yet.Therefore,on the basis of the drilling core data,the geological and geophysical characteristic regulations of Maokou Formation dolomites are studied by the three-dimensional seismic exploration data.Basedon petrophysical analyses,pre-stack simultaneous inversion was effectively carried out to predict the favorable development area.The study shows that:(1)Pwave impedance Z_p and the ration V_p/V_s attributes are the sensitive attribute for distinguishing dolomite from limestone.The distribution prediction of dolomite indicator(DIL)obtained by the integration of them show that,the central axis and the eastward area of the Wolonghe structure are the most favorable development area,and the prediction results highly accord with actual data.(2)Maokou Formation dolomite generally developed on the two wings of the fault,and the larger its thickness is,the closer with the fault.The influence on the thickness of dolomite in the lower wall of the structure by stratum reverse is smaller than that in the upper wall of the structure.