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塔里木轮古西地区奥陶系灰岩是古岩溶发育的有利场所。根据储层岩电特征的差异,将轮古西地区碳酸盐岩储层划分为孔洞型、裂缝型、裂缝—孔洞型及洞穴型四种类型。其中,裂缝型以及孔洞型储层很难形成稳定的产能;裂缝—孔洞型储层既有较好的储集能力,又有良好的渗透性能,能够形成稳定的产能,是本区一类重要产层(如Lg9、Lg42井);洞穴型储层具有最好的储集能力和渗透性能,是本区最有价值的储层类型。根据地球物理正演模拟和过井地震剖面分析,洞穴型储层在地震剖面上表现为“串珠状”强反射的特点。通过地震属性敏感性分析,优选出了平均反射强度、均方根振幅、平均能量、能量半衰时斜率以及相干属性。利用这些地震属性参数,通过模糊神经网络的方法,对碳酸盐岩储层进行综合预测与评价。多属性综合预测结果与实际钻井资料十分吻合,该区岩溶作用与断裂的关系非常密切,多呈条带状分布,展布方向与断裂发育方向具有比较高的一致性。
Ordovician limestone in the ancient Tarim Basin is an advantageous place for the development of ancient karst. According to the difference of reservoir rock electrical characteristics, the carbonate reservoirs in the Lungexi area are divided into four types: hole type, fracture type, fracture-hole type and cave type. Among them, fractures and hole-type reservoirs are difficult to form stable productivity; fractured-hole reservoirs have both good reservoir capacity and good permeability and can form a stable capacity, which is of first importance in this area (Lg9, Lg42). Cavern reservoirs have the best reservoir capacity and permeability and are the most valuable reservoir types in this area. According to the geophysical forward modeling and over-cross-section seismic profile analysis, cave reservoirs are characterized by “beaded” strong reflection on seismic profiles. According to the sensitivity analysis of seismic attributes, the average reflection intensity, root mean square amplitude, average energy, slope of energy half-decay, and coherence properties are optimized. Using these seismic attribute parameters, the comprehensive prediction and evaluation of carbonate reservoirs are carried out by means of fuzzy neural network. The results of multi-attribute comprehensive prediction are in good agreement with the actual drilling data. The karstification in this area is closely related to faults, mostly in strip-like distribution, and the distribution direction is in good agreement with the fracture development direction.