洞穴型碳酸盐岩储层识别及预测技术

Identification and Prediction Technology for Cavernous Carbonate Reservoir

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。

Paleo-karst was developed in Ordovician limestones at the west of Lungu area in Tarim basin.According to the lithologic and electric response character,the carbonate reservoir in this area can be classified into four types ： vuggy reservoir, fractured reservoir, fractured and vuggy reservoir and cavernous reservoir.The fractured and vuggy reservoirs can＇t form stable productivity;thus the fractured and vuggy reservoirs were important that can form stable productivity for good storage and permeable property.The cavernous reservoir has the most value for the best storage and permeable property.Based on geophysics forward modeling and through-well seismic section analyzing,the cavernous reservoir shows ＂a string of beads＂ strong amplitude in seismic sections.Through sensibility analyzing of seismic attributes,mean reflection strength,root-mean-square amplitude,mean energy,slope at half-life energy and coherent attribute were optimized.The carbonate reservoir was predicted and evaluated comprehensively by using the method of fuzzy neural net according to these seismic attribute parameters.The results coincided with the actual drilling data.Karstification in this area has close relationship with the fractures.The carbonate reservoirs distributed as longitudinal zonality,and their spread orientation was close to the orientation of developed fractures.