塔里木盆地塔河油田S80走滑断裂发育特征及其对奥陶系储层的控制作用

Characteristics of the S80 strike-slip fault zone and its controlling effects on the Ordovician reservoirs in the Tahe oilfield,Tarim Basin

综合运用岩心资料、测井资料、单井漏失段宽度和漏失量数据,利用高精度三维地震数据,结合多层相干属性开展塔里木盆地塔河地区S80走滑断裂带精细解析,厘定了其空间展布特征、活动强度特性及活动期次,探讨了S80走滑断裂对奥陶系储层的控制作用。研究结果表明:①S80走滑断裂带沿走向可分为西带、中带和东带,3个分带整体具有纵向上由寒武系至奥陶系叠接段数量显著增多、段长和段宽明显增加的特点,平面上由SW向NE张扭段规模减小、压扭段规模增强、平移段逐渐消失。具有“中带断裂活动强、两侧断裂活动弱”的特征。②S80走滑断裂带活动主要经历了加里东中期、加里东晚期—海西早期、海西晚期和印支期—喜马拉雅早期4个阶段。加里东中期和加里东晚期—海西早期为主要活动期。为“前两期左行,后两期右行”的走滑性质。③围绕S80走滑断裂带发育洞穴型、复合型(裂缝-孔洞型、孔洞-裂缝型)以及裂缝型3类储层。溶蚀孔洞的发育与走滑断裂分段性活动密切相关,活动性强的压扭段、平移段及活动性弱的张扭段主干断裂周缘是溶蚀孔洞发育的有利部位。④中奥陶统一间房组压扭段裂缝线密度高,中奥陶统一间房组至中-下奥陶统鹰山组纵向上裂缝线密度显著降低,溶蚀能力局限性大。中奥陶统一间房组张扭段裂缝线密度适中,中奥陶统一间房组至中-下奥陶统鹰山组在纵向上裂缝均较发育,溶蚀孔洞数量和规模相对更大,为储层的有利发育区。

A fine interpretation of the S80 strike-slip fault zone in the Tahe area of Tarim Basin is carried out by comprehensively utilizing core data,logs,the widths and total volume of the lost intervals in individual wells,highprecision 3D seismic data,and multilayer coherence attributes.Its spatial distribution,and activity intensity and stages are determined thereby,and its controlling effects on the Ordovician reservoirs are explored.The findings indicate that the S80 strike-slip fault zone can be divided into the western,central,and eastern subzones along its strike.These three subzones generally show a noticeable increase in the number,length,and width of overlapping segments from the Cambrian to the Ordovician strata vertically.Laterally,the S80 strike-slip fault zone,from SW to NE,exhibits the contraction of its transtensional segments,the expansion of its transpressional segments,and the gradual disappearance of its pure strike-slip segment.Furthermore,the activity of this fault zone proves strong in its central subzone but weak in its western and eastern subzones.The S80 strike-slip fault zone experienced four activity stages,namely the Middle Caledonian,the Late Caledonian-Early Hercynian,the Late Hercynian,and the Indosinian-Early Himalayan,with the former two stages predominating.This fault zone experienced sinistral strike-slip in the former two stages but dextral in the latter two stages.Three types of reservoirs are developed along the S80 strike-slip fault zone:cavernous,compound(fractured-vuggy and vuggy-fractured types),and fractured types.The development of dissolution vugs is closely related to the segmented activity of strike-slip faults,with the transpressional and translational segments featuring strong activity,as well as the periphery of the major faults of the transtensional segment characterized by weak activity,serving as favorable parts for the development of dissolution vugs.The transpressional segment of the Middle Ordovician Yijianfang Formation exhibits a high linear density of fractures,while those of the Middle Ordovician Yijianfang Formation to the Middle-Lower Ordovician Yingshan Formation show a significantly decreased linear density of fractures vertically,leading to a limited dissolution capacity.The transtensional segment in the Middle Ordovician Yijianfang Formation has a moderate linear density of fractures,and those of the Middle Ordovician Yijianfang Formation to the Middle-Lower Ordovician Yingshan Formation exhibit well-developed fractures and dissolution vugs with an elevated number and scale,establishing this interval as a favorable area for reservoir development.