川东北元坝西部须家河组致密砂岩裂缝发育特征及控制因素

川东北元坝西部上三叠统须家河组受晚期构造活动影响小，裂缝发育程度较中东部低，前人对其重视不够，裂缝发育控制因素不清楚。通过岩心观察、薄片鉴定、测井解释、裂缝充填物包裹体分析等多种技术手段，对元坝西部须家河组致密砂岩裂缝发育特征及控制因素开展了系统研究，明确了裂缝类型和特征参数，建立了裂缝发育模式。结果表明:①元坝西部须家河组以低角度剪切缝和成岩收缩缝为主；须三段裂缝多为方解石充填，须二段裂缝以泥质充填为主。②元坝西部须家河组裂缝可划分为3期，分别对应晚侏罗世、早白垩世晚期和晚喜山期，前2期裂缝全充填-半充填，第三期未充填。③研究区裂缝发育程度受地层变形强度、至断裂距离、单层砂岩厚度和砂岩类型的控制。九龙山背斜枢纽部位和东南翼地层曲率较大部位以褶皱相关裂缝为主，在东南翼断裂附近以断层相关裂缝为主，2类裂缝区为开发评价有利区。须三段砾岩区发育由砾缘缝和穿砾平缝组合而成的、开度小、未充填的网状缝，须二段石英砂岩发育沿层理破裂的低角度剪切缝及微裂缝，也是元坝西部须家河组气藏下一步开发评价需关注的有利区。 

Characteristics and controlling factors of tight sandstone reservoir fractures in the Xujiahe Formation of the western Yuanba area,northeastern Sichuan Basin

The Xujiahe Formation in the western Yuanba area of the northeastern Sichuan Basin was slightly affected by late tectonic activity and thus has fewer fractures relative to the central and eastern Yuanba areas. Utilizing core observation, slice identification, logging interpretation, and inclusion analysis, the characteristics and controlling factors of fractures in tight sandstone of the Xujiahe Formation of the western Yuanba area were analyzed.The results show that the study area mainly contains low-angle shear fractures and diagenetic fractures. Fractures in the 2nd and 3rd members of the Xujiahe Formation were primarily filled by calcite and clay respectively. The fractures in the Xujiahe Formation of the study area can be classified into three stages, corresponding to the regional tectonic deformations during the Late Jurassic, the end of the Early Cretaceous, and the Late Himalayan. The fractures of the 1st and 2nd stages were fully or partly filled, but the 3rd stage fracture was not filled. The development of fractures was mainly affected by the fault and fold deformation strength, lithology combination, and stratum thickness. Fractures in the hinge zone and southeast limb of Jiulongshan anticline were mainly generated by bending deformation except for the fault zone. The fault-related fracture was more plentiful in the vicinity of the fault zone. Both bending deformation fracture and fault-related fracture are favorable for petroleum development. Fractures in the conglomerate of 3rd Member of the Xujiahe Formation can terminate at or transect the gravel particle and generally show small apertures. The low-angle fractures and micro-fractures in the quartz sandstones of the 2nd Member of the Xujiahe Formation developed aligning with bedding. Both the 3rd and 2nd members of the Xujiahe Formation in the study area are favorable targets for petroleum exploration and development.