松辽盆地北部深层致密火山岩气藏天然裂缝分布特征及控制因素

天然裂缝系统控制了松辽盆地北部徐家围子断陷深层致密火山岩储层天然气的运移、聚集和成藏。明确致密火山岩储层天然裂缝主控因素是准确预测裂缝分布规律的基础。通过野外露头区裂缝描述、岩心和微观薄片裂缝分析，结合成像测井裂缝解释，对松辽盆地北部深层致密火山岩气藏中天然裂缝的发育特征进行了精细表征，并深入分析了裂缝分布特征及控制因素。研究结果表明，研究区致密火山岩中发育有原生和次生两大裂缝类型，其中次生构造裂缝最为发育，其线密度主要分布在1.0~5.0条/m，平均为2.45条/m。裂缝发育强度主要受岩石类型、岩石力学性质、岩石脆性和构造部位等因素控制。天然裂缝方位复杂多变，是受古构造应力、断层和岩石非均质性（面理）共同作用的结果。

Distribution and controlling factors of natural fractures in deep tight volcanic gas reservoirs in Xujiaweizi area,Northern Songliao Basin

The natural fracture system controls the hydrocarbon migration,accumulation and enrichment in the tight volcanic reservoirs,Northern Songliao Basin.It is of fundamental significance to illuminating the factors controlling natural fracture development in tight volcanic reservoirs for an accurate prediction of fracture distribution pattern.Using data from outcrop,core and thin section observation,as well as fracture interpretation with image logging,we finely characterize the development features of natural fractures in the tight volcanic reservoirs of the study area,and make a systematic research on the fracture distribution and its controlling factors.The results show that the fractures developed therein can be grouped into two types,including primary and secondary fractures.Among others,the secondary tectonic fractures are dominant,with a linear density ranging from 1.0 m^-1 to 5.0 m^-1,averaging at 2.45 m^-1.The fracture intensity varies greatly,mainly controlled by rock type,mechanical property,brittleness and tectonic position.The natural fracture orientation is complex and variable,a result of the combined action of paleotectonic stress,fault and rock heterogeneity (foliation).