超深层致密砂岩构造裂缝特征及其对储层的改造作用——以塔里木盆地库车坳陷克深气田白垩系为例

库车坳陷克深气田是塔里木盆地天然气上产增储的最重要战场之一，也是国家“一带一路”能源大通道的主要气源区，但产气储层埋深超过6 000m，网状缝—垂向缝发育、密度为3~12条/m，基质孔隙度平均为3.8%，基质渗透率平均为0.128×10^-3μm²。为揭示超深层裂缝对储层性质及天然气高产稳产的影响。综合岩心、薄片及成像测井资料，对库车坳陷克深气田巴什基奇克组致密砂岩储层构造裂缝特征进行了表征，并分析了构造裂缝对储层的改造作用。克深气田的构造裂缝包括近EW向、高角度为主的张性裂缝和近NS向、直立为主的剪切裂缝2组，前者充填率相对较高，后者多数未被充填；微观构造裂缝多为穿粒缝，缝宽10~100μm；构造裂缝在FMI成像测井图像上以平行式组合为主。构造裂缝对克深气田储层的改造作用主要体现在3个方面：构造裂缝直接提高了储层渗透率;沿构造裂缝发生溶蚀作用有效改善孔喉结构;早期充填裂缝仍可作为有效渗流通道。背斜高部位是构造裂缝渗透率的高值区，控制了天然气的富集高产。网状及垂向开启缝与储层基质孔喉高效沟通，形成视均质—中等非均质体，可使天然气产量高产且长期稳产。

Characteristics and reservoir improvement effect of structural fracture in ultra-deep tight sandstone reservoir: A case study of Keshen Gasfield,Kuqa Depression,Tarim Basin

The deep gas field in Kuqa Depression is an important battlefield of natural gas production and storage in Tarim Basin.It is also the main source area of the national “One Belt and One Road” energy channel,but the gas reservoir is buried deeper than 6 000m.In these deep reservoirs,netted-vertical fractures developed at the density of 3-12 items/m,with average matrix porosity and permeability of 3.8% and 0.128×10^-3μm².The characteristics of tectonic fractures in tight sandstone reservoir of Cretaceous Bashijiqike Formation (K₁bs),Keshen Gasfield,Kuqa Depression was characterized and the improvement of tectonic fractures on reservoir was analyzed using core,thin sections and image logging.There are two groups of tectonic fractures in Keshen Gasfield:EW tensile fractures with high dip angle and NS compressive vertical fractures,and the former has high filling degree while the latter was mostly unfilled.Microfractures are primarily transgranular fractures with an aperture of 10-100μm.On the FMI image,tectonic fractures are primarily parallel assemblage.The improvement of tectonic fractures on reservoir includes three aspects:tectonic fractures can directly enhance reservoir permeability,dissolution along tectonic fractures can effectively improve pore structure;early filled fractures can still be effective flowing channel.The high position of anticline has high magnitude of tectonic fracture permeability and therefore controls the enrichment and high yield of natural gas.The network and vertical opening fractures are effectively communicating with the reservoir matrix pore throat,forming the visual homogeneity-medium heterogeneous body,which can produce high yield and long-term stable production of natural gas.