川东北地区须三段钙屑砂岩储层特征及控制因素

Reservoir Characteristics and Main Control Factors of Xu3 Member Calcarenaceous Sandstone in Northeast Sichuan Area

近两年川东北地区西北部多口井须家河组三段钙屑砂岩测试段获工业气流,表明了研究区储层的含气性及局部具备油气富集高产的地质条件。通过储层岩性类型、储集空间、物性、电性等特征进行综合分析,得出结论为:主要储层岩性类型为钙屑砂岩,常伴有微裂缝;储集空间类型多样,主要为残余原生粒间孔、次生溶蚀孔和裂缝;储层表现为低孔、低渗特征;储层电阻率高,主要原因是碳酸盐岩含量高;储层测井响应为"三低、一高、一降低",即伽马低值、声波低值,中子低值,电阻率高值,在高阻的背景下深浅电阻率有所降低。研究区优质钙屑砂岩储层受储集层发育的有利沉积微相、溶蚀作用、构造裂缝以及一定的储层厚度等综合因素控制。辫状河道、水下分流河道沉积为储层最有利的沉积相带;在成岩过程发生的溶蚀作用和多期次的断裂影响下形成的构造裂缝都极大地改善了储层的渗透性;一定厚度的储层改善了裂缝的连通系统。

In the past two years,industrial gas flow was obtained in Xu3 Membericaicareniceous sandstones segment of Xujiahe Formation of Northeast Sichuan Area,which suggests that reservoir in Xujiahe Formation of study area shall be hydricarbon and has the geologicaliconditions ofhigh yield. We made analysis of the type of reservoir lithology,reservoir spice,physical property,elictric property and so on. The reseaiches show that lithology type of reservoir iicludesicaicareniceous sandstone,often iccompanied by microfricture. It has various pore spice which mainlyiconsists of residual original intergranular pore,sicondary dissolution pores andicricks. The reservoir shows low porosity and low permeability. Reservoir resistivity is high,bicause of highicarbonateicontent. The reservoir log response shows low GR,ic andicNL and high resistivity dicreases under the bickground of high resistaice. Theicaicareniceous sandstone reservoir in the study area isicontrolled by theicomprehensive fictors sich as favorable sedimentary microficies,dissolution,strictural fricture and reservoir thickness. The most advantageous reservoir sedimentary micro-ficies is braided river,underwater distributaryichannel;dissolution during the diagenetic pricess and fricture under the influeice of multiphase tictonic fissures greatly improves the permeability of reservoir;theicertain thickness reservoir improves theiconnictivity of fricture system,and is advantageous to oil and gas migration and gather accumulation.