The Application on Shale Reservoir Based on X‐CT Scan Technology

micro-nanometer scale, which is different from conventional sandstone reservoir. As a result, conventional test methods are not valid in shale reservoir. Recently, all of test methods applied in shale reservoir can be divided into two categories: (1) image analysis is observed and scaned , using various types of high resolution scanning electron microscopes (SEM); (2) Intrusive methods are based on nitrogen adsorption method (NAM) and mercury porosimetry method (MPM). Although these methods have been employed in some application, each method has its own limitions in the application on shale reservoir evaluation. First, micropore in shale are observed by various types of high resolution scanning electron microscopes, pores diameter are differ from each operator and only small area of sample can be observed ; Measurement error is produced when pores diameter are measured applied NAM,because the organic matter and clay minerals can adsorpt a amount of nitrogen, mercury porosimetry method is suitable for measuring connected mesopores and macropores, either, shale pore diameter is distributed in the nanometer scale, excessive mercury pressure may bring about induced fracture ,which influence measured value(Xu et al., 2014; Bai et al., 2013). These defects mentioned can be effectively made up by X-CT scan technology. * These shale samples were collected from Eagle Ford outcrop in USA and Well JY2HF in Sichuan Basin. All of samples were analyzed for pore structure by MX200 Micro-CT. A lot of round –shape and cone-shape biology fossils were observed in scanner images of Eagle Ford shale, these biology fossils were identified by thin sections staining , authigene siliceous minerals are not be stained (Richard Borstmayer et al., 2011); In Al-Fe-Mn discrimination diagrams value of the Eagle Ford shale fall in biogenic region(Boström K, 1973). Generally, the content of organic carbon(TOC) decreases along with the content of silica expect for biogenic silica shale. As we know, hydrocarbon can be stored in organic matter nanopore in shale, hydrocarbon saturation of Eagle Ford shale increased along with TOC Increasing; Meanwhile, biogenic silica could transform into quartz(Qin et al., 2010), which could increased brittleness of Eagle Ford shale. Pyrite were observed in scanner images of JY2HF shale, which was regarded as paleoredox proxy(Raiswell R et al., 1985). Many of the trace metal elements showed variation in the redox status of the depositional environment, redox-sensitive trace metals trend to be soluble under oxidizing conditions and less soluable under reducing conditions, this behavior makes certain trace metals to be delivered to sediment and organic matters, such as U and Ni(Nicolas Tribovillard et al.,2006). Th/U and Ni/Co were used to response to different paleoenvironments. The trace element redox proxy Th/U ratio was 0.67-2.6, Ni/Co value was 3.55-14.44, which recorded strongly reducingweakly oxidating conditions, The TOC and pyrite presented consistent with variation of redox from the bottom of Longmaxi formation . In the Tianba section in northeastern Chongqing Wufeng period and early stages of the Longmaxi period showed low biological productivity, but a great deal of organic matters were preserved in strongly reducing conditions. by contrast, higher biological productivity was observed in the late stage of the Longmaxi period, more organic matters experienced oxidation and decomposition since the content of dissolved oxygen increased(Xiong et al., 2015). Intragranular dissolved pores were formed near pyrite(Guo, 2014), because of the thermochemical sulfate reduction (TSR); pyrite crystal particle pore and pyrite dissolved pore also could be observed in Longmaxi formation shale, which influenced on the storage capacity of shale.