Study On The Characteristics And Control Factors Analysis Of Oil&Gas Reservoir Of The Upper Triassic In Southeast Ordos Basin

The area of southeast Orod basin is characterized by low degree of hydrocarbon exploration. Recently, this area of Yanchang formation is with prolific in oil&gas. But no one has studied on the sedimentary facies, diagenesis and reservoir characteristics systematically in this area. This paper goes on to research and discuss the characteristics of petrology, microscopic reservoir characteristics, diagenesis and reservoir physical properties. In this process,this paper analyses this points by means of methods under the guidance of sedimentology, reservoir sedimentology and oil geology. The methods include the detailed description and observation of drilling cores, and observation of thin-section of the cast, measurement of homogeneous temperature for inclusions, analyses of X-ray diffraction, cathode luminescence image, electron scan microscope, capillary pressure and. After the comprehensive research of reservoir, the paper holds that:The componential and textural maturities of the sandstone in Yanchang formation is lower and lithological types are mostly fine-grained arkose, which the interstitial matter is widespread but not uniform distribution. The type of cements obsedved including carbonate, clay minerals,, feldspar overgrowths, and a few laumonite, ferruginous cement. With the diagenetic evolution process development the microscopic reservoir characteristics of the sandstone observed primary pores residue and secondary pores growth after compaction, cementation and dissolution. The paper thinks the form two functions are the main reasons of decreasing reservoir quality. The secondary pores like feldspar dissolution pores appear after the dissolution are the main reason of increasing reservoir quality. The reservoir physical properties show that the porosity value is from4.42%to12.29%, the permeability value is from0.1×10-3μ m2to0.5×10-3μ m2.The reservoir is characterized by low porosity and low permeability and heterogeneity is very strong. Compared with other regions of Orods basin, the quality of reservoir is more density. The porosity evolution, the Characteristics and stages of thermal evolution of organic matter and clay mineral evolution show that the sandstone are in the mid diagenesis phase A. The dianenetic sequence being as follows:mechanic compaction→authigenic clay rim (chlorite)→utogenous kaolinite formation,quartz overgrowths→(early diagenesis) carbonnate cementation→ illite/montmorillonite mixing layer (or chlorite/montmorillonite mixing layer)→illite (chlorite) generate and fill in pore→(organic acid fluid injected) feldspar, detritus and carbonate dissolution→hydrocarbon emplacement→(later diagenesis) Iron calcite precipitation→Dolomite filling and metasomasis clastic particle. According to the characteristics of diagenesis the lithogenous phase is made. The authigenic clay rim (chlorite) and feldspar dissolution diagenetic phase is considered as advantage diagenetic phase.The characteristics is very complex by complex structures and sedimentary evolution background. The paper holds that the high quality reservoir is controlled by provenance and parent rocks properties, diagenesis and the degree of diagenetic evolution.The fractures of reservoir on one hand make the pores connect, improve the reservoir quality of the sandstones. On the other hand,act as the role that transporting petroleum.