Differences And Main Controlling Factors Of Research On Tight-sand Sedimentation And Reservoir Of The P₁s-P₂x In The Shiguhao Area Of The Northern Ordos

The terrigenously clastic rock of Neopaleozoic develop tight sandstone reservoir in the Shiguhao area of the Northern Ordos basin,and it has better oil and gas exploration breakthrough. To understand the characteristics and evolution of sedimentary facies, and spatial distribution of sand body and its main control factors,and the tight sandstone reservoir diagenetic evolution and space differentiation characteristics,It can enrich the region basic geological theory and reservoir prediction and evaluation of this area is of great significance.Based on the sequence stratigraphy, sedimentology, reservoir geology theory as the instruction, Research on predecessor's research results and project research, On the basis of the collected drilling, mud logging, well logging an 3D seismic data comprehensive analysis, Try to 3D seismic data in geomorphology and sand body characterization methods applied to the research of sedimentary reservoirs in the study area,these systemly reveals sedimentation and reservoir of tight sand of the P1s-P2 x,and its differences and main controlling factors.Comprehensive facies marks of the study show:In the study area to identify the braided river delta coastal plain swamp facies, braided river delta facies, braided river facies and meandering river facies. The Member 1 of Shanxi Formation mainly develop braided river delta-seamarsh facies, including distributary channel and distributary interchannel microfacies. The Member 2 of Shanxi Formation develop braided stream delta plain subfacies. The Lower Shihezi Formation from The Member 1 to The Member 3 shows that braid river gradually to the evolution of meandering river and flood plains become apparent.Combining of well-seismic and on the basis of seismic geomorphology and seismic attribute analysis, depicting the geomorphology in different periods and each section of the sand body exhibition,and discussing sedimentary sand body distribution and evolution characteristics under control of the geomorphology. It shows that the provenance mainly in north and northeast and northwest, In the early of the Member 1 of the Shanxi Formation,development of downcutting valley in the north west-south east,big relief,sedimentary facies distribution by valleys restrictive effect is obvious,and downcutting valleys constitute the main transmission channel sand body;In the late of the Member 1of the Shanxi Formation,due to large amounts sediment filling terrain gradually“Fill And Level Up”,valleys restrictive is abate,and forme good terrain conditions of coal accumulation, so as to develop regional stability of coal seam;the Member 2 of the Shanxi Formation overally inherited characteristic of the Member 1 of the Shanxi Formation. terrain flatten out,In the stage of the“Fill And Level Up”,Early the mutiperiodic superimposed channel sand body,A large area of patchy distribution,Sand body swing enhancement, box sand body increases. the provenance supply capacity become weaken in the middle-late of stage and the channel sand body increasingly isolated. the distributary channel of delta plain highly superimposes and Largely develop to the dying and islanding evolution in the period of the Member 2 of the Shanxi Formation. the overall terrain flat,River swinging frequent,and the characteristics of braided river has meander gradually turn up in the Lower Shihezi Formation.Based on the research of sedimentary system, researching comprehensively on tight sandstone reservoir of Each formation and discussing the main controlling factors of reservoir. It shows that the Member 1of the Shanxi Formation and The Member 1 of Lower Shihezi Formation physical property is better than The Member 2-3 of Lower Shihezi Formation. Favorable reservoirs have migrated north gradually along with “Fill And Level Up”process characteristics,Compositional maturity is slightly higher and soluble matter content such as early cementation of calcite and feldspar are slightly higher in the Member 1of the Shanxi Formation and the Member 1 of Lower Shihezi Formation, Early sediment is very important. That is laid the foundation of reservoir formation.To compared, forming different types of diagenesis combination and evolution sequence correspondingly. Cementation is stronger in the Member 3 of Lower Shihezi Formation.The Member 2 of Lower Shihezi Formation compaction density is stronger and the Member 1of the Shanxi Formation and the Member 1 of Lower Shihezi Formation dissolution is a little stronger. Diagenesis on reservoir has obvious control effect.Compaction and cementation are commonly developed in the region, and is the leading cause of poor tight reservoir. But the dissolution of minerals such as feldspar and calcite is the main constructive diagenesis.The Member1-2 of Lower Shihezi Formation have five parts with reservoir properties developed well from bottom to top in which the feldspar, calcite and siderite content is significantly lowered and kaolinite content increased. The secondary porosity lately formed by the dissolution and the inter crystal pores caused by altered kaolinite and other fractures have an obvious improvement effect on reservoir property.The relatively high maturity and More soluble cement and debris of the Member 1 of the Shanxi Formation and The Member 1 of Lower Shihezi Formation laid a foundation for the formation of the reservoir.The constructive diagenesis composite determines the current favorable reservoir development,such as Later dissolution,fracture,etc.