Reservoir Characteristics Of The First Member Of Nantun Formation In Beier Depression

Beier depression is a negative structure unit located in the southern of the central rift zone in Hailer Basin. In recent years, people find better oil and gas show in the first member of Nantun formation reservoir and the considerable results are obtained in the production process. Because of the indistinction of the reservoir characters in Beier depression, the step of exploration and development is limited. This paper applies comprehensively the seismic, logging, core and production testing to study the reservoir characteristics of the first member of Nantun formation in Beier Depression.The best types of reservoir of the first member of Nantun formation are pyroclastic rock and clastic rock in Beier Depression. The main types of clastic rock are lithic sandstone and feldspathic lithic sandstone, whose maturity is low. The secondary pore is the main reservoir space, which includes intragranular dissolved pore, interstitial material dissolved pore, corrosion intergranular pore, intragranular dissolved pore of pyroclastic. Generally, the microscopic characteristics of reservoirs are bad in the first member of Nantun formation.The reservoir's physical characteristics are low porosity and low permeability-low porosity and super-low permeability in the first member of Nantun formation in Beier depression. The secondary pore is the main reservoir space type, and this horizon is located in anomalously high porosity zone in vertical. In the plane, The Sudeerte buried hill tectonic belt and Beizhong sub-depression physical characteristics. The reservoirs are located in braided delta plain, front, fan delta plain and front subphase. The main diagenesis are compaction, cementation, metasomatism and dissolution. The compaction and cementation decrease the reservoir space, but metasomatism and dissolution enlarge the space. The main lithology of pyroclastic rock is tuff, sedimentary tuff and tuffaceous sandy conglomerate. The main diagenesis stage of reservoir of the first member of Nantun formation is A2, and diagenesis stage B is the second one. The main diagenism facies are tuffaceous corrosion diagenism facies, feldspar corrosion diagenism facies, calcite cementation diagenism facies, shale cementation diagenism facies, mud stone compaction diagenism facies and compaction and cementation diagenism facies.The paper shows that the main controlling factors are the distribution of hydrocarbon kitchen, the favorable sedimentary facies belt, favorable diagenism facies, and the existence of ancient unconformity by analyzing comprehensively seismic, well logging, logging, SEM, casting thin sections, production test, geochemical analysis data. Based on the comprehensive analysis of four main controlling factors, braided delta plain, front, fan delta plain and front subphase are the favorable sedimentary facies belts, and the favorable diagenesis facies belts are tuffaceous corrosion diagenism facies and feldspar corrosion diagenism facies. Considering the distribution of hydrocarbon kitchen and ancient unconformity, combine favorable sedimentary and diagenism facies belts to protect the high-quality reservoir.