Research On Reservoir Characteristic Of Neogene In Liubei Area Of Raoyang Depression

According to the theory of sedimentlogy, the paper has studied on the reservoir characteristics and sedimentary facies of Neogene in Raoyang Depression using the seismic,well-logging, core and analysis assay data. In the end we summarized the controlling factors of the reservoir distribution and the oil-bearing property.In the study area, the Guantao formation of Neogene can be divided into three sub-formation(Ng3,Ng2,Ng1) and the lower formation of Minghuazhen can be divided into four sub-formation(Nmx4,Nmx3,Nmx2,Nmx1),which also can be further devided into seventeen sand bed sets. The Guantao and Minghuazhen formation of Neogenehas developed braided river sedimentary facies and meandering river sedimentary facies, which can be further subdivided into six subfacies and nine microfacies. It can be recognized that braided river sedimentary facies are mianly developed in Ng3 and Ng1-1 and meandering river sedimentary facies in Ng2, Ng1-2, Nmx4, Nmx3, Nmx2 and Nmx1.The reservoir in the study area is composed of lithic arkose and feldspathic litharenite which has higher compositional maturity and higher stability in the content of feldspar and lithic. It can also be recognized that the main types of sandstone are poststone and medium-grained sandstone which had moderate sorting and subangular to subrounded rounding. Compaction, cementation and dissolution are the main diagenesistypes of the reservoir. The main pore types in the reservoir of the study area are residual intregranular primary intergranular pores, secondary dissolved pores and fissures, primary poresare commonly developed when the depth is less than 1700 m, and secondary dissolved poresare commonly developed when the depth is between 1700-2100 m.The reservoir is characterized by high porosity and extremely high permeability.The distribution of sand bodies and oil and gas migration and accumulation are mainly controlled by tectonic activity. In the eastern and central area, the oil-bearing property is better when sandstone percentage is between 30% to 50%, and there may have existed oil and gaswhen sandstone percentage is between 15% to 30%. When the connectivity probabilityamong sand bodies is between 0.8-1 it often shows good oil and gas. Oil and gas can also be distributed where it shows lower connectivity probability(less than 0.2), it can reflect the hydrocarbon accumulation in the isolated sand bodies which has thiner layer thickness. Gas and oil are mainly accumulated in main stream channel subfacies and distributary channel subfacies. The show of gas and oil is best founded in the point barsubfacies, while bank and flood plain seldom subfacies show almost no show of gas and oil. According to the relationship between reservoir and fault, and its sedimentary characteristics, finally, two favorable blocks have been predicted, including ning42 block and lu28 block.