Oil Enrichment Regularity Of Chang2 Oil-bearing Of Yanchang Formation In The East Of Jingbian Area In Ordos Basin

Ordos basin is in the north of Shanbei Slope, which is rich in Mesozoic petroleum, but the whole exploration and research of Mesozoic petroleum is still in a low level. Based on research and observation of the outcrops and the cores, data of this area such as costing thin sections, SEM(scanning electron microscopy), physical property, size analysis, porosity image, mercury source rocks, oil color-qualitative analysis, well logging and oil testing was comprehensively used in this paper. With methods and theories of stratigraphy, sedimentology, reservoir geology, logging geology and petroleum gelogy, the stratum of Chang2 Formation was divided and sublayers were compared; Analysis of the sedimentary facies and sand body distribution characteristics, study of the reservoir characteristics, carried out the hydrocarbon source rocks characteristics and oil-source correlation. On above basis, the oil enrichment regularity of Chang2 Formation(oil-bearing) in the east of Jingbian was summarized and the favorable target area was finally forecasted.According to the traditional division method, this paper divided Chang2 Formation into Chang21, Chang22, Chang23 using main and auxiliary symbol layer of this region, cyclical control and depth reference methods. And several connecting-well sections were established to make strata correlation.Through the sedimentary characteristics of studying regin, this paper belives that the Chang2 is a river sedimentary facies, Chang22 and Chang23 develop braided river deposit, Chang21 mainly develops meandering river deposit. River channel sand dam is main sand body, which development is controlled by sedimentary facies and the channel sand zonal distributes from eastnorth to weatsouth.Data analysis such as costing thin sections, mercury and physical property showes that the reservoir character of Chang2 Formation in the target area is with low compositional maturity and high structure maturity. Porosity types are intergranular pore and emposieu, the structure of porosity is mesoporous and thin throat, the reservoirs mainly in low permeability (â…¡type). Reservoir character is apparently controlled by sedimentary facies, diagenesis followed..Through the crude oil geochemical and the potential hydrocarbon source rocks analysis of Chang2, adopted previous research results about Mesozoic hydrocarbon rock of Ordos basin, through the oil-source correlation analysis, we think that they have the similar sources of organic matter and biological markers. The Chang2 crude oil from the quality oil source rocks of Chang7 Yanchang Formation of the Mesozoic hydrocarbon rock of Ordos basin.The plentiful hydrocarbon rock of Chang7 of Yanchang Formation in the sorthen area is the material foundation of the Chang2 oil-bearing, meanwhile channel sand offers reservoir space for oil enrichment. Stability distribution of argillaceous sediment in Chang1 composes favourable district covers; Basement faults of "activation" and small fractures of the development, constitute a good system for transporting oil and gas migration; Nose tectonic control the distribution of the oil and gas. On the basis of oil enrichment regularity of Chang2 Formation, several favorable areas were forecasted and the geological basis for further exploration was provided.