Research On Sedimentary Facies And Reservior Characteristics For Triassic Chang6-10Oil-bearing Formation In Jingwu Area Of Ordos Basin

The Jingwu area in the Ordos basin possesses abundant oil and gas resources, but the whole exploring extent is still low. The research of Upper Triassic Yanchang formation, important oil-bearing series, is being important theory meaning.Through the analysis of the cores and well logging data, completly research of stratigraphic classification and correlation, the analysis of sedimentary facies and sand body ultimate distribution, as well as some studies about reservoir features are made. Finally the favorable reservoir areas are assorted and pointed out.Through the research of regional stratigraghic key layers, Chang6—10oil-bearing formation of the Yanchang Formation in Jingwu area are correlated on base of typical wells selected. Thus from point to line into section, several connecting-well sections in the area are established and stratigraphic correlation of well-to-well are made. Combined methods of sedimentary cyclical control and stratigraphic thickness similarity, the Chang6-10oil-bearing formation are subdivided into13sandstone units, such as Chang101, Chang102; Chang9,, Chang92, Chang93; Chang81, Chang82, Chang83, Chang71, Chang72, Chang61, Chang62, Chang63, which are further subdived into subunits. Strata below Chang63are only researched in the article.Combined with the sedimentary characteristics and other electrical characteristics, river-delta-lake depositional systems are identified in the researched area. Anastomosing river developed during Chang10stage, during which lake basin early stuffed in the area. Shallow-middeep lake and delta fronts were the most important sedimentary subfacies during Chang9stage.That time the lake basin stabilized. Delta fronts developed during Chang8. Later, the lake basin range greatly widened and the Shallow-middeep lake subfacies developed during Chang7. The lake basin range contracted when it got to Chang6stage. Consequently, the delta fronts subfacies developed in this area. During different stage, sedimentary sand boby obviously dominated by sedimentary facies distributes in the direction of northeast-southwest.The reservoir characteristics of Chang6—10oil-bearing formation are carried out by studying their reservoir lithology characteristics, physical property and reservoir space characteristics. The results show that Chang6—10oil-bearing formationg of Yangchang Formation in the Jingwu area are mainly feldspathic sanstone. The pore form is primary intergranular pore chiefly.The reservoir in the target area is integrally low porosity and low permeability, even ultra low permeablility reservoir formation. The physical property of the reservoir is affected by the lithology, cement type, sedimentary facies and pore form. According to the physical property and pore characteristics of reservoir, combining with sedimentary facies in the area, reservior classified evaluation standard were set up. Eventually, the reservoir of Chang6-10oil-bearing formation in the area is assorted and evaluated.