The structural characteristics and distribution of sand body of the layer 7 of YanChang Formation in Ordos Basin

摘要

The tight sand in the layer 7 of YanChang Formation, Ordos Basin major develops braided river delta and gravity flow deposits. In this paper, based on previous studies on lake pelvic shape, provenance and hydrodynamic, the sand body in the research area has been systematically studied through core observation, logging data, and sedimentary theory. Various genetic types of sedimentary sand body are developed in this area, mainly as delta deposition, sandy debris flow deposits, turbidites (classic turbidites). We can identify 6 kinds of sand vertical combination type, they are the superimposed sand body(A-type), thick and uniform thickness sand body(B type), thin and uniform thickness sand body (C-type), up thinning sand body (D-type), thickening up sand body (E-type), thick and thin interbed sand body (F-type). The 6 types mainly controlled by sedimentary facies. The A-type sand body mainly developed in the delta depositional environment, the B type sand body is visible both in the delta and slope belt, while the D-type, E-type, F-type sand body are mainly developed in the deep lake. The distribution of sand body in the plane is zonal pattern.