Abstract: Structural conversion zone is an important field of oil and gas exploration and development, which is distributed in many types of compressional or extensional basins. Based on the theories of conversion zone, it is considered that there is a significant control on sand body convergence in the Syndepositional period. The Pinghu Formation in the Kongqueting area of the Pinghu Slope records the fault-depression transition. It is of significance for further exploration and development to clarify the control on the sand and facies in the structural transformation zone composed by the synsedimentary fault system in this period. Based on the interpretation of 3D seismic data and logging data, three types of parallel, collinear and overlapping transition zones in the Kongqueting area were clarified by comprehensive analyses of structural style, fault system and growth index. The tectonic conversion zone controls the formation of the paleogeomorphology between depressions and uplifts, and further controls the unloading and enrichment of sedimentary sand bodies in low-lying areas near the fault conversion point with a large accommodation space. These sand bodies developed into sedimentary microfacies, such as deluvial fan, front underwater fan and composite sand bar. Based on the matching relationship between paleogeomorphic characteristics, transformation zone types and sedimentary sand bodies, three sand-control models of flexured-parallel transfer belt, flying-geese-like collinear transfer belt and wriggling-transformed-overlapping transfer belt were determined. The former two have good sand accumulation effects. This study provides insights into subsequent exploration of tectonic lithologic reservoirs.

Key words: Kongqueting, Pinghu Formation, braided river delta, tectonic transition zone, sand control mode