Abstract: In order to understand the characteristics of the Middle and Lower Jurassic reservoirs and the distribution law of the favorable sandstone reservoirs of the Mesozoic in the Kongnan area of Huanghua depression, the characteristics and controlling factors of the reservoirs were analyzed. Accumulation models were predicted for the favorable reservoirs using available well logging, mud logging, core data, and laboratory data. The results show that, although the reservoir physical properties are relatively poor, observation of many rock thin sections indicates that the secondary dissolved pores are well developed, which greatly improve the connectivity and physical properties of the reservoirs. Further studies suggest that the secondary dissolved pores are closely related to organic acid dissolution, and the source of organic acids is related to large faults. Finally, it is proposed that the favorable sedimentary microfacies and strong dissolution control the development of good reservoirs. There are two models of organic acid dissolution, “near source - strong relation - direct transport” and “far source - weak relation - relay transport.” The favorable reservoir zones are classified into five classes, I1, I2, II, III, and IV, based on the composite evaluation of “porosity - effective sandstone thickness - burial depth - fault properties;” according to the spatial configuration of source rocks and reservoirs, the Middle and Lower Jurassic accumulations are divided into “above source” and “under source – beside source.” Their controlling factors were also discussed. Multiple wells deployed in the classes I1 and I2 favorable zones have obtained industrial oil flow, and the drilling success rate was more than 70%.

Key words: Huanghua depression, Kongnan area, Mesozoic J1+2, reservoir characteristics, favorable zones, accumulation models