| South Zhaoyuan area has problems of poor sandbody development, thin reservoirs and much lateral variation of sandstone ration in formation. Directed by subtle reservoir forming theory, this paper performs study on reservoir forming rules, establishes reservoir forming patterns and predicts favorable areas so as to conduct oil and gas exploration in this area. Study on structural features of South Zhaoyuan area shows nose structure being high in the north and low in the south and low in the east and west sides and high in the middle part. There are mainly three types of traps including anticlines, fault noses and fault blocks, with more fault blocks being fragmented and less fault noses being small. Faults and fractures development: faults develop in three groups in SN, NNW and NNE strikes. NS strike is master fracture. Sedimentary facies stucy shows that Putaohua Reservoir develops two types of sedimentary systems. Northern part is lake delta system, including deltaic frontal mouth bar, distal bar, sheet sand and predelta mud. South part is mainly lake beach bar system, including lake shore dune ridge and lake shore corcass. Putaohua Reservoir is thinning from north to south. Reservoir thickness, sandstone thickness and net pay thickness are more in the northeast and less in the southwest. Drilling data and reservoir classification show that there are four types(structural, fault, lithologic and complex) including 11 sub-types of reservoirs in Putaohua Reservoir in this area. Structural and fault reservoirs distribute in northern and central parts, and lithologic reservoirs distribute in southern part. Oil and water distribution is under the duplex control of lithology and structures with the northern part under the control of structures and the southern part under the control of lithology. Be bounded by wells Pu 35-Pu 365-Ao 233-55-Ao, in the northern part, the structural high part is the oil reservoir and oil and water are in the same layers in the low part with complication water-oil relationship, and the southern part is pure oil reservoir. According to geochemical indexes analysis, the crude oil in Putaohua reservoir of south Zhaoyuan area mainly comes from Q1 Member and N1 Member sources rocks in Gulong depression and Sanzhao depression. These source rocks, with high organic matter abundance and type II of organic matter, enter great quantity hydrocarbon discharge stage from the end of Nenjiang Formation deposition to the period before Lower Tertiary deposition. Based on the time-space relationship between hydrocarbon reservoirs distribution and hydrocarbon reservoirs generation conditions, it can be got that the hydrocarbon generation in this region is mainly controlled by 3 factors, namely, structure, lithology and source rock. There are 3 reservoirs generation periods: the first one is at the end of Nenjiang Formation; the second one is at the end of Cretaceous; the third one is at the end of early tertiary. The hydrocarbon detention effect is the main mechanism for hydrocarbon accumulation in Putaohua reservoir of Aobaota and Aonan, and the reservoir generation mode is generation in lower part and storage in upper part– migration upward through faults– accumulation in structure-lithology trap. Putaohua oil reservoir in this area is comprehensively evaluated according to the structure, predicted reservoir thickness, sedimentary facies research results and oil and gas distribution rules, exploration drilling behavior and reservoir generation condition in this area. The results suggest that there is larger exploration potential in the western ramp region, of which the central part and the southwest part are classified as the favourable area of class I, and the areas with great potential in the east arch bend region is the well field of Well Mao 201- Mao 202- Mao 6 in the southeast corner.
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