Research On Sequence Stratigraphy And Prediction Of Prospects Of Hongqi Depression In Haila'er Basin

Hongqi depression was situated in Bei'er sag of Haila'er basin with an area of 1000 km2. It can be divided into five structure unites: Northern Hongqi steep faulted zone, Hongqi meadow subdepression, Sutenuo'er subdepression, and middle uplift and Shaoerbaoge monocline. The stratigraphic sequence upward is as follows, Jiufengshan and Ganhe formation of Xinganling group in the Jurassic; Tongbomiao, Nantun, Damoguaihe and Yimin formation of Zhalainuo'er group in the lower Cretaceous, Qingyuangang group in the upper Cretaceous, Neogene and Quaternary.Based on the mechanic research of the total structural framework of the depression, it deals with the mechanism and controls of faulted down and depression sequences. Clear the role played by the structural or depositional slope break zone, especial the syndepositional fault (Hongxi fault) to depositional systems .Summarize the distributing and evolving law of all-level-order sequences in isochronous stratigraphic framework and build the 2D sequence stratigraphic model with the function of prediction.Applying sequence stratigraphy theory and method, the sequence stratigraphy framework was build to recognize 2 first-order sequence interfaces, 4 second-order sequence interfaces, 3 third-order sequence interfaces. Divided Jurassic and Cretaceous into 3 third-order sequences, basal structure sequence(below SB5), faulted down structure sequences(from T5 to T04), depression structure sequences(from T04 to now);divided faulted structure sequences into 5 second-order sequences(sequence associations), 8 third-order sequences. Clearing the inner configuration and space allocated characteristics of sequence, systems tract and sedimentary systems, confirming the main controls on the evolving of sequence stratigraphy, build sequence stratigraphy model with the function of predicting.Within the isochronous sequence stratigraphic framework (fourth order), the depositional systems of the important formation (Tongbomiao-Nantun formation), were recognized as several depositional systems such as fan delta, lacustrine, delta and fluvial systems. During structure-sediment evolved, former faulted stage filled with igneous and clastic rocks, accelerated faulted stage filled with thick fan delta- lacustrine deposits, speed faulted stage filled with quasi deep lake-fan delta deposits, steady faulted stage characteristic filled with huge scale delta, shrinking faulted stage filled with fluvial deposits, belonging to typical half-graben filled sequence.By analyzing oil and gas accumulated elements and associations in the sequence stratigraphy configuration, draw conclusions as follows: the mudstone of Tongbomiao formation is effective source rock, sands in the fan delta front and cracks in the basalt and the metamorphic rocks are reservoir rocks, and effective trap types is fan delta lithological traps, fault blocks traps, cracked trap in igneous and basal rocks, unconformity traps etc. based on the knowing the oil and gas accumulation law, divided zone into prospects in depression (fan delta front-fore fan delta, quasi deep lacustrine turbidity sand, basal faulted oil and gas reservoir association), monocline(fan delta front-front- fore fan delta, basal faulted oil and gas reservoir association), and middle uplift fault zone(fault blocks, anticline, unconformity sealed , igneous cracked oil and gas reservoir associations).