The Evolution History And Petroleum Systems Of Weibei Strike-slip Basin

In the process of petroleum geology assessment and exploration target optimization, three aspects of geological factors need more attention, ie. basin evaluation (in relation to hydrocarbon resources, exploration potential, and exploration economics), play optimization and prospect determination. Thfe comprehensive study aspects currently in fashion are characterized by basin genesis and type, deep controlling factors for basin evolution, a series of evolution events, dynamic features of basin filling, fluid kinematics and dynamics, and quantitatively dynamic simulation, and so on. Strike-slip basins being one kind of sedimentary basins play an important role in huge hydrocarbon discoveries.In recent years, the successul coopeartion between CNOOC and America-based Philips saw the discovery of Penglai 19-3 Oilfield which is located in offshore territory of EastChina, as strengthens the evidences of hydrocarbon accumulatiom existing in some sedimentary basins and structural zones associated with Tanlu strike-slip faulting. In general, the above mentioned recognition will surely widen our next exploration targets and adjust our thinking way to comprehensively study hydrocarbon resources potential and favorable petroleum zones in the strike-slip basins in relation to Tanlu Fault through the application of anvanced exploration theories and methods such as the concept of petroleum system.Weibei Basin is one of the sedimentary basins within Tanlu Fault Zone. Several decades of exploration practices make people believe that this basin bears abundant petroleum resources. The petroleum exploration in this basin becomes more and more difficult because of low level of understanding of evolution history, petroleum potential and hydrocabon distribution law of Weibei Basin. This paper is based on Dynamics of Sedimentary Basin to apply structural interpretation, sequence stratigraphy and petroleum system specially for strike-slip basins to the comprehensive analyses of Weibei Basin, furtherly target some favorable prospects. A lot of first hand data are successful in establishing the dynamic evolution process, making clear the geochemical features and distribution law of effective source rocks, simulating hydrocarbon generation evolution, and determining the controlling factors of hydrocarbon accumulation and the petroleum system boundaries of Weibei Basin. As leads to concluding the distribution law of hydrocarbon accumulations and proposing new favorable exploration zones.The leading conclusions drawn from the above analyses are as follows: 1. Weibei Basin, catelogued as pull-apart basin, is a stretching strike-slip basin whose growth and formation is controlled by Tanlu strike-slip rifting. Weibei's structural evolution underwent 5 stages: (1) strike-slip rifting during cretaceous, which is characterized by development of hugely thick volcanic and volcaniclastic rocks; (2) strike-slip rifing and depressing during the 3rd member of Kongdian Formation, the general structural framework was established; (3)-3-During the sedimentation of the 2nd Member of Kongdian Formation and Shahejie Formation, extentional faulting and depressing movement prevailed in this important stage of basin formation; (4) during Oligocene, ie. the latest stage of sedimentation of Shahejie Formation, strike-slip compressing played more actively; (4) during Neocene, the whole basin entered into its regional subsidence and compression development stage.2. On the basis of the comprehensive analyses of seismic stratigraphy and high resolution sequence stratigraphy for individual well, the filling successions are classified into 6 sequence boundaries, 2 second class sequences and 6 third class sequences, and the sequence stratigraphy framework was constructed. The basin's sedimentary environment developed from shallow to half-deep, deep lacus during rifted subsidence which formed significant source rock SQ2. Fan deltas and turbidite fan sand bodies are predominant reservoirs which were deposited in two low stand tracts SQ3 and SQ4.3.