Principles Of Hydrocarbon Accumulation And Exploration Targets Evaluation In The North Slope Of Biyang Depression

From the tectonic movement, deposition evolvement and their space-time allocationrelationship in Biyang Depression, the basin settlement history, petroleum structure analysisand other technologies and theories were adopted to analyze the formative mechanism of nosestructure, movement period of rifting, characteristics of faults distribution, depositionevolvement feature and the space-time allocation relation between deposition and tectonics inthe North Slope of Biyang Depression.The theories on reservoir formation were utilized to analyze the characteristics of reservoir, thegenesis of thick oil, the match relations of all factors for the reservoir formation process and thecontrolling elements in the North Slope. Through the discussion on hydrocarbon migration,accumulation mechanism, dominant pathway and dynamic evolvement rule, the reservoirformation model was generalized and sorts of geologic feature and hydrocarbon enrichmentrules were forecast.The hydrocarbon migration and accumulation rules in the complicated faulted-nose structurewere established, namely, the inherited tectonic-depositional slope is the pointing area;the nosestructure accumulates hydrocarbon and the faults adjust and control the reservoir formation.The cutting between the fault and the nose structure defines the model of hydrocarbonmigration and accumulation.The mechanics of nose structure in the North Slope was discussed. The tension-shear stressfield of the boundary faults in the fault subsidence results in the occurrence of a series of nosestructures in the North Slope and the magnitude of the association angle defines the distributionshape of the nose structure and sandstone body: if it is and obtuse angle, the shape is wide andgentle;if a sharp angle, the shape is narrow. The late differential compaction aggravates thescale of the nose structure. The hydrocarbon from the effective source rocks accumulatestowards the nose structure, so the nose structure of different size corresponds with thehydrocarbon accumulation area of different scale.It is presented that the transposition of the deposition (settlement) center resulting from theunbalanced movement of the boundary faults and the corresponding movement of thepalaeohigh in the North Slope further control the unbalanced occurrence of the sandstonebodies in the east and west slope and the contact relation with source rocks, thus controlling thedistribution difference of the pay beds in the North Slope.Focused on the study on reservoir formation rule and the characteristics of the fault block oilreservoir, and the lithological and stratigraphic oil pool, the formative mechanism of the nosestructure in the North Slope was further complete and the migration and accumulation model ofcomplex faulted-nose structure was established. The exploration targets in different area wereevaluated, which give a direction for the next petroleum exploration and drilling.