The Evolution Of Fluid Dynamic Field And Its Impaction On Hydrocarbon Accumulation In Xihu Depression, East China Sea Shelf Basin

Petroliferous basin is not only a low-temperature thermo-chemical reactor,it is a complex system of fluid dynamics.The the evolution of hydrocarbon generation,migration,accumulation and preservation is a composite process of chemical kinetics and fluid dynamics,the process of chemical kinetics occurred in the temperature field,pressure field,energy field and hydrodynamic field,as the results of dynamic field of energy or power source and effective heating time,and the fluid dynamics process is the oil-gas-water three-phase flow in the energy field.Xihu depression is located in the north-east of the East China Sea Shelf Basin,which is the main battlefield of oil and gas exploration,the dynamic Petroliferous basin simulation technology and a comprehensive analysis of the Petroluem geology serve as the main means of research,the study measures from the lithosphere,basin and reservoir three level:changes in the thickness of the lithosphere controls heat(energy) source of the basin,Hydrocarbon accumulation elements, such as source rock,reservoir,seal,distribute and evolute in the background of basin tectonic evolution and sedimentary filling process,the existing typical oil and gas reservoirs analysis reveals the kinetic mechanisms for hydrocarbon accumulation,then reconstructe the evolution of fluid dynamic field on the basis of Petroliferous basin simulation,a comprehensive analysis of fluid dynamic field and hydrocarbon accumulation matching relationship in the dynamic time,space,energy,flow field evolution is carried to explore the effects of fluid dynamic field dynamic evolution on hydrocarbon accumulation,and then establishs the hydrocarbon accumulation model on the basis of the comprehensive analysis.Through research,the main access to the following understanding:1.Hydrocarbon accumulation elements,organic matter analysis showed that the main maternal source rocks pinghu group to under the successive non-wood,Sham component increased, indicative of deep source rocks have a better type and hydrocarbon-generating potential;In a single compaction,the porosity reduce of sandstone is nearly liner relationship,there is a good correlation between the depth and the rock porosity,density and penetration,the rebound of sandstone marked improve reservoir properties;Xihu depression dominant hydrocarbon migration pathway are the active fault,high porosity and permeability reservoir sandstone controlled by sedimentary facies and unconformity.2.The character of fluid dynamic field and evolution.Different structural zone is heating by the uneven level of base heat flow,which is caused by non-uniform lithosphere stretching,high heat flow input high-energy into sedimentary strata in the central depression,low heat flow input low-energy into sedimentary strata in the slope depression,in the background of uneven heating and thermal fluid activity,convection along the fracture,the local and regional have strong thermal convection,isotherms with local fluctuations along the fault,are high in the centre and low in both sides on the whole,have the architecture distribution state,as the results of long accumulation time heated state,the corresponding maturity has the similar distribution characteristics to the geothermal temperature field;The analysis of well lithological composition and structure of the pressure show the compartment of Xihu Depression is include two parts:the thick seal insulating layer(pressure transition zone) and the overpressure core,the compartment seal opening have two overpressure fluid release types in the background of tectonic uplifting,erosion and the active opening fracture,including sudden tectonic events controlled and overpressure-tectonic combining controlled,during the process of overpressure fluid releasing,the top interface of compartment ruptures and pulls back,pressure funnel zone exists in the compartment,the energy and material sealed in compartment release and exchange with outside,as a result,hydrocarbon-bearing fluid release to normal pressure belt,hydrocarbon emissions and secondary emissions compiled.the distribution and evolution of lateral overpressure migration water column height shows the water column peak of pinghu formation in Xihu depression move from the centre of basin to the slope, accordingly,overpressure compaction flow discharge area wave from medial slope to the edge of the basin,the discharge area of overpressure hydrocarbon fluid form the western slope oil and gas-rich region.3.On the combination analysis basis of fluid dynamic field evolution,source rock generation and expulsion time,the evolution of physical properties of reservoir and caprock seal capacity,the period of tectonic activity and hydrocarbon filling,study the impaction of fluid dynamic field on the hydrocarbon accumulation process in the term of time matching,spatial matching,energy matching and flow field matching,the western slope overpressure compartment ruptures,in the background of thermal convection,the pressure episodic releasing and lateral dynamic compaction flow,fluid releasing from vertical fracture mainly lateral migrate to favorable traps near by the hydrocarbon migration pathway,establishing hydrocarbon episodic accumulation model,the overpressure fluid cement distributes layerly in the sedimentary formation;Central Anticline overpressure compartment ruptures many times,in the background of thermal convection and the pressure episodic releasing,fluid releasing from vertical fracture mainly vertical migrate to favorable traps near by the active faults,establishing hydrocarbon episodic accumulation model, the overpressure fluid cement distributes bulkly in the sedimentary formation.