Abstract:

Hydrocarbon migration and accumulation in continental faulted basins feature in "fault-slope controlling sand,multiple hydrocarbon transporting system,sedimentary facies and fluid potentials jointly controlling hydrocarbon accumulation".Taking the Dongying Sag in the Bohaiwan Basin as an example,this article expounds on the characteristics of facies-potential controlled reservoiring and the basic geological model of "dominant facies-low potential coupling controlled reservoiring".The research shows that the controlling effects of sedimentary facies on hydrocarbon accumulation can be divided into four categories: structural facies,sedimentary facies,lithologic facies,and petrophysical facies.They reflect hydrocarbon distribution and accumulation model from macro to micro perspectives.The basic geological mode of facies controlled hydrocarbon accumulation is "high poro-sity and dominant facies".While fluid potential control over oil and gas accumulation can be divided into the following four types,namely geopotential energy,pressure energy,interfacial energy,and hydrodynamic energy.These four types of potentials control the formation and distribution of different reservoirs with a basic geological model of "low potential controlled hydrocarbon accumulation".The coupling of dominant facies and low potential control more than 90% of the discovered hydrocarbon accumulations in the the Dongying Sag and determine the distributions and potential energy differences of different types of oil/gas reservoirs with different burial depth,and helps to explain the decreasing trend of the threshold porosity of effective reservoirs with the increasing bu-rial depth and to illustrate the mechanism that hydrocarbons can accumulate only when the internal potential of a trap being less than a half of the external potential.The reservoiring controlling model of "near source kitchen,dominant facies and low potential" can be applied in predicting the distributions of subtle oil and gas reservoirs in continental faulted basins.

Key words: fluid potential, control of facies-potential on hydrocarbon accumulation, subtle hydrocarbon reservoir, continental faulted basin, Jiyang Depression