Reservoir Control Of Predominant Petroleum Migration Pathway

Based on the data of cores,well logs,seismic and geochemical analysis,this paper combined geological and geochemical methods to study the migration of oil and gas in the middle-shallow strata of the No.1 structure of Nanpu Sag.The research aims to figure out the control effects of the predominant migration pathway,establish the migration mode,and provide guidance for oil and gas exploration in the study area.The research indicates that the oil and gas in the middle-shallow strata mainly comes from the Es1 and Ed3 source rocks in situ and Linque secondary concave.The study area is dominated by river-delta sedimentary facies,and sand bodies are generally good in physical properties and connectivity.Affected by two-stage stretching,the fracture is developed.The main fracture combination pattern is “y” type,anti “y” type and conjugate “x” type.There are two periods of oil and gas charging in the study area.The main source rock of the charging period at the end of Ed3 is the Es3 source rock but the oil and gas was lost because of strong tectonic activity.At the end of Nm charging period,the main source rocks are Es1 and Ed3 source rocks.At this time,the fault is opened,which is a good channel for vertical migration of oil and gas.The study area mainly has two modes: fault-cap rock transport and fault-sand body transport.The relationship between the fault and the cover determines whether the oil or gas mainly flows vertically or laterally.The fault-sand composite transport is divided into “single-slope” type and “roof” type.For roof-type,oil and gas cannot pass through the fracture,so that the sand body on upthrow is not filled;for “single-slope”,oil and gas can pass through the fracture,so that the sand body on upthrow is continue to be filled.