Evaluation On Tight Reservoir Characteristics Of Paleogene System In Xihu Depression

Multiple Structure obtained industrial flows in Paleogene system in Xihu depression.Santan deep sag and the central anticline belt have Reservoir of tight sandstone.Low degree of exploration in this region need further in-depth research on reservoir characteristics and distribution.Summarizing previous studies and by full use of analysis data like mud logging,core,logging,physical property and test data,the author has researched the reservoir characteristics of lithology,physical property and pore structure,determined tight reservoir cutoff and established the criterion of reservoir classification.Having a further cognition on the reservoir characteristics and distribution.Reservoir mainly develop lithic feldspar sandstone and feldspar lithic sandstone,fine grained;Various of pore types,but facial porosity is low,pore and fracture are not developed,connectivity is poor.4 types of pore structure: Coarse throat,medium throat,fine throat and capillary throat,mainly with fine throat.The core test results have shown that the reservoirs belong to mid-low porosity mid-low permeability and low-porosity low-permeability reservoirs.The research interpreted the porosity of the 22 wells using log data showing Physical properties decreased with increment of strata depth trend is obvious.Reservoirs in Huagang Formation have mid-low porosity and mid-low permeability Characteristics.Mainly with the low-porosity and low-permeability reservoirs in Pinghu Formation.Analysis of rock thin section authentication results and physical property parameters shows physical properties decreased with the decreasing grain-size,fine and medium grain is best,silt grain is worse.In the aspect of lithology,lithic feldspar sandstone is best,feldspar lithic sandstone is good,feldspathic quartz sandstone is worst.According to physical properties,pore structures and special core analysis data,Using a variety of methods to determined reservoir physical property cutoff: Porosity is 8.0%,Permeability is 0.1md,and defined 4 types of reservoirs in the study area.In southern central anticline belt developed class ? and class ? high quality reservoir.Other areas developed class ? and class ? reservoir.Vertical distribution of reservoir has certain regularity,Huagang Formation upside Member developed class ? and class ?reservoir,the main developed class ? reservoir in Huagang Formation bottom Member.Pinghu Formation developed class ? reservoir,Local development class ? reservoir,reservoir is poorer by increment of strata depth.