Fine Reservoir Description Of Lower Guantao Formation In Shan 56 Block Of Shanjiasi Oilfield

Lower Guantao Formation in Shan 56 Block of Shanjiasi Oilfield is a fault-controlled ultra heavy oil reservoir with edge-bottom water.Currently,the residual oil distribution is poorly understood due to:?1?large reservoir thickness and strong heterogeneity,?2?increasing thermal interference between wells resulted from cyclic steam stimulation,which restricts the reservoir development and production.Stratum model was established through stratum subdivision and stratigraphic correlation.The combination and distribution of fault systems were investigated with drilling data and high precision 3D seismic data,and consequently,a revised structure model was established to understand the controlling of faults on fluid distribution.The deposition of reservoir,e.g.sedimentary facies,and reservoir sensitivity and heterogeneity were studied with cores and well logs,based on which reservoir model was established.Finally,oil-water systems,especially oil-water contact,was understood based on analysis above,and the reserve for each unit was calculated based on fluid property and seepage law.The results suggest that Lower Guantao Formation in Shan 56 Block can be subdivided into 3 units and 10 layers,which is dominated by braided river delta front deposition,including underwater distributary channel,mouth bar,sand sheet and distributary bay.Specifically,the unit 1 and unit 2 are primarily underwater distributary channels,whereas the unit 3 is mouth bar and distributary bay.Sand body in Lower Guantao Formation develop well laterally,especially the sand body in unit 1 and unit 2.The barrier between unit 1 and unit 2 is stable,while barriers in three units are widely distributed.The porosity in Lower Guantao Formation ranges from18.7-42.1%with averaged value of 36.1%,and permeability ranges from 106×10^-34630×10^-3?m² with averaged value of 1986×10^-3?m².The Shan 56 Block can be divided into 8 units vertically,and the calculated reserve was 1014.2 million tons,which is comparable with the measured one?1013.9 million tons?.