Study Of Residue Oil And Reservoir Changes In High Water Cut Period In Wenxi Block

This article mainly studies of Tuha oilfield Wenxi block high water cut period of remaining oil distribution and develop,which is affected by reservoir properties,so the reservoir physical characteristics and its change after long-term water flooding are firstly studied.Mercury injection experiment and SEM is used to study the reservoir pore structure characteristics.The species and content of clay minerals are studied with X-ray diffraction experiment.The clay composition analysis interpretes the reservoir water sensitivity and the changes after long-term water flooding.Oil-water relative permeability curve and oil displacement efficiency experiment are conducted before and after long-term water flooding.Water flooding experiment with CT online scanning,combined with micro lithography glass model experimental studies of remaining oil distribution and water flooding mechanism.The glass model is used to study the mechanism and effect of enhanced oil recovery by the methods of gas drive and WAG.Results show that after long-term water flooding,the clay minerals attached to the surface of the mineral grains gradually migrate to the pore and throat of rocks,leading to the decrease of the permeability,especially for the low permeability reservoir.At this point,the migration of clay to the pore throat with the expansion effect makes the water sensitivity more severe after long-term water flooding.The water sensitivity makes the oil-water relative permeability curve presenting "convex",which is under residual oil saturation water phase permeability decreases caused by water sensitivity effect.CT online scanning experiment data and microcosmic lithography glass model visualization indicate oil displacement mechanism and the location of the remaining oil.In the end,compared with water flooding,gas drive and WAG improves oil recovery of 7.31% and 17.76% respectively.