Pore Structure Of Low Permeability Sandstone Reservoir Characterization And Water Displacement Efficiency

The low-permeability reserve recently makes up 40%-50% of the annual incremental proven reserves in Shengli. The recovery of water injection reservoir displacement is 18.62%. Therefore, to enhance the development effects of low permeability reservoirs become research hotsopt in insuring the durative and steady development.Focusing on special pore structure of low-permeability oil reservoir, the paper adopts several advanced geologic theories and technologies, such as sedimentology, grey-relational analysis, to study the pore structure and water driver efficiency of low-permeability oil reservoir in Shengli oilfield. Through the research mentioned above, the following results are achieved:（1） Study shows that mechanical compaction and filling by authigenic clay minerals and higher connate water saturation are the main factors caused the loss of permeability. By interaction between compaction and filling by authigenic clay minerals, pore structure will become extremely complicated.（2） The analysis of the pressure mercury data indicates that the pore throat average radius is short. The throat deriation coefficients were found to poorly predict permeability and the average throat radius. The sorting coefficients and the relative sorting coefficients and the throat maximum radius were positively correlated with the permeability and the average throat radius. The lithological coefficient and the feature structure coefficient and the enter pressure were negatively correlated with the permeability and the average throat radius.（3） It is different that the influence of the pore structure parameters to displacement for low-permeability-reservoir at different levels. The results showed that the relative sorting coefficient had the most greatly influence on displacement, the throat deriation coefficient had the least influence. Therefore, this paper classified the low-permeability-reservoir at different levels with different parameters.（4） Relative permeability curves of low permeability reservoir in Shengli oilfield present water-phase bipolarity characters. Lower limit of movable permeability in irreducible water state is 0.843×10^-3μm². （5） Formation damage occurs when injected water is not compatible with the reservoir. Results indicated that, 1) the damage caused by solid particle was more than 50%-60%, the damage caused by scaling was more than 30%-60%; 2) the diaplacement efficiency of compatible water was obviours higher 7-8% than not compatible water.