Experimental Study On Dual Water Resistivity Model For Laminated And Dispersed Shaly Sands

In the paper ,study on conductance mechanism of complex shaly sand reservoirs with bothlaminated shale and dispersed shale is carried out.Because effects of laminated shale anddispersed shale on conductance mechanism are different,and W-S,D-W,S-B models widely usedin oilfield can only applied in dispersed shaly sands, not in laminated and dispersed shaly sands,it is nessesary to have a study on conductance mechanism of laminated and dispersed shaly sandsto establish a new generalized resistivity model ,so as to improve evaluation accuracy on watersaturation calculated in complex shaly sand reservoirs. The work in the paper included:designand making of synthetic cores for laminated and dispersed shaly sands,experimentalmeasurement on resistivity of synthetic core samples and establishment of resistivity model forlaminated and dispersed shaly sands.Based on the theory about rock forming in sedimentology and some knowledge in reservoirphysics,permeability test of 5 factors and 5 levels for clean sands is carried out using orthogonaltest and the influence order on permeability of sand content of different grain sizes andcementing material content is obtained.Through orthogonal test,a new method of makingsynthetic cores of laminated and dispersed shaly sands is developed,and 16 synthetic coresamples with different distributions and contents are designed and done.Conductivity of synthetic core samples with different salinities and different watersaturations is measured and the relationship between conductivity of core sample saturated withdifferent saline solutions and conductivity of solution as well as the relationship betweenconductivity of core sample with different water saturations and water saturation are studied.Itshows that conductance of laminated and dispersed shaly sand may be treated as parallelconductance between laminated shale and dispersed shaly sand.Based on parallel conductance between laminated shale and dispersed shaly sand,and theassumption under which dispersed shaly sands are described with dual water conductivitymodel,a new dual water conductivity model for laminated and dispersed shaly sands isestablished.Through analyzing some factors which affect the dual water model ,it is found thatthe shale distributions largely affect the water saturation calculated by dual model, and thecementation exponent and coefficient b will also largerly affect the results calculated by dualwater model with the increase in water saturation.Compared the results calculated by doublemodel with the results of experiment measurements for 16 core samples,it shows the dual waterconductivity model for laminated and dispersed shaly sands can be applied to cleansands ,laminated shaly sands , dispersed shaly sands , laminated and dispersed shaly sands.A newway to solve for water saturation and determine parameters in proposed dual water model isgiven.After appling,the proposed double water resistivity model to data for wells #SU1and#SU3,the result shows that dual water resistivity model for laminated and dispersed shaly sandscan be applied in complex shaly sand reserviors and is a generalized resistivity model.