Study On Conduction Mechanism And Model Of Fuyu Formation In Chao-chang Area Of Daqing

Logging evaluation on low porosity and permeability reservoirs is a difficult problem for logging workers.In this paper,on the basis of coring data,core analysis data,oil testing material,and experimental measurement data,the reservoir characteristics of Fuyu formation in Chao-chang area of Daqing,such as lithology,physical property,clay minerals,formation water salinity and pore structure,are reseached using statistical methods.It is found that lithology is mainly siltstone,porosity and permeability are low,clay minerals are primarily illite and chlorite,shale volume,micropore content,and irreducible water saturation are all high.Variation rule of cementation index and saturation exponent is reseached based on core electric experimental measurement data.Since pore structure is complex and conduction mechanism is difficult to describe in Fuyu formation,pore geometric conduction theory is introduced in this paper,which is proposed by Herrick and Kennedy.Considering the results of reservoir characteristic reseach,a general resistivity model for low porosity and permeability reservoirs is established.In the model,electric conduction phases of formation in reseached area are considered to include free water,microscopic capillary pore water and clay bound water.Sevaral variables are defined which can describe effects of free fluid pore geometry,microscopic capillary pore geometry,clay bound water' pore geometry and geometrical distribution of free water on rock conductivity.And water saturation solution method of the model is also given in this paper.Influences of parameters of the model on resistivity index and resistivity are analysed.The precision of the model is verified,and parameters of the model are also determined based on core experimental data.Some log data are processed,and the results are compared with core analysis water saturation in sealed coring well and well test results.The results show that water saturation calculated with the new model is reasonable,and logging evaluation accuracy for low porosity and permeability reservoirs can be improved.