Comprehensive Study Of The Fluid Property Identification Methods Using Both Well And Mud Loggings For The Reservoir With Low Porosity And Low Permeability

Due to the low porosities of the reservoirs with low porosity and low permeability,the pore fluids usually have little effects on the responses of well logging and mud logging.Hence,using separatly of well log or mud log to identify fluid property is not so well.The researches on the fluid property identification using these two methods thus have drawn great attentions.It is of great importance to know the applicability of each fluid property identification method using well and mud loggings,which is essential for the development of a method of identifying fluid properties using the comprehensive data of well and mud loggings.This will promote the exploration and production of the reservoirs with low porosity and low permeability.It also provides the basis for the exploration and production of the unconventional reservoirs,such as the tight oil and gas formation and the shale oil and gas.Firstly,the fluid property identification methods using well and mud loggings are reviewed systematically,based on which the classification method is given.The current situations,existing problems,and the research trends of the comprehensive fluid property identification method using both the data of well and mud loggings are also analyzed.The research proposal and the technology roadmap are then provided.Secondly,fluid property identification methods using the well logging methods,such as the cross plots of the AC-RT and the(?_N-?_D)-RT,are tested in the blocks with low porosity and low permeability(Xin 451,Yin 2,and Su 77)and their applicability is analyzed.It is found that the well logging methods have the good effect to identify the dry and pay layers.However,it is hard to identify the fluid properties when the porosity is below a certain value,the application of these methods are greatly influenced by the physical properties of the reservoirs.For the formations with clay additional conductivities,the low resistivity induced will further influence the identification of the fluid properties.Thirdly,the fluid property identification methods using the mud logging methods,such as the cross plots of the Bh-(C3+C4+C5)/C2 and Pg-S2/(S0+S1),are also tested in the same blocks with low porosity and low permeability(Xin 451,Yin 2,and Su 77)and their applicability is analyzed.It is found that it is hard to use the mud logging to classify the dry and pay zones.However,its ability to identify the pay zones with low porosity is better than the well loggings.Due to the influences of the mud washing,the interpretation results given by the geochemical logging for the fluid properties in the reservoirs with relative high porosities will be a little bit lower than the real values.The gas logging can be easily influenced by the mud viscosity,bit types,which have some influences on the interpretation results before the effective corrections are made.Fourthly,using the step by step discriminant analysis method,the sensitive parameters of the well and mud loggings are extracted.The approach to identify the fluid properties using the comprehensive data of well and mud loggings is proposed based on the membership theory of fuzzy math.The examples in the targeting areas show that this approach can obtain better results than the ones using sole well logging or mud logging data(the accuracy rate increases by 10%in this case).The shortage of this approach is that it is not so effective in the formations with a little bit larger porosities and low resistivity,which need more studies in the future.Finally,the major conclusions and understandings obtained from this research are summarized,and the suggestions for the researches in the next step are also given.