Research On Logging Evaluation Methods Of Carboniferous Volcanic Reservoir In Chun Feng Oilfield

With large quantities of reserves and considerable single-well production,igneous reservoirs deserve further investigation.However,there are many difficulties in developing igneous reservoirs,such as highly variable lithologies and lithofacies.complexity of reservoir space,conductive mechanism,heterogeneity,parameter evaluation,fluid identification,etc.Therefore,the in-depth investigation should be carried out to establish a series of logging evaluation methods and techniques for igneous reservoirs.Taking the carboniferous igneous reservoirs in Chun feng Oilfield as the object of the research,based on the logging,well testing,NMR and FMI,this paper aims to research on lithology and fluid identification,reservoir space characteristics,determination of reservoir petrophysical parameters,validity evaluation,etc.According to the actual igneous rock development and logging response of study areas,lithology identification of the igneous reservoirs,with the thought of “Step by Step Separation”,were investigated by the combination of Conventional Logging Cross-plot Method,Fisher Discrimination Method and TAS Cross-plot Method.Besides,the type of reservoir space and its development feature in research zone were analyzed by different materials,such as core samples,electric imaging,section identification,so that the relationship between different types of reservoirs space and logging responses or lithologies.In addition,the matrix parameters of different lithologies were confirmed with petrophysical experiments and logging data and the fractures identification were conducted by NMR,electrical imaging and logging data,especially for the method of fracture identification by conventional logging data.The calculation model of matrix porosity and fracture porosity of igneous reservoirs were also built on the basis of different lithologies,including the exploratory research of saturatione calculation,the Conventional Logging Cross-plot Method and the Rwa Discrimination Method were conducted,based on types of lithologies and reservoir spaces.The validity of porosity and fracture identification were performed by thin section,conventional logging data with new techniques such as NMR,electrical imaging XMAC.Therefore,the logging evaluation methods of igneous reservoirs,which were adapted to this research zone,were established in final.According to the methods above,the results showed that the development of the lava class in igneous rock was more complete,especially andesites.The main reason of effective reservoirs formation was development of corrosion and fractures;The calculation accuracy of matrix porosity which depended on lithologies was higher than conventional methods.The similarity between simplified dual laterolog models and fracture porosity calculated by imaging logging were rather strong,excepting the difference in order of magnitudes.Although the saturate calculation existed error with physical truth,the evaluation results could also provide references.The effects of fluid identification method based on types of lithologies and reservoir spaces were relatively better.On the whole,the volcanic breccia had the best physical properties and its reservoirs developed most completely.Meanwhile,the tuff reservoirs developed the least.