The Fast Logging Evaluation Method For Measuring TOC In The Mudstone Of Wufeng-longmaxi Formation In Zhaotong Region And A Newly Developed Software Of The Method

The shale of Wufeng-Longmaxi Formation in Sichuan Basin is an important formation for shale gas exploration and development in South China and has extensive exploration potential.Comparing with the shale formation in North America,the shale layers in this research has its own specificity,the methods for evaluating TOC,such as ?logR method and multivariate regression,are inapplicable to this investigated formation.A precise method for evaluating TOC is needed.In this paper,shale layers of Wufeng-Longmaxi Formation in Zhaotong region of Sichuan Basin is studied.Through comprehensive analysis on cores,rock slices,log data and the geochemical test data,the feature of the shale and the organic matter of the formation is discussed.Combined the geologic feature and the principle of conventional method of evaluation TOC by logging data,the limitation of those method is discussed.Based on the geological feature and the limitation of other methods in TOC evaluation,a new TOC evaluating method that based on different shale types is proposed.The main achievement is as below:1?Quartz,clay and carbonate are the main components of the shale,while massive bedding and laminated bedding are the main sedimentary structures.The maturity and abundance of organic matter reach the limit of commercial shale gas reservoir.Some organic matter is carbonized.2?The calculated result from ?logR method is much lower than tested TOC data.It can be conclude that the carbonization of organic matter and compressed rock are the main reasons of inapplicability of ?logR method in this research area.The heterogeneity of rock matrix can also affect the accuracy of calculated result from ?logR method.The result of multivariate regression is undesirable because of heterogeneity of the formation.3?Through the analysis on the response of well log to organic matter,it found that the components of rock matrix and the structures reduce the precision in TOC evaluation and a new TOC evaluating method that based on different shale types is proposed.The detail of the method is as below: according to the components and structures of this shale,the shale is divided into several different types,such as silty mudstone,calcareous mudstone,massive mudstone and laminated mudstone,and then apply the multivariate regression method in each type shale.A newly developed software of the method is realized.4?The method has a fine application in well Zhaotong 4,well Zhaotong 6 and well Zhaotong 8,the correlation index is above 0.8 between calculated and tested TOC data.It indicates that this method is applicable in research area and has promotional value in TOC evaluation using log data.