Fine Logging Evaluation Of Shale Gas Reservoir In The Weiyuan-Changning Area

Shale gas has become a hot spot of unconventional natural gas exploration and development in the world,it exists in almost all basins.The hydrocarbon accumulation and forming mechanism characteristics of shale gas reservoir are different from conventional gas reservoir,as the porosity,mineral composition and the depth of burial vary greatly,shale gas can be quite differently in industrial exploitation value,and the domestic shale gas logging evaluation technology is relatively weak.Therefore,it is necessary to establish a detailed evaluation methods for shale gas reservoirs and to predict the favorable shale gas reservoir areas.For that reason,taking the Weiyuan-Changning area,Sichuan Basin shale reservoir as an example,combining with the data of geology,well logging and core experiment,the following work is carried out:(1)Studied on logging response characteristics of shale gas reservoir by collecting conventional and special logging data,the application of different logging projects in geology and engineering is summarized,and optimized shale gas well logging series according to the actual needs in the different stages of exploration and exploitation.(2)The principle and applicability of various methods for distinguishing and identifying shale gas reservoirs were thoroughly analyzed,the accuracy of each method were evaluated.It was ultimately determined to take the conventional logging data combination method together with the bulk density TOC indication method as the reservoir identification method of shale gas reservoir in research area,and established the recognition division standard,what can provide an important basis for accurate classification and identification of shale gas reservoirs.(3)The "Five indexes" evaluation methods of shale gas reservoir were formed:a model of "six elements" rock volume of organic shale is established,and calculated the formation of mineral components by multi mineral optimization method and multiple regression method;established theoretical model for calculating physical parameters and a model for core data fitting;established total organic carbon content calculation models of density method,uranium curve method,multiple regression method and kerogen method,the calculation accuracy of each method is compared and the applicability evaluation is carried out;discussed the calculation methods of adsorption gas and free gas content;shale brittleness index is evaluated by elastic parameter method and mineral composition method,taking into account the limitations of the two methods,a new method,named modified mineral composition,has been established.(4)According to foreign experience,combined with geological and reservoir conditions of the study area,determined criteria for evaluation factors,the weights of each evaluation index are determined based on AHP.Based on the VB6.0 visual language,a program for predicting the favorable zone of shale gas was developed by using the fuzzy mathematics method,which was applied to the shale gas block in Weiyuan-Changning area and achieved better results.According to the above study,the well logging evaluation of the study area was carried on in the paper,and evaluated the actual well in Longmaxi Fm-Wufeng Fm,Southeast Chongqing,the result shows that the logging evaluation method established in this paper has certain popularization in different areas.Finally,it has formed a set of well logging evaluation methods and reasonable standards for marine shale gas reservoirs in the study area,it can provide some help for further exploration and development of the work area.