CBM reservoir log and fine geo-model analysis techniques:Taking CBM in Surat basin as an example

Deep geological knowledge of CBM reservoir log and geo-model are very important aspects that will influence the development effect of CBM gas field. Targeted at the low rank coal-bedding strata,the CBM project in Surat basin Australia had hundreds of wells that were measured in large time span. Also,these wells are in different well- spacing but in big variance in production rate. The reservoir study in old days was only to focus on the coal member,which is too coarse to meet the need of finer development and higher production rate. According to actual production need,the authors propose a set of techniques of deeply understanding reservoir. The first one is to build a multi-level framework of high resolution coal sequence strata in order to reveal the rules of coal ply space distribution and drainage area. The second is to create a workflow to do the log normalization so as to accurately interpret the coal thickness in wells. And then based on all analysis above,a coal-ply based model is built to explicate the complex of coal and the gas in place of gas field. This study has built a coal-based multi-stage high resolution sequence framework in order to depict pinch-out,merge features and drainage area of coal ply. Fine-coal log interpretation and quantitative complex li- thology based on log normalization ensure the accuracy of coal ply and other lithology. Five micro-facies concept model was built. Gas field ply-based geo-model will be used to test the future regional stochastic swamp-based geo-model so as to reasonably optimize whole regional development plan and improve production rate based on the learning from ply model.