Tectonic evolution and probability distribution of CBM resources in Jixi Basin

Jixi Basin is one of the important target areas for exploration among the external basins in the eastern part of Songliao Basin.Several sets of coal seams developed during Early Cretaceous with wide distribution and abundant reserves,and they are also important source rocks.On the basis of studying the characteristics of geological structure in Jixi Basin,the subsidence history of Well Ji--D1 was recovered.The curves of subsidence history reflect that the basin experienced the express faulting subsidence in early stage,but three times of short-term uplifts and erosions happened during this period.From the deposition of Houshigou Formation in the upper part of Lower Cretaceous,the basin began to enter a relatively stable period of settlement.After the deposition of Hailang Formation,long time(about 28 Ma) uplift and erosion has taken place in the region,which was the main structural deformation period in the evolution history of Jixi Basin,and also was the formation period of basic structural pattern in the basin.According to the related parameters of coal seams formed by the express faulting subsidence in early stage and calculated the amount of coal-bed methane resources using Monte--Carlo method,the resources are 8.17×1011 m3,5.36×1011 m3 and 2.41×1011 m3 respectively at the probability of 0.1,0.5 and 0.9.