The Comparison Of Continental Shale Gas Resource Calculation Methods

Compared with the marine shale reservoirs,the continental shale reservoirs have the characteristics of smaller reservoir distribution range,faster lateral change,stronger reservoir heterogeneity and thinner longitudinal distribution,and the complexity of the lateral and vertical distributions of the continental shale gas leads to the accuracy calculation of land-based shale gas resources as a hot and difficult spot in recent years.The calculation methods of marine shale gas resources are more mature,which mainly adopt the genetic method,volumetric method and analogy method,while the study of complex continental shale gas is still at the initial stage,especially the computational researches of continental shale gas are relatively weak.In this paper,the advantages and disadvantages of shale gas resource calculation methods such as analogy method,statistical method,TOC genetic method and comprehensive method are studied by investigating a large number of related journals at home and abroad.The TOC genetic method,volumetric method and analogy method are used to calculate and compare the gas resources of Chang 7 Oil Formation in the GanQuan area of Ordos basin.Based on the geological characteristics of shale gas in the study area,lithology is identified qualitatively and quantitatively by core observation and logging interpretation.On this basis,the area,thickness,gas content(adsorbed gas content and free gas content),porosity,gas saturation,gas compression factor,gas volume coefficient,original gas/oil ratio,unit organic carbon generation,analogy similarity coefficient,total organic carbon and exhaust coefficient needed by three methods of land shale gas resources are determined by multiple regression analysis,graph method,?1gR method and empirical formula.The sizes and distribution of the amount of resources and the abundance of resources are studied.The consequences of the resource calculation show that the results of shale gas resources calculated by TOC genetic method,the volumetric method and the analogy method are different to some extent by the combined effect of the key parameters.The amount of resources calculated by the volumetric method is relatively large,about 18969.8 × 108m3,the amounts of resources calculated by TOC genetic method and gas content analogy method are relatively close,respectively about 13912.2 × 108m3and 13902.1 × 108m3,The results of the resource abundance calculated by three methods are relatively close,range from 0.6 × 108m3/km2 to 5.7 × 108m3/km2,with an average of 3.6 × 108m3/km2.The abundance of shale gas resources in the ShangXiaSiWan-GanQuan area is the largest on a flat surface.Comparative study of the results of shale gas resources and resource abundance by three methods concluded that,although the theory of TOC is more complete but in practice more difficult because of the hardness to get exhaust coefficient;The volumetric method requires a higher degree of exploration for the supply area and the accuracy of the calculation is not as good as the genetic method,but the operability is higher;Gas content analogy method has a strong human subjectivity,and Barnett shale as a standard area belongs to Marine,which vary to continental shale has in some extent,compared with the TOC genetic method and the volumetric method,the accuracy is not high.