A method to calculate displacement factors using SVM

In order to improve the precision of mining subsidence prediction, a mathematical model using Support Vector Machine （SVM） was established to calculate the displacement factor. The study is based on a comprehensive analysis of factors affecting the displacement factor, such as mechanical properties of the cover rock, the ratio of mining depth to seam thickness, dip angle of the coal seam and the thickness of loose layer. Data of 63 typical observation stations were used as a training and testing sample set. A SVM regression model of the displacement factor and the factors affecting it was established with a kernel function, an insensitive loss factor and a properly selected penalty factor. Given an accurate calculation algorithm for testing and analysis, the results show that an SVM regression model can calcu- late displacement factor precisely and reliable precision can be obtained which meets engineering requirements. The experimental results show that the method to calculation of the displacement factor, based on the SVM method, is feasible. The many factors affecting the displacement factor can be consid- ered with this method. The research provides an efficient and accurate approach for the calculation of displacement in mining subsidence orediction.

APPLICATION OF SINTAP TO THE SAFETY ASSESSMENT OF X65 PIPELINE STEEL

The recently developed European flaw assessment procedure, structural integrity assessment procedure（SiNTAP） is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. As one of the basic input data, fracture toughness crack tip opening displacement （CTOD） tests are conducted at 0℃ and performed according to the requirements of the standard of BS7448. For the heat affected zone （HAZ） specimens, the microstructure observation is performed to insure that the tip of the crack is located in the coarse grain zone. The result explains the dispersity of the test values. In structural integrity assessment procedure-fracture assessment diagram（SINTAP FAD） method, the failure curves of welded joints at level 1 and 3 are derived from the tensile test results. The results of the assessment show that all assessment points are located within the failure lines of analysis level 1 and 3. So the welded joint of the pipeline is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.

Application status and research progress of CO_(2) fracturing fluid in petroleum engineering:A brief review

This paper comprehensively reviews the application and research progress of CO_(2) fracturing fluids in China,highlights the existing issues and puts forward suggestions for future development.Three types of fracturing fluid systems containing CO_(2),namely,CO_(2) dry fracturing fluid,CO_(2) energized fracturing fluid,and CO_(2) foam fracturing fluid,are categorized based on the mass ratio and process difference between CO_(2),water,and treatment agents.Field applications in China reveal several problem to be resolved:(1)The application scope of CO_(2) fracturing fluids is restricted to depleted reservoirs,re-fracturing of old wells,and medium-deep reservoirs with low formation pressure coefficients;(2)different types of CO_(2) fracturing fluids require different processes and ground supporting equipment;(3)optimization of CO_(2) compatibility,functionality,temperature and salt tolerance,as well as the cost of treatment agents is necessitated;(4)existing CO_(2) fracturing fluid system fail to perform well with low friction,low filtration,and high sand-carrying capacity.(5)there lacks a targeted industry standard for evaluation of performance of CO_(2) fracturing fluid system and treatment agents.Therefore,in order to meet the goals of CCUS-EOR,CCUS-EGR,or integration of fracturing,displacement and burial by CO_(2),efforts should be made in the aspects that followed,including in-depth investigation of the mechanism of CO_(2) fracturing fluids,the adaptability and compatibility between existing equipment,different CO_(2) fracturing fluid systems and processes,and construction of treatment agents,low-density proppants and highperformance systems of recyclability and industrial-grade.In addition,optimization of CO_(2) fracturing fluid system based fracturing design is also crucial taking such related factors such as overall reservoir geological conditions,petrophysical properties,CO_(2) transportation,and well site layout into consideration.