Shale Gas Fracturing String Design And Mechanics Analysis

With the rapid development of world economy, the consumption and demand of energyis rising. Unconventional energy, including shale gas is becoming more and more important.The United States is the earliest country who makes shale gas mining large-scale in the world,its mining history can be traced back to as early as1921. In the1920s it began to modernindustrial production and in the mid70s into the large-scale stage of development, while ourcountry is just at the beginning stage. As a kind of unconventional natural gas, the productionof shale gas is lower, and fracturing is an important means of improving its yield. Foreigncountries have already formed a serious of relatively mature fracturing technologies of shalegas, and our country is still at the experimental stage. So it is of important practicalsignificance to develop the design and mechanical analysis of shale gas fracturing string.This thesis made a comprehensive research of the working principle and applicableconditions of the domestic and international shale gas fracturing technology, summarizingtheir respective advantages and disadvantages as the theoretical guidance of this paper’sresearch direction. The paper designed a kind of double packers-multistage fracturing string,designed the structure and selected the down hole tools on the basis of the multistagefracturing and backwashing well function, making it has a simple structure, convenientconstruction, high reliability, perfect function characteristic. A spline model of3D welltrajectory was created based on the basic inclinometer data of well trajectory, which cancalculate deviation angle, azimuth angle, curvature and torsion of well trajectory at any depth.According to the corresponding parameters we can optimize the size of the fracturing string,determining the largest outside diameter or maximum length of the tool-string. Syntheticallyconsidering the axial force, weight of tubing string, fluid pressure and viscous frictionresistance, the friction and anti-force of well wall, string mechanical model is established tomake stress calculation and strength check on the fracturing condition.A software of the shale gas fracturing string stress analysis was developed by VBlanguage. In the preprocessor part of this software you can input, modify and fit the basicinclinometer data of well trajectory and basic parameters of tubing and casing. Aftercalculation is finished we can view well track horizontal projection and vertical projection drawing and3d coordinate figure. Main part can calculate the depth of large diameter toolsand stress distribution of the string under the condition of fracturing, calculation results willbe saved in the form of excel and the load, stress and deformation curve along with thechange of well bore can be viewed.