Study On Optimization Design Of Well Trajectory For Coalbed Methane Cluster Well

As an economical and effective new well type,cluster well has the characteristics of saving space,low cost of investment,quick effect,easy management and large gas control area,which has been widely used in the mining of coalbed methane.In the process of developing coalbed methane with cluster wells,a very important problem is the design of well trajectory of the cluster well.The design of the well trajectory is related to the quality of the drilling,the cost and the cycle of the drilling,and the difficulty of the construction.Because the cluster well need to arrange many wells on a drilling platform,the matching of the wellheads of the cluster wells and the corresponding targets is also a very important problem in the design of the cluster wells.Therefore,it is of great significance to study the design of well trajectory of the cluster well and the matching of wellheads and targets to guide the efficient development of coalbed methane by using cluster wells.The main factors of the design of well trajectory of the cluster wells are analyzed in this paper,which are mainly divided into two aspects: the influence factors above the cluster well target and the influence factors below the target.On the basis of the analysis of the influence factors,based on the basic calculation model of the two-dimensional and three-dimensional well trajectory,the optimization model of the two-dimensional and three-dimensional well trajectory and a three-dimensional well trajectory optimization model based on the virtual target are established by making the depth of kick off point,the hole curvature and the angle of inclination of the well and so on as the constraints and the shortest well trajectory length as the optimization target.The optimization model is solved according to the optimization theory.The results have shorter well trajectory length and lower hole curvature and angle of inclination of the well than the conventional well trajectory design.In this paper,the matching optimization model and the matching flow of the wellhead target matching in the process of factory operation are given.Finally,the exploitation of the coalbed methane by using the spoon-shaped well trajectory is put forward in view of the problem of "dead gas zone" under the drilling platform in the process of the development of the coalbed methane with the conventional cluster wells.This method can increase the coalbed methane production below the drilling platform and realize the efficient and low cost development of coalbed methane.