Coal Seam Gas Pressure Cracking Horizontal Well And Multi-branch And Well Test Theory Research

Coalbed gas is an Associated minerals of coalbed,belonging to the unconventional natural gas,has a certain resource distribution in China.As the migration process of coalbed gas is characterized by the phenomenon of desorption,diffusion and so on,its flow has certain particularities.Currently the main development mode is adopting fractured horizontal well and multilateral well technology.Based on a great amount of literature about coalbed gas reservoir well test analysis,we set the well test analysis models of different reservoirs by using point-source approach.Applying semi-analytical method,we obtained the solution in Laplace domain,and with the help of computer programming,the typical curves of fractured horizontal wells and multilateral Wells of coalbed can be easily plotted with Stehfest algorithm and different regimes can be identified then.The main ideas carried out from this research are the following:(1)The coalbed which can be consider as a dual-medium model is mainly consist of a matrix and fracture system.The desorption and diffusion phenomena in coalbed can be described by the Langmuir adsorption isotherm and Fick's law respectively.(2)Set up the dual-medium reservior well analysis model of fractured horizontal well and multilateral(considering infinite conductivity fracture)well with different boundary conditions.Apply point-source function method for analysis solution,then draft the typical curve with the aid of programming.(3)Identify the flow regimes of fractured horizontal well,cluster multi-branch wells and fishbone multilateral wells base on the typical curve,and deeply analyze the effect of sensitive factor,such as storability ratio,storability ratio and inter-porosity flow coefficient and inter-porosity flow coefficient on the pseudo-pressure responses.