Study On Productivity Evaluation Of Multilateral Wells

Multilateral wells are regarded as the revolutionary technology of the petroleum industry,and it has an important influence on the development of oil and gas reservoirs.Under certain conditions,comparing with the conventional horizontal well,multilateral wells can effectively increase the contact area and improve the single well deliverability.Studying on productivity evaluation of multilateral well is the frontier project of multilateral well technology.For spatial multilateral well,Firstly,box-shaped oil reservoir seepage model proposed by Furui is applied to the gas reservoir,and taking the partial penetration skin proposed by Babu into account,the percolation model of horizontal well with arbitrary length in gas reservoir is established.Secondly,we give full considerations to the flow pressure drop of various wellbore parts.Thirdly,the coupling model of gas reservoir percolation and wellbore pressure drop is established to study on the productivity of spatial multilateral well,the partial penetration skin of infinitesimal section proposed by Ding Zhu is considered in the coupling model.Taking a multilateral well with two branchs as an example,the production of each branch and the total production is calculated,and the interference between the branchs is also analyzed.Mainly using the pseudo three-dimensional idea,conformal transformation,the principle of mirror image as well as the theory of potential superposition,and considering the anisotropy effect to study on the production formula of multilateral well,in which the branchs are located in the same layer with perfect symmetric distribution.The influence factors of productivity are also analyzed.For the multilateral horizontal wells that located in the same layer with non complete symmetry,this thesis obtains the productivity equation of two branches and four branches horizontal gas well according to the law of equivalent percolation resistance,and some factors influencing productivity are analyzed.For the fishbone shaped multilateral wells,the flow region is divided into the inner flow region and the external flow region.Based on the conformal transformation and the law of equivalent percolation resistance,and this thesis considers the effects of anisotropy effect and non-Darcy flow effect,so the analytical formula for productivity of a fishbone multilateral is established.