Study On Evaluation Of Horizontal Well Productivity In Low Permeability Reservoir

In this paper,the productivity of horizontal well in Low-permeability Reservoir is studied.On the basis of the deep investigation of the relevant literatures at home and abroad,this paper makes a comparative study on the applicable conditions,influencing factors and productivity forecast results of the typical horizontal well productivity prediction models,and puts forward a formula for predicting the productivity of the horizontal wells in low-permeability reservoirs considering the influence of wellbore friction resistance.Firstly,based on the model assumption and the derivation process of the typical horizontal well productivity prediction model,the applicable conditions of various horizontal well productivity prediction models are summarized systematically.Aiming to the weakness that pf expression is not given in the Yudandan prediction model,the mathematical expression of pf and the formula of capacity calculation are proposed,and the Yudandan formula is perfected.Secondly,the horizontal wellbore is divided into several micro-segments based on the research of wellbore friction,the pressure drop of micro-element section and the total pressure drop along the micro-element section when the fluid flow into the horizontal section in different forms are deduced,and it is introduced into the horizontal well productivity prediction model,and on the basis of the existing horizontal well productivity formula,a new horizontal well productivity formula considering the wellbore friction is deduced.Then,in view of the problem that the productivity of horizontal well in Low-permeability reservoir is affected by starting pressure gradient,skin coefficient,wellbore friction,the problems of geological and engineering factors,such as the length of horizontal section,compare the productivity of conventional horizontal wells,the productivity of horizontal wells considering start-up pressure gradients,the productivity of horizontal wells considering the skin coefficient,and the productivity of horizontal wells considering the frictional resistance of wellbore are compared.Finally,Petrel software is used to model the BM project,using the existing typical horizontal well productivity formula and the productivity formula that this paper deduces to make the initial distribution of the wells in the different development schemes of BM Reservoir.And then eclipse software is introduced to simulate and predict the three kinds of development schemes of the reservoir.It is found that it is better to develop the low permeability reservoir with horizontal well than the straight well by comparing three kinds of development schemes.