Study Of Productivity Evaluation Of Multilateral Well And Optimum Design Of Injection And Production

Multilateral well is a new type of well,which can effectively exploit deepwater reservoir and complex reservoir,like mluti-layer reservioir, low permeability reservoir, heavy oil reservoir, thin-layer reservoir and fractured reservoir in lower cost. Although applicated in the world and our country,using multilateral well to exploit reservoir is a complex system project. Productivity evaluation of multilateral well is the Primary problem to build and perfect the theory of this new type well.In this paper, productivity evaluation model of multilateral well is derived and built by nodal analysis method,considering coupling of reservoir seepage and wellboe flow.Also the IPR cure is ploted to predict productivity.Here,the multilateral well is classified to two kinds,vertical main wellbore and horizontal main wellbore.The factors effecting multilateral well's productivity is sensitively analyzed by using muliti-segment well model.The research results show that when lateral branch's angle is almost 90 degree in the case of permited drilling conditions,oil production is the most.Without considering the drilling cost,the longer lateral branch's length,the more oil production.Locating lateral branch on the two ends of the main branch can get more oil production.Locating lateral branch on the toe-end of the main branch is better than locating on the heel-end.The number of lateral branches is determined by drilling footage.When the drilling footage is fixed,the more lateral branches, the more oil production.When the drilling footage is not fixed,the more lateral branches, the less oil production.Lateral branch should be seperately located on both sides of the main branch in non-symmetric form.In order to maintain the formation pressure and ensure the reservoir of high liquid supply capability,the technology of using vertical well to injection gets extensive and sophisticated application.In the water flooding process,the conflict between injection and production is very serious.The complexity of multilateral well's structure makes the injection-production relation more seriously.So researching multilateral well's injection-production relation to obtain reasonably well pattern form and well spacing principle is very important to enhancing the effect of injedtion and production.In this paper,micro well pattern is introduced to research the optimization of injection well and production well location. The research results show that the inverse oblique micro well pattern is the best micro well pattern.Locating the injection well far away from the position of lateral branch in the trailing direction can fully play multilateral well's advantage.The five point well pattern is the best and has the weakest interference. The research results of the most disadvantage oblique micro well pattern in five point well patern show that the bigger deflection angle of lateral branch,the better exploiting result.Meanwhile,positive deflection angle is better than negative deflection angle.The lateral branch in the right position of injection well has a optimal length,not the longer ,the better.The point of lateral branch on the main branch lying near the heel-end and far away from injection well can bring bigger recovery percentage.By researching the optimization of oblique micro well pattern,three strategies ,adjusting lateral branch's deflection angle,reducing lateral branch's length and adjusting injection wells'injection ratio are proposed to improve the five point well pattern's injection effect . The research results show that the five point well pattern's injection effect is improved obviously .