Study On The Productivity Of Fractured Horizontal Wells

With the virtue of larger drainable area and high production, horizontal wells play an important part in exploiting oil reservoirs with low permeability. Sometimes due to the low permeability, large seepage resistance and low connectivity in the low permeable reservoir, the production of the horizontal wells are still very low. Therefore, in order to satisfy the economical exploitation demand, it becomes necessary to fracture the horizontal wells to enhance the production and ultimate recovery.Because productivity predicting is always used to instruct fracturing designs before practicing in oil field, with the increasing amount of fractured horizontal wells, how to do that is becoming an significant research field. Among all the methods, analytic formula and numerical simulation model are the most traditional ways with their own advantages and disadvantages. However, analytic model is usually used to predict the productivity of one phase flow, while numerical simulation model is applied in two or more phases flow.This thesis tries to systematically analyze different ways of predicting the productivity of fractured horizontal wells:(1) Based on the horizontal well sectionalized hydraulic fractured technology actual condition, combining the shape of formed fractures and the fluid peculation mechanism together, and according to superposition theory, we present a new model to forecast the production of the fractured horizontal wells with numerous fractures mutual disturbance.(2) According to reservoir-fracture grid system and IMPES differential method, this paper established a three-dimensional and two phases formula numerical simulation model to predict productivity of fractured horizontal wells. In the model, reservoir and fractures are in same fluid flow system, form a huge seven diagonal linear equation group after difference. Line Successive Over Relaxation(LSOR) can be used as one method to calculate the equation. Meanwhile, several conditions are considered in simulation, such as variation of fracture conductivity with time and effect caused by fluid flowed rapidly in fractures.(3) According to the mathematical models, several factors that influnce the productivity are analyzed, such as fracture conductivity, fracture length, fracture space, fracture number, reservoir permeability and non-equality fracture length.The paper studied in details for the above aspects contents, and some of them are novel and different. Based on the systematical study, this paper preliminary established a set of relatively whole fundamental theory models for productivity predicting of hydraulically fractured horizontal wells, and it can be used to guide the hydraulically fractured horizontal wells.