Research Of Productivity Of Horizontal Well In Low Permeability Reservoir

At present, there has been many cases in developing low permeability reservoir by usinghorizontal wells home and abroad. If horizontal well can be used to develop low permeabilityreservoir, not only effective displacement pressure can be built and pressure drop around thewellbore can be lowered, but also more number of fractures can be throughed. It is significantto predict productivity of horizontal well in low permeability reservoir correctly, because it isinvolved in optimal design of horizontal well, development effect and economic efficiency.Based on the determination of TPG, stable productivity of horizontal wells is derived byprinciple of superposition. The influencing factors of stable productivity of horizontal wellsare analysed including TPG, coefficient of deformation, anisotropy factor, horizontal welllength, reservoir thickness. Basic seepage differential equation of one-dimensional radial fluidflow is established for performance of horizontal wells in low permeability reservoir. In orderto solve the equation, Laplace transform is used and Laplace space solution is obtained, andthen physical space solution is got by Stehfest numerical inversion. Further more, thechanging regularity of dimensionless bottom hole pressure(BHP) is analyzed on the basis offixed prodution and the changing regularity of dimensionless production is analyzed on thebasis of fixed BHP.In the process of deriving stable productivity of fractured horizontal wells in lowpermeability reservoir, it is vital to get the output of every fracture by using EquivalentFiltrational Resistance Method(EFRM). The productivity equation from this text is comparedwith other four different formula. Then applicable conditions of every formula and optimizednumber of fractures are gained. For non-steady-state productivity of fractured horizontal well,mathematical model was established which is in situation of a box-type reservoir. Solutionwas got by the Green Function and Source Function method. Then analytical formulas wasgained. On the basis of that, the changing regularity of output of every fracture were analysedand output of fractured horizontal well in a condition of different number of fractures wascompared.In research of productivity of horizontal well in areal well pattern, filtrational resistancewas defined in low permeability reservoir. Productivity of horizontal well was derived by EFRM in a condition of four-spot, five-spot, seven-spot and nine-spot well pattern withvertical well and horizontal well combination. In addition, the influencing factors ofproductivity of horizontal well in a condition of areal well pattern are analysed including TPG,penetration ratio, formation thickness. Productivity of horizontal well in a condition of arealwell pattern with horizontal wells was treated by numerical simulation approach. It is firstproposed that the influence of TPG was reflected by relative permeability of oil. Then lowpermeability reservoir can be processed by the common numerical simulation software.