Productivity evaluation of horizontal well in heterogeneous reservoir with composite water aquifer

Abstract

Horizontal well is an important way to develop thin reservoir with edge-bottom water aquifer. For the horizontal well near oil–water contact, the reservoir have the features of edge water and bottom water at the same time. The productivity formula of horizontal well in pure edge water or pure bottom water reservoir is not fully applicable to this type of reservoir. For the heterogeneous reservoir with composite water aquifer, the horizontal well is divided into multiple well sections by using the concept of multi-segment well. Based on the seepage mechanics theory and potential superposition principle, considering the mutual interference between multi well sections, the productivity formula of horizontal well in heterogeneous reservoir with composite water aquifer is established. The new productivity formula considers the effect of reservoir heterogeneity, the quasi-linear flow of lateral edge water and the ellipsoidal flow of vertical bottom water. It can effectively determine the influence range and drainage distance of edge water in a heterogeneous reservoir with composite water aquifer. According to the test data of horizontal wells in Weizhou 11-1 oilfield, the drainage distance b of edge water is fitted and used to predict the productivity of new wells, and the result is very good. The research result lays a foundation for productivity prediction of horizontal well in heterogeneous reservoir with composite water aquifer.

Enhanced Oil Recovery Through Balanced Production Techniques in Horizontal Wells of Bohai A Oilfield

“…In a parallel study, Yuan et al [24] developed a theoretical approach for wellbore pressure in a reservoir of infinite size with closed top and bottom boundaries under stable conditions. This led to the formulation of a three-dimensional steady-state productivity model for horizontal wells in bottom water reservoirs:…”

A novel model for predicting the productivity index of horizontal/vertical wells based on Darcy's law, drainage radius, and flow convergence

“…Naturally, the reservoir energy may drain oil from the sides or bottom of the well if there is edge water or bottom water aquifer, respectively [ 5 ]. Thus, the integral of the drainage radius is from the well to the external drainage of the reservoir, while that of the pressure drawdown is from the flowing well pressure to the reservoir pressure.…”

“…The production rate and pressure drawdown of an oil well are connected by the expression in Eq. (1) , which is the inflow performance equation [ [1] , [2] , [3] , [4] , [5] ]: Thus, oil operators can derive the expression for the productivity index of oil wells using Eq. (2) : …”

“…Many scholars have studied the PI of horizontal wells [ 5 , 6 , 14 ] and vertical wells [ 1 , 2 , 12 ] over the years. The main components adopted in the studies are Darcy's equation, reservoir geometry, and the flow regime, which varies for vertical or horizontal wells.…”

“…As the reservoir energy drives the fluids toward the well, the radial flow comes from all directions within the formation's thickness [ 1 , 10 ]. There might be an edge [ 5 ] or bottom water [ 17 ] in the aquifer. The linear flow comes from the movement of fluids through a non-changing cross-section, with both ends open to the flow and no fluids crossing the lateral or vertical sides [ 1 , 8 ].…”