Horizontal Well Pressure Analysis

Publisher Website
Google Scholar
Abstract
This paper presents an analysis of the pressure transient behavior of a horizontal well or a drainhole. The performance of horizontal wells and fully penetrating vertical fractures is compared. Dimensionless wellbore pressures are computed for two classical boundary conditions; namely infinite-conductivity and uniform-flux. Results are presented as pseudoskin factors and as type curves. In addition to conventional pressure versus time type curves, derivative type curves using pressure-time predictions are presented. The derivative approach we discuss here is new to the petroleum literature and is applicable to a broader range of problems than that considered here. Computations suggest that horizontal well productivity is governed by two parameters: 1) the dimensionless well length, LD (LD=L/(2h)kz/k, where L is the length of the well, h is the formation thickness, and kz and k are the vertical and horizontal permeabilities, respectively), and 2) the dimensionless well radius, rwD, (the ratio of well radius to well half-length if the formation is assumed to be isotropic). Results indicate, that horizontal well productivity (infinite-conductivity) is almost identical to that of a fully penetrating vertical fracture of infinite-conductivity if the dimensionless horizontal well length, LD, is greater than 4.0. This result shows that horizontal wells may perform better than vertically fractured wells, if non-ideal aspects associated with vertically fractured wells such as limited conductivity or height, are taken into account. Results have been obtained for LD in the range 0.1 ≤ LD ≤ 100 and dimensionless well radius, rwD, in the range 10−4 ≤ rwD ≤ 10−2; these ranges should encompass expected values of horizontal well length, reservoir height, and ratio of vertical and horizontal permeability. Pressure responses and pseudoskin factors are calculated for four different well locations within the productive interval. The pseudoskin factors are insensitive to well location.

This publication has 10 references indexed in Scilit: