Abstract

This paper investigates the rate-pressure behavior of a horizontal oil well with a fully penetrating wellbore producing during the boundary dominated flow regime. Based on linear regression analysis of simulator results, two empirical inflow performance relationships (IPRs) are developed to estimate well performance. A future performance relationship is also developed to allow estimates of future rate-pressure behavior from current test information. The IPR relationships are compared to other horizontal IPRs available in the literature and yield reasonable estimates of well behavior over a wide range of operating conditions.

Introduction

The number of horizontal well drilled by the oil and gas industry has escalated rapidly since the mid-1980's primarily because the wells offer production solutions where conventional technology either fails or produces results that are less than desirable. The major advantage of a horizontal well is to increase the reservoir contact area and thereby enhance well productivity or injectivity. Compared to a vertical well, the horizontal well can achieve higher ultimate recovery and produce at higher flow rates in certain reservoir conditions. The horizontal well may be a viable economic alternative for naturally fractured reservoirs, low permeability reservoirs and in reservoirs with oil and gas coning problems. In many improved oil recovery applications, the horizontal well may be a suitable alternative for both production and injection.

Over the years, the productivity of horizontal wells has been the subject of numerous studies. From these studies, several analytical solutions have been proposed to estimate horizontal well performance.[1–5] These solutions are based on single-phase flow principles and may not be appropriate for two-phase, oil-gas flow.

In time, several investigators have utilized reservoir simulators to study the behavior of a horizontal well producing from solution-gas drive reservoirs.[6–10] These investigations have led to proposed empirical inflow performance relationships (IPRs) to predict the rate-pressure behavior of horizontal oil wells.

In 1968, Vogel[11] presented an empirical IPR for an oil well producing from a solution-gas drive reservoir. This IPR for two-phase, oil-gas flow was based on the analysis of simulation results and gained quick acceptance by industry as it was simple to apply and yielded acceptable results. Fetkovich and others soon followed with similar type IPRs for boundary-dominated flow in oil wells. These relations were developed for vertical wells and may not be appropriate for horizontal oil wells.

Plahn et al.[6] were early investigators who studied the multiphase behavior of horizontal wells in a solution-gas drive reservoir. They used a reservoir simulator to investigate the well behavior and the effect of various reservoir rock and fluid properties on that behavior. From this work, the authors developed a set of type curves that could be used to forecast production from horizontal oil wells producing at their maximum rate.

In 1989, Bendakhlia and Aziz[7] utilized a commercial reservoir simulator to study the performance of horizontal oil wells producing from solution-gas drive reservoirs. Their work paralleled that of Vogel for vertical wells. Based on their simulation results they concluded that the inflow performance curves were not significantly affected by reservoir rock and fluid properties; however, they did find the curves were influenced by the stage of reservoir depletion. They proposed the following IPR for horizontal oil wells.

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