Pressure-Transient Responses of Horizontal and Curved Wells in Anticlines and Domes

Abstract

This paper presents a discussion of the pressure-transient responses of horizontal wells in anticlinal structures and curved and undulating wells in slab reservoirs. It confirms that, in the absence of a gas cap, conventional horizontal-well models may be used to approximate the flow characteristics of the systems in which the trajectory of the well does not conform to the curvature of the producing structure. If a gas cap is present, however, the unconformity of the well trajectory and producing layer manifests itself, especially on derivative characteristics when the gas saturation increases around the well. In general, the most significant deviations from the conventional horizontal-well behavior are observed during the buildup periods following long drawdowns. In these cases, the pressure-transient analysis is complicated and requires detailed numerical modeling of the well trajectory and reservoir geometry in the vertical plane. Numerical Simulation of Horizontal-Well Responses In this paper, we have used two finite-difference formulations of transient flow for a horizontal well (see Appendix A). The first formulation was for single-phase flow, and the second formulation was for two-phase flow of oil and gas (the relative permeabilities used in this work are presented in Appendix B). In the latter, we have neglected gas solubility in oil for simplicity. (Solution gas

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“…where r eq is the equivalent radius (Peaceman 1978;Al-Mohannadi et al 2007) and r w is the wellbore radius. Equations (3.10) and (3.11) form a system of linearized equations for reservoir and wellbore pressures and this set of equations is solved using an approximate factorization technique.…”

“…This partially results from the inherently three-dimensional nature of the flow (the radial symmetry observed in vertical wells does not occur in the same way for horizontal wells). Therefore, due to its importance for reservoir engineering applications, much research has been done considering horizontal wells (Al-Mohannadi et al 2007;de Souza et al 2014;Shahbazi et al 2015). It is important to note that in the last decades many works have been produced aimed at optimizing recovery in unconventional hydrocarbons reserves, as for example, tight oil (Wang et al 2013;Hu et al 2017).…”

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“…Mohannadi et al (2003) [17] presented a solution for the pressure-transient responses of horizontal wells in anticlinal structures and curved wells in flat reservoirs. He investigated the validity of conventional horizontal-well models use in the absence of gas cap.…”