SPE Journal
Volume 10, Number 3, September 2005, pp. 286-296

Summary

The need for accurate well-productivity models with arbitrary well trajectories spurred a revival in analytic solution methodology for fluid transport problems. Analytic formulations often depict single-phase flow throughout the reservoir. The Babu-Odeh horizontal-well solution for a box-shaped reservoir with spatially invariant properties is generalized here to allow closed-form solutions for heterogeneous media. A reservoir is decomposed into interacting regions, each with its own reservoir properties and associated analytic potential flow solution. Using established boundary element techniques, pressure and flux continuity are imposed at selected interface points to solve for the steady material exchange between regions.  Constant pressure and zero flux features (fractures and barriers) are easily entertained at region boundaries. The 2D, pseudosteady-state solution for heterogeneous media is embedded within a reservoir performance feedback loop of a powerful gradient search method to produce a robust optimal infill well placement algorithm. Utilizing this approach, new criteria are developed concerning optimal placement of vertical wells for primary production with respect to heterogeneity, asymmetry, and anisotropy. The semianalytic method has been extended to 3D flows to serve as a compute engine for a new generation of reservoir management and optimization tools.

Introduction

Well-placement strategy in infill programs is strongly dependent upon the reservoir development plan and the present stage in that overall plan. Often, well patterns are deployed based upon uniform permeability models; however, the role of reservoir heterogeneity can be formidable. Most wells are placed as production wells and selectively converted to injectors as fields mature and interwell communication patterns become increasingly important. While reservoir engineers have numerical simulation methods capable of reservoir performance feedback with regard to candidate well placement, many of these models have inherent restrictions on the ability to accurately model well performance. Few reservoir engineers have the luxury to discretize on the level of the wellbore radius, but rather rely on block-centered, wellbore coupling correlations. Well production engineers utilize models with fine-scale discretization; however, their inflow performance predictions can be limited in reservoir scope.

© 2005. Society of Petroleum Engineers

View full textPDF ( 1,419 KB )

History

• Original manuscript received: 3 February 2004
• Revised manuscript received: 18 April 2005
• Manuscript approved: 21 April 2005
• Version of record: 15 September 2005