Horizontal Injection and Production Wells for EOR or Waterflooding

Abstract

This paper describes the potential benefits of using combinations of horizontal injection and production wells for EOR processes or waterflooding. Our results show that a very favorable configuration occurs when two opposed horizontal wells are drilled from injection and production wells so that the opposed laterals are parallel in the patterns, and extended until the horizontal segments almost meet midway between the like wells. Compared to five-spot patterns with vertical wells, opposed horizontal wells can increase injectivity (injection rate per applied pressure drop) by as much as a factor of ten, depending on well spacing and formation thickness. Areal sweep efficiency can be increased by 25% to 40%. The horizontal-well advantages are greatest for thin formations with wide spacing, and decline significantly for thick formations and/or close spacing. Also, for a given injection pressure, the pressure gradient in the bulk of the reservoir can average several times greater when using opposed horizontal wells than when using vertical wells. This could significantly improve microscopic displacement efficiencies for EOR processes, such as micellar/polymer flooding, that are sensitive to interfacial tensions. Because of the better sweep efficiencies, faster flooding rates, and/or lower injection pressures that are possible with horizontal wells, all EOR methods should benefit by their use. For example, polymer floods can be improved by the higher injectivity and lower rates of shear at the injection sandface. The advantages of horizontal wells for CO2 flooding include: (a) delayed CO2 breakthrough because of the better sweep efficiency, (b) the potential for maintaining the MMP in more of the reservoir with no increase in the injection pressure, (c) better injectivity at the same pressures, and (d) the opportunity to convert more pumped producers to flowing wells. Thermal EOR was not investigated in this work, but the cited references show that horizontal wells have been successful in several field applications and more projects are being planned.

Potential for Polymer Flooding Reservoirs with Viscous Oils

“…Another important change since the time when earlier screening criteria for polymer flooding were developed (Taber et al 1997a(Taber et al , 1997b has been the dramatic increase in the use of horizontal wells. Use of horizontal wells significantly reduces the injectivity restrictions associated with vertical wells, and injector/producer pairs of horizontal wells can improve areal sweep and reduce polymer use requirements (Taber and Seright 1992).…”

Reservoir Characterization, Production Characteristics, and Research Needs for Fluvial/Alluvial Reservoirs in the United States

“…The demonstration of improved methods for designin~drillin~evaluatin~and completing horizontal wells will help to fuxther reduce costs and expand applicability of horizontal wells. Horizontal wells have been successfully employed in the following applications (1) mtural.ly fractured reservoirs to intersect fracture systems, (2) thin or low permeability reservoirs to increase area to flow, (3) gas storage reservoirs to meet peak deliverability demands, (4) more permeable reservoirs to solve gas or water coning problems, and (5) as injection or production wells in waterfloods and EOR projects to increase injection rates or to improve sweep effiaency (Mutalik and Joshi 1993;Coffin 1993;and Taber and Seright 1992). Although horizontal wells are more expensive than vertical wells, the productivity increases and recovery improvements typically more than justify the increased expenditures OTT 1993).…”

Increased Production Results from Pilot Horizontal Waterflood in Osage County, Oklahoma

“…Horizontal waterflooding, and specifically horizontal injection wells, have been the subject of numerous studies and technical papers in recent years. [2][3][4][5][6] Joshi, in a follow up to his 1991 book 7 , investigated and summarized the current applications of horizontal technology in 2003. 8 This paper emphasizes the lessons learned in the process of conducting the project and the adjustments made to further enhance oil recovery.…”