Horizontal Injection and Production Wells for EOR or Waterflooding
- J.J. Taber (NM Petroleum Recovery Research Center) | R.S. Seright (NM Petroleum Recovery Research Center)
- Document ID
- Society of Petroleum Engineers
- Permian Basin Oil and Gas Recovery Conference, 18-20 March, Midland, Texas
- Publication Date
- Document Type
- Conference Paper
- 1992. Society of Petroleum Engineers
- 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.4 Enhanced Recovery, 5.6.4 Drillstem/Well Testing, 5.4.9 Miscible Methods, 1.6.6 Directional Drilling, 5.8.7 Carbonate Reservoir, 5.3.9 Steam Assisted Gravity Drainage, 1.6 Drilling Operations, 5.3.2 Multiphase Flow, 5.7.2 Recovery Factors, 2.4.3 Sand/Solids Control, 5.4.6 Thermal Methods, 5.2.1 Phase Behavior and PVT Measurements, 2 Well Completion, 5.4.1 Waterflooding, 6.5.2 Water use, produced water discharge and disposal, 1.6.9 Coring, Fishing, 2.5.2 Fracturing Materials (Fluids, Proppant), 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.4.2 Gas Injection Methods, 5.5 Reservoir Simulation
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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 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 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.
The use of horizontal wells has been increasing very rapidly throughout the oil industry as advances in drilling techniques continue. In many reservoirs, horizontal wells can help solve a number of oil production problems. However, in spite of a tremendous increase in literature references, little information is available on horizontal-well applications for EOR methods. A survey of the extensive horizontal-well literature is beyond the scope of this paper, but reviews, books, SPE Reprint Series, and published articles (over one thousand, even excluding newspaper articles) show that horizontal wells are still used primarily in problem reservoirs or to solve specific production problems. These include: low-permeability formations especially fractured formations such as the Austin Chalk, low-permeability gas reservoirs, unusual gas sources such as coal-bed methane or Devonian shale, gas or water coning, thin formations, and viscous oil.
Most of the EOR activity has been in the area of thermal recovery, primarily for steam stimulation and steam drives, where both horizontal injection wells and production wells have been tried. A potential for gas EOR production wells have been tried. A potential for gas EOR projects with horizontal wells is indicated by recent simulation projects with horizontal wells is indicated by recent simulation and model studies for inert gash and CO2 injection. The interest in horizontal-well waterflooding is very recent with most reports or publications appearing in 1991 and 1992.
Although there is relatively little published information on the use of horizontal injection wells, other than for thermal recovery, the need for patterns of both horizontal injection and production wells, or opposed vertical fractures, to increase the production wells, or opposed vertical fractures, to increase the rate of flooding in EOR processes has been mentioned. This paper describes the improvements in sweep efficiency and flooding rates that are possible if horizontal wells are used for waterflooding or for any EOR method which requires the use of both injection and production wells. In addition, the potential for increased microscopic displacement efficiency at potential for increased microscopic displacement efficiency at the faster rates (with no increase in well-head pressure) is examined for some of the EOR methods.
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