Determination of fluid-phase-specific petrophysical properties of geological core for oil, water and gas phases
Inventors
Vinegar, Eva • SINGER, PHILIP M. • Hirasaki, George J. • CHEN, Zeliang • Wang, Xinglin • Vinegar, Harold J.
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Assignees
Vinegar Technologies LLC • William Marsh Rice University
Member
Rice UniversityRice University is a leading research university in Houston, Texas, recognized for its emphasis on scientific discovery, innovation, and interdisciplinary collaboration. The institution is committed to academic excellence, impactful research, and community engagement, offering robust undergraduate and graduate programs in engineering, natural sciences, social sciences, humanities, business, and the arts. Rice is distinguished by its history of collaboration with organizations such as NASA, fostering advances in space science, biotechnology, energy research, and artificial intelligence.
Rice University is a leading research university in Houston, Texas, recognized for its emphasis on scientific discovery, innovation, and interdisciplinary collaboration. The institution is committed to academic excellence, impactful research, and community engagement, offering robust undergraduate and graduate programs in engineering, natural sciences, social sciences, humanities, business, and the arts. Rice is distinguished by its history of collaboration with organizations such as NASA, fostering advances in space science, biotechnology, energy research, and artificial intelligence.
Publication Number
US-11921069-B1
Publication Date
2024-03-05
Expiration Date
Abstract
The following invention is used for determining the relative permeability of a fluid in a rock for three different phases: water, oil, and gas, in both conventional and unconventional formations. The permeability of a phase describes how much it can flow in porous media given a pressure gradient and is useful in evaluating reservoir quality and productivity. The following invention is a method to determine the three-phase relative permeabilities in both conventional and unconventional formations using NMR restricted diffusion measurements on core with NMR-active nuclei, combined with centrifugation of the core. In addition, the tortuosity, pore size (surface-to-volume ratio), fluid-filled porosity, and permeability is determined for each of the three phases in a rock.
Core Innovation
The invention is a method to determine three-phase relative permeabilities and other fluid phase-specific petrophysical properties (FPS-PP) for water, oil and gas in geological core using NMR restricted diffusion measurements on core with NMR-active nuclei combined with centrifugation of the core. The invention determines, for each of the three phases, tortuosity, pore size (surface-to-volume ratio), fluid-filled porosity, permeability, and relative permeability curves for two specific phases, and further derives body-to-throat ratio (BTR) and related parameters as part of the FPS-PP set.
The background identifies that in petroleum reservoirs two or three phases occupy pore space and that it is difficult to effectively measure permeability for each of the three phases using current methods. The invention addresses the need for quantifying fluid phase-specific petrophysical properties of three different phases (water, oil and gas) in both conventional and unconventional formations to support evaluation of reservoir quality and productivity.
The method uses multi-nuclear NMR restricted diffusion measurements (including 1H and 19F as exemplified) together with automated centrifugation with effluent volume and time-dependent flow-rate measurements to compute FPS-PP for each phase, and employs relations such as a modified Carman-Kozeny equation to relate tortuosity, porosity, pore-body diameter (from S/V = 4/d), and BTR to phase-specific permeabilities. [procedural detail omitted for safety]
Claims Coverage
Independent claim 1 defines a combined measurement and computation method with six main inventive feature areas.
NMR restricted diffusion measurements with multiple nuclei
Subjecting the geological core to NMR restricted diffusion measurements for multiple NMR-active nuclei with at least two different hydrocarbons for at least the oil and gas phases, as recited in the claim.
Centrifugation over drainage or imbibition cycles
Centrifuging the geological core over multiple drainage or imbibition cycles so as to produce effluent from the geological core [procedural detail omitted for safety].
Monitoring time dependence of effluent flow rate
As the geological core is centrifuged, measuring a time dependence of a flow rate of effluent from the geological core to obtain production versus time data.
Computation of three-phase FPS-PP
Computing, from results of the NMR restricted diffusion measurements and from the time dependence of the flow rate of effluent, all of FPS-PPWATER, FPS-PPOIL and FPS-PPGAS.
Definition of FPS-PP group
The FPS-PP group is explicitly defined as consisting of: (A) a fluid-phase-specific tortuosity value; (B) a fluid-phase-specific porosity value; (C) a fluid-specific-phase pore diameter; (D) a fluid-phase-specific body-to-throat ratio; (E) a fluid-phase-specific permeability; and (F) a fluid-phase-specific relative permeability curve for two specific phases.
Use of phase-specific measurements in permeability relations
Employing measured phase-specific quantities (tortuosity, porosity, pore-body diameter from S/V = 4/d, and BTR) and using relations such as a modified Carman-Kozeny equation to determine phase-specific permeabilities and relative permeability relations for X = w, o, g.
Claim 1 covers a combined approach of (i) multi-nuclear NMR restricted diffusion measurements, (ii) centrifuge-based effluent flow-rate monitoring, and (iii) computation of a defined FPS-PP set (tortuosity, porosity, pore diameter, body-to-throat ratio, permeability, and relative permeability curves) for each of water, oil and gas, using measured phase-specific inputs and permeability relations.
Stated Advantages
Useful in evaluating reservoir quality and productivity.
Useful in deciding on casing, perforating, and whether to deploy a pump in a well.
The centrifuge measurement is gravity-stable (no viscous fingering).
Centrifuge measurement can measure extremely small values of krw (useful for endpoint saturations).
1H and 19F have the highest signal-to-noise ratio among discussed nuclei and are easy to retune between, improving detectability.
Documented Applications
Determining phase-specific petrophysical properties (tortuosity, pore size, body-to-throat ratio, porosity, permeability, and relative permeability curves) for water, oil and gas in both conventional and unconventional formations.
Evaluating reservoir quality and productivity during primary, secondary and tertiary production.
Supporting decisions regarding casing, perforating, and whether to deploy a pump in a well.
Determining locations in accordance with FPS-PPWATER, FPS-PPOIL, and FPS-PPGAS and drilling one or more horizontal or vertical wells in accordance with the determined locations.
Performing additional operations in accordance with determined locations, including capping and perforating, and deploying a pump.
Constructing a three-phase relative permeability model from oil/water and oil/gas relative permeability curves using linear interpolation.
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