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Thermal single-well injection-withdrawal tracer tests for determining fracture-matrix heat transfer area

Description: Single-well injection-withdrawal (SWIW) tracer tests involve injection of traced fluid and subsequent tracer recovery from the same well, usually with some quiescent time between the injection and withdrawal periods. SWIW are insensitive to variations in advective processes that arise from formation heterogeneities, because upon withdrawal, fluid parcels tend to retrace the paths taken during injection. However, SWIW are sensitive to diffusive processes, such as diffusive exchange of conservative or reactive solutes between fractures and rock matrix. This paper focuses on SWIW tests in which temperature itself is used as a tracer. Numerical simulations demonstrate the sensitivity of temperature returns to fracture-matrix interaction. We consider thermal SWIW response to the two primary reservoir improvements targeted with stimulation, (1) making additional fractures accessible to injected fluids, and (2) increasing the aperture and permeability of pre-existing fractures. It is found that temperature returns in SWIW tests are insensitive to (2), while providing a strong signal of more rapid temperature recovery during the withdrawal phase for (1).
Date: January 15, 2010
Creator: Pruess, K. & Doughty, C.
Partner: UNT Libraries Government Documents Department

Oil Recovery Increases by Low-Salinity Flooding: Minnelusa and Green River Formations

Description: Waterflooding is by far the most widely used method in the world to increase oil recovery. Historically, little consideration has been given in reservoir engineering practice to the effect of injection brine composition on waterflood displacement efficiency or to the possibility of increased oil recovery through manipulation of the composition of the injected water. However, recent work has shown that oil recovery can be significantly increased by modifying the injection brine chemistry or by injecting diluted or low salinity brine. This paper reports on laboratory work done to increase the understanding of improved oil recovery by waterflooding with low salinity injection water. Porous media used in the studies included outcrop Berea sandstone (Ohio, U.S.A.) and reservoir cores from the Green River formation of the Uinta basin (Utah, U.S.A.). Crude oils used in the experimental protocols were taken from the Minnelusa formation of the Powder River basin (Wyoming, U.S.A.) and from the Green River formation, Monument Butte field in the Uinta basin. Laboratory corefloods using Berea sandstone, Minnelusa crude oil, and simulated Minnelusa formation water found a significant relationship between the temperature at which the oil- and water-saturated cores were aged and the oil recovery resulting from low salinity waterflooding. Lower aging temperatures resulted in very little to no additional oil recovery, while cores aged at higher temperatures resulted in significantly higher recoveries from dilute-water floods. Waterflood studies using reservoir cores and fluids from the Green River formation of the Monument Butte field also showed significantly higher oil recoveries from low salinity waterfloods with cores flooded with fresher water recovering 12.4% more oil on average than those flooded with undiluted formation brine.
Date: September 1, 2010
Creator: Robertson, Eric P.
Partner: UNT Libraries Government Documents Department

Report on the U.S. DOE Geothermal Technologies Program's 2009 Risk Analysis

Description: NREL conducted an annual program risk analysis on behalf of the U.S. Department of Energy Geothermal Technologies Program (GTP). NREL implemented a probabilistic risk analysis of GTP-sponsored research, development, and demonstration (RD&D) work, primarily for enhanced geothermal systems (EGS). The analysis examined estimates of improvement potential derived from program RD&D work for two types of technology performance metric (TPM): EGS-enabling technologies potential and EGS cost improvement potential. Four risk teams (exploration, wells/pumps/tools, reservoir engineering, and power conversion) comprised of industry experts, DOE laboratory researchers, academic researchers, and laboratory subcontractors estimated the RD&D impacts and TPM-improvement probability distributions. The assessment employed a risk analysis spreadsheet add-in that uses Monte Carlo simulation to drive the Geothermal Electric Technology Evaluation Model (GETEM). The GETEM-based risk analysis used baseline data from the experts' discussion of multiple reports and data sources. Risk results are expressed in terms of each metric's units and/or the program's top-level metric: levelized costs of electricity (LCOE). Results--both qualitative comments and quantitative improvement potential--are thorough and cohesive in three of the four expert groups. This conference paper summarizes the industry's current thinking on various metrics and potential for research improvement in geothermal technologies.
Date: February 1, 2010
Creator: Young, K. R.; Augustine, C. & Anderson, A.
Partner: UNT Libraries Government Documents Department

DOE 2009 Geothermal Risk Analysis: Methodology and Results

Description: This presentation summarizes the methodology and results for a probabilistic risk analysis of research, development, and demonstration work-primarily for enhanced geothermal systems (EGS)-sponsored by the U.S. Department of Energy Geothermal Technologies Program.
Date: February 1, 2010
Creator: Young, K. R.; Augustine, C. & Anderson, A.
Partner: UNT Libraries Government Documents Department