Browsing by Author "Holtz, Mark H."

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Assessing impacts to groundwater from CO2-flooding of SACROC and Claytonville oil fields in West Texas
(2006) Smyth, Rebecca C.; Holtz, Mark H.; Guillot, Stephen N.
Comparison of groundwater above two Permian Basin oil fields (SACROC Unit and Claytonville Field) near Snyder, Texas should allow us to assess potential impacts of 30 years of CO2-injection. CO2-flooding for enhanced oil recovery (EOR) has been active at SACROC in Scurry County since 1972. Approximately 13.5 million tons per year (MtCO2/yr) are injected with withdrawal/recycling amounting to ~7MtCO2/yr. It is estimated that the site has accumulated more than 55MtCO2; however, no rigorous investigation of overlying groundwater has demonstrated that CO2 is trapped in the subsurface. Mineralogy of reservoir rocks at the Claytonville field in southwestern Fisher County is similar to SACROC. CO2-EOR is scheduled to begin at Claytonville Field in Fisher County in early 2007. Here we have the opportunity to characterize groundwater prior to CO2-injection and establish baseline conditions at Claytonville. Methods of this study will include: (1) examination of existing analyses of saline to fresh water samples collected within an eight-county area encompassing SACROC and Claytonville, (2) additional groundwater sampling for analysis of general chemistry plus field-measured pH, alkalinity, and temperature, stable isotopic ratios of hydrogen (D/H), oxygen (18O/16O), and carbon (13C/12C), and (3) geochemical equilibrium and flowpath modeling. Existing groundwater data are available from previous BEG studies, Texas Water Development Board, Kinder Morgan CO2 Company, and the U. S. Geological Survey. By examining these data we will identify regional groundwater variability and focus additional sampling efforts. The objective of this study is to look for potential impacts to shallow groundwater from deep CO2-injection. In the absence of conduit flow from depth, we don’t expect to see impacts to shallow groundwater, but methodology to demonstrate this to regulators needs to be established. This work is a subset of the Southwest Regional Partnership on Carbon Sequestration Phase 2studies funded by the Department of Energy (DOE) in cooperation with industry and government partners.
Assessment of Geological Storage Capacity of the Southeastern U.S. for CO2 in Brines and Economic Use for EOR
(SECARB Industry Briefing, 2006-01-18) Hovorka, Susan D.; Holtz, Mark H.; Smyth, Rebecca C.; Nunez Lopez, Vanessa; Kim, Eugene; Breton, Catherine L.; Scanlon, Bridget R.; Reedy, Reedy C.; Paine, Jeffrey; Tinker, Scott; Duncan, Ian
Frio pilot in CO2 sequestration in brine-bearing sandstones: The University of Texas at Austin, Bureau of Economic Geology, report to the Texas Commission on Environmental Quality to accompany a class V application for an experimental technology pilot injection well.
(2003-12) Hovorka, Susan D.; Holtz, Mark H.; Sakurai, Shinichi; Knox, Paul R.; Collins, Dan; Papadeas, Phil; Stehli, Donald
Identification of Remaining Oil Resource Potential in the Frio Fluvial/Deltaic Sandstone Play, South Texas
(1994) Holtz, Mark H.; McRae, Lee E.
The Frio Fluvial/Deltaic Sandstone (Vicksburg Fault Zone) oil play of South Texas has produced nearly 1 billion stock tank barrels (BSTB) of oil, yet still contains about 1.2 BSTB of unrecovered mobile oil and an even greater amount of residual oil resources (1.5 BSTB). More than half of the reservoirs in this depositionally complex play have been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define incompletely drained and untapped reservoirs as suitable targets for near-term recovery. Interwell-scale geological facies models of Frio fluvial/deltaic reservoirs will be combined with engineering assessments and geophysical evaluations to characterize Frio fluvial/deltaic reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. These results will lead directly to the identification of specific opportunities to exploit these heterogeneous reservoirs for incremental recovery by recompletion and strategic infill drilling. Reservoir attribute data were statistically analyzed from oil and gas fields throughout the geographic area covered by the Frio Fluvial/Deltaic Sandstone oil play. General reservoir attributes analyzed in detail included porosity, initial water saturation, residual oil saturation, net pay, reservoir area, and fluid characteristics. Statistical analysis of variance demonstrated no difference between oil reservoir attributes and gas reservoir attributes, indicating that oil and gas reservoirs are subsets of a larger genetically similar population. Probability functions that describe attribute frequency distributions were determined for use in risk-adjusting resource calculations. Different functions were found to be most applicable for the various petrophysical reservoir attributes.
Opportunities for Additional Recovery in University Lands Reservoirs -- Characterization of University Lands Reservoirs, Final Report
(1990) Tyler, N.; Bebout, Don G.; Garrett, C. M., Jr.; Guevara, Edgar H.; Hocott, Claude R.; Holtz, Mark H.; Hovorka, Susan D.; Kerans, C. (Charles), 1954-
In 1984, The University of Texas System funded a Bureau of Economic Geology project, "Characterization of University Lands Reservoirs," to assess in detail the potential for incremental recovery of oil from University Lands reservoirs by extended conventional methods. The objectives of the 5-year project were to quantify the volumes of unrecovered mobile oil remaining in reservoirs on University Lands, to determine whether the specific location of the unrecovered mobile oil could be delineated through integrated geoscience characterization of individual reservoirs, and to develop strategies to optimize recovery of this resource. Unrecovered mobile oil is mobile at reservoir conditions but is prevented from migrating to the wellbore by geologic complexities or heterogeneities. This final report describes results of the 5 years of research conducted on University Lands reservoirs. One hundred and one reservoirs, each of which has produced more than 1 million stock tank barrels (MMSTB) of oil, were included in a resource assessment and play analysis undertaken (1) to determine the volumes and distribution of all components of the University Lands resource base and (2) to select reservoirs for detailed analysis. These reservoirs collectively contained 7.25 billion barrels (BSTB) of oil at discovery, have produced 1.5 BSTB, and contain 200 MMSTB of reserves. Ultimate recovery at implemented technology is projected to be 24 percent of the original oil in place; thus, 5.5 BSTB of oil will remain after recovery of existing reserves. Unrecovered mobile oil (exclusive of reserves) amounts to 2.2 BSTB, and immobile, or residual, oil totals 3.3 BSTB.
Reduction of Greenhouse Gas Emissions through Underground CO2 Sequestration in Texas Oil and Gas Reservoirs
(1999) Holtz, Mark H.; Nance, Peter K.; Finley, Robert J.
Today, energy and environmental questions are often viewed from conflicting perspectives. However, perhaps there are solutions to some of these problems that can satisfy multiple objectives. This report explores the technical feasibility and economic potential for capturing CO2 from coal- or lignite-fired utility boilers and applying the CO2 as an enhanced oil recovery (EOR) process in the mature oil provinces of Texas. This capture accomplishes twin goals—sequestering a substantial amount of CO2 for an extended period and increasing the efficiency of oil recovery. The types of CO2 sources are diverse. To mitigate their impact, a number of management strategies are available, ranging from effluent reduction to capture and sequestration. One alternative is to utilize mature oil reservoirs to form a set of sequestration reservoirs. From the oil production side, one challenge for the domestic oil industry during the next millennium will be to profitably employ advanced technology to increase resources from existing reservoirs. Many advanced recovery strategies hold potential for accomplishing this goal. One promising area is enhanced oil recovery through the use of CO2 flooding. The potential incremental oil production from these methods is significant.
Reservoir Characterization Applying Residual Gas Saturation Modeling, Example From the Starfak t1 Reservoir, Middle Miocene Gulf of Mexico
(2005-05) Holtz, Mark H.; Lake, Larry W.; Bryant, Steven
Because of a complex interplay between faulting, stratigraphy, and water drive, it is often difficult to determine original and remaining gas volumes inproduced Miocene offshore Northern Gulf of Mexico gas reservoirs. Faults can be numerous, and their throws can often be too small to detect using conventional 3D seismic analysis. These faults can also be sealing, forming reservoir-flowcompartments, or nonsealing faults that die out within the reservoir. The fluvial-deltaic depositional environment, along with unconformable valley fills,multiplies this reservoir complexity because it produces both flow barriers and widely varying petrophysical properties. These complexities result in multiple gas-water contacts and a wide range of residual gas saturation to water influx,thus rendering difficult gas volume calculations. The hypothesis of this work is that this difficulty can be overcome by developing empirical residual nonwetting phase functions that can be applied within a geocellular reservoir model derived from integrating geologic,geophysical, and engineering concepts. An example of such a model is given for the Starfak T1 reservoir, offshore Louisiana. An integrated reservoir characterization approach was taken with anemphasis on developing an empirical model for calculating maximum residual gas saturation (Sgrm). A method was created for calculating Sgrm based on interrelationships between petrophysical properties. The model is developed as a function of porosity, permeability, capillary pressure, and initial water saturation.With a Delaunay cell representing an ideal pore, pore geometry characteristics were generated that represent a theoretical basis for the Sgrm model. The pore geometry character in the form of pore body to pore throat aspect ratio was determined for varying porosity in the ideal pore. The Sgrm model was then compared with wireline log analysis in an aquifer-swept versus upswept zone and applied in a three-dimensional (3D) geocellular model. To calculate Sgrm in gas reservoirs, a new empirical model was developed. The model is a function of porosity. Results show that in a porous medium containing primary intergranular porosity, as porosity decreases the aspect ratio increases, thus increasing Sgrm through the likely mechanism of snapoff. Further, an equation was developed that determines residual nonwetting phase saturation as a function of aspect ratio. Comparison of wireline gas saturation calculated from original versus aquifer-flushed zones further corroborates the porosity-Sgrminverse relationship. Additionally, a new practical crossplot was developed based on the inverse Sgrm – porosity character that facilitates the recognition of aquifer-swept zones. It is also shown that applying the Sgrm model when integratingseismic data into a geocellular model can help guide this integration through improved material balance.
Revitalizing a Mature Oil Play: Strategies for Finding and Producing Unrecovered Oil in Frio Fluvial-Deltaic Reservoirs of South Texas
(1994) McRae, Lee E.; Holtz, Mark H.; Knox, Paul R.
Advanced reservoir characterization techniques are being applied to selected reservoirs in the Frio Fluvial-Deltaic Sandstone (Vicksburg Fault zone) oil play of South Texas to maximize the productivity of resources in this mature oil play. This mature play has already produced nearly 1 billion barrels (Bbbl) of oil, yet still contains about 1.6 Bbbl of unrecovered mobile oil and nearly the same amount of residual oil resources. More than half of the reservoirs in this depositionally complex play have already been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define untapped, incompletely drained, and new pool reservoirs as suitable targets for near-term recovery methods. Primary technical objectives of this project are to develop interwell-scale geological facies models of Frio fluvial-deltaic reservoirs and combine them with engineering assessments and geophysical evaluations in order to characterize the Frio fluvial-deltaic reservoir architecture and flow unit boundaries and to determine the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. These results will lead directly to the identification of specific opportunities to exploit these heterogeneous reservoirs for incremental recovery by recompletion and strategic infill drilling.
Revitalizing a Mature Oil Play: Strategies for Finding and Producing Unrecovered Oil in Frio Fluvial-Deltaic Sandstone Reservoirs of South Texas
(1996) Knox, Paul R.; Holtz, Mark H.; McRae, Lee E.
Domestic fluvial-dominated deltaic (FDD) reservoirs contain more than 30 Billion barrels (Bb) of remaining oil, more than any other type of reservoir, approximately one-third of which is in danger of permanent loss through premature field abandonments. The U.S. Department of Energy has placed its highest priority on increasing near-term recovery from FDD reservoirs in order to prevent abandonment of this important strategic resource. To aid in this effort, the Bureau of Economic Geology at The University of Texas at Austin began a 46-month project in October 1992 to develop and demonstrate advanced methods of reservoir characterization that would more accurately locate remaining volumes of mobile oil that could then be recovered by recompleting existing wells or drilling geologically targeted infill wells. Reservoirs in two fields within the Frio Fluvial-Deltaic Sandstone (Vicksburg Fault Zone) oil play of South Texas, a mature play which still contains 1.6 Bbbl of mobile oil after producing 1 Bbbl over four decades, were selected as laboratories for developing and testing reservoir characterization techniques. Advanced methods in geology, geophysics, petrophysics, and engineering were integrated to (1) identify probable reservoir architecture and heterogeneity, (2) determine past fluid-flow history, (3) integrate fluid-flow history with reservoir architecture to identify untapped, incompletely drained, and new pool compartments, and (4) identify specific opportunities for near-term reserve growth. To facilitate the success of operators in applying these methods in the Frio play, geologic and reservoir engineering characteristics of all major reservoirs in the play were documented and statistically analyzed. Finally, to assist operators in identifying the reservoirs most prospective for reserve growth, and therefore most worthy of detailed characterization efforts, a quantitative quick-look methodology was developed to prioritize reservoirs in terms of reserve-growth potential.
Revitalizing a Mature Oil Play: Strategies for Finding and Producing Unrecovered Oil in Frio Fluvial-Deltaic Sandstone Reservoirs of South Texas
(1996) Holtz, Mark H.; Knox, Paul R.; McRae, Lee E.
The Frio Fluvial-Deltaic Sandstone (Vicksburg Fault Zone) oil play of South Texas has produced nearly 1 billion barrels (Bbbl) of oil, yet it still contains about 1.6 Bbbl of unrecovered mobile oil and nearly the same amount of residual oil resources. More than half of the reservoirs in this depositionally complex play have been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define untapped, incompletely drained, and new pool reservoirs as suitable targets for near-term recovery. Interwell-scale geological facies models of Frio fluvial-deltaic reservoirs are being combined with engineering assessments and geophysical evaluations in order to characterize reservoir architecture and flow-unit boundaries and to determine the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. These results will help identify specific opportunities to exploit these heterogeneous reservoirs for incremental recovery by recompletion and strategic infill drilling. Progress during the third project year centered on technology transfer activities. The reserve-growth potential of reservoirs in two fields within the play, Rincon field in Starr County and Tijerina-Canales-Blucher field in Jim Wells County, was documented in a Topical Report published by DOE and in this report. Specific opportunities to exploit untapped and incompletely drained compartments were identified. Results of this effort were also presented at both local and national technical meetings and in two courses hosted by related programs. Preparations have begun for two workshops centered around the activities of this project, as well as the construction of a microcomputer-based Geologic Reservoir Characterization Advisor (GRCA). The short courses, scheduled for April and June 1996, along with the GRCA, will demonstrate for operators of this mature play the potential that remains in reservoirs threatened by premature abandonment and will document methods for locating and efficiently recovering the tremendous remaining resource. The integrated multidisciplinary characterization methodology demonstrated in this project is applicable to reservoirs throughout the Frio Fluvial-Deltaic Sandstone play, to other fluvial-deltaic plays within the Gulf Coast, and more broadly to any mature fluvial-deltaic play in the United States.
Source-Sink Matching and Potential for Carbon Capture and Storage in the Gulf Coast
(Proceedings of the 2006 UIC Conference of the Groundwater Protection Council, 2006) Ambrose, William A.; Breton, Caroline L.; Duncan, Ian; Holtz, Mark H.; Hovorka, Susan D.; Núñez-López, Vanessa; Lakshminarasimhan, Srivatsan
Current global levels of anthropogenic CO2 emissions are 25.6 Gigatons yr. Approximately 1 Gigaton comes from the Texas, Louisiana, and Mississippi Gulf Coast, representing 16 percent of the U.S. annual CO2 emissions from fossil fuels. The Gulf Coast region provides an opportunity for addressing the problem. Geologic sequestration results from the capturing of CO2 from combustion products and injecting the compressed gas as a supercritical fluid into subsurface brine aquifers for long-term storage. The Gulf Coast overlies an unusually thick succession of highly porous and permeable sand aquifers separated by thick shale aquitards. The Gulf Coast also has a large potential for enhanced oil recovery (EOR), in which CO2 injected into suitable oil reservoirs could be used first for EOR and then for large-volume, long-term storage of CO2 in nonproductive formations below the reservoir interval. For example, there are numerous opportunities for locating CO2 injection wells either in fields for EOR or in stacked brine aquifers near potential FutureGen sites, where a near-zero emission facility would generate primarily hydrogen and CO2 as by-products. We estimate that in the Gulf Coast, outside of the traditional area of CO2 EOR in the Permian Basin, an additional 4.5 billion barrels of oil could be produced by using miscible CO2. At $60 per barrel, this incremental production is estimated to have a wellhead value of $270 billion that could generate more than $40 billion in taxes.
Strategies for Reservoir Characterization and Identification of Incremental Recovery Opportunities in Mature Reservoirs in Frio Fluvial-Deltaic Sandstones, South Texas: An Example from Rincon Field, Starr County
(1995) McRae, Lee E.; Holtz, Mark H.; Hentz, Tucker F.; Chang, Chin-Yung; Knox, Paul R.
Fluvial-deltaic sandstone reservoirs in the United States are being abandoned at high rates, yet they still contain more than 34 billion barrels of unrecovered oil. The mature Oligocene-age fluvial-deltaic reservoirs of the Frio Formation along the Vicksburg Fault Zone in South Texas are typical of this class in that, after more than three decades of production, they still contain 61 percent of the original mobile oil in place, or 1.6 billion barrels. This resource represents a tremendous target for advanced reservoir characterization studies that integrate geological and engineering analysis to locate untapped and incompletely drained reservoir compartments isolated by stratigraphic heterogeneities. The D and E reservoir intervals of Rincon field, Starr County, South Texas, were selected for detailed study to demonstrate the ability of advanced characterization techniques to identify reservoir compartmentalization and locate specific infield reserve-growth opportunities. Reservoir architecture, determined through high-frequency genetic stratigraphy and facies analysis, was integrated with production history and facies-based petrophysical analysis of individual flow units to identify recompletion and geologically targeted infill drilling opportunities.
Update of Atlas of Major Texas Oil Reservoirs Data Base and Atlas of Major Texas Gas Reservoirs Data Base
(1993) Holtz, Mark H.; Garrett, C. M., Jr.; Tremblay, Thomas A.
Updating both the "Atlas of Major Texas Oil Reservoirs: Database" (Holtz and others, 1991) and the "Atlas of Major Texas Gas Reservoirs: Database" (Garrett and others, 1991) centered on updating cumulative production data current to December 31, 1992, for reservoirs already in the database and adding new significant-sized reservoirs (cumulative production greater than 1 million barrels of oil equivalent) to the databases. Addition of new reservoirs to the database resulted in the modification of existing plays or the determination of new plays. Play boundaries were also modified to accommodate the additional reservoirs. Oil and gas production data used for the cumulative production update and the determination of significant-sized reservoirs were obtained from Dwight's Energy data. For reservoirs already included in the Atlas databases, annual production values were added to the cumulative production already determined by the Bureau of Economic Geology (BEG) or reported by the Railroad Commission of Texas. For new reservoirs, the cumulative production values reported by Dwight's Energy data were applied. Oil reservoirs originally listed in both databases because of large gas production were combined and now are listed only in the updated Oil Atlas database.