12 research outputs found
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REDUCING RISK IN LOW-PERMEABILITY GAS FORMATIONS: UNDERSTANDING THE ROCK/FLUID CHARACTERISTICS OF ROCKY MOUNTAIN LARAMIDE BASINS
An anomalous velocity model was constructed for the Wind River Basin (WRB) based on {approx}2000 mi of 2-D seismic data and 175 sonic logs, for a total of 132,000 velocity/depth profiles. Ten cross sections were constructed through the model coincident with known gas fields. In each cross section, an intense, anomalously slow velocity domain coincided with the gas-productive rock/fluid interval. The anomalous velocity model: (1) Easily isolates gas-charged rock/fluid systems characterized by anomalously slow velocities and water-rich rock/fluid systems characterized by normal velocities; and (2) Delineates the regional velocity inversion surface, which is characterized by steepening of the Ro/depth gradient, a significant increase in capillary displacement pressure, a significant change in formation water composition, and acceleration of the reaction rate of smectite-to-illite diagenesis in mixed-layer clays. Gas chimneys are observed as topographic highs on the regional velocity inversion surface. Beneath the surface are significant fluid-flow compartments, which have a gas-charge in the fluid phase and are isolated from meteoric water recharge. Water-rich domains may occur within regional gas-charged compartments, but are not being recharged from the meteoric water system (i.e., trapped water). The WRB is divided into at least two regionally prominent fluid-flow compartments separated by the velocity inversion surface: a water-dominated upper compartment likely under strong meteoric water drive and a gas-charged, anomalously pressured lower compartment. Judging from cross sections, numerous gas-charged subcompartments occur within the regional compartment. Their geometries and boundaries are controlled by faults and low-permeability rocks. Commercial gas production results when a reservoir interval characterized by enhanced porosity/permeability intersects one of these gas-charged subcompartments. The rock/fluid characteristics of the Rocky Mountain Laramide Basins (RMLB) described in this work determine the potential for significant, relatively unconventional, so-called ''basin-center'' hydrocarbon accumulations. If such accumulations occur, they will be characterized by the following critical attributes: (1) Location beneath a regional velocity inversion surface that typically is associated with low-permeability lithologies; (2) Anomalous pressure, both over- and underpressure, and when, less commonly, they appear to be normally pressured, they are not in contact with the meteoric water system; (3) A significant gas component in the regional multiphase fluid-flow system (water-gas-oil) that occurs beneath the regional velocity inversion surface; (4) Domains of intense gas charge (i.e., high gas saturation) within the regional multiphase fluid-flow system; (5) Compartmentalization of the rock/fluid system to a far greater extent beneath the regional velocity inversion surface than above it (i.e., convection of fluids across the regional velocity inversion surface is reduced or eliminated depending on the nature of the capillary properties of the low-permeability rocks associated with the inversion surface); (6) Commercial gas accumulations occurring at the intersection of reservoir intervals characterized by enhanced porosity and permeability and gas-charged domains; (7) Productive intersections of reservoir intervals and gas-charged domains, which are controlled by the structural, stratigraphic, and diagenetic elements affecting the rock/fluid system; and (8) No apparent meteoric water connection with the gas accumulations and gas columns up to several thousand feet in height. Because some of these critical attributes are not associated with conventional hydrocarbon accumulations, a new set of diagnostic tools are required in order to explore for and exploit these types of gas prospects efficiently and effectively. Some of these new diagnostic tools have been discussed in this report; other have been described elsewhere. In order to maximize risk reduction, it is recommended when exploring for these types of gas accumulations in the RMLB--or for that matter, anomalously pressured gas accumulations anywhere in the world--that highest priority be given to: (1) Evaluating gas distribution in the fluid system, and (2) Predicting enhanced porosity and permeability in the rock system
A Feasibility Study of the Integration of Enhanced Oil Recovery (CO2 Flooding) with CO2 Storage in the Mature Oil Fields of the Ordos Basin, China
AbstractRich in energy resources, China's Ordos Basin Shares many similarities with Wyoming's Powder River Basin. As a result, the experience and expertise pertaining to energy development in the Powder River Basin should prove helpful in the Ordos Basin. The b reserves are ranked fourth. The coal deposits in the Ordos Basin account for 39 percent of total Chinese coal reserves (3.98 trillion tonnes), and six of the thirteen largest coal mines in China are located in the basin. The overlapping development of relatively new coal conversion industries with existing oil and gas industries in northern Shaanxi Province is creating an opportunity to apply the systematic approach developed in Wyoming: the integration of geological CO2 storage and CO2-EOR. The coal conversion industry (i.e., coal-to-methanol, coal-to-olefins, etc.) provides affordable, capture-ready CO2 sources for developing large-scale integrated CO2-EOR and carbon storage projects in the Ordos Basin, China. Compared with other CCUS projects, the ability to use CO2 from the coal- conversion industry for CO2-EOR and subsequent geological CO2 storage will make integrated projects in the Ordos Basin more cost-effective and technologically efficient.The low porosity, low permeability, low oil saturation, anomalously low reservoir pressure, and high reservoir heterogeneity of the target storage formations in the Ordos Basin make using CO2 for enhanced oil recovery much more challenging here than in the US. These reservoir characteristics together constitute a major reason that CO2- EOR is not widely employed in the Ordos Basin, even though sources of highly concentrated CO2 (coal conversion plants) have been available for years. Comparisons of reservoir and crude oil properties in the Ordos Basin with the current US CO2-EOR screening guidelines reveal that gravity, viscosity, crude oil composition, and formation type of the Ordos reservoirs all are favorable for CO2 miscible flooding. The major challenges in deploying EOR result from anomalously low reservoir pressure, low porosity, and higher reservoir heterogeneity
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Anomalously Pressured Gas Distribution in the Wind River Basin, Wyoming
Anomalously pressured gas (APG) assets, typically called ''basin-center'' gas accumulations, represent either an underdeveloped or undeveloped energy resource in the Rocky Mountain Laramide Basins (RMLB). Historically, the exploitation of these gas resources has proven to be very difficult and costly. In this topical report, an improved exploration strategy is outlined in conjunction with a more detailed description of new diagnostic techniques that more efficiently detect anomalously pressured, gas-charged domains. The ability to delineate gas-charged domains occurring below a regional velocity inversion surface allows operators to significantly reduce risk in the search for APG resources. The Wind River Basin was chosen for this demonstration because of the convergence of public data availability (i.e., thousands of mud logs and DSTs and 2400 mi of 2-D seismic lines); the evolution of new diagnostic techniques; a 175 digital sonic log suite; a regional stratigraphic framework; and corporate interest. In the exploration scheme discussed in this topical report, the basinwide gas distribution is determined in the following steps: (1) A detailed velocity model is established from sonic logs, 2-D seismic lines, and, if available, 3-D seismic data. In constructing the seismic interval velocity field, automatic picking technology using continuous, statistically-derived interval velocity selection, as well as conventional graphical interactive methodologies are utilized. (2) Next, the ideal regional velocity/depth function is removed from the observed sonic or seismic velocity/depth profile. The constructed ideal regional velocity/depth function is the velocity/depth trend resulting from the progressive burial of a rock/fluid system of constant rock/fluid composition, with all other factors remaining constant. (3) The removal of the ideal regional velocity/depth function isolates the anomalously slow velocities and allows the evaluation of (a) the regional velocity inversion surface (i.e., pressure surface boundary); (b) detection and delineation of gas-charged domains beneath the velocity inversion surface (i.e., volumes characterized by anomalously slow velocities); and (c) variations within the internal fabric of the velocity anomaly (i.e., variations in gas charge). Using these procedures, it is possible to construct an anomalous velocity profile for an area, or in the case of the Wind River Basin, an anomalous velocity volume for the whole basin. Such an anomalous velocity volume has been constructed for the Wind River Basin based on 1600 mi of 2-D seismic data and 175 sonic logs, for a total of 132,000 velocity/depth profiles. The technology was tested by constructing six cross sections through the anomalous velocity volume coincident with known gas fields. In each of the cross sections, a strong and intense anomalously slow velocity domain coincided with the gas productive rock/fluid interval; there were no exceptions. To illustrate the applicability of the technology, six target areas were chosen from a series of cross sections through the anomalous velocity volume. The criteria for selection of these undrilled target areas were (1) they were characterized by anomalous velocity domains comparable to known gas fields; (2) they had structural, stratigraphic, and temporal elements analogous to one of the known fields; and (3) they were located at least six sonic miles from the nearest known gas field. The next step in the exploration evolution would be to determine if the detected gas-charged domains are intersected by reservoir intervals characterized by enhanced porosity and permeability. If, in any of these targeted areas, the gas-charged domains are penetrated by reservoir intervals with enhanced storage and deliverability, the gas-charged domains could be elevated to drillable prospects. Hopefully, the work described in this report (the detection and delineation of gas-charged domains) will enable operators in the Wind River Basin and elsewhere to reduce risk significantly and increase the rate and magnitude of converting APG resources to energy reserves
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Riverton Dome Gas Exploration and Stimulation Technology Demonstration, Wind River Basin, Wyoming
This project will provide a full demonstration of an entirely new package of exploration technologies that will result in the discovery and development of significant new gas reserves now trapped in unconventional low-permeability reservoirs. This demonstration includes the field application of these technologies, prospect definition and well siting, and a test of this new strategy through wildcat drilling. In addition this project includes a demonstration of a new stimulation technology that will improve completion success in these unconventional low permeability reservoirs which are sensitive to drilling and completion damage. The work includes two test wells to be drilled by Snyder Oil Company on the Shoshone/Arapahoe Tribal Lands in the Wind River Basin. This basin is a foreland basin whose petroleum systems include Paleozoic and Cretaceous source beds and reservoirs which were buried, folded by Laramide compressional folding, and subsequently uplifted asymmetrically. The anomalous pressure boundary is also asymmetric, following differential uplift trends. The Institute for Energy Research has taken a unique approach to building a new exploration strategy for low-permeability gas accumulations in basins characterized by anomalously pressured, compartmentalized gas accumulations. Key to this approach is the determination and three-dimensional evaluation of the pressure boundary between normal and anomalous pressure regimes, and the detection and delineation of areas of enhanced storage capacity and deliverability below this boundary. This new exploration strategy will be demonstrated in the Riverton Dome� Emigrant Demonstration Project (RDEDP) by completing the following tasks: 1) detect and delineate the anomalous pressure boundaries, 2) delineate surface lineaments, fracture and fault distribution, spacing, and orientation through remote sensing investigations, 3) characterize the internal structure of the anomalous pressured volume in the RDEDP and determine the scale of compartmentalization using produced water chemistry, 4) define the prospects and well locations as a result on this new exploration technology, and 5) utilize new completion techniques that will minimize formation damage and optimize production
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RIVERTON DOME GAS EXPLORATION AND STIMULATION TECHNOLOGY DEMONSTRATION, WIND RIVER BASIN, WYOMING
This project will provide a full demonstration of an entirely new package of exploration technologies that will result in the discovery and development of significant new gas reserves now trapped in unconventional low-permeability reservoirs. This demonstration includes the field application of these technologies, prospect definition and well siting, and a test of this new strategy through wildcat drilling. In addition this project includes a demonstration of a new stimulation technology that will improve completion success in these unconventional low permeability reservoirs which are sensitive to drilling and completion damage. The work includes two test wells to be drilled by Snyder Oil Company on the Shoshone/Arapahoe Tribal Lands in the Wind River Basin. This basin is a foreland basin whose petroleum systems include Paleozoic and Cretaceous source beds and reservoirs which were buried, folded by Laramide compressional folding, and subsequently uplifted asymmetrically. The anomalous pressure boundary is also asymmetric, following differential uplift trends
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RIVERTON DOME GAS EXPLORATION AND STIMULATION TECHNOLOGY DEMONSTRATION, WIND RIVER BASIN, WYOMING
The new exploration technology for basin center gas accumulations developed by R.C. Surdam and Associates at the Institute for Energy Research, University of Wyoming, was applied to the Riverton Dome 3-D seismic area. Application of the technology resulted in the development of important new exploration leads in the Frontier, Muddy, and Nugget formations. The new leads are adjacent to a major north-south trending fault, which is downdip from the crest of the major structure in the area. In a blind test, the drilling results from six new Muddy test wells were accurately predicted. The initial production values, IP, for the six test wells ranged from < one mmcf/day to four mmcf/day. The three wells with the highest IP values (i.e., three to four mmcf/day) were drilled into an intense velocity anomaly (i.e., anomalously slow velocities). The well drilled at the end of the velocity anomaly had an IP value of one mmcf/day, and the two wells drilled outside of the velocity anomaly had IP values of < one mmcf/day and are presently shut in. Based on these test results, it is concluded that the new IER exploration strategy for detecting and delineating commercial, anomalously pressured gas accumulation is valid in the southwestern portions of the Wind River Basin, and can be utilized to significantly reduce exploration risk and to increase profitability of so-called basin center gas accumulations