US Fractured Reservoirs Proposal
Back to Gibson Grams • Back to US products index •
Back to Gibson Grams • Back to US products index •
The purpose of this project is to describe the relationship between basement faults, fractures, and other weak zones, and tight gas sand reservoirs — especially fractured reservoirs. Basement features are often clearly expressed in magnetic and gravity data, and their impact on the sedimentary section can be inferred if the tectonic history of an area is known broadly. Observation shows that many basement features do have impact on the section, but the relationship is poorly understood in detail. We will attempt to discover systematic characteristics in gravity and magnetic expressions that will make such data useful as an inexpensive, predictive tool for exploration for fractured reservoirs. Through geophysical modeling and integration with deep well information, the geological meaning of the geophysical data will be defined.This in turn will be used to identify likely areas of similar structural development in less well-explored areas, resulting in specific analogs and extensions of existing plays and production.
The fundamental goal of this project is to provide support for inexpensive exploration techniques (gravity and magnetics) that will enhance the search for deep gas reservoirs in the United States. The techniques and knowledge gained will be of particular value to the small independent companies that are exploring today. They are not able or willing to afford basic research such as this project, even though it should materially reduce their costs. The final product is expected to be a practical document, designed to help guide exploration at the play level, and in some places, at the prospect level. Small companies frequently are not able to invest in regional studies of any sort, and in gravity and magnetic analyses in particular. This project will bring a first-level interpretation of such data to smaller companies at very reasonable cost to them. Inasmuch as the majors are conducting and supporting regional studies less and less, the smaller companies will need a new source for such information. This project is designed to provide one source for such applied research, conducted much as it would have been in a major oil company's technical services center. The Principal Investigator's work at Gulf Oil's Tech Services Center provides the experience to ensure this approach.
The project is expected to result in specific locations that may be construed as leads or extensions of plays, and in some cases analogs to existing production may de defined. The results will support upstream exploration as well as development of fractured-reservoir fields.
The observation that gravity and magnetic "lineaments" are related to oil and gas accumulations has a long history. Within the past 15 years, understanding of the relationship between gravity and magnetic features and geologic aspects of the basement have become clearer, though in general only the observation of a coincidence is made, and the actual genesis, history, and detailed nature of the basement features is unknown. For example, the observation that basement lithologic contacts in Kentucky coincide with surface faults in the nonmagnetic sedimentary section is simple to make (Fig. 1). Why do the intrabasement contacts propagate into the section as faults? Are there places where they do not produce faults, but do fracture the rocks? What is the timing of the structural or fracture development? How far do they extend, both vertically and horizontally? These are some of the questions that are usually unanswered by such observational studies.
A second example is the Williston Basin, where Laramide (Late Cretaceous) rejuvenation of Precambrian (Archean and Proterozoic) basement features has produced structures (Cedar Creek and Nesson Anticlines; Fig. 2). On a more subtle observational level, it appears that northeast-trending lineaments defined in gravity and magnetic data may have affected the depositional environments of Mississippian carbonates, important hydrocarbon reservoirs (see Fig. 3). It has been postulated (Gibson, 1988; Gibson, 1995) that slight tectonic movements may have contributed to the development of oolite shoals, thus controlling the locations of hydrocarbon accumulations. These ideas have not been quantified. One goal of this proposed study would be to discover the specific structural and historical events in areas like the Williston Basin that led to the creation of reservoirs by activity on basement features.
Abundant information about the geology of deep gas reservoirs is now available through the Atlases supported by the Gas Research Institute. This project would use those data as a starting point, and would quantify the relationship between reservoir properties, especially fractures, and features identifiable in gravity and magnetic data.
This project would use the existing published gravity and magnetic data base in the United States. In general, this coverage is excellent and adequate for purposes of quantification at small to medium scale, as well as at large scale in some places. No new data acquisition is proposed.
The goal of the project would be to evaluate selected prospective areas of the United States in terms of prospectivity for deep gas reservoirs. This proposal is for in-depth analysis in three major basin areas: The Appalachian, Michigan, and Rocky Mountain Basins (including the Great Basin in Nevada). If you are interested in other areas, let us know and if there is enough interest, other or additional areas will be added to this project.
Phase I. Detailed interpretations of gravity and magnetic maps in conjunction with the geologic information in the Gas Atlases will identify fields and regions within basins where basement features appear to affect the deep reservoirs. The tectonics of such areas will be described in as much detail as possible to pin down the expected structural styles (compression, extension, wrench; fracturing related to folding, oblique faulting, etc.).
Phase II. The gravity and magnetic data will then be modeled to identify the most reasonable alternatives for the generating mechanism (e.g., basement fault of what type, basement lithologic contact, mineralogical concentration, etc.). The model study will be integrated with what is known about the geology in existing reservoirs, and predictions will be made about expected conditions away from the known producing fields.
The final product will be a series of interpretation maps, suites of modeled cross-sections, predictive maps showing inferred analogs, and a written report. The report would include some color and film overlays as appropriate with folded maps in a pocket or separate packet. Reproducible copies of all maps are included in participation costs. In addition, all participants will receive a free week (6 days) of confidential consulting, designed to provide more specific information in areas of interest of participating companies. This work (value, $3,000) can be conducted at Gibson Consulting's office or in-house, with the client paying any required travel expenses.
Gibson, R.I., 1988, Basement tectonic interpretation of the United States exclusive of Alaska and Hawaii: Proprietary report, 160 p., 29 separate maps. Gibson, R.I., 1995, Basement tectonics and hydrocarbon production in the Williston Basin: An interpretive overview: Seventh Intl. Williston Basin Symp., p. 3-9. Atlas of Major Rocky Mountain Gas Reservoirs (1994) Atlas of Major Gas Reservoirs in the Appalachian Basin (1993) This proposal is submitted as an industry-supported project with participation on a proprietary, non-exclusive basis. Original supporters will enjoy lower costs as well as a 6-month exclusive period, after which time Gibson Consulting may market the project to late participants according to the fee schedule given below.
A minimum of five (5) participants is required for the project to be initiated.
Early Participation. Companies that commit to support the project initially will pay a total of $12,000. Half ($6,000) would be invoiced on commencement of the project (see Schedule, below) with the remainder invoiced upon delivery of the final report.
Late Participation. Companies committing to support the project after work has been underway for 4 months, but before the completion of the project will pay a total of $18,000, with half invoiced on committment and the remainder on delivery. The report will be available for purchase by other, non-participating companies (six months after delivery to existing participants) at a cost of $25,000. This late purchase price will not be reduced for a minimum of 3 years.
This work is anticipated to require seven months to complete.
The Principal Investigator, Richard I. Gibson, has more than 25 years experience at interpreting gravity and magnetic data for hydrocarbon exploration. He is the only geoscientist in the world who has made detailed, exploration-oriented analyses of five continent-scale gravity or magnetic data sets. In the United States, he has already accomplished much of Phase I of this analysis, in a proprietary analysis entitled Basement Tectonic Interpretation of the United States exclusive of Alaska and Hawaii. That work was a 7-month, first-pass integrated interpretation of gravity and magnetic data that was supported by three oil companies in 1988. The report lacks the quantification proposed in Phase II, and it was geared toward all exploration targets rather than deep gas reservoirs. Also, the study was almost entirely of the observational type, with no attempt to deduce the genesis of specific features that had impact on the prospective section. The report is proprietary but the information would be available to Gibson Consulting for this analysis. In addition, Gibson is the author of a map entitled Interpreted Magnetic Basement Terrane Map of the United States, which identifies basement features and delineates major cratonic blocks and intrabasement lithologic contacts. The map was prepared at 1:2,500,000 scale to facilitate comparison with the published geologic map of the U.S. See our web site for further information.Other continent-scale interpretation projects accomplished by Gibson include 6-month analyses of the gravity maps of Africa and South America, and a year-long detailed interpretation of the magnetic map of the entire Former Soviet Union. The latter study is a proprietary project that has been purchased by eight major oil companies on five continents.
In addition, Gibson has performed basin-scale analyses of gravity and magnetic data from all over the world. These geological interpretations provide the framework that permit him to quickly identify the significance to hydrocarbon exploration of the basement almost anywhere in the United States, and indeed in many parts of the world. Specific experience includes numerous projects in Rocky Mountain basins, as well as the Appalachian Basin. Gibson worked with the Cincinnati Arch Consortium (Ohio, Indiana, and Kentucky state geological surveys) in defining the East Continent Rift System, a Late Proterozoic basin in which the Middle Run Formation was deposited. It has at least some potential for gas accumulations.
Gibson Consulting, a sole proprietorship (small business) of Richard I. Gibson, is based in Cardwell, Montana. We have extensive library resources in-house. We have three computers with CD-ROM readers and writers, scanners, and standard office software (word processor, spreadsheet, database, mapping, graphics, publishing, etc.) installed. Laser and color ink-jet printers, FAX, and copy capabilities are available in-house.
Please refer to our Web site for more information on Gibson Consulting and its products, and to the biographic page for more information on Richard I. Gibson. If questions remain, we can provide more information.
Back to Gibson Grams
Back to US products index