Geophysical Technologies Research Articles

The application of geophysics during evaluation of the Century zinc deposit

During the period 1990 to 1995, experimental programs using high‐resolution geophysics at several Australian operating mines and advanced evaluation projects were undertaken. The primary aim of those programs was to investigate the application of geophysical technology to improving the precision and economics of the ore evaluation and extraction processes. Geophysical methods used for this purpose include: 1) borehole geophysical logging to characterize ore and rock properties more accurately for improved correlations between drill holes, quantification of resource quality, and geotechnical information. 2) imaging techniques between drill holes to map structure directly or to locate geotechnical problems ahead of mining. 3) high‐resolution surface methods to map ore contacts and variations in ore quality, or for geotechnical requirements. In particular, the use of geophysics during evaluation of the Century zinc deposit in northern Australia demonstrated the potential value of these methods to the problems of defining the lateral and vertical extent of ore, quantitative density determination, prediction of structure between drill holes, and geotechnical characterization of the deposit. An analysis of the potential benefit of using a combination of borehole geophysical logging and imaging suggested that a more precise structural evaluation of the deposit could be achieved at a cost of several million dollars less than the conventional evaluation approach based on analysis from diamond drill‐hole logging and interpolation alone. The use of geophysics for the Century evaluation also provided substance to the possibility of using systematic geophysical logging of blast holes as an integral part of the ore extraction process. Preliminary tests indicate that ore boundaries can be determined to a resolution of several centimeters, and ore grade can be estimated directly to a usable accuracy. Applying this approach routinely to production blast holes would yield potential benefits of millions of dollars annually through improved timeliness and accuracy of ore boundary and quality data, decreased dilution, and improved mill performance. Although the indications of substantial benefits resulting from the appropriate and timely use of geophysics at Rio Tinto’s mining operations are positive, some challenges remain. These relate largely to the appropriate integration of the technology with the mining process, and acceptance by the mine operators of the economic value of such work. Until the benefits are demonstrated clearly over time, the use of geophysics as a routine component of evaluation and mining is likely to remain at a low level.

Whither geophysical technology? The views of the vendors

The first SEG Annual Meeting covered by TLE was in 1982. The biggest computer advertisers (each with a two-page spread in TLE's convention preview issue) were Control Data Corporation, ELXSI, and Sperry Univac. They were gone within a few years, as were some (if not most) of their successors. Cray, the dominating supercomputer presence at conventions in the late 1980s, was mergered into convention semiobscurity in the 1990s. However, in a recent transaction that went virtually unnoticed by the major news media, Cray was resold and might be primed (unlike Prime computers, which failed to make it out of the 1980s) for a convention comeback.

Introduction and review

The application of geophysical technology in the exploration for, and appraisal of, hydrocarbon accumulations in the basins of northwest Europe is a fundamental part of the exploration process. As exploration in the North Sea matures and geo-scientists are evaluating prospects of ever decreasing size, the ability to image both the geometry of the trap and the nature of the material contained within the trap is of paramount importance. Although exploration on the Atlantic margin is at a relatively immature phase, the recently discovered large fields are combination structural/stratigraphic traps and are therefore best illuminated with state-of-the-art geophysics. Appraisal and development drilling is also reliant on high quality seismic data to map both the distribution and quality of reservoirs across fields. The complex nature of the exploration targets and the inhomogeneity of reservoirs continually challenge geophysicists to improve techniques from acquisition through processing to innovative interpretative analysis. The five years since the 4th Conference on the ‘Petroleum Geology of Northwest Europe’ (Parker 1993) have seen tremendous advances in seismic processing which has sustained exploration in areas where the prospects are relatively small. There are nine papers in this section of the Proceedings. Three relate to innovative seismic acquisition techniques. The paper by Leach describes the use of the vertical cable seismic technique on the Strathspey Field in the North Viking Graben. The technique deploys cables suspended vertically in the water column with hydrophones located along the cables. The processed data are significantly improved when compared to the pre-existing data. . .

Mapping shallow underground features that influence site-specific agricultural production

Modern agricultural production practices are rapidly evolving in the United States of America (USA). These new production practices present significant applications for nonintrusive subsurface imaging. One such imaging technology is GPR, and it is now being incorporated within site-specific agriculture in the detection of soil horizons, perched water (episaturation), fragipans, hydrological preferential flow paths, and soil compaction. These features traditionally have been mapped by soil scientists using intrusive measurements (e.g., soil augers, soil pits, coring tools). Rather than developing a tool for soil mapping, our studies are targeting the identification, dimensioning, and position of subsurface features that directly influence agricultural productivity. It is foreseen that this information will allow for an increase in agricultural efficiency through infield machinery automation, and it will also greatly enhance development of highly efficient crop production strategies. The field sensing methodologies that we have developed using existing geophysical technologies are highly dependent upon both the soil and site characteristics due to seasonal variations. The GPR applications presented herein were conducted primarily in a region of loess soil that extends east of the Mississippi River into western Tennessee. GPR studies were also conducted in central Tennessee on the Cumberland Plateau within a region of shallow, sandy loam soils. Additional studies were conducted on the karst area of central Kentucky. Although targeting site-specific agriculture, our results and procedures may benefit the traditional users of GPR technology. We suggest that large-scale agricultural applications of the technology would be enhanced by integrating global positioning (GPS) technology in future hardware and software products.

Examination of the gravity & electromagnetic survey methods applied to coal exploration in the area of the Southern Gunnedah Basin

The New South Wales Department of Mineral Resources (DMR) and the Japanese New Energy and Industrial Technology Development Organisation (NEDO), have entered into a Joint Coal Exploration Research Agreement aimed at developing advanced coal exploration technologies with particular emphasis on geophysical technologies. As part of the first year’s project an investigation into the applicability of gravity and transient electromagnetic geophysical methods for coal exploration was undertaken.The Caroona coal prospect has a resource of high quality multi-seam coal lying within relatively complex geology. While significant drilling has been undertaken in the area, a number of aspects of the geology cannot be adequately identified by drilling. The area is known to contain thrust faulting and igneous intrusions. The coal seams are covered by 40-80 m of alluvial materials, which can reduce the seismic energy transmission for conventional seismic surveys.Trial gravity and electromagnetic surveys were undertaken to test the potential of these geophysical methods and to supplement the seismic data. The aim was to provide a much better estimate of the bedrock-alluvium interface and to define the distribution of intrusions and faulting.The field work involved undertaking a gravity and electromagnetic survey along a 3.5 kilometre traverse which coincides with a seismic survey line (L972) in the Caroona area. It is believed that the integration of these geophysical methods has facilitated the extrapolation of geological models derived from the seismic interpretations. The regional geophysical coverage that can be provided by these techniques is extremely cost effective and will assist the evaluation and modeling of areas involving complex geology.In the Caroona area the preliminary results have shown that the gravity and electromagnetic data has defined the alluvium thickness and structural zones.

SEG continues its support of promising young scientists, engineers

In the continuing advance of science and technology in geophysics, it is good to know that intelligent and excited students are preparing themselves for a bright future. Nowhere was this more evident than at the 49th International Science and Engineering Fair (ISEF), 10-16 May 1998, in Fort Worth, Texas. Students from the United States and 29 other countries presented 940 projects. The ISEF brings together first-place winners from local and regional science fairs from around the world. In this competition, students demonstrate and explain their projects to teams of judges and the public.

Pre-investigation of the subsoil developments in construction of the 4th Elbe Tunnel Tube

The procedure adopted for pre-investigation of the subsoil for the 4th Elbe Tunnel Tube set new standards in geotechnical /geological subsoil investigation using geophysical methods. The objective for the construction measure was to apply state-of-the-art science and technology in geophysics. In a far-ranging investigation programme, various methods and groups of methods were tested and evaluated through laboratory tests on a 1:1 scale and through in-situ applications. The paper describes the investigation methods and testing programme.

CARL H. SAVIT—THE HUMAN SIDE

Two years will have passed since Carl left us in March 1996. For someone like me, he will never leave. A number of “in memoriam” articles, written by people who knew Carl very well, highlighted Carl's achievements as a professional, a mentor, an industry spokesman, a visionary, and as a major contributor to advancements in geophysical technology.

97/03477 Use of corelles geological and geophysical technology for coal prospecting

97/03477 Use of corelles geological and geophysical technology for coal prospecting

The role of professional societies in continuing education

Why does anyone in the geophysics business care about continuing education? For the individual geophysicist the reasons to consider participating in continuing education probably boil down to wanting to stay competitive in the job market. For companies, it is much the same — they want to maintain their competitive edge by having their employees apply geophysical technology as effectively as possible.

Review article: Geophysics and CD-ROM technology

Review article: Geophysics and CD-ROM technology

Hybrid inversion of shallow geophysical data for the location of subsurface targets

In order to rapidly, safely and economically gather data about a waste site, nonintrusive shallow geophysical sensor technologies are used to map the surface of a site. The major thrust of this investigation is to locate buried man-made material (such as 55-gallon steel drums), using nonintrusive shallow geophysical methods. Two sensor data sets are dependently optimized to determine the six free parameters describing rectangular bounding boxes which totally encompass subsurface targets. A conservative bounding box approach is used to estimate the location and volume of the waste, but does not yield an unacceptably large volume to be remediated. This hybrid inverse approach has proven to facilitate solving problems involving nonuniqueness issues, as well as significantly reduce execution time. The two geophysical sensors employed in this investigation are the total field cesium vapor magnetometer and the EM61 time domain sensor. Results from data sets surveyed at a site at Sandia National Laboratories, in...

Future geophysical technology trends

What are our profession’s major technical challenges in the future and how are we to prepare to meet them? What will be the impact of research done today on industry’s bottom line in the years to come? What are the emerging technologies of today that will significantly change the way we conduct our business? How can we benefit from important technological breakthroughs originally aimed at other industries (e.g., defense, aerospace, medical)? Conversely, can petroleum‐related geophysical technology play a role in other domains? This paper highlights my views on future technology trends. Feedback from the Research Committee’s Subcommittee on Future Technology Trends helped to form some of these views. I will attempt to answer some of the above questions based on what is known today and what has been learned from past experience in technology forecasting.

Future geophysical technology trends: NPC members’ view

The oil and gas industry depends critically upon technology. This is not new and is well recognized. Each of us knows that technologies in use today either did not exist a few years ago or were not as refined, readily available, or cost‐effective as at present.

GEOTECHNICAL PROCESSES AND MANAGEMENT STRATEGIES FOR MATURE BASINS: A CASE STUDY OF THE GIPPSLAND BASIN

During the 1990s, exploitation and exploration processes in the Gippsland Basin have been expanded to cater to a surge in mature field redevelopment activity, and have supported continued activity in the more traditional functions of exploration and development of new resources.The first major field redevelopment project was initiated in 1991 on the West Kingfish Field. Since 1991, similar programs conducted on the Mackerel, Perch, Fortescue and Kingfish Fields have significantly mitigated oil production decline in the basin. The success of the field redevelopment programs has been attributed to the use of multi-disciplinary field teams, the use of high end geophysical interpretation technologies, and the ability of the field teams to integrate and synthesise often voluminous quantities of production and geotechnical information to identify drilling opportunities.Areas where we continue to improve field redevelopment geotechnical processes include decreasing data acquisition and analysis cycle time, and advancing the precision of geotechnical predictions.With over 30 years of intensive exploration activity in the Gippsland Basin placing it in a mature phase of development, focus on the risk management of exploration activities has increased. Focussed research efforts to both develop new geotechnical technologies and more accurately assess the limitations of currently utilised technologies have also been undertaken to ensure an economically viable exploitation and exploration strategy for the basin.The structure of geotechnical teams in the 1990s has seen production and exploration functions amalgamate to ensure that the benefits of operations synergies provided by the high level of platform drilling activity are fully realised. This is enabling the knowledge from intensive field drilling programs to be more readily applied to the evaluation of exploration opportunities. Field re-development drilling activities are at historically high levels and are predicted to remain so into the foreseeable future. Given the mature nature of exploration in the basin, future exploration activities will be undertaken within the defined limits of our technologies to ensure the opportunity to achieve continued economic success is maximised.

1994 SEG Presidential Address — Geophysics: The exploration risk reducer

During the past decade, the importance of geophysics in the exploration and production of oil and gas has grown steadily; and geophysics now displaces a significant amount of drilling activity. These changes have resulteddirectly from advances in geophysical technology, with 3‐D seismic imaging arguably the most significant advance in petroleum‐industry technology in recent years. However, technological advances and applications of those advances must continue if geophysics is to continue to grow in importance. At the same time, a global marketplace for geophysics has emerged, providing numerous professional and commercial opportunities for geophysicists. SEG has played a major role in both the globalization of geophysics and the development of geophysical technology. This article, a written version of my Presidential Address at the 1994 Annual Meeting in Los Angeles, provides my perspectives on the state of thegeophysical industry, the importance of geophysical technology, and SEG’s role in advancing the...

Imaging sediments under salt: Where are we?

In this paper we review the evolution of geologic thought and geophysical technology that preceded the research workshop “Imaging Sedimentary Structures Under Salt” at SEG’s 1993 SEG Annual International Meeing in Washington, DC. Two of us (RWW and SWN) organized the workshop. This special issue of TLE contains some of the presentations. The workshop had the largest attendance of any at the convention, indicating the high interest in subsalt exploration.

Lies, damned lies, and statistics

Touting the value of geophysics is an important function of SEG and should also occupy the attention of most geophysicists. Exploration managers generally don't seek technology on which they can spend money; rather, they seek ways to enhance exploration success and are willing to use technology if they perceive it to be cost-effective. Each of us should assume responsibility for demonstrating the benefits of geophysical technology to those making exploration decisions.

Geophysical technology transfer symposium: Russian airborne geophysics and remote sensing

A unique symposium, Russian Airborne Geophysical and Remote Sensing Technology, was convened in September 1992 at the Colorado School of Mines. Its purpose was to expose Americans to the latest Russian technology, survey practices, and future development plans in, principally, airborne magnetics and gravimetry. A minor part of the symposium, however, was devoted to airborne radar (Sar) and laser (Lidar) measurements.

Directions in geophysical technology: A supply and demand concept

Four hundred and fifty‐six papers, distributed in 59 sections and spread over four days, comprised the Technical Program of SEG’s 1991 Annual International Meeting and Exposition. Expanded abstracts were published in two volumes of 1100 pages. Within the sum total of this work, one would expect to find an expression for the current state of geophysical exploration technology.