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- Volume 22, Issue 2, 2004
First Break - Volume 22, Issue 2, 2004
Volume 22, Issue 2, 2004
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I/O aims to convert E&P industry to digital full wave imaging technology
By A. McBarnetInput Output, the company synonymous with the supply of land and marine seismic acquisition technology, is emerging from the turbulence of the last few years in the geophysical services industry, led by a man with a plan. Andrew McBarnet reports. Less than a year into the CEO job, Bob Peebler has already made some big changes at Input Output (I/O), convinced that the company has to catch a new wave of technology. ‘In the future,’ he says, ‘we don’t see the core competence of I/O as a manufacturer. It will be in working with E&P companies and contractors to understand imaging problems, developing technology, and being a project architect. We will continue to manage our part of the manufacturing process but more and more on an outsourced basis.’ The radical rethink of I/O’s business strategy is nothing more than you would expect from the man who spent much of the 1990s building Landmark Graphics into one of the big two integrated geoscience and engineering software solution companies, and the man often spoken of as an industry visionary. Peebler’s vision these days is that I/O should lead a new technology cycle based on digital full wave imaging, which has applications in the growing area of 4D and multi-component seismic surveys as well as conventional 2D and 3D. Since the mid 1990s I/O has been quietly pioneering digital sensor technology which makes imaging of both the ‘p’ and ‘s’ wave data possible, with momentum building in the last couple of years. A key ingredient is the MEMS (Micro Electro Mechanical Systems) micro g accelerometer developed by I-O and produced at a facility in Stafford, Texas established in 1997. Last year saw the unveiling of the first commercial VectorSeis digital sensor and System Four cablebased recording unit for land seismic, offering multi-component data acquisition capability, something of a breakthrough for an industry thirsty for innovation.
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Earning community trust in Ecuador
Authors G. Schultz and N. SotoLand seismic crews have to adapt to working in every kind of environment around the world. In this illustrated article Gehrig Schultz and Norberto Soto describe how one PGS Onshore operation found the solution to carrying out seismic acquisition in a jungle region of Ecuador in the face of objections, local and international. At the edge of the Amazon jungle a short flight east of the cool mountain valley where the Andean capital, Quito, sits surrounded by high snow capped peaks and a smoking volcano, PGS Onshore’s Crew 360 has been busy meeting the challenge of seismic acquisition in the jungle and the special local conditions that govern such surveys. The crew is acquiring its second 3D survey in Ecuador’s oil rich Oriente Basin for state oil company, PetroProduccion, as part of a project to redevelop the mature Sacha Field. Discovery of the Sacha Field and other nearby giant fields attracted immigration to the area by poor peasants called ‘colonos’ pursuing economic opportunities and free land. The colonization, in turn, led to commercial development, including logging, mining and agriculture. In Ecuador, as in any developing nation, forested lands were cleared to support this growing population. Today, the oil boom’s economic opportunities have been replaced by increasing poverty as the ‘colonos’ can now only operate marginal cattle ranches and small struggling coffee, cocoa and oil palm plantations. The poor jungle soils only produced profitable crop yields for three or fours years, until minerals were depleted from the thin jungle soils. The worldwide collapse of coffee prices has eliminated the main source of income for many small farmers. Small groups of traditional indigenous tribes still inhabit the remote, undisturbed jungle areas, living very much in the way they have for centuries. Environmental damage during the early years of oil field development has led local farmers and indigenous groups to distrust the petroleum industry. This distrust led local stakeholders and international non-governmental organizations (NGOs) to actively challenge oil exploration activity in the area, with demands for reclamation of damaged areas and a share in the benefits from the production. The biggest challenge in executing a 3D survey in Ecuador’s Oriente region is operating a high quality seismic crew safely and efficiently in this complex and turbulent social environment. Evidence of the complex social environment is demonstrated by recent job delays and cancellations in the area. One major international seismic company finally declared force majeure on a project and closed its Ecuadorian operation after repeated protests and even temporary confinement of its field crews. Six months of standby due to constant permit problems and conflicts with NGOs on the block adjacent to Sacha, where PGS Onshore is present, caused another competitor to cease operations. Other contractors have been delayed months and reportedly have had thousands of dollars of seismic recording equipment destroyed by sabotage.
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Land seismic crews and instrumentation: past, present and future
By B. HeathBob Heath describes the somewhat volatile history of land seismic survey technology and operations and how UK company Vibtech is developing a new approach to some age-old problems. We should start by making what some would think is an unnecessary statement, namely that the majority of end-users of geophysical data are oil companies! This may seem rather obvious but the problems faced by the land acquisition industry indicate that it may not be obvious enough. If we accept this statement, we might also agree that the end-users of geophysical instrumentation, in some important sense, are also the oil companies. Any acquisition system which ignores the market generated by oil-company requirements is just asking for difficulties. The recent history of this market, which has not witnessed the growth of other high-tech businesses, seems to demonstrate that the real needs of the data end-users are too often ignored. This may explain why some agree with one bank which stated that parts of the industry demonstrate an unsustainable business model (or words to that effect). For decades, instrumentation manufacturers used contemporary electronics technology to produce systems fitting the perceived needs of end-users. The market for such products depended on how well their functionality suited the type of survey required by the oil companies. In the seventies, the limitations of the technology forced the electronics to be confined to the central system. This required data to flow along miles of twisted pair conductors in analogue spread cables. The weight and susceptibility of the equipment to various problems meant we could not easily record more than a hundred channels - as a ballpark figure. However, the technology met the need for relatively simple 2D surveys, and prices charged to acquire such data were not generally seen as excessive. The end-users supported a market of more than 1000 crews worldwide or about 100 000 channels.
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Land seismic: needs and answers
By D. MougenotDenis Mougenot, chief geophysicist of Sercel, the French-based manufacturer of seismic acquisition systems, provides examples of how his company is tackling needed improvements in land seismic acquisition technology. The geophysical industry has been struggling to achieve profitability for some time (IAGC, 2003). In such a market, some seismic acquisition system manufacturers realize that contractors will only spend their precious capital on equipment for which they can get a near term return. This has led these manufacturers to focus their development effort on system improvements that enable contractors to collect more seismic data per day, in other words to be more productive. This article describes some of these specific productivity enhancements. Improvements are illustrated by the features in the Sercel SN388 system and by the revolutionary 408UL system introduced in late 1999. These two 24-bit recording systems are widely used by contractors and represent together about 750 000 channels and 600 central units. Changes that have contributed to faster acquisition and better data quality are considered. Improvements in seismic acquisition productivity have contributed to reducing the cost of seismic data and have helped the industry reduce the cost of finding and recovering oil and gas. These improvements can give some insight into future evolutions. It is well known that an oversupply of crews within the seismic contracting industry and the demand for lower prices in new contracts have both contributed to an understanding that lower data acquisition cost is a survival need for contractors. At the same time geophysical demands have required higher fold as well as larger offsets and uniform azimuthal distributions. Together this means that while demand for lower costs increases, the density and number of traces produced is also on the increase. In this context of low cost per trace and high fold per survey, seismic crews must improve their productivity to be profitable. Many factors can influence the productivity of seismic crews. Many of these factors are not influenced by the acquisition system, for example, geophysical planning, logistical planning, personnel choices, contractual issues, HSE, local culture, oil company requirements, to name just a few. But there are also many ways that the acquisition system can impact how much data is collected per day. Productivity improvements can come from 1) shorter time to troubleshoot the line; 2) shorter lost time between records; 3) the ability to record more lines and channels; 4) a new paradigm for acquisition field equipment, the use of a Link between multiple single channel units rather than the old technique of a fixed number of channels in boxes and cables; 5) automated QC so that the observer doesn’t need to spend so much time visually inspecting records; 6) multi-fleet vibrator techniques that allow operating without a delay for vibrator move-up; 7) overlapping record techniques, such as Slip-Sweep that allow collection of multiple records simultaneously; 8) built-in redundancy to allow a system to continue operation even with the inevitable damaged cable; 9) high enough system uptime and reliability to allow 24-hour acquisition in some areas; 10) very low power operation to minimize battery handling and replacement; and 11) lighter weight field equipment.. All of these issues will be discussed further in this article.
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Pore fluid and porosity mapping from seismic
Authors J. Dvorkin and S. AlkhaterWe use rock physics to map pore fluid and porosity from seismic data in a vertical section between two wells. First, well log data are used to establish an effective-medium model that links the impedance to pore fluid and porosity. Next, stacked seismic data are used to produce P-wave impedance inversion. Finally, the rock physics transform is applied to the impedance section to identify pore fluid and produce a porosity section. For decades, the main use of seismic data has been to delineate sedimentary bodies and tectonic features in the subsurface. The mission of exploring inside the geological body is a relatively recent development. Mapping porosity, lithology and other reservoir bulk properties inside the geological body has become possible due to the recent dramatic improvement in seismic acquisition, imaging and inversion quality, as well as the accompanying advances in rock physics. Rock physics provides transforms between a reservoir's elastic properties and its bulk properties and conditions, including porosity, lithology, pore fluid and pore pressure. Such transforms are known as trends. Trends are built from controlled experiments where both the elastic and bulk properties of rock are measured on the same samples under the same conditions. The most commonly used source of such experimental data in modern rock physics is the borehole measurement. For example, an empirical impedance–porosity trend developed from sonic, density and porosity curves can be applied to a seismic acoustic impedance volume in order to map porosity in 3D. However, it is always advantageous not only to find an empirical trend but also to understand the physical laws that determine the trend or, in other words, find an appropriate effective-medium model. Such rationalization of an empirical trend by effective-medium modelling generalizes the trend, determines the domains of its applicability, and thus reduces the risk of using the trend outside the immediate data range. Here, we illustrate the rational-rock-physics approach by mapping porosity in a large producing gas/oil reservoir. Well data are used to establish a transform from impedance to porosity, based on rock-physics theory. This transform is then applied to a vertical impedance section obtained from stacked seismic data via inversion. The reservoir under examination consists of relatively soft sands. As a result, the acoustic impedance of the gas-saturated sand is much lower than that of the oil- and water-saturated sand. This large impedance difference allows us to identify the pore fluid from P-wave data only, without using offset information. As a result, we map both pore fluid and porosity, using only stacked seismic data.
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Seismic transmission and electrical resistivity tomography for the delineation of mine galleries in the Raniganj Coalfield,India
Authors S.K. Nath and S. ChakrabortySubsidence, fire, flooding and other kinds of environmental hazards related to shallow coal workings in the Raniganj Coalfield necessitated stabilization of the abandoned galleries at North Searsole, Bansra and Dhandadih. The working coal-seams at these collieries are Kenda bottom, Purandip bottom and Jambad top, respectively. For an accurate location of the network of galleries in the coal-seam, seismic transmission and resistivity tomographic methods are applied and the results are reported here. In the 2D tomographic formulation for both seismic exploration and electrical resistivity measurements, the genetic algorithm is implemented for an optimal solution even starting with poor initial models. The residual traveltime and transfer-resistance 2D distributions are generated to analyse the quality of the data recorded in the field. In these images, each cell corresponds to one source–receiver pair for each different cross-hole combination. All the colliery data are tested for their quality, preliminary 1D model generation and the construction of final velocity and resistivity images, depicting the coal-seams with or without voids/galleries. The estimated tomograms show the lateral S- or P-wave velocity and resistivity variations at different depths in the North Searsole, Bansra and Dhandadih collieries. While seismic tomography could depict the dry voids in the coal-seam at North Searsole and Bansra, resistivity tomography failed to do so, due to small resistivity contrasts between the void and the coal-seam bed. At Dhandadih, however, where the galleries are waterlogged, both seismic and resistivity tomography imaged the voids successfully. Generally, in all the cases, the coal-seams are better delineated by electrical resistivity tomography than by seismic tomography.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)