Dry Holes Research Articles

Prospect risk, pot odds, and efficient drill or no-drill decision making: What the exploration business can learn from high-stakes poker

A decision to proceed with risk ventures, such as exploration wells, requires three basic estimates: the cost, if the venture fails; the reward, if the venture succeeds; and the chance of success (risk). These three estimates are combined to derive the expected value and expected rate of return, which are critical to decisions to proceed or not to proceed with the risk venture. However, although cost and reward are seen as relatively “hard” numbers, based on measurable quantities and established price forecasts, risk is commonly seen as a “soft” number, an opinion based on incomplete knowledge. Decisions may be deferred, seeking more constraint on the risk estimate; this delay can be counterproductive. An alternative approach is used by professional poker players to make an equivalent decision. In that business, too, the chance of winning is harder to constrain than the cost and reward. Instead of seeking to fine-tune the risk, players compare a rough estimate of chance with “pot odds,” an easily calculated number (the chance of winning needed to break even), and use this comparison to make the right decision efficiently. This approach can also be used in the exploration business. Pot odds of a prospect can be calculated using expected dry hole costs and the predicted value of a discovery. Comparison with the estimated chance of success may indicate whether we already have enough information to make the appropriate decision or whether further work is justified. This may improve business decision-making efficiency or provide a sense check on decisions already made.

Do technical studies reduce subsurface risk in hydrocarbon exploration: and if not, how do they add value?

Abstract The title ‘The Value of Outcrop Studies in Reducing Subsurface Uncertainty and Risk’ might suggest that we expect new information to improve prospect risk, but this is not correct. Gaining new information generally does change our estimate of prospect risk: the change may be up or down, and the average of all possibilities is zero change. You cannot acquire data for the purpose of increasing the probability of success. We should expect that: (a) the expected value of the risk of a single prospect, post-data, is equal to the prior (pre-data) value; and (b) risk should become worse for the majority of prospects. New information adds value, not from changing pre-drill risk, but from decisions made as a consequence. The main value added is from identifying prospects not to drill, thereby saving the cost of likely dry holes, and by choosing the ones to test first, accelerating revenue from a successful outcome. Further value is added if the new information leads to the identification of new prospects or new plays, or suggests follow-on potential elsewhere in the region. Value may also be added if the new information is negative for a whole region, enabling us to focus our attention elsewhere.

Source Rocks And Sorcerers: Decoding The Origin Of The Niger Delta Petroleum

Against the present-day credo of the organic origin of petroleum, it may be difficult to believe that in the early days of the oil industry, the abiogenic (inorganic) origin of petroleum held sway. In 1877, Russian Scientist Mendeleev (of the Periodic Table fame) proposed that metal carbides deep within the earth reacted with water at high temperatures to form acetylene which subsequently condensed to form heavier hydrocarbons (as is readily demonstrated in the lab). CaC2 + 2H2O = C2H2 + Ca(OH)2 In 1890, Sokoloff propounded that `bitumina', originated from meteorites and that this petroleum was extruded from the earth's interior into the surface sediments. They were the first Sorcerers. Others (eg. Vernadsky, Kudryavtsev) were to follow with differing concepts of the Inorganic Origin of petroleum including Volcanic Origin Theory, Earthquake Outgassing, etc. Their views received great support from their peers (and still linger in some quarters!). Then came the period in the early 1900s when advances in the knowledge of the composition of petroleum saw the ascendancy of the Theory of Organic Origin. In particular, the discovery of the optical activity of petroleum (Walden, 1906) and of the presence of chlorophyll porphyrins (Treibs, 1934) confirmed the low temperature origin and history of petroleum and thus cemented the Organic Theory. Subsequently, the search for petroleum moved to the great sedimentary basins of the world. The successes scored seemed to put paid to the inorganic Theory. The organic Sorcerers seemed to have won. Or did they? In the 1990s, a new set of Sorcerers led by T. Gold reignited the Inorganic Theory. Largely supported by the state-owned Swedish electricity utility Vattenfall, he caused a deep well (6.5 km by 1997) to be drilled into the crystalline basement rocks in Sweden in search of predicted petroleum of inorganic origin but the outcome was a dry hole. Was that the end of the Inorganic Theory? Perhaps, not.

Seal potential of shale sequences through seismic anisotropy: Case study from Exmouth Sub-basin, Australia

Sedimentary rocks with sealing potential can cap a reservoir by impeding the upward movement of hydrocarbons. An effective seal should have three qualifying factors of geometry, integrity, and capacity. Mapping seismic horizons and faults across the area of study reveals much about the geometry and integrity of the sealing unit. Capacity, however, depends on capillary pressure measurements of core and cuttings samples. Modeling capacity of seals away from and between wells has traditionally involved simple gridding techniques or association with most likely geologic or seismic facies. We have developed a different approach in using seismic data and applying it to the evaluation of sealing potential. Shales are the most common seals in petroleum systems. Seismically, well-developed shale units that have undergone compaction are likely to be anisotropic and are typical vertical transverse isotropic media. Seismic data with suitable acquisition parameters were processed to extract [Formula: see text] and Thomsen’s parameters of weak seismic anisotropy, tied to the vertical seismic profile data at wells. The spatial distribution of [Formula: see text] has shown a good correlation with capillary measurements of well samples. Hence, 3D modeling of epsilon was used as a weight factor to guide the capillary pressure ([Formula: see text]) values away from the wells. Capillary pressure values were then mapped on the fault planes to high grade the analysis of sand-shale juxtaposition. Our results helped to explain the distribution of successful wells and dry holes within the study area.

Looking for Oil From More Angles

Seismic Data New generation of seismic promises big advances Selling new offshore seismic survey methods can be reduced to two goals: “We want more of everything at less cost.” That maxim was offered by Andrew Long, chief scientist of geoscience and engineering, imaging, and engineering for Petroleum Geo- Services, one of the players in this intensely competitive, economically depressed, technology-driven business. While the science behind using sound waves to image underground formations is baffling to outsiders, the two avenues for doing it better are not. There are improvements in data acquisition covering sound sources, receivers, and survey methods. And there is the mathematics and computer power needed to process and extract more information from the constantly growing amount of data gathered. Faster, Better Seismic Surveys by Making Many Sounds at Once The pace of a seismic survey can be measured by the number of shots taken per day. Huge onshore surveys have shown that allowing 10 or more sound sources working at the same time without any coordination can drastically reduce the time needed to gather data over a large area, and get better data as well. “One of the biggest surprises is we have gotten almost universally better data from our simultaneous source surveys,” said Craig Beasley, a Schlumberger Fellow and chief geophysicist at WesternGeco. More data are gathered from more angles for a more accurate picture of what is below, said Beasley, who explained that one flashlight can help you see in a dark basement, but it is better with two and more is better. The Hunger for the Lowest Frequencies Takes Data Gathering in New Directions The word “broadband” is used to sell a lot of what is new in offshore seismic. It can mean different things depending on who is speaking. But most often, it is applied to things used to gather scarce signals at the lowest frequencies. Gathering more low-frequency data is the “holy grail’ in broadband, said Craig Beasley, chief geophysicist at Western- Geco, which is part of Schlumberger. They are valuable for determining rock properties and imaging deep formations. Seemingly small gains can be big. “Moving down from “3 to 1.5 (Hz) does not sound like a lot. But in octaves, it is a whole other octave,” he said. Intractable Problem and Big Payoff Sell a Seismic Acquisition Innovation The Mad Dog field was a major discovery for BP in the late 1990s, but developing it looked like a high-risk proposition. The problem was the field was an early discovery beneath the thick layer of salt covering much of the deepwater US Gulf of Mexico. Shooting seismic through the salt resulted in murky images that increased the risk of development wells that produced little or nothing, which could turn a 4-billion-bbl field into a marginal investment. BP needed to solve the problem because it had leased a large number of deepwater blocks where the industry was drilling a growing number of dry holes due to poor subsurface imaging. “It was pretty common knowledge in the industry that you have this problem. But what are you going to do about it?” said John Etgen, a distinguished advisor in seismic imaging at BP. The problem is salt distorts sound waves as they travel down and are reflected back up. The salt is like broken eyeglasses. It acts as “big, very complex lens distorting the sound waves.”

Neotropical dry forest wildlife water hole use and management

Se estudió el uso diurno por especies faunísticas p 1 3de un ojo de agua natural (QDl y otro artificial (AW ) a finales de la época seca de 1990 en el Area de Conservacion de Guanacaste, Costa Rica. En total 9 19 individuos (seis especies de mamíferos y una de ave cinegética) consumieron agua de QD y 7 13 individuos (cuatro especies de mamíferos) de AQ. Se estimó que en un dia, las especies de vida silvestre estudiados tomaron 29.7 1 y 27.3 1 de agua de QD y AW, respectivamente. El total de agua consumido o evaporado de cada ojo de agua durante 24-horas fue estimado en 44.6 1 en QD y 4 1 . 1 1 en AW, con base en: al agua bebida durante 12 h por las especies seleccionadas, b) agua bebida por todos los otros individuos durante 24 h (QD = 1 4.85 1, AW = 13.65 1) y c) evaporación diaria (QD = 0.04 1, AW = 0.0 1 1). Para abastecer AW durante una epoca seca de 120 días, la administración del parque debe proveer 4 932 1 de agua. Se discute las implicaciones de manejo en las regiones de bosque seco neotropical.

Pitfalls in the seismic interpretation of fault shadow events — Vicksburg formation of south Texas

Reliance on prestack time-migrated seismic data to define structural highs without incorporating all subsurface data and without taking into account the regional and local lateral depositional trends may result in dry holes or poorly positioned production wells due to local velocity changes, which are usually caused by some depositional or structural phenomenon. Tying check-shot control to depositional units may reveal those phenomena and permit assumptions to be made about velocities in areas beyond check-shot control points. We discovered a significant gas accumulation in an area surrounded by dry holes and marginal wells in the Vicksburg Formation in McAllen Ranch Field, Hidalgo County, Texas, by treating a seismic velocity anomaly as a geologic problem and by simple application of arithmetic and geometry to a 3D velocity model. Due to the effects of the anomaly, seismic data displayed in time gave no indication of the existence of a 325 ha (800 ac), 150 BCFG anticlinal structure. A subsurface model that accounted for the velocity anomaly was able to predict its extent and severity by readily identifiable thickness changes in the anomalous units. The resulting discovery yielded a sevenfold increase in field production within a two-year time span.

The Umiak field discovery, Northwest Territories, Canada

This paper examines the discovery process in terms of changing exploration paradigms and describes a field discovered because of this change in mindset. Prior to the Umiak discovery all wells in the Mackenzie Delta had been drilled on structural highs. Reevaluation of two 30-yr-old dry holes along with existing two-dimensional (2-D) seismic data resulted in discovery of the Umiak gas field. This reappraisal led to recognition that a stratigraphic trap might exist between these two wells drilled in the early 1970s. The Kilagmiotak M-16 well contained 290 m (951 ft) of porous sandstone in the Eocene Taglu Formation, whereas the Umiak J-37 well, up dip and 11 km (6.8 mi) to the west, had no sandstone in the same interval. Examination of 2-D seismic lines found evidence of an updip sandstone pinchout beneath an angular unconformity on a tilted fault block. Strata in the tilted fault block below the unconformity contain strong amplitudes and flat spots. Interpretation of a subsequent three-dimensional (3-D) survey supported the play. A partnership of Alberta Energy Company (operator, now Encana), Anadarko, and Gulf Canada (now ConocoPhillips Canada) drilled the Umiak N-16 discovery well during 2004. Gas and some oil was found in gently dipping Eocene Taglu shoreface and delta front sandstones, and within gently folded foreset beds of the Eocene Richards Formation above a mid-Eocene unconformity. The Umiak N-05 appraisal well drilled a year later confirmed the discovery. Together these two wells delineate the fourth largest onshore gas accumulation on the Mackenzie Delta.

Seismic attributes and acoustic impedance inversion in interpretation of complex hydrocarbon reservoirs

Seismic attributes along with seismic inversion are used to study a challenging reservoir facies from Boonsville field in north central Texas. Two thin reservoirs, Upper Caddo and Lower Caddo, separated by a nonproductive thin limestone formation are investigated. Seismic was not an unambiguous indicator of the Caddo reservoir. The Caddo event exhibits doublet character reflections when productive facies are present. However, this character proved to be a false diagnostic of the Caddo reservoir. Wells drilled on interpreted doublet reflections turned out to dry holes penetrating two thin limestone units instead.First, some modern poststack processing techniques are used to remove incoherent noise and improve the data resolution and interpretability. Seismic instantaneous attributes (i.e., amplitude, phase, and frequency) are then calculated to infer seismic expressions of the reservoir and the limestone formations. Next, spectral decomposition is performed to study the frequency responses of the different lithotypes. Interestingly, the attribute images and frequency maps could distinguish between the different investigated units. However, some limestone units show up similar to the Lower Caddo formation in the frequency images. Model-based acoustic impedance inversion is carried out on seismic lines spanning both zones. Acoustic impedance sections reveal that producing wells and dry wells penetrate different formations. The cosine of instantaneous phase attribute along with impedance sections supports the above interpretations and displays more clearly where the Caddo reservoir is traversed and where it is not. This study demonstrates that integration of modern poststack processing and novel seismic attributes can lead to extract more key information about challenging reservoirs with less ambiguity.

A simple and practical method for estimating undiscovered hydrocarbons for a specified timeframe

A simple approach has been developed to predict yet-to-find (YTF) hydrocarbons to be discovered in a basin within a specified timeframe. The methodology uses basic exploration and resource data to address the requirement of oil companies, governments, utilities and financial institutions so that these understand the resources available for future markets within a defined timeframe (e.g, in the next 15 years). In contrast, conventional approaches to estimate the YTF in a moderately mature basin tend to predict the ultimate resource of a basin, unqualified by time. Such techniques reply on data-intensive geological assessments or use the parabolic form of a log-log plot of cumulative hydrocarbon resource against field rank, coupled with an extrapolation of a cumulative resource against field rank (the creaming curve) to an asymptote. The approach uses annual exploration data, dry hole and discoveries, and the discovery size. Three parameters are defined for the forecast period: the average number of wells per year, the average chance of a discovery, and its average size. Low, mid and high case values of each parameter are estimated, and these are combined probabilistically to produce P90, P50, P10 YTF volumes. These become end points for the forecast period, that are used to extrapolate the creaming curve. Iterating with the input parameters optimises forecasts with respect to the historical dataset. The approach can be extended to predict future field size distributions. Forecasts are made for the Bonaparte, Browse, Carnarvon and Perth Basins. The total P50 undiscovered gas resource for these basins for the next 15 years is estimated at 25.1 Tcf.

Local nanostructuring of gold thin films through dewetting induced by Ga+ irradiation

Dewetting of ion-irradiated metal films is a consequence of the local melting occurring during the irradiation. In this study we present the dewetting evolution of Au thin films bombarded with Ga+ ions in a focused ion beam system, pointing out the different surface patterns observed in films having different starting thickness and morphology. In fact, in ion-irradiated films thicker than 2nm the typical features of dewetted liquids appear, i.e. enlarging dry holes surrounded by metal interconnections. On the other side, a different behavior is observed in thinner discontinuous films, where a dense distribution of circular nanoparticles is formed upon irradiation. We studied the dependence of Au nanoparticles distribution obtained for different ion energies and fluences, determining that a maximum fluence of ∼2×1014Ga/cm2 can be used to achieve a monomodal distribution of nanoparticles with regular shape, before detrimental effects of sputtering occur.

Conquering Change in Oil and Gas: How To Build a Learning Organization

Talent & Technology Former United States Secretary of State Colin Powell likes to tell the story of how Israeli Prime Minister Shimon Peres put his arm around his shoulder after the dissolution of the Soviet Union in 1991, and said, “We have lost our enemy; all we have now are problems.” Peres was certainly thinking of dangers that threaten all nations: poverty, famine, religious radicalization, desertification, drugs, proliferation of nuclear weapons, and ecological devastation. While it is not immune from global threats, the oil and gas industry faces its own set of persistent and continuously emerging challenges that drive change in the industry. They are Innovation: technology to boost output, processes that promote efficiency, new industry structures and alliances. Tim Dove, president and chief operating officer of Pioneer Natural Resources, said that hydraulic fracturing means that there are no dry holes. As a result, he believes that exploration and production firms have become similar to manufacturing companies. Their success depends on efficient operations. Capital: how much oil can be produced at what cost. The amount of oil that can be recovered is no longer constrained by geology. As George King, a global technology consultant for Apache Corporation, told the Wall Street Journal, “the constraint on how much oil can be produced isn’t geological ... we face technical and economic limits more than anything else.” Talent: accelerated attrition of baby boomers in the senior ranks. Industry firms face the rising practice of “poaching” of high potential leaders. On the other hand, firms struggle to accelerate young professionals into the “age of accountability” as leaders. The local Dallas chapter of Young Professionals in Energy has more than 4,100 members, making it one of the largest trade organizations in Texas. Andy Long, its 26-yearold chairman, has established a mentor program to connect its members and college students with industry veterans. Global: opportunities worldwide are not limited to the majors. Heyco Energy Group, an exploration company that has been active in the Permian Basin since the 1960s, today holds positions in 1.4 million acres in Spain and United Kingdom. Science and technology have turned the basin into “the hottest spot on earth,” according to Chief Executive Officer George Yates, and we “asked ourselves ‘where could we succeed given our experience and advances in technology?’ Europe was an obvious place.” Bruce Bullock, director of Maguire Energy Institute at Southern Methodist University’s Cox School of Business, boils down the industry’s challenges to financial performance. “The industry has to find ways through technology, efficiency, science, and other strategies to really improve its financial results over the next several years.” The drive for financial performance demands change leadership skills from all levels of management, and a new perspective on change. Business typically has used three perspectives on change, each with its own implementation method.

A study of the effects of drying and sintering on the performance of organic photovoltaic devices

The effects of different processing methods on the performance of organic photovoltaics (OPVs) for the hole extraction layer and printed metal layers were studied. Four different methods (hot plate, air oven, vacuum oven and far-infrared oven) were utilized to dry hole extraction layers formed from aqueous nano-particle dispersions. The far-infrared oven showed the best drying characteristics and the sheet resistance was 69Ω/□ in 240s. To sinter a screen printed silver electrode, six different methods (hot plate, air oven, vacuum oven, far-infrared oven, UV lamp and microwave oven) were employed. The microwave oven yielded the most effective sheet resistance drop, as low as 0.06Ω/□ in 20s when the power of the microwave oven was 400W. Using the fast processing methods developed in this study, the processing time can be reduced by about 40% without a loss in the performance of prepared devices.

Evaluation of the Newburg Sandstone of the Appalachian Basin as a CO2 geologic storage resource

The West Virginia Division of Energy is currently evaluating several deep saline formations in the Appalachian Basin of West Virginia that may be potential carbon dioxide (CO 2) sequestration targets. The Silurian Newburg Sandstone play, developed in the 1960s and 1970s, primarily involved natural-gas production from reservoir rock with well-developed porosity and permeability. High initial pressures encountered in early wells in the Newburg indicated that the overlying Silurian Salina Formation provides a competent seal. Because of the large number of CO 2 point sources in the region and the favorable reservoir properties of the formation (including an estimated 300 bcf of natural-gas production), the Newburg Sandstone was evaluated for the potential geologic storage of CO 2. Within the Newburg play, there are several primary fields separated geographically and geologically by saltwater contacts and dry holes. Previous studies have determined the storage potential within these individual fields. This study shows that the Newburg is more suitable for small-scale injection tests instead of large-scale regional storage operations.

The Last of the Wildcatters: The Life and Times of Harvey Rhoads in His Own Words ed. by Tai Kreidler and H. Allen Anderson (review)

Reviewed by: The Last of the Wildcatters: The Life and Times of Harvey Rhoads in His Own Words ed. by Tai Kreidler and H. Allen Anderson Kay Goldman The Last of the Wildcatters: The Life and Times of Harvey Rhoads in His Own Words. Edited by Tai Kreidler and H. Allen Anderson. (Waco: Eakin Press, 2012. Pp. 220. Illustrations, notes, index. ISBN 9781934645635, $18.95 cloth.) The Last of the Wildcatters: The Life and Times of Harvey Rhoads in His Own Words is the story of Harvey Rhoads's life as he described it in interviews [End Page 226] given between 1994 and 2002. Because most of the book is quoted verbatim from the interviews, it is essentially a memoir that includes very little analysis or interpretation. Rhoads begins his story with his family genealogy and then describes his youth in Dallas, Texas. After December 7, 1942, Rhoads tried to enlist in the U.S. Navy but was rejected for medical reasons; however, eighteen months later he was accepted and sent to the Pacific. His stories of being stationed on Guiuan Island in the Philippines are noteworthy because he describes everyday life on the island, which was without electricity. Existing on C-rations and cold showers, Rhoads lost fifty-five pounds, dropping from 190 pounds to 135 before the generators arrived. Despite some deprivations, Rhoades spent his days sailing around the island in his commanding officer's small boat and taking other sailors to beaches and on fishing trips. After the war, Rhoads returned to Dallas and found a job with Atlantic Refining, later Atlantic Richfield, where he was trained as a geological map draftsman. He also learned to be an oil scout by poking around wells being drilled by other companies. After about a decade of working for the large oil companies, Rhoads quit to become an independent oil man. Often taking farmout leases, Rhoads drilled some dry holes and some solidly producing wells, and he lived the boom and bust life like other independent oil men. Throughout his interviews, Rhoads defines most of the oilfield terms he uses, and he does an admirable job of providing a concise description of the Tidelands controversy. He also includes a few humorous incidents such as the night he nearly stepped on a large rattle snake as he bounded up the ladder of a drilling rig. He was technically trespassing since the well did not belong to him, and the operators had killed the snake and tied it to the ladder as a joke. Rhoads crafts a picture of himself as a hardworking, devout conservative who lived by strict principles of right and wrong and did not make compromises. But the editors never challenge this impression even when Rhoads willingly circumvented state and federal regulations. During the years when oil was sold by a two tier-system— small stripper wells that brought $33 per barrel and oil from wells producing more than ten barrels brought only $5—Rhoads drilled a well that he knew was going to be a good producer. He planned to frack his new well, but he delayed that procedure until the well was classified as a stripper. Thus he was able to sell his oil at the higher price even though the well was producing more than ten barrels a day. This action dodged the intent of the regulation, surely a compromise of sorts. Despite its shortcomings, the book provides an accurate depiction of the audacious men and later women who earned their living drilling oil wells. It also offers insight into the unstable nature of the oil business, [End Page 227] especially as lived by those men and women who were independent producers and those who are still earning a living in that precarious industry. Kay Goldman Texas A&M University Copyright © 2013 The Texas State Historical Association

Numerical Investigation Based on Orthogonal Design of Structural Parameters on Large-Diameter DTH Hammer Bit

To achieve cutting transport with air reverse circulation in dry and shallow large-diameter holes of rock-socketed pile, and to solve the technical problem with airlift and pump reverse circulation, a large-diameter reverse circulation bit innovatively designed based on ejecting. Meanwhile, the orthogonal design method applied to explore the application feasibility of ejector theory in use of in air reverse circulation drilling. Through theory analysis, three key geometry parameters of air reverse circulation bit have proved to have direct affect on the function of cutting transport, including the diameter of nozzles (Dn), the number of nozzles (N), the angle of inclination (θs). The results have shown that reverse circulation effect of large-diameter bit designed based on ejecting is valid and stable. Further while the air volume of GQF-16 hammer bit goes to 90m3/min, a configuration of parameters with Dn=20mm, N=3, θs=35°are the most ideal parameter combinations.

Studies on geothermal power generation using abandoned oil wells

In this paper, abandoned “dry hole” oil wells are simulated as a source of geothermal power for generating electricity. Isobutane is chosen as the working fluid. It is heated by the geothermal energy from geologic formation and drives the turbine to generate electricity. A model based on transient formation heat transfer is presented. Furthermore, a numerical simulation for an abandoned well with a depth of 6000 m is performed. The result shows that the outlet temperature of fluid leaving the recovery well gradually decreases with the system operating time increasing and ultimately approaches stability. The stabilized time of the system can be shortened by either the increasing formation thermal conductivity or the decreasing inlet velocity of fluid entering the injection well but is not significantly influenced by the formation heat capacity. The net power depends on the total obtained heat and the outlet temperature of fluid leaving the recovery well. And increasing the inlet velocity can increase the total obtained heat but lower the fluid outlet temperature. Consequently there is an optimal inlet velocity of fluid entering the injection well to maximize the net power for a specified geothermal heat source.

The Audit We Had to Have: The Economic Record, 1960–2009

The Economic Record, one of the world's oldest economic journals, has a distinguished history. The flagship journal of the Economic Society of Australia and New Zealand was launched in 1925 and is approaching its 100th birthday. We undertake a forensic examination of the journal over the last 50 years, exploring issues like its content, most‐cited articles and most frequent contributors. This article discusses the journal's internationalisation but also identifies how Australia's top economists have, for the most part, faithfully persisted with it. The changing nature of academic publishing is explored through the patterns of collaboration, citations and dry holes.

Pre-discovery seismic modelling and prediction of the Deep Panuke Late Jurassic carbonate bank gas discovery, offshore Nova Scotia

Abstract Deposition of the Abenaki Formation carbonate complex began during the Middle Jurassic, shortly after the interpreted onset of western Atlantic sea-floor spreading, and continued through Late Jurassic time, resulting in thick carbonate deposits along the Jurassic shelf edge. This carbonate complex was the exploration target of 16 wells drilled from 1970 to 1989. Although there were no discoveries in the carbonate objectives, oil was discovered in Cretaceous siliciclastics in structural drape closures overlying the carbonate margin. The Province of Nova Scotia decided to undertake a technical study to further the interest in the carbonate bank objective while the shallow oil play was being developed. Subsequently, in 1989, two studies were undertaken to investigate a porosity play in the Jurassic Baccaro Member of the Abenaki Formation because significant porosity had been encountered in a number of the dry holes that targeted the carbonate margin, particularly the Demascota G-32 well. The first study modelled porosity in several wells utilizing one-dimensional (1D) and wedge models, and amplitude v. offset (AVO) models. The Demascota G-32 well was used to seismically identify and model several types of potential hydrocarbon-bearing prospects along the bank. Modelling indicated that zones of 11–14% porosity with a minimum thickness of 10 m could be detected. However, a thickness of 50 m was required to resolve the top and base of the porosity. The AVO model for the Demascota well demonstrated that an increase in amplitude with offset (AVO effect) in the presence of gas and fracturing (which dramatically decreases Poisson’s ratio) should be detectable and may be useful in identifying prospects in this type of play. The assumption of a fractured reservoir was reasonable due to the number of seismically identified faults at the front of the carbonate bank and the description of fractures in conventional cores taken in the Baccaro Member. The second study involved acquiring a pair of dip and strike seismic lines adjacent to the Demascota well and reprocessing them to preserve relative amplitudes while providing a high-resolution, stacked section, especially at the Baccaro Member level. Interpretation of these lines was undertaken in the AVO domain. An increase in amplitude with offset was observed up-dip of the Demascota G-32 well that indicated a fractured, gas-filled porous zone could exist up-dip of this well. Following these studies, 3D seismic data was acquired over the shallower Panuke Oil Field and similar studies were conducted on that dataset in 1997. As a result, Encana drilled a structural high containing bright amplitude reflectors and encountered over 100 m of net gas pay in vuggy and cavernous limestones and dolomites in 1999. This validated the earlier studies, confirming that these reservoirs could be seen on seismic data and proved that economic gas reservoirs exist in the carbonate bank. These results should encourage exploration along the extensive, sparsely drilled Late Jurassic carbonate margins bounding offshore eastern North America and its conjugates in the Central Atlantic Region.

First in situ tests of a new electrostatic resistivity meter

If field applications of the electrostatic method are limited to roughly the first ten metres due to the necessity of staying in a low‐induction number domain, the possibilities it opens in urban area surveying, dry hole resistivity logging, non‐destructive testing and laboratory studies of the complex resistivity justify the design of a new multi‐frequency resistivity meter presenting a very low‐input capacitance and high‐phase sensitivity. After a first series of sample measurements in the laboratory, the new resistivity meter was tested in two different field contexts: the mapping of building remains in a Gallo‐Roman archaeological site under a flat meadow and the assessment of the thickness of anthropogenic layers in a town. The first test allowed a direct comparison with previous galvanic resistivity measurements and proved a very good agreement between the magnitude and spatial distribution of electrical resistivity. The second test established its reliable measuring abilities in a disturbed environment.