bluuebunny/crossref_metadata_2025 huggingface dataset:
DETERMINATION OF RESERVOIR DISTRIBUTION OVER THE BLACKBACK/TERAKIHI OIL FIELD, GIPPSLAND BASIN, AUSTRALIA
Authors: Gross M.D.
Published: August 2017

The Blackback/Terakihi oil accumulation is located within the Gippsland Basin permit Vic-P24 on the edge of the present-day continental shelf in water depths ranging from 300 to more than 600 m. Accurate structural mapping, depth conversion and delineation of the reservoir units remain as major uncertainties associated with this oil and gas accumulation. To date three wells, Hapuku-1, Blackback-1 and Terakihi-1 have been drilled on the structure and a 3D seismic survey interpreted.The top of the Latrobe Group structure is a complex erosional remnant somewhat laterally offset from a deep-seated northeast to southwest trending, faulted anticline. Most of the hydrocarbons intersected to date have been encountered within the top of the Latrobe Group closure. All three wells drilled to date have intersected oil at the top of the Latrobe Group in three markedly different reservoir units. These reservoirs range in age from Late Cretaceous to Eocene, with porosity ranging from less than 12 per cent to 26 per cent and permeability from less than 1 md to greater than 3000 md.Given the extreme variation in reservoir quality and the field's location in relatively deep water, delineating the distribution of reservoir units using all available data remains crucial.The generation of seismic attribute maps such as dip, dip azimuth and horizon amplitude slices, calibrated on existing well penetrations has played a major role in delineating a complex reservoir distribution at the top of the Latrobe Group. The calibration of high amplitude seismic events with a high impedance channel infill unit of Eocene age was supported by modelling using SIERRAR modelling software.The integration of existing well control, seismic stratigraphy and fault geometry together with seismic attribute mapping and modelling has resulted in a more tightly constrained estimate of the field reserves.
THE INTEGRATION OF GEOLOGY AND GEOPHYSICS TO POST-WELL EVALUATIONS - EXAMPLE FROM BELUGA-I, OFFSHORE NORTHERN AUSTRALIA
Authors: Anderson Alan D. , Durham Murray S. , Sutherland Andrew J.
Published: August 2017

The Beluga 1 well was drilled in May 1991 in Permit NT/P41 in the Arafura Sea to test a seismically identified stratigraphic trap in Late Jurassic - Early Cretaceous age syn-rift sediments on the southern flank of the Malita Graben. A continuous high amplitude seismic event defined a lithologic package prognosed as a rift infill sand prone fan sequence interpreted to have been sourced from the adjacent southern platform.The target section penetrated by the well was found to consist predominantly of a uniform sequence of bioturbated fine sandstones with poor porosity and almost nil permeability indicating distal deposition.Post well evaluation of Beluga 1, utilizing a variety of well and seismic measurements, showed evidence for several episodes of basin inversion within the juvenile Malita Graben. Reinterpretation resulted in a new structural and depositional model which accounted for the well result and has implications for future exploration in this area and lowstand fan studies in general.
COAL SEAM RESERVOIR SIMULATION
Authors: Stevenson M.D. , Pinczewski W.V. , Meaney K. , Paterson L.
Published: August 2017

Numerical reservoir simulation in coal seams is different from conventional reservoir simulation because of the capacity for coal to adsorb large amounts of gas, including methane, carbon dioxide and nitrogen, and the need to model coal as a dual porosity system. These factors require specialised numerical simulators written to address these particular issues. This paper describes the development and applications of a reservoir simulator, SIMED II, to a number of applications in the coalbed methane context. SIMED II is an implicit finite-difference code developed to describe simultaneous gas and water flow in coal when there is more than one gas component present. Applications presented in this paper include (1) history matching and forecasting in vertical wells, (2) evaluation of dewatering during the cavity completion method of stimulating coal seams, (3) economic evaluation of nitrogen injection for enhanced coalbed methane recovery, and (4) application to the design and development of gassy coal mines involving gas drainage from horizontal wells. These applications have been directed at locations in the Sydney and Bowen basins in Australia, and the San Juan basin in the USA.
ACCIDENT INVESTIGATION USING THE TRIPOD METHOD
Authors: Wheelahan Bernard
Published: August 2017

Accidents provide important learning points to prevent future mishaps. In its approach to accident prevention one technique that Shell uses is the Tripod accident analysis tree.In the past there has been a tendency in all organisations to blame accidents on the people who suffer them and to see unsafe acts as arising from the stupidity, carelessness or recklessness of particular individuals. Accident investigations frequently cite 'human error' as the cause and many people still see such errors as the beginning and end of the accident sequence. The three more tangible components of such accident investigations are unsafe acts, failures of defences and the accidents themselves. Such unsafe acts or 'active failures' are often seen as the most important part of the accident story. In reality the story has its beginnings much earlier in areas such as Design, Procedures, Training or Maintenance Management, areas known as 'latent failures',To better understand the underlying causes of accidents, in 1988 Shell commissioned a behavioural research program called Tripod. Tripod does not address unsafe acts and hazards directly, but places them in context in a model of an accident which seeks to define the underlying organisational factors that provoke unsafe acts, and that allow errors to turn into accidents. The research has established that latent failures may be categorised into a small number of disruptive processes. These latent failures are incorporated into an accident diagram in the form of a 'tree', and improve our understanding of the causes of accidents, and direct our recommendations for improvement into areas that are likely to be the most effective.
ESSO/BHPP BASS STRAIT SAFETY-ACHIEVING WORLD CLASS PERFORMANCE
Authors: Pike P.J. , Smith M.G. , Gill R.S. , Savva S. , Fisher A.J.
Published: August 2017

This paper describes the key initiatives Esso Australia Ltd (Esso) has undertaken to improve employee and contractor safety performance to world class standards.Esso produces 50M litres of crude oil per day and up to 25 million cubic metres of gas per day (peak winter demand) from 13 manned and three unmanned satellite platforms in Bass Strait, and two onshore oil/gas/LPG processing plants. Esso operates the facilities on behalf of the Esso/BHP Petroleum joint venture. Over 1400 employees and two million contractor work hours per year are involved in the operations.In 1992, Esso employees worked over 2.8 million hours with no Lost Time Injuries (LTI's). As of October 1, 1993, Esso employees have worked over 5.2 million hours LTI free for the first time in over 22 years of operations in Bass Strait. Employee Total Injuries (LTI's plus medical treatment injuries plus restricted work cases) are also significantly down over the period.In 1992, contractors working on Esso managed sites worked 2.2 million hours and sustained nine LTI's, for a frequency per million hours of 4.1. This was about half of the previous year's performance. Eight of these injuries occurred in the first half of 1992. Over the past 15 months, there have been two contractor LTI's equating to a LTI frequency of 0.7. Contractor Total Injuries are also significantly down over the period.In addition to occupational injury performance, the number and severity of operational incidents such as hydrocarbon releases and fires are also down.This improved safety performance and operations integrity is the culmination of a major effort to create a culture where safety is an integral part of our business and where everyone is committed to working safely.
SOLID STATE 13C NMR FOR CHARACTERISING
SOURCE ROCKS
Authors: Wilson Michael A. , Fargue Eric La , Gizachew Dawit
Published: August 2017

13C NMR has been used to measure the fraction of carbon which is aromatic, fa, in coaly source rocks from the Brent group, North Sea. Both cross-polarisation and Bloch decay techniques have been used. Good correlations are found with fa and inertinite content, and with Hydrogen index measured by Rock-Eval. Mean vitrinite reflectance was only found to correlate with fa when vitrinite concentrates were compared. These results demonstrate the potential of 13C NMR to estimate source rock potential in cases where Rock-Eval or petrographic analyses can give anomalous results.
TROUBLESHOOTING VITRINITE REFLECTANCE PROBLEMS USING FAMM: A GIPPSLAND AND OTWAY BASIN CASE STUDY
Authors: Ellacott M.V. , Russell N.J. , Wilkins R.W.T.
Published: August 2017

'Fluorescence alteration of multiple macerals' (FAMM) is a multi-parameter microprobe technique developed by CSIRO to provide the petroleum industry with an objective method of estimating thermal maturity of organic matter in sedimentary rocks. The technique is closely related to vitrinite reflectance methods, although the identification of vitrinite is not necessary; FAMM is based on the fluorescence alteration characteristics of vitrinite, inertinite and liptinite macerals in a sample. It is a powerful tool for the identification of casings, reworked material and hydrogen-rich (perhydrous) vitrinite, and has the capacity to correct for the effects of vitrinite reflectance suppression.The technique has been tested on Cretaceous coals from the Latrobe Group in Volador-1, offshore Gippsland Basin, where the identification of vitrinite is unequivocal, and on dispersed organic matter (DOM) in various clastic lithologies from the Cretaceous Waarre and Eumeralla Formations intersected by Flaxmans-1 and Port Campbell-4, onshore Otway Basin, where the identification of vitrinite is difficult and subjective.For the Volador-1 sequence, the FAMM-derived vitrinite reflectance (equivalent reflectance) and the measured vitrinite reflectance (VR) are similar, although the VR data are more scattered about the VR-depth regression line. The variability in the vitrinite reflectance data is largely due to compositional variation in the vitrinite. This variation however does not affect the equivalent vitrinite reflectance data to the same degree.In the sections intersected by Flaxmans-1 and Port Campbell-4, FAMM data indicate that vitrinite reflectance suppression is responsible for the large deviations of the measured values from the VR—depth regression line. In some of these samples the suppression effect may be as much as 0.20 per cent absolute.The FAMM technique offers a valuable supplement to VR determinations, or even a valid alternative in many practical situations.
RESEARCH WITH A PURPOSE IN THE AUSTRALIAN PETROLEUM INDUSTRY
Authors: Wyld Irene , Godfrey Bruce
Published: August 2017

Research—defined broadly as any activity in the concept to delivery continuum—is critical to the success of the present thrust for development of a competitive Australia. It provides the key to maintenance of existing competitive advantages, and the development of new competitive advantages both within Australia and in export markets. Nowhere is this more important than in the Australian petroleum industry (oil and gas). This industry contributes in the order of $10 billion annually to Australia's balance of trade. Yet until recently little research has been undertaken by Australian petroleum companies to support their exploration and production activities here.There is now recognition by Australian petroleum companies that research must be undertaken by them to support access to prospective areas, enhance exploration success, maximise production and minimise environmental damage. The contribution which research can make to the growth of the industry will only accrue if that research is targeted on priorities which meet the short, medium, and long-term needs of the industry. To define these priorities APEA, working in conjunction with ERDC, has produced a research and development strategy for the Australian upstream petroleum industry.The priorities resulting from this process cover the areas of exploration, production efficiencies, reservoir management, environmental effects and safety. Implementation of the strategy is occurring via ajoint Petroleum R&D Committee. ERDC's role in this process is to manage its investment in the projects resulting from the strategy to maximise the chances of successful implementation of the outcomes for the benefit of the industry and Australia.
SOURCE, MIGRATION AND ENTRAPMENT OF HYDROCARBONS AND CARBON DIOXIDE IN THE OTWAY BASIN, VICTORIA
Authors: Mehin Kourosh , Link Alby G.
Published: August 2017

Salinity distribution, structure, carbon dioxide occurrences, facies and thermal gradient variations and gas isotope studies in the onshore Victorian Otway Basin indicate that the migration of fluids from the Eumeralla Formation source rocks, and the entrapment of hydrocarbons in the Waarre Formation reservoir sands of the Port Campbell Embayment, are closely associated with the presence of three major fault systems. Hydrocarbon accumulation appears to take place where high salinities and normal rift-valley faults are in closest proximity to a structural trap. The large carbon dioxide occurrences are thought to be associated with volcanism and deep vertical fault conduits.Although there are, as yet, considerably fewer exploration wells in the Tyrendarra Embayment/Portland Trough, present studies are nevertheless indicating that broadly similar migration and salinity/fault relationships probably exist in this western portion of the basin. Drilling and analytical results also show this end of the basin to be prospective for not only gas but also oil.
THE OFFSHORE CARPENTARIA BASIN-GULF OF CARPENTARIA, NORTH QUEENSLAND
Authors: McConachie B.A. , Stainton P.W. , Barlow M.G. , Dunster J.N.
Published: August 2017

The Carpentaria Basin is late Jurassic to early Cretaceous in age and underlies most of the Gulf of Carpentaria and surrounding onshore areas. The Carpentaria Basin is stratigraphically equivalent to the Eromanga and Papuan Basins where similar reservoir rocks produce large volumes of hydrocarbons.Drillholes Duyken–1, Jackie Ck–1 and 307RD12 provide regional lithostratigraphic and tectonic control for the Q22P permit in the offshore Carpentaria Basin. Duyken–1 penetrated the upper seal section in the Carpentaria Basin and a full sequence through the overlying Karumba Basin. Jackin Ck–1 intersected the lower reservoir units and a condensed upper seal section of the Carpentaria Basin. Coal drillhole 307RD12 tested the late Jurassic to early Cretaceous reservoir section in the Carpentaria Basin and also intersected an underlying Permian infrabasin sequence.Little is known of the pre Jurassic sedimentary section below the offshore Carpentaria Basin but at least two different rock packages appear to be present. The most encouraging are relatively small, layered, low velocity, channel and half-graben fill, possibly related to Permian or Permo-Triassic sedimentary rocks to the east in the Olive River area. The other packages consist of poorly defined, discontinuous, high velocity rocks believed to be related to those of the Bamaga Basin which have been mapped further north.During the period 1990-1993 Comalco Aluminium Limited reprocessed 2188 km of existing seismic data and acquired 2657 km of new seismic data over the offshore Carpentaria Basin. When combined with onshore seismic and the results of drilling previously undertaken by Comalco near Weipa on northwestern Cape York Peninsula, it was possible to define a significant and untested play in the Carpentaria Depression, the deepest part of the offshore Carpentaria Basin.The main play in the basin is the late Jurassic to early Cretaceous reservoir sandstones and source rocks, sealed by thick early Cretaceous mudstones. Possible pre-Jurassic source rocks are also present in discontinuous fault controlled half-grabens underlying the Carpentaria Basin. New detailed basin modelling suggests both the lower part of the Carpentaria Basin and any pre Jurassic section are mature within the depression and any source rocks present should have expelled oil.
ENVIRONMENTAL AUDITING: THE DYNAMICS OF PLANNING, MANAGING AND GAINING VALUE FROM THIS KEY ACTIVITY
Authors: Morozow Oleg
Published: August 2017

Much has been said and written about environmental auditing. That which has, has concentrated on:descriptions of the process;the variety of audit types and reasons for undertaking audits; andmethodologies or systems of audit (audit protocol).Little attention has been paid to the human and organisational dynamics of an environmental audit; yet it is this factor, probably above all else, that determines the value that such a process can yield.The composition of the audit team, planning for the audit itself, the management and administration of the audit and finally the audit report, follow-up and implementation, are critical factors in ensuring that the process is both valuable and value adding.Undertaken well, and with due cognisance of the above factors, audits can provide a valuable indicator of systems effectiveness, levels of compliance with regulations, assessment of risk factors and, through documentation and reporting, demonstrate the application of the process of due environmental diligence.Key elements of a successful audit include:ownership of the process by those who's activities are being audited;the professionalism and inter-personal skills of the auditor;due reference to the positive aspects of systems and groups who work well and deserve recognition; andthe overall determination of the organisation to maximise and utilise positively the information recorded during the process.There must be an open and positive communication between the three key groups—the auditors, those 'being audited' and those administering the audit. The ultimate recipients must feel that the people who are responsible for the audit will not just 'hit and run' but will stay the distance to ameliorate identified problem areas.
THE EVOLUTION OF AN ENVIRONMENTAL MONITORING PROGRAM
Authors: Goff H. B. , Farrell P. D.
Published: August 2017

Production of South Pepper Oilfield commenced in 1987. Since that time the North Herald and Chervil fields have been brought on line and have produced in excess of 18 million barrels of oil. Initially environmental management and monitoring strategies attempted to understand and predict changes to the ecosystems caused by acute impacts such as a major oil spill. Over the life of the project the emphasis in environmental monitoring has shifted from measuring for acute effects to measuring on a more sensitive scale to predict and monitor the chronic impacts of oilfield operations. Monitoring efforts consequently have changed emphasis so that a better understanding of impacts is now possible due to the introduction of a more rigorous experimental design.
APPLICATION OF ECOTOXICOLOGY TO ENVIRONMENTAL MANAGEMENT IN THE AUSTRALIAN OFFSHORE OIL AND GAS INDUSTRY
Authors: Evans Louis H. , Spickett Jeffery T. , Bidwell Joseph R. , Rippingale Robert J. , Brown. Helen L.
Published: August 2017

Environmental impact from offshore oil and gas exploration and production is likely to arise from five main sources—produced formation water, drilling fluids and cuttiftgs, industrial chemicals used in production activities, accidental oil spills and the physical disruption of the marine environment by coastal and offshore engineering works. The principle task of environmental managers is to evaluate the risk of impact on the marine environment from their company's activities and to formulate and implement company policy and procedures aimed at minimising this risk. Of critical importance is the determination of the extent and scope of the environmental program designed to control and monitor impacts.The development of environmental management programs in the oil and gas industry involves two main processes—ecological risk assessment and formulation of a monitoring program. This review outlines the steps involved in ecological risk assessment with specific reference to the offshore oil and gas industry. Information is presented on the basic principles involved in risk assessment, the main source of environmental impact from offshore oil and gas exploration and production and the different approaches that can be used to predict and monitor impacts. Approaches for improving the cost efficiency of ecotoxicological testing are discussed. Results of recent ecotoxicological studies on a biocide preparation and two corrosion inhibitors used in oil and gas production activities on the North West Shelf are also presented.
COMPETITIVE ACCESS TO AUSTRALIAN GAS MARKETS—IMPLICATIONS FOR EXPLORATION AND DEVELOPMENT
Authors: Holmes Leanne , Mander Sally L. , Fisher Brian S.
Published: August 2017

Access to profitable markets is one of the key factors influencing the incentives to explore for and develop gas reserves. Recent reviews of gas markets in Australia and attempts by gas buyers and sellers to negotiate interstate gas sales have focused attention on the need to remove barriers to competition and trade. Possible barriers include policies pursued by some state governments that restrict interstate sales of gas and limit its use in some markets. Structural features of gas markets in Australia, including monopoly control over pipeline access, are also potential barriers to new gas discoveries competing for markets. A number of recent developments and proposals could influence access to gas markets in Australia. The most significant are moves to establish a framework for open access to interstate pipelines. These developments could encourage further gas exploration and development, by reducing uncertainty about market access and giving gas producers and large consumers the opportunity to directly negotiate sales on their own negotiated terms.
VENTURING ABROAD—SETTING UP OPERATIONS OVERSEAS
Authors: Wells B. E.
Published: August 2017

This paper provides a brief insight into the fiscal regimes for international exploration and production,covering some of the management problems, mostly from a financial perspective, that are faced in setting up operations overseas.Any move overseas means another set of local regulations to understand and plan for. Difficulties of language, culture and regulatory structure need to be faced. There must be a high level of understanding of local conditions and selection of staff with local knowledge, well trained and honest with the backup of an established system of internal controls and audit.The organisational structure of the tax planning and compliance functions should be considered. Functions controlled by head office will be most effective when operating activities are low. Progressing to a larger scale of activity may demand daily involvement in tax matters and require local experience.Countries impose, to varying degrees, exchange control regulations. These can inhibit the flow of funds back to the parent company, minimising immediate benefits from the project unless there are re-investment opportunities within the country. Restrictions on the repatriation of funds may serve to increase home country borrowing requirements—if the regulations require the conversion of surplus funds to local currency, a foreign exchange risk exposure is created and has to be managed.Wherever the international involvement leads us there is one over-riding aim, to obtain a return on investment commensurate with the risk. Everything else which impinges on that rate of return, whether it relates to tax changes, contract terms or exchange control regulations, must be compensated for or resisted to maintain the rate of return.
FUND RAISING AND THE PROSPECTUS
Authors: Sharwood Michael , Seman Kim
Published: August 2017

Corporate regulation of fund raising has increased steadily since the 1960s, especially since the Corporations Law commenced in 1991. As a result of the Corporations Law and of amendments to the Listing Rules of Australian Stock Exchange Limited, it is now more complex and costly to raise funds for exploration.The fund raising concept of `offer to the public' has been replaced with a general prohibition on the offering of securities, subject to certain exceptions which are inconsistent in their application and limited in their usefulness.Although the ASC's objective was to obtain uniformity of administration and implementation of the Corporations Law, in the authors' opinion, it has failed to do so and, in addition, has demonstrated a wholly uncommercial and impractical approach to registration and post-vetting of prospectuses.A further impediment to fund raising is the ASX Listing Rule requiring a spread of 500 shareholders, each of which must hold a parcel of shares worth at least $2 000, before admission to the Official List may be granted.
HAZARD RECOGNITION AND ASSESSMENT—A CASE STUDY
Authors: Turner Phillip R.
Published: August 2017

Hazard recognition and the assessment of associated risk should be considered as an integral part of a company's safety management system. Whilst this is generally accepted, the systems for handling hazard data such as a 'Hazards Register' are often separate from other incident reporting systems, eg. the accident data base.Accidents and potential hazards, however, may pose the same level of risk to an organisation. Philosophically, after an accident occurs it reverts to being a potential hazard, albeit with a greater understanding of its actual causes and outcomes; yet it is often treated differently from other hazards of equal potential. Only at the point in time of occurrence can an accident be considered anything but a potential hazard. There is no logical reason to create separate systems for handling these data yet typical industry response is to do just that. The reporting of hazards should not be separated from the normal incident reporting system within an organisation.The development and implementation of an integrated risk classification method and incident reporting system is discussed in this paper as a case study.
CLIMATE CHANGE: A 1994 SCIENCE SUMMARY
Authors: Mitchell C.D.
Published: August 2017

New observations of the chemical composition of the atmosphere are reshaping scientific understanding of the global sources and sinks of the greenhouse gases. Current trends in the atmospheric concentrations of some of these gases are reviewed, with reference to new work emerging from Antarctic ice cores.Accompanying an understanding of the composition of the atmosphere, is the need to understand the processes which drive the global climate system, including interactions between the atmosphere and oceans. Studies of climatic processes therefore form the scientific underpinning for the development of numerical models that describe the response of the global climate system to observed changes in the composition of the atmosphere.Success or failure in efforts to improve model simulations can be assessed using a variety of objective statistical tests. Examples of such tests show demonstrable progress in the ability of global climate models to simulate the present day climate realistically.Since confidence in the regional details of climate predictions from climate models is low, considerable effort is being devoted to developing models capable of providing improved regional estimates of climate change and in practice a variety of models not limited to the global-scale models are used in this work. In the meantime, several approaches to assessing the potential impacts of climate change are possible. These are discussed with special reference to tropical cyclones and east coast lows.Throughout this review emphasis is placed on recent Australian contributions to the field, most notably work conducted within CSIRO.
THE CANADIAN EXPERIENCE WITH ACCESS TO LAND
Authors: Kelso Philip F.
Published: August 2017

The Canadian Provinces, with emphasis on the Western Canada Basin, have established a well-regulated and certain statutory framework to govern access by explorers and producers to both Crown and private petroleum rights. Canada's legal framework has many similarities to that provided for onshore exploration in Australia, but the Province of Alberta provides for much shorter periods of exploration drilling activity before licences and leases revert to the Crown. Amendments in 1975 and 1976 spurred a significant increase in drilling within Alberta as operators were required to either test deeper pools or have them revert to the Crown. In addition, Alberta has a system of public tender for Crown petroleum lands which provides a very competitive environment for land access. The question is posed as to whether similar legislative changes should be imposed by the State and Territory governments in Australia in an effort to allow access by smaller and, perhaps, more aggressive players to large acreages still locked up in onshore Australia.
THE NATIVE TITLES ACT 1993—THE PETROLEUM INDUSTRY AND THE FUTURE
Authors: Hooke Frank M.
Published: August 2017

The judgement of the High Court of Australia in 1992 in Mabo v. Queensland has had a major impact on land law in Australia.The Native Titles Act, 1993, is the first of what will be many steps in a long, complex legislative program to integrate 'native title', into Australia's land law.Those drafting the Native Title Act seemed to have concentrated on dealing with 'native title' issues in isolation and to have ignored or put to one side the need for it to mesh with other aspects of land law. This has created uncertainty for many users of land and will require review.Although the contrary was intended, the Act creates, in practical terms, significant uncertainty for renewal of existing oil and gas exploration and production titles. It also has implications for applicants for new titles and in due course for farmouts and assignments.Eventually additional legislation will be required to clarify the relationship of native title with the other areas of land law.
RESERVOIR CHARACTERISATION OF THE TOOLACHEE UNIT 'C' IN THE MOOMBA/BIG LAKE AREA: FOCUSSING ON MINIMISING RISK
Authors: Mackie S.l. , Grasso C.A. , McGuire S.R.
Published: August 2017

Mackerel, the third largest oil field in the Gippsland Basin, is a mature field with over 80 per cent of reserves produced from 18 original development wells.The initial Mackerel development was based on a fairly simplistic reservoir model incorporating the results of the four exploration wells. The net to gross was anticipated at 90 per cent throughout the reservoir and no significant permeability barriers were expected. After 10 years of production a review of field performance indicated the reservoir was not as homogenous as first anticipated.Redevelopment of the Mackerel Field began in 1990 following the acquisition of the first of two high resolution 3D surveys and culminated in the drilling of 18 additional wells from the Mackerel platform during 1993 and 1994. It was these 3D surveys which changed the entire reservoir model of Mackerel to one of a far more compartmentalised nature.Seismic attribute analysis, when calibrated to 2D forward modelling was used to predict intra-reser- voir seals and the distribution of poorer quality reservoir; both not previously recognised over the field. The truncation points of the intra-reservoir seals against the main field-wide trapping unconformity were accurately mapped using seismic attributes and image enhancement techniques such as ER Mapper. Previously undetectable fault extensions, with throw around 10 m, can act as partial flow barriers and were recognised for the first time via 'sun-angle illumination' of azimuth maps. This allowed optimum well placement and helped explain historical field performance. Horizon slicing techniques and the calibration of volume attributes were used to establish depositional environments and seal capacity of the predicted intra-reservoir seals.The drilling results have shown that over the production life of the Mackerel Field the reservoir consists of a number of drainage compartments, each separated by seismically resolvable intra-res- ervoir seals.The redevelopment of the Mackerel field increased production rate by 18 thousand barrels per day (kBD) in 1993, and proved additional capture reserves of which approximately 40 percent can be directly attributed to the 3D seismic data and the applied interpretation techniques.
POROSITY GENERATION AND RESERVOIR POTENTIAL OF OULDBURRA FORMATION CARBONATES, OFFICER BASIN, SOUTH AUSTRALIA
Authors: Kamali M.R. , Lemon N.M. , Apak S.N.
Published: August 2017

Porosity generation and reservoir potential of the early Cambrian Ouldburra Formation in the eastern Officer Basin is delineated by combining petrographical, petrophysical and sedimentological studies. The shallow marine Ouldburra Formation consists of carbonates, mixed carbonates and clastics, clastics and evaporites. Detailed analysis of more than 100 samples shows that dolomitisation resulted in substantial secondary porosity development within the carbonates. Secondary porosity has also been generated within the mixed siliciclastic-carbonate zone by carbonate matrix and grain dissolution as well as by dolomitisation. Prospective reservoir units correspond to highstand shallow marine facies where short periods of subaerial exposure resulted in diagenetic changes.Sedimentary facies and rock character indicate that sabkha and brine reflux models are applied to dolomitisation within the Ouldburra Formation. Dolomite mainly occurs in two stages: common anhedral dolomites formed early by replacement of pre-existing limestone, and saddle dolomite and coarse crystalline dolomite formed during the late stages of burial diagenesis, associated with hydrocarbon shows. The dolomite reservoirs identified are ranked on the basis of their porosity distribution and texture into groups I to IV. Dolomites with rank I and II exhibit excellent to good reservoir characteristics respectively.The Ouldburra Formation shows many depositional and diagenetic similarities to the Richfield Member of the Lucas Formation in the Michigan Basin of the USA. Substantial oil and gas production from middle Devonian shallow water to sabkha dolomites makes the Richfield Member an attractive reservoir analogue to the Ouldburra Formation.
INFLUENCE OF PLATE TECTONIC RE-ORGANISATIONS AND TECTONIC SUBSIDENCE ON THE MESOZOIC STRATIGRAPHY OF NORTHWESTERN AND SOUTHEASTERN AUSTRALIA: IMPLICATIONS FOR SEQUENCE STRATIGRAPHIC ANALYSIS
Authors: Ross M. I.
Published: August 2017

Determining and predicting the interplay of plate tectonic events, subsidence, flexure and depositional systems is important in frontier exploration, play concept development, and maturation modelling. A circum-Australian plate tectonic model is here tied to an internally consistent global plate tectonic model to determine the timing and orientation of changes in the lithospheric stress regime induced by plate tectonic changes. One-and three-dimensional geohistory results for the Otway Basin and North West Shelf/Exmouth Plateau are presented, based on an integrated sequence stratigraphic framework. These geohistory results compare the timing and types of changes in subsidence rate to the changes in lithospheric stress due to plate tectonic changes. Changes in tectonic subsidence rate appear to be discrete events related to plate tectonic changes; subsidence events bound major transgressive-regressive facies cycle packages ('supersequences') in a basin. The recognition of sequence system tracts and especially system tract boundaries within a 'supersequence' is enhanced or diminished by processes occurring only during certain phases of the supersequences. Recognition of lowstand systems tracts and sequence boundaries is improved due to erosion during the regressive phase of the supersequence. Conversely, during the transgressive phase of the supersequence, transgressive and highstand system tracts are emphasised and recognition of flooding surfaces improved. Good reservoir sands form during enhanced lowstands, while good source and sealing shales form during enhanced transgressions.In the southeastern Australian Otway Basin, every perturbation of the tectonic subsidence rate during the Late Cretaceous can be correlated directly to a local and/or global plate tectonic event, and each supersequence is bounded by tectonic events. In the North West Shelf/Exmouth Plateau region of Western Australia, the situation is complicated during the Berriasian by uncompensated f lexural load effects related to the rapid formation and filling of multiple Barrow Delta depocentres. Two supersequences correlate to tectonic events, while one supersequence is bounded by a f lexural subsidence event unrelated to regional or global plate tectonic events. Hence not all perturbations of the tectonic subsidence curve are related to tectonic events, and not all supersequences are bound by tectonic events. Without three-dimensional geohistory techniques, it is impossible to isolate the flexural load effects from the effects of plate tectonic events.
UPLIFT AND EROSION ON THE ASHMORE PLATFORM, NORTH WEST SHELF: CONFLICTING EVIDENCE FROM MATURATION INDICATORS.
Authors: Beardsmore G.R. , O'Sullivan P.B.
Published: August 2017

The Ashmore Platform is situated to the north of the Browse Basin, on the North West Shelf, off the coast of Western Australia. Apatite fission track analysis (AFTA™), vitrinite reflectance and fluo­rescence alteration of multiple macerals (FAMM) measurements were undertaken on drill cuttings material recovered from the Late Triassic sequence of the oil exploration well, Ashmore Reef-1.Vitrinite reflectance measurements indicate that the Late Triassic sequence is currently experienc­ing maximum temperature. However, reflectance methods were suspected of being unreliable due to suppression of the reflectance, a common problem when dealing with marine influenced sediments. The FAMM technique was used to provide an alter­native maturity estimate using the same speci­mens. The FAMM results suggested that vitrinite reflectance is suppressed and that the true matu­rity is higher than conventional reflectance mea­surements predict.The results also suggest that some of the cuttings material from the sampled level is contaminated by material from higher in the Late Triassic sequence. Both the AFTA™ and FAMM data show bi-modal populations from some depths. It was possible to distinguish between the two populations and esti­mate the maturity of the caved material. FAMM and AFTA™ results together imply that maximum palaeotemperature was reached in the Mid-Creta­ceous, corresponding to a major unconformity in the well.The FAMM results do not agree with published maturity estimates based on conodont alteration indices (CAI), which suggest that temperatures have only recently and rapidly reached current levels. The AFTA™ results can also be interpreted to support this model. Furthermore, sonic velocity data in Miocene limestone suggests post-Miocene erosion, which would be expected to be associated with a temperature drop.
WESTERN OTWAY CRAYFISH GROUP TROUGHS
Authors: Cockshell C. D. , O'Brien G. W. , McGee A. , Lovibond R. , Perincek D. , Higgins R.
Published: August 2017

Commercial volumes of hydrocarbons have been discovered in Early Cretaceous synrift sediments of the Crayfish Group of the Penola Trough, western Otway Basin. Four other such depocentres are recognised using available seismic and drilling data. A standard nomenclature is proposed for the major structural elements observed in this part of the Otway Basin.Various tectonic models proposed for the Early Cretaceous rift history of the Otway Basin are reviewed and tested using true dip analysis of seismic events and sandbox modelling experiments. Results support a generally north-south direction for rift extension in the Tithonian-Barremian. This implies that the ENE trending Robe Trough is the headwall rift compartment (although with 20°obliquity), whereas the NW trending Penola Trough is a more oblique or transtensional rift compartment.
THE OTWAY BASIN: EARLY CRETACEOUS RIFTING TO NEOGENE INVERSION
Authors: Buffin A.J. , Sutherland A.J. , Gorski J.A.
Published: August 2017

Borehole breakouts and hydraulic fractures in­ferred from dipmeter and formation microscanner logs indicate that the minimum horizontal stress (σh) is oriented 035°N in the South Australian sector of the Otway Basin. Density and sonic check-shot log data indicate that vertical stress (σv) increases from approximately 20 MPa at a depth of one km to 44 MPa at two km and 68 MPa at three km. Assum­ing a normal fault condition (i.e. σy > σH > σh), the magnitude of σh is 75 per cent of the magnitude of the maximum horizontal stress (σH), and the magni­tude of σH is close to that of av. Sonic velocity compaction trends for shales suggest that pore pressure is generally near hydrostatic in the Otway Basin.Knowledge of the contemporary stress field has a number of implications for hydrocarbon produc­tion and exploration in the basin. Wellbore quality in vertical wells may be improved (breakouts sup­pressed) by increasing the mud weight to a level below that which induces hydraulic fracture, or other drilling problems related to excessive mud weight. Horizontal wells drilled in the σh direction (035°N/215°N) should be more stable than those drilled in the σH direction, and indeed than vertical wells. In any EOR operations where water flooding promotes hydraulic fracturing, injectors should be aligned in the aH (125°N/305°N) direction, and off­set from producers in the orthogonal σh direction. Any deviated/horizontal wells targeting the frac­tured basement play should be oriented in the σh (035°N/215°N) direction to maximise intersection with this open, natural fracture trend. Hydrocar­bon recovery in wells deviated towards 035°N/215°N may also be enhanced by inducing multiple hydrau­lic fractures along the wellbore.Considering exploration-related issues, faults following the dominant structural trend, sub-paral­lel to σH orientation, are the most prone to be non-sealing during any episodic build-up of pore pres­sure. Pre-existing vertical faults striking 080-095°N and 155-170°N are the most prone to at least a component of strike-slip reactivation within the contemporary stress field.
THE SAWPIT STRUCTURE—EVALUATION OF A FRACTURED BASEMENT RESERVOIR PLAY IN THE OTWAY BASIN
Authors: Moriarty N.J. , Taylor R.J. , Daneel G.J.
Published: August 2017

The 1992 exploration well Sawpit-1, drilled in the Penola Trough of the western Otway Basin, recovered a minor amount of oil (1.5 BBL) from fractured basement. This oil recovery, the first in the basin from rocks older than the Eumeralla Formation, has opened up a new oil play. Fractured basement reservoirs, which can be prolific producers, require prediction of fracture orientation and intensity to be appraised and developed successfully. Such information was sought from a detailed structural analysis of fault attributes (including dip, vertical displacement and heave) using 3D seismic data acquired over the structure in 1993.This 3D seismic data set, acquired at twice the group interval and less than one-quarter the fold of 2D data in the area, has provided the best imaging to date of the complex rifting events of the Sawpit region. Structural analysis of fault attributes indicates an initial south-southwest direction of extension in the Late Jurassic/Early Cretaceous for the Penola Trough, rather than oblique extension as suggested by some authors. This south-southwest extension orientation favours the formation of moderate to high angle fractures trending west-northwest to northwest. Present day minimum horizontal stress is favourably oriented approximately northeast-southwest for these fractures to be open. Interpretation of the 3D seismic data indicates Sawpit-1 probably intersected northeast trending fractures that are oriented perpendicular to the maximum horizontal compressive stress direction and therefore likely to be closed.A deviated well drilled from the northeast would be optimally oriented to intersect northwest trending basement fractures and test a play that has significant oil potential.
ORIGIN OF PETROLEUM IN THE BOWEN AND SURAT BASINS: GEOCHEMISTRY REVISITED
Authors: Boreham C. J.
Published: August 2017

A detailed regional geochemical study of over 70 oils and condensates, eleven natural gases and over a hundred core samples from potential source rocks enable resolution of the generation and migration history of petroleum in the Bowen and Surat Basins. Biomarker analysis confirms a pre-Jurassic source for the petroleum. Stable carbon-isotope analysis further indicated a Permian-sourced petroleum and was able to differentiate a very minor and localised Triassic source contribution. The dominant source for the petroleum is terrestrial land plants as well as a minor contribution from bacteria and marine algae. In the north, Late Permian lower delta plain and alluvial Permian coals show the higher liquid potential compared with upper delta plain facies, while in the Taroom Trough, coals in the Blackwater Group have the highest liquid potential compared with mudrocks of the Blackwater Group, and sediments of the Back Creek Group. Initial liquid expulsion from the source rock occurred at vitrinite reflectance (Ro) of 0.65-0.7 per cent and continued to Ro of 1.05 per cent. This was followed by the main phase of gas generation between 1.05 per cent
FIGHTING FRACTURED FLAMINGO—LESSONS FROM RAMBLER-I, TIMOR SEA
Authors: Lowry D. C.
Published: August 2017

Exploration well Rambler-1, located in the Timor Sea, presented an unusual set of engineering and evaluation problems when drilling a thick section of Flamingo Group (Jurassic–Cretaceous). The well encountered normally pressured open fractures where drilling mud was lost, and at least two mildly overpressured fractures that flowed small quantities of gassy oil into the well-bore. In these circumstances it was difficult to find the right combination of casing, mud density, cement plugs and lost circulation material to drill the well in a controlled and efficient manner.Fine grained sandstone in the Flamingo Group gave moderate mud log shows and two cased-hole RFTs recovered oil. However, cased-hole DSTs of the same intervals recovered only small volumes of filtrate. This remarkable behaviour is attributed to the RFTs recovering oil from porous cement that had been impregnated with oil from the lower of the overpressured fractures.Any future wells drilled near the axis of the Sahul Syncline are likely to encounter similar problems and awareness of the lessons learned in Rambler–1 can improve drilling and evaluation strategies.