bluuebunny/crossref_metadata_2025 huggingface dataset:
PROSPECTIVITY: IS IT THE REAL CULPRIT FOR THE DECLINE IN ONSHORE EXPLORATION?
Authors: Foley G.S.
Published: August 2017

In 1987 a total of 163 exploration wells were drilled in Australia's onshore basins. In 1993 the number was 47 and although the forecast for 1994 is slightly higher, activity levels over the next few years are expected to stay low. During the 1987—93 period over 60 per cent of all exploration wells were drilled in the Cooper/Eromanga and Bowen/Surat basins. Not a single exploration well was drilled in a number of basins during the period. There is a general perception amongst industry and investors that the majority of Australian's onshore basins are not prospective. A review of past exploration pro­grams in the frontier and emerging basins suggests that this perception is valid. As a result, the smaller companies, which are responsible for the majority of wells drilled in such basins, have found it diffi­cult to attract risk capital and, consequently, activ­ity levels have fallen to the current levels. Not withstanding the results of past exploration efforts, detailed financial analysis of the best oil plays in the Canning, Perth and Surat basins suggests that the potential returns from exploration and develop­ment activities are extremely attractive. Forecast internal rates of return exceed 50 per cent. Each play was subjected to sensitivity analysis to deter­mine the break-even point for exploration and de­velopment success rates, field sizes, well volumes, initial production rates, exploration and develop­ment capital costs, fixed and variable operating costs and corporate tax rates. The results suggest that the economics are considerably more robust than generally believed. The task confronting in­dustry is to convince the stock market that attrac­tive returns can be generated from at least three onshore basins so capital can be raised to exploit available opportunities.
THE IMPORTANCE OF WETTABILITY AND WETTABILITY TESTING METHODS USED IN THE OIL INDUSTRY
Authors: Clinch S.R.J. , Boult P.J. , Hayes R.A.
Published: August 2017

The wettability of a petroleum reservoir governs the location of fluids within its pore space and hence the movement of fluids through it during production. Properties that may be affected by wettability include resistivity, capillary pressure, relative permeability and rock strength as well as behaviour during waterflood and enhanced oil recovery. Generally every reservoir is initially assumed to be water wet. When production problems arise, the wettability of a reservoir will only be questioned when all other possibilities have been accounted for. By correctly determining the wettability of a reservoir more accurate models can be provided for reservoir simulation, which in turn will improve the prediction of future field performance.Many methods of varying difficulty and accuracy can be used to measure wettability. However, they can only be as good as the quality of the fluid samples used. It is important to understand that reliable results are only obtained when sample contamination is minimised and experimental control is maximised. Some wettability experiments can be carried out at reservoir conditions, which may be more representative, but also more susceptible to contamination.In an oil reservoir either oil or brine can be the most wetting phase and gas is normally the least wetting phase. From a thorough investigation of downhole logs and production data it may be possible to identify wetting anomalies. Examining formation pressure data is the most recent method proposed for determining wettability.
THE KIMMERIDGIAN MARL IN THE TIMOR SEA: RELEVANCE TO REGIONAL GEOLOGICAL EVOLUTION AND POSSIBLE HYDROCARBON PLAYS
Authors: Gorter J. D. , Kirk A.S.
Published: August 2017

Lower Kimmeridgian marls in the Sahul Syncline have a distinct seismic character and can be used to define the limits of depocentres, but the reflector is difficult to map in the Vulcan Sub-basin. The top of the carbonate is an unconformity in shelfal areas and on uplifted structures, but in the depocentres, where a distinctive and thin limestone is present at the top of the marls, there is no evidence of missing section. The limestone, which is interpreted to reflect the paraconformity of the 139 Ma Type 1 sequence boundary, consists of the amalgamated condensed highstand overlying the 139.5 Ma condensed section, and the condensed transgressive systems tract of the overlying C. perforans shelf margin wedge.The underlying Upper Jurassic section is an important source interval in the Vulcan Sub-basin and the regional extent of the reflector may approximate the area in which Oxfordian source beds were deposited. Regional isochore mapping may also delineate areas of potential silled, fault-bounded depocentres within the greater Sahul Syncline that were in existence during latest Callovian to early Kimmeridgian time. Structures located within the fetch of these depocentres should be ideally placed to trap migrating hydrocarbons sourced from restricted marine shales of Oxfordian age.Erosion accompanying the 138 Ma lowstand has removed some or all of the marls and the C. perforans sediments from structures uplifted during the contemporaneous mid-Kimmeridgian tectonism. Major sea level falls, probably also associated with tectonic movements at the 136, 135 and 134 Ma sequence boundaries, could have led to further erosion or non-deposition on high blocks. Given sufficient time and suitable lithology, fresh water diagenesis and leaching of these marls may have led to the development of secondary porosity with later sealing by post-Kimmeridgian shales, especially where the interval contains coarser clastics as along the flank of the Flamingo High.
GLOBALLY SYNCHRONOUS COMPRESSIONAL PULSES IN EXTENSIONAL BASINS: IMPLICATIONS FOR HYDROCARBON EXPLORATION
Authors: Davidson J. K.
Published: August 2017

It is possible to interpret many continental stresses on the Global Stress Map (Zoback, 1992) in terms of plate tectonics. Plate tectonics on a constant radius earth predicts a state of zero stress in Australia, except for northerly to northeasterly compression along the northern margin where Australia interacts with the Pacific Plate. However, the continent is everywhere in a state of significant horizontal compression, generally directed towards its centre.In southeastern Australia the current maximum horizontal compressional stress is directed northwestwards. While Gippsland Basin and Bass Basin developed under extensional stress from the Late Jurassic to Recent, there have been pulses of similarly directed compression in the Pliocene to Recent, Mid Miocene, Early Miocene, Late Eocene to Early Oligocene, Early Eocene, Paleocene, Campanian, Late Albian to Early Cenomanian, Aptian and Valanginian(?).Most of these pulses can also be demonstrated in such widely separated areas as the Carnarvon Basin in northwestern Australia, the Capricorn and Surat/Bowen Basins in eastern Australia, southern England, the Viking Graben in the North Sea and Pacific Guatemala. Pulses in the Portlandian, Callovian, Early Jurassic, Late Triassic and Mid Triassic appear to be similarly synchronous while two events in the Early Permian have been recognised also.Near-surface compressional pulses contemporaneous with lower crustal extension can be explained by continental flattening on an expanding earth. Such an interpretation is consistent with the centrewards horizontal compressional stresses observed in the Australian continent since at least the Late Triassic.Since an expansion pulse results in increased ocean basin capacity, compressional pulses have a strong tendency to coincide with the major sea level falls on the Haq et al (1987) global eustatic cycle chart.The orientations of horizontal compressional stresses appear to have varied little since the Late Triassic. If a basin axis is approximately perpendicular to those stresses the basin may record all compression pulses. However, repeated compression sub-parallel to a basin axis may induce movement on wrench faults which can be a threat to seal integrity.
COMPRESSIONAL CONTROL ON SEDIMENT AND FACIES DISTRIBUTION SW NAPPAMERRI SYNCLINE AND ADJACENT MURTEREE HIGH, COOPER BASIN
Authors: Apak S.N. , Stuart W.J. , Lemon N.M.
Published: August 2017

The northeast-trending Nappamerri Syncline and its flanking high to the southeast, the Murteree-Nappacoongee (NM) Trend, show structural development throughout the deposition of the Permo-Triassic Cooper Basin sequences. Pre-existing topography, such as around Moomba, influenced early depositional patterns within the area. Rates of sedimentation were influenced by the rate of uplift of source areas around the basin, largely as a consequence of buckling. Periods of active tectonism resulted in non-deposition and stripping of sediments from uplifted blocks while deposition continued in deeper areas. Hangingwall blocks, pushed up along reverse faults, strongly influenced the areas of sedimentation and the facies being deposited. This is particularly evident along the NM Trend. Phases of uplift were immediately followed by increased sedimentation where fluvial deposition dominated. The effect of displacement along the northwest-trending basement lineaments was to subdivide the northeast trends into compartments which contain similar facies within each time slice. Adjacent compartments may display different facies and different tectonic histories. An inversion episode, particularly evident in the Big Lake/Moomba area, resulted in a reversal of the depocentre and was related to phases of Sakmarian compression.Facies distribution and sandstone percentage maps of the chronostratigraphic units of the Patchawarra Formation suggest that a northeast-trending major channel system entered this part of basin along the NW edge of the Murteree area.
THE HYDROCARBON POTENTIAL OF THE PENOLA TROUGH, OTWAY BASIN
Authors: Lovibond R. , Suttill R.J. , Skinner J.E. , Aburas A.N.
Published: August 2017

The Penola Trough is an elongate, Late Jurassic to Early Cretaceous, NW-SE trending half graben filled mainly with synrift sediments of the Crayfish Group. Katnook-1 discovered gas in the basal Eumeralla Formation, but all commercial discoveries have been within the Crayfish Group, particularly the Pretty Hill Formation. Recent improvements in seismic data quality, in conjunction with additional well control, have greatly improved the understanding of the stratigraphy, structure and hydrocarbon prospectivity of the trough. Strati-graphic units within the Pretty Hill Formation are now mappable seismically. The maturity of potential source rocks within these deeper units has been modelled, and the distribution and quality of potential reservoir sands at several levels within the Crayfish Group have been studied using both well and seismic data. Evaluation of the structural history of the trough, the risk of a late carbon dioxide charge to traps, the direct detection of gas using seismic AVO analysis, and the petrophysical ambiguities recorded in wells has resulted in new insights. An important new play has been recognised on the northern flank of the Penola Trough: a gas and oil charge from mature source rocks directly overlying basement into a quartzose sand sequence referred to informally as the Sawpit Sandstone. This play was successfully tested in early 1994 by Wynn-1 which flowed both oil and gas during testing from the Sawpit Sandstone. In mid 1994, Haselgrove-1 discovered commercial quantities of gas in a tilted Pretty Hill Formation fault block adjacent to the Katnook Field. These recent discoveries enhance the prospectivity of the Penola Trough and of the Early Cretaceous sequence in the wider Otway Basin where these sediments are within reach of the drill.
PORT CAMPBELL REVIEWED: METHANE AND CHAMPAGNE
Authors: Foster J.D. , Hodgson A.J.
Published: August 2017

Gas fields in the Port Campbell Embayment cur­rently supply all the natural gas markets (non-LPG) in western Victoria as well as commercial quanti­ties of carbon dioxide (C02) to industrial markets. Initial discoveries made between 1979 and 1981 were brought on-stream in 1986 with production from the North Paaratte field. Another substantial discovery was made in 1988, the Iona gas field, followed by the Boggy Creek C02 field in 1991, then the My lor and Langley fields in 1994. Discovery of Mylor marked the first recovery of oil from the Late Cretaceous Waarre Formation. Extensive 2D seis­mic data sets have been recorded in the region since 1979, and the first 3D seismic survey in the Otway Basin was carried out in 1993 extending beyond the area of the initial discoveries. No data on the fields have been published for nearly a decade and little detail about the structural and stratigraphic geol­ogy of the Late Cretaceous in the area has been documented. Summaries of the fields are presented incorporating many insights gained from interpre­tation of the 3D seismic data and its verification by the 'rotary lie detector'.
SEISMIC STRUCTURE AND EXTENSIONAL DEVELOPMENT OF THE EASTERN OTWAY BASIN-TORQUAY EMBAYMENT
Authors: Cooper G.T.
Published: August 2017

The Eastern Otway Basin exhibits two near-or-thogonal structural grains, specifically NE-SW and WNW-ESE trending structures dominating the Otway Ranges, Colac Trough and Torquay Embayment. The relative timing of these structures is poorly constrained, but dip analysis data from offshore seismic lines in the Torquay Embayment show that two distinct structural provinces developed during two separate extensional episodes.The Snail Terrace comprises the southern structural province of the Torquay Embayment and is characterised by the WNW-ESE trending basin margin fault and a number of small scale NW-SE trending faults. The Torquay Basin Deep makes up the northern structural province and is characterised by the large scale, cuspate Snail Fault which trends ENE-WSW with a number of smaller NE-SW trending faults present.Dip analysis of basement trends shows a bimodal population in the Torquay Embayment. The Snail Terrace data show extension towards the SSW (193°), but this trend changes abruptly to the NE across a hinge zone. Dip data in the Torquay Basin Deep and regions north of the hinge zone show extension towards the SSE (150°). Overall the data show the dominance of SSE extension with a mean vector of 166°.Seismic data show significant growth of the Crayfish Group on the Snail Terrace and a lesser growth rate in the Torquay Basin Deep. Dip data from the Snail Terrace are therefore inferred to represent the direction of basement rotation during the first phase of continental extension oriented towards the SSW during the Berriasian-Barremian? (146-125 Ma). During this phase the basin margin fault formed as well as NE-SW trending ?transtensional structures in the Otway Ranges and Colac Trough, probably related to Palaeozoic features.Substantial growth along the Snail Fault during the Aptian-Albian? suggests that a second phase of extension affected the area. The Colac Trough, Otway Ranges, Torquay Embayment and Strzelecki Ranges were significantly influenced by this Bassian phase of SSE extension which probably persisted during the Aptian-Albian? (125-97 Ma). This phase of extension had little effect in the western Otway Basin, west of the Sorrel Fault Zone, and was largely concentrated in areas within the northern failed Bass Strait Rift. During the mid-Cretaceous parts of the southern margin were subjected to uplift and erosion. Apatite fission track and vitrinite reflectance analyses show elevated palaeotemperatures associated with uplift east of the Sorell Fault Zone.
THE OTWAY BASIN: EARLY CRETACEOUS RIFTING TO NEOGENE INVERSION
Authors: Perincek D. , Cockshell C.D.
Published: August 2017

A regional seismic interpretation ot the on shore Otway Basin has been completed and used to determine the basin's structural history.Sedimentation commenced in the Tithonian-Berriasian with the deposition of the volcanogenic Casterton Formation and continued into the Berriasian-Barremian with the deposition in elongate half graben, of thick fluviolacustrine sediments of the Crayfish Group, typically thickening dramatically towards the bounding faults. The NW to W trend of Crayfish Group depocentres and their major bounding faults suggest that the initial extension direction was N-S to NE-SW in the Late Jurassic-Early Cretaceous. Dextral transtensional movement occurred along the Trumpet Fault in the west of the basin and was complemented by sinistral transtension on the major NNE striking faults of the Torquay Sub-basin in the east during this period.The dip direction of the pre-Barremian bounding faults changes a number of times along the northern margin of the basin. These changes occur across transfer/accommodation zones of complex faulting and folding, not over discrete transfer faults.Faulting and related uplift resulted in partial erosion of the Crayfish Group from a number of structural highs, prior to the Aptian. The half graben faults are overlain by Eumeralla Formation indicating that active rifting had ceased by the Aptian in the onshore Otway Basin. Further erosion occurred following post-Albian faulting and uplift prior to the Paleocene, in particular within the eastern part of the basin.During deposition of the Sherbrook Group in the Late Cretaceous, fault reactivation produced minor, shallow grabens within the older half graben systems. Major movement also continued along the Tartwaup Fault Zone, resulting in basin deepening toward the SW. This fault activity continued into the Paleocene-Early Eocene during deposition of the Wangerrip Group. In the Eocene, the Southern Ocean spreading rates changed from slow to fast, resulting in the late-Early Eocene deltaic sediment of the Upper Wangerrip Group covering some of the earlier extension faults. Compression, resulting in right-lateral wrenching and inversion of previous faults, occurred during the Miocene-Recent. Pliocene-Holocene volcanic activity occurred along zones of weakness related to these fault systems.
GAS DETECTION IN THE ONSHORE OTWAY BASIN USING ARRAY SONIC WAVEFORM DATA
Authors: Buffin A.J. , Sutherland A.J. , Gorski J.A.
Published: August 2017

The Otway Basin and in particular the onshore Penola Trough has recently become a focus for gas exploration. Gas identification in sandstones of the Lower Cretaceous Pretty Hill Formation, the primary reservoir target in this trough, has proved difficult using traditional wireline log analysis. A resistivity contrast associated with gas and water sands is not observed on well logs and poor hole conditions affect pad tools suppressing the gas cross-over response on density-neutron logs. Identification of gas sands has historically relied on mud logs, pressure and test data.The array sonic tool records the entire waveform and records shear and Stoneley waves in addition to compressional waves. Obtaining 'slowness' from shear and Stoneley waveforms opens up a new range of applications including gas detection. Wave theory predicts that a small percentage of gas in the pore space significantly increases the compressional slowness whereas the effect of gas on the shear slowness is much less pronounced. The shear to compressional slowness ratio (Vp/Vs) is therefore a powerful tool for gas detection.Acoustic array sonic waveforms were recorded over the Pretty Hill Formation in the recent onshore Otway Basin wells Katnook-4, Haselgrove-1 and Haselgrove-2 using Schlumberger's Sonic Digital Tool (SDT). A Vp/Vs ratio value less than 1.7 was established as representative of sands containing gas. The productivity of these gas sands was confirmed by wireline, open hole and cased hole tests in Haselgrove-1 and Haselgrove-2. The uppermost reservoir section in Katnook-4 was gas-bearing but proved to be tight on test.In a reservoir such as the Pretty Hill Formation, where hydrocarbon identification is rendered difficult by conventional logging suites, acoustic array sonic waveform data help to distinguish gas sands from water sands.
DUE DILIGENCE—A LEGAL COMPLIANCE PROGRAM
Authors: Sandman M.S.
Published: August 2017

Every responsible corporate citizen both within and outside the hydrocarbons sector has an obligation to comply with all laws applicable to its operations. It is clear that modern developments in the law affecting companies, their directors, officers and employees exhibit a strong and consistent trend to impose personal and corporate liability for breaches of the law. Increasing exposure to such liability must be managed by the adoption and effective implementation of a management system which will generate evidence of the exercise of proper diligence to ensure compliance. This is the basis of a Legal Compliance Program.The implementation of a Legal Compliance Program will involve the following aspects:Identification of the company's exposure to laws requiring compliance as part of its day to day operations.Analysing the nature of the compliance required.Imposition of responsibility to ensure compliance.Compliance auditing.A Legal Compliance Program will assist in ensuring that the major legal risks and exposures in the organisation are identified, reported and managed.The responsibility for compliance lies with everyone in the organisation. All employees are responsible for compliance with the laws applicable to their assigned duties and responsibilities.Programs must be established to ensure compliance by each Department and a procedure should be set in place to provide for periodic compliance audits. Such audits should be undertaken with the co-operation and assistance of department personnel and should be programmed in such a way as to give reasonable assurance that the company's obligations for compliance with laws is achieved.It is an on-going process which must be flexible to account for changing laws and changing processes and procedures.In the hydrocarbons industry, with the requirement to establish due diligence in all areas and particularly with regard to compliance with environmental laws, a legal compliance program will provide the following benefits:It will reduce the likelihood of breaching laws relevant to the company's operations.It will help to establish a due diligence defence in appropriate circumstances.It will provide for personal accountability of employees at all levels.It will assist in public relations in the advent of adverse public exposure.It will assist in developing a good working relationship with the regulatory authorities if they can be persuaded that an effective legal compliance program has been established.To the extent that assurance is given that laws are being complied with, it will minimise the risk of prosecutions, investigations and litigation and have a consequential saving in legal costs which would otherwise be incurred.
MEASURING THE ECONOMIC PERFORMANCE AND VALUE OF COMPANIES
Authors: Kasian P.A.
Published: August 2017

Accounting performance measures such as earnings per share growth and return on equity and their related valuation measures (price to earnings and price to book ratios) have severe limitations in comparing the economic performance of companies and explaining how the market prices stocks. Although the traditional cash flow-based valuation methodologies as taught in business schools are, in theory, more sound approaches, they suffer problems in practical implementation. In particular, the large number of forecasts and arbitrary decisions that need to be made in deciding upon an appropriate discount rate prevent meaningful back testing of the approach. Hence the validity of the assumptions being made are always open to question. This approach also fails to provide a measure of a company's actual current performance but rather measures forecasted performance.Cash flow return on investment (CFROI) overcomes many of these limitations. It measures the rate at which assets are generating cash flow while explicitly taking into account the distortions caused by inflation, asset age, asset life, and different mixes of depreciating and non-depreciating assets. CFROI spread, the difference between a firm's performance and its market-derived cost of capital, has a much higher correlation with how the market values companies. It has provided a useful insight into Santos' share price performance as well as the efficiency with which the company utilises its asset base relative to other Australian and US oil and gas companies. The CFROI also lends itself to the valuation of individual companies in such a way that it enables meaningful back testing to be performed. Using Santos as an example it was found that the assumptions implicit in this approach are applicable to oil and gas companies.
SCHOOL-INDUSTRY LINKS: A VALUE ADDING PROCESS
Authors: Mazzone J. A.
Published: August 2017

The establishment of links between SAGASCO Resources Limited (SAGASCO) and secondary schools in the city and country regions of South Australia has provided benefits to both the petroleum industry and to the students and teachers at the schools. Links between Penola High School in the southeast of South Australia and Hamilton Secondary School in Adelaide began in 1993 and have continued to the present. Feedback from the schools has been positive and significant. The two schools have overwhelmingly endorsed the links and have benefited both in curriculum development and in gaining a glimpse of industry operations that is not found in textbooks. The benefits from the link process has also revealed a cascade effect in which students and teachers have utilised information on the petroleum industry and incorporated it into reports, publications and texts that have been further used by the schools and the community, thus enhancing the original link process. Links with schools require stronger support by the petroleum industry to meet the needs of schools and to provide balance to the often negative profile of our industry in the community both in the immediate and longer term.
FOREIGN INVESTORS AND CORPORATIONS SHARPEN FOCUS ON AUSTRALIA
Authors: Baker S. T.
Published: August 2017

The rising participation of foreign corporations and equity investors at every level of the Australian industry, is a sure sign of this region's exploration and fiscal attraction. It is time notice is taken of the specific reasons for this, learn from it and derive some benefit from it. Australian companies seeking to attract equity capital from overseas should be keenly aware of what is sought after, and package their attributes accordingly. Companies seeking corporate relationships, may have some hidden assets to offer and could easily undersell themselves. Finally, companies seeking to diversify overseas run the risk of mis-allocating resources into areas of lesser return. The penalty for this is takeover.
EAST SPAR FIELD—FROM DISCOVERY TO SALES
Authors: Pitt G. M. , Kuryiowicz L. E. , Campbell IP. F.
Published: August 2017

The East Spar field is located 40 km west of Barrow Island on the North West Shelf, offshore WA, and con­tains 23.6 G.m3 (834 Bscf) of proven and probable wet gas in-place in the Early Cretaceous Barrow Group. The trap is structural, but with negligible time closure.At the time of the discovery and early appraisal of East Spar in late 1993, a rapid deregulation of the gas market was taking place. In combination with the concept of a gas pipeline to the central WA Goldfields region, a marketing 'window of opportunity' was created for the East Spar field, if the development could be crystallised in the available period of 9 months. This required ap­praisal drilling, geotechnical studies, reservoir engineer­ing and facilities engineering to be advanced on parallel fronts, with close co-ordination and communication be tween all disciplines.The concept of an alliance between the East Spar Joint Venture and the engineering/construction contractors was identified as a way of retaining flexibility to alter the development concept during this period, and provide other benefits during the subsequent construction phase. This alliance was ultimately formed to include represen­tatives from WMC (on behalf of the East Spar Joint Venture (ESJV)), Kvaerner-R J Brown and dough Engi­neering.The East Spar facilities will comprise a subsea comple­tion and gathering system, with all produced fluids being piped to processing facilities on Varanus Island. The treated gas will then be transported to the mainland via the existing sales gas pipeline to the onshore Dampier to Bunbury pipeline, which connects with the Goldfields Gas pipeline. The condensate will be exported from Varanus Island by tanker. First sales are expected in October 1996
RESERVOIR CHARACTERISATION OF A LOW RESISTIVITY GAS FIELD-OTWAY BASIN, SOUTH AUSTRALIA
Authors: Scholefield T. , North C.P. , Parvar H.L.
Published: August 2017

The Katnook, Haselgrove and Ladbroke Grove Fields of southeastern SA are characterised by a lack of resistivity contrast above and below known gas-water contacts, poor hole conditions, complex mineralogy and fresh formation water. A multi-disciplinary review of all available data to characterise the Pretty Hill Sandstone reservoir by integrating core, log and engineering data has enabled a comprehensive picture of reservoir heterogeneity and its influence on log response and well performance to be determined. The availability of extensive core throughout the 6 wells has resulted in the accurate modelling of reservoir porosity and the derivation of a facies-dependent, quantitative permeability log which closely matches drill stem test and production test derived permeability thickness (kh). Previous water saturation assumptions have been shown to be optimistic with Leverett J Function water saturation averaging 50-60 per cent through the reservoir. Detailed facies modelling from the cores extrapolated into areas with no core control has led to the derivation of a geological model which, when integrated into a 3D simulation, has resulted in calculated pressures within 1 per cent of those measured and has enabled the prediction of the pressure response from highly compartmentalised portions of the reservoir. Simulation-derived, material balance and volumetric original-gas-iti-place for the Katnook Field now agree to within 5 per cent.The study has resulted in changes to previously accepted evaluation procedures for wells targeting the Pretty Hill Sandstone.
THE STAG OILFIELD
Authors: Crowley J. , Collins E.S.
Published: August 2017

The Stag Oilfield is located approximately 65 km northwest of Dampier and 25 km southwest of the Wandoo Oilfield near the southeastern margin of the Dampier Sub-basin, on the North West Shelf of Western Australia,.The Stag-1 discovery well was funded by Apache Energy Ltd (formerly Hadson Energy Ltd), Santos Ltd and Globex Far East in June 1993 under a farmin agreement with BHP Petroleum Pty Ltd, Norcen International Ltd and Phillips Australian Oil Co. The well intersected a gross oil column of 15.5 m within the Lower Cretaceous M. australis Sandstone. The oil column intersected at Stag-1 was thicker than the pre-drill mapped structural closure.A 3D seismic survey was acquired over the Stag area in November 1993 to define the size and extent of the accumulation. Following processing and interpretation of the data, an exploration and appraisal program was undertaken. The appraisal wells confirmed that the oil column exceeds mapped structural closure and that there is a stratigraphic component to the trapping mechanism. Two of the appraisal wells were tested; Stag-2 flowed 1050 BOPD from a 5 m vertical section and Stag-6 flowed at 6300 BOPD on pump from a 1030 m horizontal section.Evaluation of the well data indicates the M. australis Sandstone at the Stag Oilfield is genetically related to the reservoir section at the Wandoo Oilfield. The reservoir consists of bioturbated glauconitic subarkose and is interpreted to represent deposition that occurred on a quiescent broad marine shelf. Quantitative evaluation of the oil-in-place has been hampered by the effects of glauconite on wireline log, routine and special core analysis data. Petrophysical evaluation indicates that core porosities and water saturations derived from capillary pressure measurements more closely match total porosity and total water saturation than effective porosity and effective water saturation.A development plan is currently being prepared and additional appraisal drilling in the field is expected.
HYDROCARBON POTENTIAL OF MANILA BAY AND ADJACENT AREAS
Authors: Rillera F. G. , Durkee E. F.
Published: August 2017

The first ever exploratory well in the Manila Bay sector of the Central Luzon Basin, Philippines was drilled in mid-1995. The well yielded encouraging results. Although it failed to reach its main objective between 2,900 and 3,350 m (9,500 and 11,000 feet) and was not tested due to technical problems, the drilling results provided valuable geological information which has substantially upgraded the hydrocarbon prospectivity of the area.Manila Bay 1A/1AST was drilled to a total depth of 2,265 m (7,430 feet) and penetrated an over-pressured, potentially gas-bearing Late Miocene-Pliocene carbonate reservoir between 1,995 and 2,210 m (6,546 and 7,252 feet). Gas (C1 to C4) in the mudstream while drilling and streaming cuts and fluorescence in certain samples, attest to the generative potential of the southern sector of the Central Luzon Basin. Furthermore, the results demonstrate the development of previously unrecognized excellent shelfal carbonate reservoirs on the southwestern margin of the basin.A second well in Manila Bay is planned for drilling in first quarter 1996, to fully appraise the gas potential of the Late Miocene-Pliocene carbonate section and to explore the deeper primary objective of possible Middle Miocene or older age carbonates. In parallel, exploration plans are also being drawn to confirm possible similar features in the onshore area immediately north of Manila Bay.Any commercial hydrocarbon discoveries in Manila Bay and/or this adjacent onshore area would constitute economically significant sources of indigenous energy for Metro Manila and the rapidly industrializing adjacent provinces.
SUPPRESSED VITRINITE REFLECTANCE AND ITS EFFECT ON THERMAL HISTORY MODELLING IN THE BARROW AND DAMPIER SUB-BASINS.
Authors: Kaiko A. R. , Tingate P. R.
Published: August 2017

The Barrow and Dampier Sub-basins form an important offshore petroleum province containing major oil discoveries associated with Triassic to Cretaceous reservoirs and source reeks. Constraining the timing cf oil generation and migration within the sub-basins has been hampered by difficulties in assessing thermal maturity using vitrinite reflectance data. Jurassic-Cretaceous formations of predominantly marine origin yield vitrinite reflectance values that are often lower than expected compared to the present day thermal conditions. The two main explanations put forward by workers for this situation are that:a recent increase in thermal gradients has occurred; orthe vitrinite reflectance is suppressed, and this suppression is related to the marine environment of deposition.Thermal history analysis of 65 wells throughout the Barrow and Dampier Sub-basins has confirmed, using multiple maturity parameters, that vitrinite reflectance data are suppressed over large parts of the study area.Thermal history modelling and the confirmation of vitrinite reflectance suppression has enabled revised estimates of pr esent maturity to be made. Maturity levels based on measured reflectance data and values calculated from thermal information exhibit large differences, related to suppression; up to 1,500 m in the depth to the 0.7 per cent R(1 iso-reflectance surface. Vitrinite reflectance suppression, if not taken into account, also strongly affects modelling of uplift and erosion, and the timing of onset of maturity for petroleum generation. Variations of up to 100 Ma have been noted between histories based on measured vitrinite reflectance and those taking vitrinite reflectance suppression into account.
THE SEISMIC EXPRESSION OF THREE-DIMENSIONAL SANDBOX MODELS
Authors: Sherlock D.H. , Evans B.J. , Ford C.C.
Published: August 2017

Analogue sandbox models provide cheap, concise data and allow the evolution of geological structures to be observed under controlled conditions in a laboratory. Seismic physical modelling is used to study the effects of seismic wave propagation in isotropic and anisotropic media and to improve methods of data acquisition, processing and interpretation. These two independent geological modelling techniques have been linked for the first time, to combine and expand the existing benefits of each method.Seismic physical modelling to date has employed solid models, constructed with pre-determined structures built into the model. Previous attempts to adapt this technology to unconsolidated materials failed due to the severe energy attenuation of seismic waves in cohesionless grain matrices, and excessive signal scatter due to scaling limitations of the geological feature size to wavelength ratio. This paper presents our research to overcome these problems and thereby allow the successful seismic imaging of sandbox models.A number of techniques have been developed to combine these two independent modelling methods and results show that it is possible to image several layers within the models, demonstrating the potential to interpret complex geological structures within such models. For seismic modelling, the main advantages are that the seismic data collected from these models contain natural variation that cannot be built into solid models, which results in a more realistic image, and the cost and construction time of the models are also dramatically reduced. For sandbox modelling, the recording of seismic data over them allows far more detailed interpretation of the structures than previously possible and also allows direct comparison with field data for the first time, to substantiate or negate an existing interpretation.
RECENT EXPERIENCE WITH EXTENDED LEAK-OFF TESTS FOR IN-SITU STRESS MEASUREMENTS IN AUSTRALIA
Authors: Enever J.R. , Yassir N. , Willoughby D.R. , Addis M.A.
Published: August 2017

The historical and theoretical backgrounds of standard and extended leak-off tests with respect to in-situ stress measurement are discussed and compared with hydraulic fracture stress measurement as practised in other industries. The relative advantages of extended leak-off tests compared with standard tests in this context are discussed and a case made for the extended test procedure. The diagnostics of pressure records obtained from extended leak-off tests are discussed in light of extensive experience obtained from hydraulic fracture stress measurement, with reference to a number of extended leak-off tests conducted in Australia. A conclusion is reached that extended leak-off tests can potentially provide data of quality comparable with that obtained from ideal hydraulic fracture stress measurement, allowing resolution of the in-situ stress field with reasonable reliability in many cases. The results of some Australian extended leak-off tests are discussed and contrasted with corresponding data obtained from standard leak-off tests. A trend is revealed from this data for extended leak-off tests to produce a lower estimate of the minimum stress magnitude than standard leak-off tests.
LABORATORY TESTING FOR RESERVOIR ENGINEERS AND GEOLOGISTS—BE A DRIVER, NOT A PASSENGER!
Authors: Williams N.
Published: August 2017

A detailed review by Santos of all its laboratory activities has revealed that nearly all laboratory work must be very closely tailored to the needs of the reservoir in question in order to produce meaningful results. The practice of just ticking a few items from the laboratory catalogue as if one were ordering breakfast in a hotel is fatal. Instead intensive preparation of procedures is required—this may involve months of discussion with the laboratory, development of new procedures tuned to the particular reservoir, testing of these procedures and modification, etc. Often the preparation for the laboratory work will begin long before the rock or liquid samples arrive at the laboratory.Nearly all of Santos' Eromanga Basin oil reservoirs are thin (typically 30 to 40 ft gross column), have no gascap, and lie in the transition region of the capillary pressure curves. However the cores were traditionally analysed by the laboratories assuming the reservoirs extended far beyond the transition zone. This led to major inconsistencies in the results, and difficulties in comparing core results to log analysis. Procedures were developed appropriate to transitional reservoirs. Experiments were run with the new procedures. These experiments have revealed many of the hitherto unappreciated properties of transitional reservoirs, leading to a better understanding of end point saturations, log analysis, reservoir seals and how to treat reservoirs which have leaked. Low invasion coring appears to be particularly well suited to transitional reservoirs.The new laboratory procedures imply that most of our oil reservoirs are being very well swept, at least on a microscopic scale. This may have significant implications for EOR.After realising the effort that is required to keep core analysis on track Santos then extended this thinking to all laboratory work. This has led to improvements in our ability to analyse oils, waters, muds, clays and in our ability to conduct 'multi-disciplinary experiments', i.e. experiments extending across more than one laboratory. At the end of the day we are achieving better log analysis, better estimates of original hydrocarbons in place and better estimates of oil remaining after primary production.
THE EVOLUTION OF STABLE FOAM AS A DRILLING MEDIUM
Authors: Rovig J.
Published: August 2017

In the late 1960s Stable Foam was developed by Chevron USA as a lightweight circulation medium to clean out production sand in depleted (depleting) wells. In employing this new medium they found that Stable Foam's compressible bubble structure provided up to 10 times the carrying capacity of many common liquid based circulating fluids.These early successes led the industry to expand the use of Stable Foam from cased hole production clean outs to drill-ins, gravel packing, drilling in lost circulation zones, coil tubing, and today its utilisation as an Underbalanced Drilling fluid in depleted reservoirs.Through this evolution Stable Foam has had its successes and failures as well as unique operational concerns which has affected its consideration and utilisation.The following is a breakdown of the major hurdles which have been addressed and overcome, consequently positioning Stable Foam as a viable option for wider use in Underbalanced Drilling:Foam compatibility in water, oil, salt and high temperature environments.MWD and Directional Drilling performance with a compressible fluid.Surface pressure control while drilling.Surface separation and processing of a three phase well return fluid to provide a zero discharge closed loop circuit.
THE 'RIGHT TO NEGOTIATE' UNDER THE NATIVE TITLE ACT 1993
Authors: Davie C.R.
Published: August 2017

One of the most controversial and complex aspects of the Commonwealth Native Title Act 1993 is the so-called 'right to negotiate' which is conferred on both registered native title holders and on native title claimants where a Government seeks to take action which would adversely affect any native title held or claimed. Whilst the concept behind the 'right to negotiate' is essentially a simple one, the attempt of the drafters to reconcile many competing land interests has led to an especially complex regime with particular pitfalls for those associated in the petroleum and natural resources industries. This paper is written with a view to explaining the effect of the 'right to negotiate' provisions for petroleum exploration and production companies. In this writer's view, there are aspects of the current legislation which strike the wrong balance between Aboriginal and development interests. The new Federal Government has foreshadowed that it will introduce amendments to the Act, and by the time this paper is presented at the Darwin Conference there could be substantial changes in the offing.
COOPERATIVE INDUSTRY APPROACH TO ENVIRONMENTAL INVESTIGATIONS IN THE TIMOR SEA
Authors: Pinceratto E.J. , Oliver G.
Published: August 2017

For more than 20 years, oil and gas exploration and production activities have been conducted in the Timor Sea region, including the Sahul Shelf. The Shelf is a large, shallow platform off the Northern Australian Coast, considered to be a recently drowned part of the Australian Platform. Seismic surveys have indicated submerged banks on the edge of this Shelf. Until recently, little was known of the physical nature of these banks, or their ecology.Environmental management of petroleum exploration and development activities in the area is required to avoid potentially impacting the surrounding environment. Accurate information on ecological systems is therefore required in order to design detailed Environmental Management Plans which aim to minimise impacts and protect the environment.BHP Petroleum and Woodside Offshore Petroleum, as operators of permits in the area, independently conducted baseline environmental investigations. This information was exchanged, and the cooperative effort between BHPP and Woodside resulted in a significantly improved environmental resource database, which will aid in the planning and implementation of effective environmental management of petroleum operations.The studies included:Accurate bathymetric surveys to determine the geomorphology of the banks.Acquisition of side-scan sonar for interpretation of substrate features and the preparation of preliminary habitat maps.Remotely Operated Vehicle (ROV) surveys to ground truth habitats, and to determine their distribution and species composition.Grab and drop-core sampling to validate ROV film and provide material for chemical and physical analysis.Collecting current data, to aid in the formulation of management strategies for the disposal of drilling discharges and for oil-spill contingency planning.Deep-water benthic trawling to determine the abundance and composition of epi-benthic macrofauna.The main conclusions were that submerged banks are reef-systems that have variable density of coral cover, which are dependant on depth (light intensity), and substrate type. Thirty metres is assumed to be the maximum depth for reef-flat coral growth. The outer rims of the banks support the highest density of coral growth, probably due to the prevailing strong currents which provide greater feeding opportunities and which maintain bare substrate suitable for colonisation. Bank slopes may support a moderate density of coral cover to 60 m. Where conditions are less favourable for coral growth, reef-flats support the macro-algae assemblages dominated by the coralline alga Halimeda, which contributes between 10–60 per cent substrate cover.Deep-water benthic habitats (>300m) support a low-abundance epi-benthic macrofauna.