Source array design to attenuate multiples in a hardwater bottom area - conclusions from an experimental seismic survey carried out on the North-West shelf of Australia

The newly acquired 3,590 km2 Demeter 3D high resolution seismic survey covers most of the North West Shelf Venture (NWSV) area; a prolific hydrocarbon province with ultimate recoverable reserves of greater than 30 Tcf gas and 1.5 billion bbls of oil and natural gas liquids. The exploration and development of this area has evolved in parallel with the advent of new technologies, maturing into the present phase of revitalised development and exploration based on the Demeter 3D.The NWSV is entering a period of growing gas market demand and infrastructure expansion, combined with a more diverse and mature supply portfolio of offshore fields. A sequence of satellite fields will require optimised development over the next 5–10 years, with a large number of wells to be drilled.The NWSV area is acknowledged to be a complex seismic environment that, until recently, was imaged by a patchwork of eight vintage (1981–98) 3D seismic surveys, each acquired with different parameters. With most of the clearly defined structural highs drilled, exploration success in recent years has been modest. This is due primarily to severe seismic multiple contamination masking the more subtle and deeper exploration prospects. The poor quality and low resolution of vintage seismic data has also impeded reservoir characterisation and sub-surface modelling. These sub-surface uncertainties, together with the large planned expenditure associated with forthcoming development, justified the need for the Demeter leading edge 3D seismic acquisition and processing techniques to underpin field development planning and reserves evaluations.The objective of the Demeter 3D survey was to re-image the NWSV area with a single acquisition and processing sequence to reduce multiple contamination and improve imaging of intra-reservoir architecture. Single source (133 nominal fold), shallow solid streamer acquisition combined with five stages of demultiple and detailed velocity analysis are considered key components of Demeter.The final Demeter volumes were delivered early 2005 and already some benefits of the higher resolution data have been realised, exemplified in the following:Successful drilling of development wells on the Wanaea, Lambert and Hermes oil fields and identification of further opportunities on Wanaea-Cossack and Lambert- Hermes;Dramatic improvements in seismic data quality observed at the giant Perseus gas field helping define seven development well locations;Considerably improved definition of fluvial channel architecture in the south of the Goodwyn gas field allowing for improved well placement and understanding of reservoir distribution;Identification of new exploration prospects and reevaluation of the existing prospect portfolio. Although the Demeter data set has given significant bandwidth needed for this revitalised phase of exploration and development, there remain areas that still suffer from poor seismic imaging, providing challenges for the future application of new technologies.

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Exploration success on the North West Shelf via continuous application of seismic technologies

The APPEA Journal ◽

10.1071/aj08013 ◽

2009 ◽

Vol 49 (1) ◽

pp. 205

Author(s):

Mark Thompson ◽

M Royd Bussell ◽

Michael Wilkins ◽

Dave Tapley ◽

Jenny Auckland

Keyword(s):

Seismic Imaging ◽

Leading Edge ◽

Seismic Survey ◽

Water Contact ◽

North West ◽

Depth Migration ◽

Petroleum Systems ◽

The North ◽

Continuous Application ◽

Near Term

Expansion of the North West Shelf Venture (NWSV) production infrastructure is driving plans for sequential development of the small satellite fields. The desire for additional gas reserves has fuelled increased exploration and appraisal drilling in recent years with encouraging results. The NWSV area is a complex geologic environment with multiple play levels, petroleum systems and trapping styles. Seismic imaging is poor in many areas, primarily due to multiple contamination. In 2004, the NWSV acquired the leading edge, regional Demeter 3D Seismic Survey. Since then, continuous application of improved processing techniques, such as 3D Surface-related Multiple Elimination (SRME) and Pre-Stack Depth Migration (PreSDM), have been key to providing significant imaging enhancements. Exploration drilling based on Demeter data resulted in three significant new gas discoveries. Pemberton–1 (2006) explored Triassic sub-cropping sands in a horst block at the southwestern end of the Rankin Trend. The well encountered an upside gas column due to the presence of intra-Mungaroo Formation shales providing a base-seal trapping geometry. Lady Nora–1 (2007) tested the fault block west of the Pemberton horst and encountered a 102 m gross gas column with gas on rock. The upside result accelerated a near term appraisal opportunity at Lady Nora–2 (2008). Persephone–1 (2006) drilled a down-thrown Legendre Formation dip closure in the Eaglehawk graben. Success relied on the sealing potential of the North Rankin Field bounding fault. In spite of pressure depletion associated with over 20 years of production, Persephone–1 encountered a 151 m gross gas column at virgin pressures and a different gas-water contact to North Rankin. The result demonstrated active and significant fault seal along the major North Rankin Field bounding fault. These recent, successful exploration wells have resulted in identification of follow-up drilling opportunities and a drive for ongoing seismic imaging improvements. The discoveries have material impacts on NWSV development plans for the Greater Western Flank and in the vicinity of the Perseus, North Rankin and Goodwyn gas fields.

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THE STAG OILFIELD

The APPEA Journal ◽

10.1071/aj95008 ◽

1996 ◽

Vol 36 (1) ◽

pp. 130 ◽

Cited By ~ 1

Author(s):

J. Crowley ◽

E.S. Collins

Keyword(s):

Water Saturation ◽

Vertical Section ◽

Far East ◽

Total Porosity ◽

Analysis Data ◽

Effective Porosity ◽

Seismic Survey ◽

North West ◽

The North ◽

Southeastern Margin

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.

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DEVELOPMENT OF THE NORTH RANKIN FIELD, NORTH WEST SHELF, AUSTRALIA

The APPEA Journal ◽

10.1071/aj82017 ◽

1983 ◽

Vol 23 (1) ◽

pp. 164

Author(s):

M. David Agostini

Keyword(s):

Seismic Survey ◽

Process Equipment ◽

Two Phase ◽

Gas Field ◽

North West ◽

The North ◽

Christmas Trees ◽

High Level ◽

Inflow Performance ◽

Standard Steel

The North Rankin gas field discovered in 1971, has been evaluated by a series of appraisal wells and refinement of this is underway through the use of a 3D seismic survey. Extensive production testing on two wells was used to establish reservoir fluid characteristics, inflow performance and to predict reservoir behaviour.The North Rankin 'A' platform has been constructed of a standard steel jacket design. Components of the structure were built in Japan, Singapore, Geraldton, Jervoise Bay and Adelaide. Provision exists for 34 wells to be drilled from the structure to exploit the southern end of the North Rankin field.Simultaneous drilling and producing activities are planned, requiring well survey and deviation control techniques that will provide a high level of confidence. Wells will be completed using 7 inch tubing, fire resistant christmas trees, and are designed to be produced at about 87 MMSCFD on a continuous basis. Process equipment on this platform is designed to handle 1200 MMSCFD and is intended primarily to dry the gas and condensate and to transfer gas and liquid to shore in a two phase 40 inch pipeline. The maintenance of offshore equipment is being planned to maximise the ratio between planned and unplanned work.The commencement of drilling activities is planned for mid 1983, with commissioning of process equipment occurring in the second quarter of 198 The North Rankin 'A' platform will initially supply the WA market at some 400 MMSCFD offshore gas rate, requiring 7 wells. The start of LNG exports is planned for April 1987. The intial gas for this will be derived from the North Rankin 'A' platform.

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Improvements in development strategy for the Stag Oil Field, North West Shelf, Australia—implications for production success and drilling risk minimisation

The APPEA Journal ◽

10.1071/aj11071 ◽

2012 ◽

Vol 52 (2) ◽

pp. 657

Author(s):

Paul Anderson ◽

Paul Bingaman ◽

Sam Betts ◽

Kyle Graves ◽

Fred Fernandes ◽

...

Keyword(s):

Development Strategy ◽

Oil Field ◽

Seismic Survey ◽

Ocean Bottom ◽

Injection Wells ◽

Horizontal Drilling ◽

North West ◽

The North ◽

Avo Inversion ◽

Water Breakthrough

Located on the North West Shelf of Western Australia, the Stag Oil field has proven to be a prolific reservoir, having produced more than 55 million barrels (MMbbls) of oil since 1998. This has not been without its challenges, however; with premature water breakthrough from injection wells occuring in several wells, potentially stranding large volumes of oil in the ground. Using the multicomponent processing and joint amplitude-versus-offset (AVO) inversion of an ocean bottom cable (OBC) seismic survey acquired in late 2007, new light has been shed on the distribution of unswept oil. This data has led to the succesful drilling of six wells and a marked increase in field production. Additionally, the seismic data has also been used to minimise drilling risks by using seismic coherency to steer the well around potential problems with a significant impact on well costs due to reduction of wellbore problems associated with horizontal drilling in the Muderong shale. To date, four wells have been drilled using this technique, resulting in a significant decrease in non-productive time while drilling during the most recent drilling campaign, which has a significant impact upon the profitability of these late-stage development wells.

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The prospectivity of the Late Triassic intervals in the outboard Exmouth Plateau, Western Australia

The APPEA Journal ◽

10.1071/aj19173 ◽

2020 ◽

Vol 60 (2) ◽

pp. 742

Author(s):

Tom Paten

Keyword(s):

Seismic Survey ◽

Quality Data ◽

Late Triassic ◽

High Quality ◽

Exploration Process ◽

North West ◽

Exmouth Plateau ◽

The North ◽

Amplitude Versus Offset ◽

Northern Carnarvon Basin

The Exmouth Plateau is a deep-water plateau on the Australian continental margin underlain by 10–15 km of flat-lying, tilted and block-faulted Paleozoic–Mesozoic sedimentary rocks, which were deposited predominantly during periods of extension before continental break-up commenced in the middle Jurassic. The recent acquisition of the Mawson MC3D broadband seismic survey provides a modern, high-quality dataset located ~230 km to the north-west of Dampier, in the outboard Exmouth Plateau, in a relatively under-explored portion of the Northern Carnarvon Basin. The Late Triassic Mungaroo Formation is the primary reservoir target for the majority of the exploration in the Exmouth Plateau to date. A detailed investigation into the reservoir potential and prospectivity of the Mungaroo Formation is possible by utilising this modern dataset. The high-quality data presents a high-resolution view of the Rhaetian carbonate reef platforms and pinnacle reef complexes that are present within the Mawson survey footprint, revealing an under-explored play type within the region. The development of a detailed stratigraphic framework through the Late Triassic–Jurassic, combined with the use of attribute analyses and amplitude versus offset products can help de-risk identified prospects and highlight further prospectivity during the exploration process.

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Deep crustal structure of the North-West African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)

Tectonophysics ◽

10.1016/j.tecto.2015.06.019 ◽

2015 ◽

Vol 656 ◽

pp. 154-174 ◽

Cited By ~ 12

Author(s):

Y. Biari ◽

F. Klingelhoefer ◽

M. Sahabi ◽

D. Aslanian ◽

P. Schnurle ◽

...

Keyword(s):

Crustal Structure ◽

Seismic Data ◽

West African ◽

Seismic Survey ◽

Wide Angle ◽

North West ◽

Reflection Seismic ◽

The North ◽

Deep Crustal Structure

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IMPROVEMENTS IN SEISMIC IMAGING, IO JANSZ GAS FIELD NORTH WEST SHELF, AUSTRALIA

The APPEA Journal ◽

10.1071/aj05009 ◽

2006 ◽

Vol 46 (1) ◽

pp. 135

Author(s):

J. Hefti ◽

S. Dewing ◽

C. Jenkins ◽

A. Arnold ◽

B.E. Korn

Keyword(s):

Image Quality ◽

Processing Parameters ◽

Interdisciplinary Teams ◽

Seismic Survey ◽

Gas Field ◽

North West ◽

The North ◽

Seismic Acquisition ◽

History Of ◽

Close Cooperation

The Io Jansz gas field is situated in the Carnarvon Basin on the North West Shelf of Australia. It is Australia’s largest gas field, estimated to hold over 20 TCF of gas reserves and covering an area of over 2000 km2. Following a series of appraisal wells and a 3D seismic survey, this field is moving rapidly towards development. Image quality of the 3D provided significant uplift over existing 2D surveys in the area. Expectations for resolution and business targets have been met through careful planning and the provision of staged deliverables.Despite the exceptional data quality, a number of technical challenges were encountered that led to operational changes and adaptations by the project team. Source height statics and severe image distortion due to overburden are examples of some of the challenges addressed. Consideration of the exploration history of this field and its associated imaging gives insight into the improvements in image quality that can be realised by careful selection of acquisition and processing parameters, high levels of quality control (QC) and modern processing algorithms. The ultimate success of this project was achieved through close cooperation within interdisciplinary teams comprised of partner technical staff and the seismic acquisition and processing contractor.

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WANDOO—A NEW TREND

The APPEA Journal ◽

10.1071/aj93045 ◽

1994 ◽

Vol 34 (1) ◽

pp. 586

Author(s):

Ernie Delfos ◽

Malcolm Boardman

Keyword(s):

Oil And Gas ◽

Three Dimensional ◽

Lower Jurassic ◽

Source Rocks ◽

Seismic Survey ◽

Unconsolidated Sediments ◽

North West ◽

The North ◽

Initial Discovery ◽

A Minor

In June 1991 a flow of 4 560 barrels of 19° API oil per day, from a depth of 600 m, heralded the discovery of a new hydrocarbon trend along the eastern margin of the Dampier Sub-basin on the North West Shelf of Australia. Wandoo–1 recovered oil and gas from lower Cretaceous sands associated with the M.australis dinoflagellate zone (Barremian), and gas from lower Jurassic Aalenian sands.The main reservoir at Wandoo is the M. australis Sandstone Member of the Muderong Shale. This is interpreted to be a shelfal shoal sand deposited in a minor regression phase during the regional transgression of the Muderong Shale. This reservoir is split into two main lithotypes, a glauconitic subarkose to subarenite, and an overlying greensand. Oil and gas have been recovered from both units, which are considered contiguous for reservoir definition. General reservoir parameters are exceptional. Since the initial discovery a 3D seismic survey has been acquired and appraisal drilling has proven approximately 250 MMSTBOIP.The unusual features of the field necessitated innovative exploration techniques and the need for a strong appraisal program. These techniques included a six streamer, high resolution, three dimensional seismic survey and its associated processing; development of methods to recover and preserve core in extremely unconsolidated sediments; use of non destructive core analysis methods such as nuclear magnetic resonance; and petrophysical analysis that incorporates the resistivity suppression problems of glauconite. Without core a very pessimistic view would have been taken of the M. australis Sandstone reservoir.The Wandoo discovery is on an exciting new trend previously overlooked due to the shallowness of reservoirs, lack of locally recognised source rocks and the dominance of other oil and gas trends in the Dampier Sub-basin and Barrow Sub-basin to the south.

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DISCOVERY OF THE WANAEA AND COSSACK OIL FIELDS

The APPEA Journal ◽

10.1071/aj90003 ◽

1991 ◽

Vol 31 (1) ◽

pp. 22

Author(s):

A.N. Bint

Keyword(s):

Upper Jurassic ◽

Oil Field ◽

Oil Fields ◽

Seismic Survey ◽

Gas Oil ◽

Water Contact ◽

North West ◽

The North ◽

Reservoir Development ◽

Oil Water

Exploration of the Dampier Sub-basin on the North West Shelf of Australia commenced with a reconnaissance seismic survey in 1965. In 1969 Madeleine-1, the first well drilled on the Madeleine Trend, encountered water bearing Upper Jurassic sandstones. Following acquisition of a regional grid of modern seismic in 1985 and 1986, and comprehensive hydrocarbon habitat studies, the Wanaea and Cossack prospects were matured updip from Madeleine 1. They were proposed to have improved reservoir development and an oil charge.The Wanaea Oil Field was discovered in 1989 when Wanaea-1 encountered a gross oil column of 103 m in the Upper Jurassic Angel Formation. The well flowed 49° API oil at 5856 BPD (931 kL/d) with a gas-oil ratio of 1036 SCF/STB. Two appraisal wells were drilled in the field in 1990.The Cossack Oil Field was discovered in 1990 when Cossack-1 encountered a gross oil column of 54 m also in the Angel Formation. The oil-water contact is 18 m deeper than in Wanaea-1. Cossack-1 flowed 49° API oil at 7200 BPD (1145 kL/d) with a gas-oil ratio of 98 SCF/STB.The Angel Formation reservoir consists of mass flow sandstones interbedded with bioturbated siltstones. Sandstone porosities average 16 to 17 per cent for both the Wanaea and Cossack Fields. Permeabilities average about 300 mD at Wanaea and about 500 mD at Cossack.An extensive 3-D seismic survey was conducted over the Wanaea and Cossack Fields in 1990. Final reserves calculations await interpretation of this survey, but it is clear that the combined Wanaea and Cossack oil reserve is the largest outside Bass Strait.

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