Planning for Success - Acquiring Australia’s First 4D Time Lapse Survey over a Gas Field, Pluto Reservoir, North West Shelf

Fitzpatrick, Jeremy; Pemberton, George

doi:10.3997/2214-4609.201700806

Cited by 3 publications

(1 citation statement)

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“…Of note was the use of steerable sources to assist with repeatability and towing the streamers deep (20 m) to minimise noise. A discussion on the acquisition and the detailed pre-survey planning is given in Fitzpatrick and Pemberton (2017). The acquisition report (PGS 2016) will be available once the seismic data is released by the National Offshore Petroleum Titles Administrator (NOPTA).…”

Section: Acquisitionmentioning

confidence: 99%

Pluto 4D—Australia's first 4D over a gas field is an outstanding success

Tilbury¹,

Gerhardt²

2018

The APPEA Journal

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The Pluto 4D seismic survey is Australia’s first 4D survey acquired over a gas field and has been an outstanding success despite the prior high technical risk of not being able to detect 4D differences above the background noise. At the time of the Pluto 4D monitor survey, the Pluto field had been on production for three years and nine months and produced approximately 1 Tcf of gas. The first monitor survey was acquired by PGS between November 2015 and February 2016 using dual sources and 12 streamers of 7050 m (geostreamer configuration). Also of note was the use of steerable sources to assist with repeatability, and towing the streamers at 20 m to minimise noise. Data was processed by CGG to pre-stack depth migration (PreSDM), took 12 months to deliver and required significant interaction between Woodside geoscientists and CGG to ensure an excellent 4D product. 4D feasibility studies carried out before acquisition showed that saturation changes (related to water ingress) were expected to show strong 4D responses near the gas water contact (GWC) and would be interpretable if the monitor survey was run after approximately three to four years of production. If the monitor survey was delayed, it showed that the pressure response became too large, swamped the 4D differences and made interpretation difficult or impossible. Strong ‘hardening’ responses on the 4D difference volumes are interpreted as water ingress into the field. Hardening responses are seen in all reservoir sequences in the Triassic from the TR27 to the TR32 units and range from strong (obvious) to weak (possible). Several examples are shown – the strongest response is seen in the large Triassic (TR27.3) valley within an essentially shale prone unit, which shows water ingress into the valley and moving upwards from the GWC towards the producing well. The results/insights from the 4D data have provided excellent control points for the history matching of the Pluto Field.

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Section: Acquisitionmentioning

confidence: 99%

Pluto 4D—Australia's first 4D over a gas field is an outstanding success

Tilbury¹,

Gerhardt²

2018

The APPEA Journal

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Pluto gas field: Successful placement of an infill well based on 4D seismic monitoring

Peterson

Gerhardt

2020

The Leading Edge

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Seismic 4D monitoring technology has not been as widely employed for gas fields as it has for oil. Many gas fields rely on depletion drive, which has a 4D seismic response that can be uncertain and difficult to predict. On the other hand, aquifer-supported gas fields with measurable water ingress have a reasonable chance of success in terms of generating an interpretable 4D amplitude signal. Pluto gas field in the North West Shelf of Australia falls into this category. Following discovery in 2005, Pluto was appraised by five wells, which found a consistent gas gradient and gas-water contact across the entire field and its various reservoirs. Gas production began in 2012. Time-lapse seismic feasibility studies concluded that gas-saturation changes could be observed with a monitor seismic survey acquired three to four years after first gas. The Pluto 4D Monitor 1 survey was acquired at the start of 2016 and revealed both hardening and softening anomalies. Hardening is interpreted as water ingress (expected) and softening as gas expansion (unexpected). The Pluto 4D results provided important insights into reservoir connectivity and discontinuities. Large hardening anomalies at the TR27 (lower) level can be clearly seen in the data, showing avenues for water ingress. More importantly, a large softening anomaly below the original gas-water contact in the TR29 (upper) reservoir is interpreted to be gas expansion into the aquifer created by a U-tubing effect around a possible barrier in the gas leg. This suggests that the entire TR29 reservoir may not be accessed by the producing PLA04 well. Based on this 4D interpretation, the PLA07 well was drilled and completed in 2019 to produce the TR29 gas updip from the gas expansion anomaly and to increase Pluto field recovery.

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A Campaign of 4D Seismic Monitor Surveys on Australia's Northwest Shelf

Thomas

Harrowfield

Fitzpatrick

et al. 2020

SPE Asia Pacific Oil &Amp; Gas Conference and Exhibition

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We showcase an innovative campaigning and business-focused approach to reservoir monitoring of multiple fields using 4D (time-lapse) seismic. Benefits obtained in terms of cost, speed and the quality of insights gained are discussed, in comparison with a piecemeal approach. Challenges and lessons learned are described, with a view to this approach becoming more widely adopted and allowing 4D monitoring to be extended to smaller or more marginal fields. An offshore seismic acquisition campaign was planned and successfully executed for a sequence of four 4D monitor surveys for fields located within 250 km of each other on the greater Northwest Shelf of Australia. The four monitors were acquired in H1 2020 comprising (in this order): Pluto Gas Field M2 (second monitor), Brunello Gas Field M1 (first monitor), Laverda Oil Field M1 and Cimatti Oil Field M1. Cost savings expected from campaigning were realised, despite three cyclones during operations, with success largely attributed to detailed pre-survey planning. Also important were the choice of vessel and planning for operational flexibility. The baseline surveys were diverse and required careful planning to achieve repeatability between vintages over each field, and to optimise the acquisition sequence – minimising time required to reconfigure the streamer spreads between surveys. The Cimatti baseline survey was acquired using a dual-vessel operation; modelling, combined with now-standard steerable streamers, showed a single-vessel monitor survey was feasible. These optimisations provided cost savings incremental to the principal economy of sharing vessel mobilisation costs across the whole campaign. Both processing and evaluation (ongoing at the time of writing) are essentially separate per field, but follow a consistent approach. Processing is carried out by more than one contractor to debottleneck this phase, with products, including intermediate quality control (QC) volumes, delivered as pre-stack depth migrations. While full evaluation of the monitor surveys to static and dynamic reservoir model updates will continue beyond 2020, key initial reservoir insights are expected to emerge within days of processing completion, with some even earlier from QC volumes. Furthermore, concurrent 4D evaluations are expected to result in fruitful exchanges of ideas and technologies between fields.

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Planning for Success - Acquiring Australia’s First 4D Time Lapse Survey over a Gas Field, Pluto Reservoir, North West Shelf

Cited by 3 publications

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Pluto 4D—Australia's first 4D over a gas field is an outstanding success

Pluto 4D—Australia's first 4D over a gas field is an outstanding success

Pluto gas field: Successful placement of an infill well based on 4D seismic monitoring

A Campaign of 4D Seismic Monitor Surveys on Australia's Northwest Shelf

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