Using 4D Seismic Data to Understand Production-Related Changes in Enfield, NWS Australia

Smith, Megan M.; Gerhardt, Andre; Bourdon, Laurent; Mee, Benjamin

doi:10.1071/aseg2007ab137

Cited by 5 publications

(4 citation statements)

References 2 publications

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“…When such 3-D surveys are repeated over time, after subtraction from the original 3-D data, the difference is known variously as the repeat 3-D difference volume or the time-lapse 4-D image volume. This can show missed pay zones, and provided that seismic reflection data quality is high having signal-to-noise ratios of around 12:1 (Smith, 2007), it becomes possible to sense changes in oil and gas location, and pressure effects which allow improved production management and step-out production wells to be drilled (Smith et al, 2007). Consequently, oil and gas monitoring for production management over time has been demonstrated as assisting the resource management decision processes.…”

Section: Introductionmentioning

confidence: 99%

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Towards the e-field: Continuous Monitoring of Pore Fluid Phase using Horizontal Wells

Evans

Hartley²,

Keshavar

2009

SPE Middle East Oil and Gas Show and Conference

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The electric or e-field has been discussed at length in literature, in terms of the methodology of continuously remotely monitoring oil field production over a long term using vertical and horizontal wells, and transmitting data back to a monitoring centre. Conventional vertical well monitoring methods is adequate to monitor at points around an oil field but continuously monitoring where fluids are moving requires monitoring over an area using horizontal wells.Recent research has shown that seismic methods can show subtle changes in pore fluid phase which enhances the potential for long term monitoring where pore pressure is reducing, where injected water or CO 2 flood options have been chosen, and areas where gas is being replaced by water. If we can marry the use of slim-hole horizontal sensor cables with this recent demonstration of the detection of phase changes, then we have the tools for the first applied e-field scenario.During 2007, laboratory tests injecting different amounts of CO 2 into pore water showed that by monitoring the seismic transmission through a simulated rock, there was a change in seismic frequency response and transmission amplitude. Physical modeling has shown that a horizontal slim-hole well drilled to test the ability to put sensors in a horizontal well, can then be used for remote reservoir surveillance. A seismic source which walks around at the surface, produces data which is then processed to produce an indication that this method can be used as a first step for determining pore fluid properties over an area. This paper presents the results of the experiments on pore fluid phase and discusses how the use of horizontal wells allows the ability to develop the e-field concept towards reality.

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Section: Introductionmentioning

confidence: 99%

“…Enfield top reservoir 4-D difference map showing potential gas cap movement (afterSmith et al, 2007).…”

mentioning

confidence: 99%

Towards the e-field: Continuous Monitoring of Pore Fluid Phase using Horizontal Wells

Evans

Hartley²,

Keshavar

2009

SPE Middle East Oil and Gas Show and Conference

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“…To improve our understanding of the model we acquired an additional 3D swath (Monitor 2) over an injector ('Injector A') in the southern part of the field that was shut in at the time of the first monitor survey, but turned on 2 days before the acquisition of Monitor 2 (see Smith et al, 2007). The 4D difference between Monitor 2 and Monitor 1 is caused exclusively by a pressure increase of 1100 psi around the injector, as minimal saturation changes are likely to have occurred in the short time between the monitors except very close to the injector.…”

Section: Matching Model and Measured 4d Datamentioning

confidence: 99%

“…The field commenced oil production in July 2006 and a 4D seismic monitor survey was acquired in February 2007 (Ridsdill- Smith et al, 2007). A rock physics model was constructed both to support the acquisition of a monitor only 7 months after production start-up and to help quantify the interpretation of the monitor results after the survey was acquired and processed.…”

Section: Introductionmentioning

confidence: 99%

The role of rock physics for the Enfield 4D seismic monitoring project

Wulff

Gerhardt

Ridsdill-Smith

et al. 2008

Exploration Geophysics

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Abstract. The Enfield rock physics model was constructed to enable 4D feasibility studies and interpretation of the 2007 Enfield 4D seismic monitor survey. The rock physics model links reservoir static and dynamic parameters to impedances, using log data from five wells in the field, laboratory core measurements taken from cores on Enfield and neighbouring fields, and theoretical rock models from the literature. The reservoir is modelled by a sand-shale mix: sand properties are described using a modified critical porosity model whereas shale properties are generated from log data averaging. The dynamic properties in the model include saturation and pressure. Saturation is modelled using Gassmann's formula assuming homogeneous mixing. The reservoir sand velocity-pressure relationship is described by an empirical model fitted to dry core plug measurements. An assessment of the effect of uncertainty is included for both the saturation and pressure elements of the model. The resultant rock physics model was used before the acquisition of the seismic monitor survey to assess the likelihood of detecting a 4D seismic signal only 7 months after production start-up. Our modelling results indicate that the strong pressure build-up around the water injectors would result in a detectable 4D seismic signal and this prediction is confirmed by the successful 4D seismic monitor data acquired in 2007. The rock physics model has been validated against the 4D monitor data and is being used to quantify the 4D interpretation, linking the observed 4D response back to predicted pressure and saturations changes in the field.

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