New ideas in geophysical technology
Permanent Reservoir Monitoring - it's time has come!
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FEATURED SPEAKERS
Martyn Millwood Hargrave
» Chief Executive Officer
» Ikon Science
Full Agenda
Wednesday, March 21, 2012
London
The Geological Society
Our March 21st Forum covered a range of exciting new innovations, from 'broadband' 3D offshore to the introduction of ideas from medical imaging into interpretation.
However, the clearest theme to emerge was that PRM - Permanent Reservoir Monitoring - is absolutely key to understanding the dynamics of oil and gas reservoirs. Some key points are:
- interpretation of time-lapse/4D seismic is currently 'phenomenological' that is, we see changes over time that seem to be linked to production but we don't understand the rocks well enough to say why or how.
- new reservoir engineering observations can only be understood if rocks contain aligned micro-cracks and fractures, at high densities, dilating and expanding as reservoir pressures alter, and capable of rapid change.
- P wave reflectivity poorly characterises such rocks; shear waves (and P wave velocities) do a much better job: this leads to the conclusion that geophysical reservoir monitoring requires 3 component, and frequent, measurement.
- fibre optics have great potential for PRM systems.
One might say PRM = Proper Reservoir Monitoring!
David Bamford is well known around the oil & gas industry both as an explorer and a geophysicist. He holds a Physics degree from the University of Bristol and a Ph.D in Geological Sciences from the University of Birmingham.
Since 2004, he has been a non-executive director at Tullow Oil plc, being recruited for this position especially for his exploration knowledge. He serves on the Nominations and Remuneration Committees, and was chairman of the latter, and Senior Independent Director, for 3 years prior to his retire from the board at the end of April 2014.
He was on the board of Premier Oil from May 2014 to May 2016.
He retired from BP plc in 2003, his last four positions being Chief Geophysicist (1990-1995), Business Unit Leader (General Manager) for first West Africa and then Norway (1995-1999), and finally Head of Exploration until 2003.
He has served on the boards of Paras Ltd, a small exploration and IS/IT consulting company in which he held 22% equity, until its sale to RPS Energy in 2008 and Welltec a/s, a Danish well engineering company, as the nominee of the private equity investor Riverside. From 2012 to 201 he was on the board of ASX-quoted Australia Oriental Energy as a non-executive director.
He was a founder of Richmond Energy Partners, a small oil & gas research house, and several media companies that focus on the oil & gas sector, and has served as an advisor to Alliance Bernstein, Opus Executive, the Parkmead Group plc, and Kimmeridge Energy LLP. Since retiring from BP, he has undertaken asset and company valuation projects for investment banks, hedge funds and small oil companies.
New Eyes Exploration New Eyes Exploration, founded by David Bamford, explores new ways to discover Oil and Gas. More... | |
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Martyn founded Ikon Science in 2001. He has over 30 years experience in new ventures and technology application in the oil and gas industry, working in International Geoscience and commercial roles for GSI Inc, Candecca Resources plc, Hardy Oil and Gas, Jebco Inc, Acre Oil plc and BG Plc. Prior to IKON Science, he was Managing Director of IKODA Ltd and built the company from a start up to one of the largest independent upstream consulting groups dealing with some of the highest profile upstream deals over the past decade including the North Caspian PSA negotiations and awards to the OKIOC consortium and related deals including a half billion dollar disposal of these assets.
He has a long term interest in the public role of Geoscience and has provided this expertise on the board of a number of Industry R&D "think tanks" such as the Petroleum Science and Technology institute (PSTI) and Centre for Marine and Petroleum Technology (CMPT). He is currently a member of the CeREES Geo-Energy board of Durham University. He has been a founding shareholder or director of a number of oil companies including the Africa focused AIM listed Fusion Oil and Gas plc, Virgo Energy plc a private oil and gas explorer sold to Encore oil plc in 2006 and Ophir Energy Plc.
Martyn earned an Honours degree in Geology from Durham University UK and a post graduate qualification in Geophysics from Queen Mary College University of London. He is an active member of the Society of Exploration Geophysicists, Institute of Petroleum, and the Petroleum Exploration Society of Great Britain.
Ikon Science Ikon Science is a global geoprediction technology company providing industry leadership in the predi More... | |
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Talk Description Seismic vessels have essentially operated in the same manner for the past sixty years. The principles of an acoustic source and hydrophone receivers have remained the same. Sensors have been placed on the seabed, in cables or nodes, but the majority of all marine seismic remains by towed streamer. Unfortunately the data quality is affected by the ghost - the result of an almost perfect reflection of the acoustic wavefield from the sea surface. Up-going waves are reflected back as down-going waves with a reversed polarity, and interfere constructively for certain frequencies and destructively for other frequencies. This phenomenon occurs both on the source side and on the receiver side and the affected frequencies depend solely on source and receiver tow depths. In 2007 PGS launched a dual-sensor streamer and broadband seismic became reality. The ability to separate the up-going and down-going wavefields is set to revolutionise the quality of marine seismic. In 2011 PGS took the next step and developed a ghost free source. Removal of both acquisition effects provides a broader bandwidth with improved noise characteristics ideal for accurate imaging and reservoir property analysis.
In this presentation we will review the enabling technologies, but mainly concentrate on the value of the resulting data for exploration and production. Improved imaging results from better penetration. Reservoir delineation and geobodies detection are improved due to increased signal to noise ratios and broader bandwidth. The broadening of the low frequencies represents a key improvement for lithology and fluid prediction and seismic reservoir property estimation. The need for a-priori information is considerably reduced by relying more on the data and less on a low frequency background model. As we will demonstrate, increased reliability on the data also delivers increased confidence in the resulting estimated properties and leads to reduced risk.
In concluding, we will also look ahead to future developments – use of the separated wavefields and also a towed streamer for electromagnetics. |
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Talk Description Observing reservoir dynamics
1. When a reservoir, any reservoir, is put under production, fluid compositions change, for example oil may be partially replaced by water or gas, gas may be expelled from oil, and so on. However, what is also well-documented and of significance is the fact that fluid pressures drop, changing the ‘internal stresses’ on the reservoir rock. Tempting as it may be, however, it is not possible to understand the (time-varying) geophysics of reservoir rocks by theorising an isotropic pore space responding to fluid changes and changing ‘internal stress’…………
2. Several studies have shown that the hydraulic conductivities of faults and fractures in reservoirs can be influenced by geomechanical perturbations due to production operations and it is reasonable to anticipate that such dynamic permeabilities will be manifest as changes in flow-rates at production and injection wells. Heffer & co-workers (Edinburgh University) have shown that statistical correlations in flow-rate fluctuations between wells from fields in the North Sea appear to bear out this expectation; they are characterised by high correlations over very large separation distances between wells, and appear to be stress-related and fault related. Heffer has proposed that the most likely geomechanical mechanism to explain such orientational characteristics of correlations relative to stress state is dilatation or compaction of aligned compliant fractures in en echelon patterns and at critical densities, also previously proposed by others as active in the nucleation of shear failure. This mechanism is also consistent with an independent empirical feature of production data: the observed frequencies of directionalities in flooding schemes.
3. These reservoir engineering observations lead to the conclusion that time-lapse geophysics - any observations of any reservoirs over time - must be based on the understanding of the physics of fluid-filled, parallel, compliant, fractures/micro-cracks – dilating or compacting as the reservoir is produced. This physics, this New Geophysics, has been documented over many years by Crampin, based on understanding and observing the effects of closely-spaced stress-aligned fluid-saturated microcracks on seismic shear-wave splitting (SWS) in the crust and upper mantle. Critically, seismic observations of P-wave propagation and P-waves are relatively insensitive to fluid-saturated microcracks, whereas SWS is wholly determined by parallel microcracks and can be measured with first-order accuracy. Thus SWS is a second-order quantity (small changes in shear-wave velocities) that can be read with first-order accuracy- thus there is tremendous resolution.
4. Consequently, there are significant implications for geophysical, especially seismic, monitoring of reservoir dynamics: • First of all, we can say that conventional 4D seismics – towed streamer surveys for example – only discern changes in P-wave reflectivity and thus offer at best an incomplete view of reservoir dynamics, one that is unquantifiable, allowing only empirical comparisons, • Secondly, a complete, quantifiable, view of reservoir dynamics requires 3C seismic acquisition (and strengthens the case for permanent installations). • Thirdly, changes in stress can be monitored by changes in SWS so that stress-accumulation before fractures in reservoirs (and earthquakes and volcanic eruptions) can stress-forecast the time, magnitude, and estimate location of impending fractures (and earthquakes and eruptions). |
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Talk Description In this age of increasing oil demand and reducing reserves, great importance is being attached to techniques to increase reservoir yield. An important element in this is a better understanding of the location and movement of oil and other fluids within the reservoir, and one of the key future tools will be seismic imaging of the reservoir through Permanent Reservoir Monitoring (PRM) using networks of seismic sensors installed on the seabed above the reservoir. This application, which is becoming increasingly widely adopted, makes great demands on the reliability and stability of the sensors over an operating lifetime which can be in excess of 20 years. Other important factors are the ability to safely install such systems in water depths of up to 3,000m. We describe the Stingray approach to PRM, which involves the use of fully fibre-optic sensors. These are robust, simple, electrically passive sensors which require no underwater electronics, and are combined together using a highly efficient multiplexing architecture. This architecture means that large numbers of sensors can be combined together using a small number of optical fibres, so minimising cable and connector requirements. We describe how we have optimised this architecture to maximise reliability, and we describe how sensor stability has been achieved through a combination of careful mechanical design and rigorous qualification. Finally we explain how system deployment techniques have been optimised to minimise cost and risk during the installation phase. All these attributes combine to ensure that the full value of PRM is recognised throughout the operating lifetime of the field. |
Phil Nash, Chief Scientist of Stingray Geophysical, a TGS Company, has 25 years’ experience of fibre-optic sensor development, beginning with deployment in 1986 of the world’s first seabed optical hydrophone array while working for Marconi. He later held various positions in UK defence research laboratories and QinetiQ, where he pioneered the use of fibre-optic acoustic technology for non-defence applications such as seabed seismic. He has published over 35 papers and authored 15 patents. He currently has overall responsibility for the core “listening with light®” technology used in Stingray PRM systems. He has a BSc in Physics from Imperial College, London and is a Fellow of the Institute of Physics.
Stingray Geophysical Ltd Stingray Geophysical, a TGS Company, provides advanced Permanent Reservoir Monitoring (PRM) solution More... | |
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Gaynor has a PhD in Neurophysiology and therefore brings a unique approach to arriving at solutions in volumetric seismic interpretation. She has spent over a decade with ffA, been involved in over 300 seismic interpretation projects and has unparalleled expertise in applying image processing techniques to answer some of the most challenging interpretation enigmas. During this time, Gaynor has been instrumental in developing geology driven workflows so that the software produced by ffA is both intuitive and effective. In her current role as Director of Geoscience Operations, Gaynor oversees the Services division of the company and guides the development of new leading edge Geological Expression workflows to accelerate progress in global Exploration and Production, as well as to keep ffA at the forefront of innovation.
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