Chris Christie, 5th January 2009
TWO initiatives that could help produce maps of hydrocarbon location, and thus enable more accurate targeting of reservoirs, were launched at the end of June, having been submitted to a call for proposals issued in 2007.
“Joint 3D inversion of full-wavefield P, S and CSEM data” is being undertaken by researchers at Imperial College, London, and Aberdeen company OHM (Offshore Hydrocarbon Mapping).
The call for proposals was the result of a discussion process involving not only ITF and its members, but also the UK’s Government-industry initiative, PILOT, and Oil & gas UK. It invited R&D proposals that focused on the use of advanced imaging technologies and their processing to improve the industry’s ability to target reserves.
A number of surveying techniques are used for oil&gas exploration, of which seismic is the most broadly applied. Non-seismic survey methods in use include gravity and electromagnetic (EM)-based techniques.
Poxon: “Our discussion process highlighted that ultimate capability of survey techniques comes from their integration, and the greatest gain is considered to be when seismic and EM technologies can be combined, leading to a greater understanding of subsurface properties and helping to de-risk the exploration process. This will pose a significant challenge, but given that, historically, a high percentage of wells drilled are dry, helping to reduce this percentage and the associated expenditure is a valuable prize for the industry.”
Seismic uses the reflection characteristics of acoustic signals from different surfaces to identify structures where hydrocarbons might be present. It offers the possibility of good spatial resolution and defines geological structure accurately, but struggles to provide information about pore fluids or permeability.
In contrast, controlled-source electromagnetic techniques (CSEM) measure the resistive properties of subsurface structures, which relates strongly to hydrocarbon content and to the interconnectivity of pore space. Both CSEM and seismic techniques produce vast quantities of data, the analysis of which involves a complex computing process called inversion. In general terms, the data from different data sets is inverted separately and the results are brought together to identify areas where there is a likelihood that hydrocarbons are present.
The OHM/Imperial project is taking the approach of combining the different data outputs and inverting them jointly, and this joint inversion is the key to mapping the location of hydrocarbon reserves with an accuracy that is not currently possible.
Poxon added: “One of the really exciting things about this potentially game-changing project is that it brings together the complementary expertise of Professor Mike Warner at Imperial College – who is pushing forward the boundaries of the underpinning science in this area – with OHM, which has been at the forefront of developing and applying CSEM technology since its spin-out from Southampton University in 2002.”
However, just a few months since project initiation, OHM is in discussions that could lead to a possible takeover. This is due to trading difficulties.