Continued investment in new technologies used to interpret hydrocarbon-bearing rock structures is a crucial factor in maximising recovery of the UKs remaining offshore resource of up to 24 billion barrels of oil equivalent (boe).
With industry tackling ever deeper and more complex reservoirs, the challenge of extracting commercial amounts of oil and gas is growing all the time. Major innovations are being developed in advanced seismic imaging technologies to enhance understanding of reservoir structures and to more accurately target reservoirs with commercial potential.
Seismic surveys are one of several geophysical methods used to provide information about oil and gasbearing structures. In offshore areas a ship usually tows a submerged airgun array, to produce short bursts of sound energy, and a set of streamers several kilometres in length. Each streamer contains a dense array of hydrophones, like microphones, that collect and pass to recorders sound echoes reflecting from the rock layers below. To improve reservoir identification it is important to develop the clearest possible images of the rock strata.
Wider frequency range and improved resolution
Conventional 3D data acquisition processes are being rapidly replaced by new broad bandwidth technology which enables seismic data to be recorded across a much wider spectrum of frequencies, from low frequency waves for deeper penetration of the subsurface to high frequencies generating higher resolution images.
As recently as June 2012, Schlumberger launched a new towed marine technology called IsoMetrix (see main image above). It records broad band seismic data using a new point-receiver multi-sensor streamer to produce a dense isometric grid of data (see image right). This will provide exceptionally detailed images of complex subsurface structures. The innovation has achieved a step change in imaging, which Steven Calthrop, Global Account Manager at WesternGeco Schlumberger, describes as “like the medical industry moving from a 2D X-ray to a 3D CAT scan”.
These improvements have been game changers, enabling operators to renew their banks of existing seismic data and dramatically improve their imaging and understanding of existing reservoirs, as well as creating possibilities to expand into new ones.
The technological advances go some way towards explaining why, despite the recent decline in exploration activity, the few exploration wells drilled in 2011 (Oil & Gas UK 2012 Economic Report) were relatively successful commercially and translated into a total discovered volume of 200 to 300 million boe.
Common Data Access Limited (CDA), the Oil & Gas UK subsidiary which administers the industrys Seismic DataStore (see image above), preserves seismic data for future reference and analysis and plays an important role in encouraging exploration. By making data acquired from seismic surveys more widely available to exploration companies on the UK continental shelf, CDA helps the industry to avoid duplication of work and reduces the cost of exploring for new oil and gas reserves.
While in the past certain exploration areas may have posed technical, financial and geophysical challenges, the high quality seismic data now available helps operators seeking to maximise recovery to focus on drilling activities where they believe that the best returns lie.