Seismic on demand for BP’s born-again Valhall field
  from: Offshore Engineer
  by: Andrew McBarnet
  Friday, July 11, 2003

BP is scoring a world first with its decision to install a permanent 4D seismic cable acquisition system on its Valhall field, offshore Norway. Details of the so called Life of Field Seismic (LoFS) project were released at the EAGE annual gathering in Stavanger last month and immediately became the show’s hottest topic. OE seismics editor Andrew McBarnet reports on this and other highlights at Europe’s premier event for the geoscience community.

In crude terms, BP with partners Amerada Hess, Shell and Total are now looking forward to the field, currently producing at around 80,000 b/d, continuing in production until at least 2028. At the beginning of this year Valhall had produced 471 million stb of oil, on the way to a newly set target of 1050 million stb of oil by 2028, and who knows, maybe more.

Arguably the most keenly anticipated technology being deployed on Valhall is the NKr350 million LoFS permanent 4D seismic installation, details of which were made known at last month’s European Association of Geoscientists and Engineers (EAGE) annual conference and exhibition in Stavanger. For a hard-pressed geophysical services industry scrambling to survive shrinking demand for traditional seismic survey work, LoFS offers the prospect of an emerging reservoir management market in which BP has been something of a pioneer.

The company began experimenting with permanent 4D seismic in the late 1990s on the Foinaven field, west of Shetland. On Valhall, BP intends to bury in the seabed more than 120km of specially developed multi-component seismic cable covering 35km2 around the producing reservoirs. Cable trenching operations by Halliburton company Subsea 7 began early last month and were expected to last seven weeks, in time for the first data acquisition programme in late August. The cable array design comes from OYO Geospace, following a two year R&D programme, and is made up of thousands of four component sensors (three geophones and one hydrophone) embedded in the cable. This configuration is vital. Hydrophones, used in conventional marine seismic towed streamer applications, only measure the pressure (p) waves of reflected seismic. The addition of geophones, effective on the seabed or on land, can measure shear (s) waves. In this case the s-waves should allow BP to ‘see’ through the Valhall gas cap, which would otherwise be a serious obstruction to seismic imaging.

The network of cables being laid will be connected by an umbilical to the main Valhall platform facility. From there, the seismic data acquired during shooting over the reservoir, as much as seven terabytes, will be transferred by fibre optic cable to shore for processing by Petroleum Geo-Services (PGS) based in BP’s offices in Stavanger but making use of its major processing centres in Oslo and Houston.

BP says that the application of LoFS on Valhall could mean an increase in production of as much as 60 million barrels. The expectation comes from the perceived benefits of repeated 3D seismic imaging over the same location, if the surveys can be accurately repeated. BP is planning six surveys over 18 months, which is probably over-cooking the egg, but the company is understandably keen to see if the system works. It means, for example, that PGS will have to deliver processed data in 30-60 days, the quick turnaround providing BP with a totally new form of near real-time reservoir management.

Success of what is being called ‘seismic on demand’ will be measured by whether the company’s multi-disciplinary teams onshore can quickly discern changes in the behaviour of the Valhall reservoir, particularly the movement of hydrocarbon fluids, by comparing images from the different seismic surveys carried out over time. In the best scenario, the data will point the way to better informed reservoir production decisions, not to mention fewer dry holes. Although at this stage uncertain of the outcome of its investment in LoFS, BP is hoping that it will be able to apply the technology to other fields, either already in production or from the word go to a new field development. The industry as a whole will be watching closely, because the potential upside is huge in terms of increased output from existing reservoirs.

From a technical standpoint, the key to LoFS and, for that matter, all 3D time-lapse (4D) operations is repeatability. Operators need to be sure that the conditions of each survey are as similar as possible. By permanently burying the seismic recording equipment, a major element of the positioning equation is removed compared with a towed streamer repeat survey operation where wind, tide, and survey geometry all complicate precise repetition. The main concern about buried cable is the durability of the sensor recording equipment over time, which is why OYO Geospace has built considerable redundancy into the system.

This leaves the accurate shooting of each survey as the main variable and potential headache for the LoFS technology. With no towed streamers to worry about, BP intends to use a suitably equipped standby vessel to shoot each survey on the Valhall field. It is contracting Scottish company Concept Systems, an acknowledged expert in seismic navigation and positioning, to come up with a fast-track solution to the problem of positioning, QC control and data management to ensure that the shooting of each survey is the same.

A complication is that the amount of data generated by multicomponent recording is much greater than conventional marine seismic, and data handling is more complex. Concept is expected to adapt its existing technology offerings, which have already been deployed in ocean bottom cable multi-component surveys where data management and operation control are issues (OE March 2000). BP is said to be looking for a high degree of automation to both improve repeatability and reduce costs.

The full list of BP’s technology partners on the LoFS project also includes Bolt (generation of seismic sources), Facilium (project engineering, procurement and management services), Fugro (vessel and source positioning), Input/Ouput (digital source control system), Rovde (vessel provider and marine operator), and Westland Projects (source handling and vessel engineering).

Ottesen took no hostages in pointing out, among other things, that the industry’s human capital is ageing and not being replaced, that R&D spending in the industry has got completely out of whack, and that attempts to ‘commoditize’ advanced technology will be selfdefeating.

The facts of life were, according to Ottesen, that 96% of the world population increase now occurs in the developing regions of Africa, Asia and Latin America, and this percentage will rise over the next 25 years. Over the same 25 years, the world’s population of people aged 65 and older will more than double. ‘Since the early 1980s the number of people employed in our industry has fallen by 50%’ he said, ‘and it continues to fall. And we still struggle with recruitment!’

The kicker, in his view, was that the average age of the industry’s workforce is advancing each year. In the mid-80s the average age of G&G personnel was 32, today it is 50. To replenish the world’s energy resources over the next 25 years, Ottesen said that industry will have to replenish and diversify its human resources by recruiting from the growing young populations of developing countries where, by 2025, the average age will be 30 compared with 45 in developed countries.

The last 10 years have also seen a major shift in R&D spending. Operators have dropped their spend by nearly $2 billion over the last decade while service companies have more than doubled their investment in R&D over the same time period. Ten years ago the total was nearly $4 billion, today it is less then $3 billion. If the trend continues, Ottesen predicted that service companies may soon own 50% of the combined R&D investment dollars and the total may well fall short of what the world will need to support its growing energy needs.

Nor is investment in advanced technology a guarantee of success. Ottesen noted that the return on 3D seismic technology fell far below expectations to the point where companies could no longer afford to stay in business. Maybe capacity was overbuilt in a very capital-intensive business, he admitted, and maybe the technology was applied when it didn’t provide incremental value. But this did not excuse the trend set by oil companies out to cut their short-term cost at the expense of the long-term value of 3D seismic. Ottesen said they had contributed in a major way to the current dire state of the seismic marketplace.

He also expressed alarm at a similar drive in the industry to commoditize all elements of oilfield services without regard to the value new technology and innovative processes will deliver. Lower prices are easy for most of us to understand, he said, as should be the value of performance and innovation. ‘All sorts of methods are being applied to price, but none to value: the reverse auction is the most recent method, the primary effect of which is to lower price on all deliverables regardless of value . . . It is easy to measure the size of the invoice for any given well, what is much more difficult is to assess the value the well ultimately produces. Today’s short-term focus comes with the assumption that the long term will take care of itself. Believe me, it will not.’

For service companies to survive under the commodity scenario, their focus will naturally shift from creating value through new technology for their customers to efficient delivery of low cost, baseline technology faster and more efficiently. Ottesen warned that the majority of the remaining oil reserves, especially in mature markets like the United States and the North Sea, could not be recovered efficiently using today’s baseline technology.

If the industry continued to commoditize new technology and ignore the value it adds, Ottesen said there will be no more success stories like Troll, which would not have happened had the market environment and procurement methodology of today existed back in the mid-90s.

‘Producers are expecting increased recovery and the service industry can help achieve it,’ he concluded, ‘but it will require cooperation and focus on the creation of value.’ Without this, even Norway will realize significantly less then the NKr2000 billion it is hoping for in future revenues, and the majority of hydrocarbons will stay in the ground. OE