Mark Riding
Schlumberger
Deepwater has quickly evolved from a challenge into an opportunity. The technical limits that constrained deepwater drilling and development have been pushed back. To be sure, the deepwater arena is not for the faint of heart or the underfinanced. Significant challenges exist, and the time-gap between discovery and production remains quite lengthy. The sheer size of the required investment, time to payout, and longevity has deterred some from taking the plunge. However, the majority are re-evaluating their position and asking "How can we add an element of deepwater to our exploration and production reserve portfolio?"
The well-known hot-spots include the Gulf of Mexico, Brazil, and West Africa. There, phases of exploration have given way to project development, and deepwater activity is high and growing. Thanks to greatly improved technology and data processing, exploration risk is subsiding. Tremendous breakthroughs have been made in imaging beneath salt and basalt to uncover thick, extensive potential reservoir structures. Exploratory wells have penetrated pays containing billions of barrels of producible reserves. Both drilling and production depth records have been set in the GoM, and success rates there have transcended the traditional dry-hole ratios of the past.
With success comes enthusiasm. Promising deepwater areas span the globe. Locales like offshore Madagascar, the Horn of Africa, Greenland, the Atlantic Margin, and south of the Arabian Peninsula, as well as two new areas offshore Brazil have been designated as "emerging markets" — ripe targets for the drill bit.
Several promising frontier areas have been identified that could keep the industry busy for many years to come, such as offshore Eastern Canada and New England, USA, and the Canadian Arctic. In the Eastern Hemisphere are the far offshore reaches of the Barents Sea and the Norwegian Sea. Farther south are areas in the Eastern Mediterranean, notably Israel, where Noble Energy has discovered gas in 5,000 ft (1,524 m) of water, and offshore Morocco and Western Sahara. The East Coast of Africa acknowledges possible areas in the South Somali basin, and the Far East has several deepwater frontier areas stretching from the Bay of Bengal to the South China Sea and offshore Northeast Kalimantan. Rounding up the world tour is the Northwest Australia and Timor basins.
As recently as 2007, ultra deepwater drilling rig availability was a constraint, with fleet utilization steady at 100%, and day rates soaring above $600,000 for high-specification drilling units. Even today, deepwater rigs are fully contracted before they leave the shipyard, many even before their keels are laid. A quick census as of January 2010 identifies 41 deepwater floaters with capabilities between 4,500 ft (1,372 m) and 7,500 ft (2,286 m) of water, 42 ultra deepwater units with capabilities between 7,500 ft and 12,000 ft (3,658 m) of water, and nine in the shipyard. Of the ultra deepwater bracket, four rigs are rated to 12,000 ft of water, as are two of the nine rigs still under construction.
Technology has come to the rescue recently to ease the demand for deepwater drilling units slightly. For example, Shell is developing its BC-10 project offshore Brazil using a 2D generation semisubmersible rig with a dry stack. The ability, in some cases, to get more performance out of earlier generation drilling units has relieved the strain on the deepwater fleet to a certain extent.
Deepwater provides some fairly daunting challenges. As if the water depth were not enough, reservoirs are often buried under thick layers of salt that make obtaining definitive answers from seismic prospecting problematic. The presence of carbonate rocks, thin beds/laminations, and turbidities can create additional reservoir characterization challenges. However, a combination of acquisition and processing technologies has improved our ability to image these deep set structures.
Drilling is a challenge as well. Penetrating thousands of feet of salt is difficult under the best of conditions. But many ultra deepwater wells have either reservoirs or shallow hazards located only one or two thousand feet below the mud line. These formations are characterized by a very narrow margin of safety between the pore pressure gradient and the fracture pressure gradient. Drillers must walk a virtual tightrope between losing circulation and risking a blowout. Once again, technology has provided a solution, giving the ability to maintain dynamic equivalent circulating density (ECD) and to monitor it in real time.
Once industry has drilled the salt and the shallow unconsolidated strata just beneath the mudline, there is a further challenge to drill precisely to tap the ultra-deep buried targets in areas like the GoM's Lower Tertiary Trend. With total well depths approaching 40,000 ft (12,192 m), the challenges of ultra-high hydrostatic pressure loom. These conditions stress logging instruments to their limit. But the industry is working to meet the harsh environment challenges with more HP/HT-rated equipment; wireline-conveyed and logging-while-drilling-conveyed. Thanks to numerous extended-reach-drilling (ERD) experiences, ultra-deep high-bandwidth mud-pulse telemetry capability has been certified to at least 42,000 ft (12,802 m). This provides both geosteering control capability and real-time log data transmission to the surface.
Deepwater production is particularly susceptible to flow assurance issues which govern the success of the fluid journey from reservoir to point of sale. Understanding the reservoir fluid helps to ensure that any development plan—from exploration through abandonment—is technically viable and designed for optimal long-term operations throughout the field's life. Measurement technology exists to identify both the production fluid's multiphase flow rate as well as its propensity to precipitate wax, hydrates, asphaltenes, or scale. And advanced technology, be it production chemistry, production engineering, production operations, or flow assurances helps operators mitigate these depositions so they can flow their wells freely.
No industry rises to challenges like the oil and gas industry. It has been ever thus, and will continue to be. Man's conquest of the deep is analogous to the conquest of space. Time, technology, and the right people will ultimately win the day.
This page reflects viewpoints on the political, economic, cultural, technological, and environmental issues that shape the future of the petroleum industry. Offshore Magazine invites you to share your thoughts. Email your Beyond the Horizon manuscript to Eldon Ball at [email protected].More Offshore Issue Articles
Offshore Articles Archives
View Oil and Gas Articles on PennEnergy.com
