Drilling advances

	Vol. 224 No. 10
ROBERT E. SNYDER, EXECUTIVE ENGINEERING EDITOR

Rotary steerable slimhole system. Schlumberger Oilfield Services has signed a contract with Shell UK Ltd. and BP Exploration Operating Co. Ltd. to develop a rotary steerable system for slimhole drilling and through-tubing rotary drilling (TTRD) applications. It says that, with the push to maximize production from mature reservoirs where drilling targets are becoming smaller and smaller, it had to find a way of reducing drilling costs and sidetracking from an existing but obsolete well – TTRD is a good way of doing that.

 The new system will offer a step-change in the cost of drilling with rotary steerable technology when applied through tubing since there is no need to pull the completion string for redrills. The system is expected to reduce the cost of accessing infill-drilling targets and enable economic recovery of small pockets of trapped hydrocarbons in tough environments, such as existing fields in the North Sea. 

Schlumberger plans to develop and build the new system by 2005, using its experience with the PowerDrive Xtra 475 rotary steerable system for 6-in. holes, as was described in World Oil, November 22, 2002. 

Such systems have major implications in mature areas like the North Sea, where the trend is toward field life extension. Cost discipline is crucial on redrills designed to drain small pools. Drilling smaller holes as the primary size for infill sidetracks removes the cost of preparing the well by cutting and pulling the tubulars in place to accommodate a larger hole tool. The system will be developed and built at the Schlumberger Global Drilling Technology Center located in Stonehouse, Gloucestershire, UK.

DOE projects to advance drilling. To meet the increasing challenges of drilling for natural gas, the Department of Energy has selected two new projects to advance drilling performance. Managed by DOE’s Strategic Center for Natural Gas, the projects support the President’s National Energy Policy, which calls for boosting domestic production of gas to ensure an adequate future supply. 

For the two projects: MASI LLC, an M-I L.L.C./ActiSystems, Inc. JV, will conduct a two-phase project to determine how micro-bubbles called aphrons help seal permeable and fractured wellbore rock during drilling to minimize reservoir damage. An aphron is a uniquely structured micro-bubble of air or gas created by combining surfactants and polymers in drilling fluid. With damage to the gas reservoir minimized, drillers can use conventional drilling equipment to complete wells that previously would have required more expensive drilling methods. DOE says this two-year project has a total budget of $1,234,607, with DOE’s share at $568,845. Coincidently, this issue has a technical article on aphron-based fluid application, by M-I and NAM (see page 37).

In the second project, Terralog Technologies will undertake a comprehensive research project to advance basic understanding of physical mechanisms involved in combining percussion and rotary drilling. The combination provides significant improvement in penetration rates in hard-rock environments.

 However, the fundamental rock mechanics associated with percussion drilling have not been fully defined and adequately modeled. And there are no practical simulation tools available to help design and optimize such operations. Thus, cost and reliability concerns have limited the widespread application of percussion. By addressing these needs, the project will help recover untapped gas resources in deep, hard-rock environments. The two-year project has a total budget of $650,656. DOE’s share is $520,525.

Horizontal wells off Brazil. Denmark’s Maersk Olie og Gas AS, the only foreign oil major to take part in the first day of Brazil’s fifth annual oil round in August, said it hopes to drill long horizontal wells at its four offshore areas. For Brazil, it would be a new method, and the operator hopes it will increase productivity, especially on tight reservoirs. Maersk bought the rights for two shallow-water blocks in the Santos basin, one in partnership with Petrobras, which bought 70 of 83 oil blocks sold the first day. 

Maersk paid for the S-M-610 block, that it will develop on its own, and S-M-611, in which Petrobras has a 40% stake. The two blocks were adjacent to the one Maersk acquired in the previous sale. The geology there is similar to traditional areas in Denmark and Qatar, where Maersk routinely drills horizontal wells of about 4,000 m. The company is in the phase of geological studies in Brazil and presently has no drilling obligation.

Coal bed methane in Alaska. In Anchorage, a drilling experiment is tapping what development boosters say is a huge but neglected resource – methane gas from Alaska’s enormous coal reserves. Alaska reportedly has 40% more coal than the contiguous 48 states combined, and its coal beds could hold a staggering 1,000 Tcf of methane, enough to fuel the entire country for decades, according to the US Geological Survey. 

After years of talk about the state’s promise and a few industry false starts, Denver-based Evergreen Resources hopes to deliver Alaska’s first commercial CBM. The company has started drilling test wells in a forested area 50 mi outside Anchorage. If exploration succeeds, Evergreen hopes to supply the Anchorage area, where a gas shortage looms. Successes could also lead to much wider development. Now, barely 9% of US gas production comes from CBM. That level could rise to 20% over the next decade. 

The North Slope holds 80% of Alaska’s estimated CBM, a supply that could feed a proposed 3,500-mi gas pipeline from Prudhoe, officials say. Alaska lawmakers passed a bill exempting CBM and other shallow gas wells from regulations applying to deeper, higher-pressured oil wells. The industry says the bill removes unnecessary development obstacles. Obviously, the environmentalists are not so happy. 

Bob Palmer goes to work. Not the real Bob Palmer – he retired in May. The new Rowan jackup, christened August 16, was expected to begin a contract with El Paso Production in September. The Bob Palmer has 713-ft legs which allow it to work in 550-ft water. A LeTourneau Super Gorilla XL design, it is the deepest-rated and, at a cost of $240 million, the most expensive jackup ever built. It was built at LeTourneau’s Vicksburg, Mississippi, shipyard. Final outfitting took place at Rowan’s Sabine Pass facility.