Drilling developments

Sept. 2002 Vol. 223 No. 9  Drilling Developments

Robert E. Snyder,  Executive Engineering Editor

JIP on underbalanced drilling in marine environments. Currently, underbalanced drilling (UBD) procedures have been used in about 100 marine locations by most major operators. Primary use has been where casing is set and cemented into or on top of a subnormal or pressure-depleted formation, which is then drilled under- or near-balanced to avoid lost circulation and reservoir damage. And new dual-gradient drilling techniques may be viewed as a subset of UBD."

In U.S. OCS waters, MMS has required wells to be drilled overbalanced. For it to allow UBD in wells under its jurisdiction, it must be shown that it can be conducted in a safe and efficient manner. To that end, Maurer Technology and Texas A&M are going to conduct a joint industry research project (JIP) to enable state and federal regulators, and the drilling industry to be proactive in defining situations where UBD can be successfully applied offshore. This project will also extend to other international marine areas and regulators.

Maurer says, to achieve underbalanced conditions offshore, a lighter liquid drilling fluid is often adequate. In some situations, foam or gas-injected fluids are required to lower wellbore pressure below formation pressure. Rheological behavior of these fluids is complex, and steps for controlling the well are more complicated. This project proposes to modify an existing UBD simulator and combine it with risk-based analysis. A study of UBD techniques for the Gulf of Mexico and other marine environments will also be conducted. The simulations will determine anticipated surface and downhole pressure, as well as surface injection rates required to provide proper hole cleaning.

An important part of the project will quantify benefits to the reservoir through use of UBD. The improvements, or lack thereof, will be based on historical records for offset wells. As part of this analysis, a questionnaire will be sent to GOM operators to assess the number of leases now uneconomical for development, but which might become economic if UBD is adopted. Significant oil and gas production might be provided if UBD were applied to the GOM.

In addition, the project will: 1) address well-completion issues such as zonal isolation, gravel packing, expandable screens and slotted liners in various UBD-well geometries; 2) develop design criteria for surface / downhole equipment to be utilized; 3) develop procedures for performing risk analyses of UB marine drilling operations, evaluating consequences and severity of any surface equipment failures—covering all possible contingencies, plus downhole problems such as stuck pipe, washouts, etc.; 4) compare the well-control safety of UBD to conventional drilling operations; and 5) document approved safety cases for marine applications. This will include a review of approved plans for North Sea and Latin America.

Information, findings and conclusions developed will be transferred to the MMS, other sponsoring regulatory organizations, industry sponsors and students at Texas A&M University, through publications, workshops and courses. A workshop will be conducted at the end of the project to present the material to the funding organizations to train them in how to use the new findings. A crucial project element will be to identify additional training recommendations which would further enhance safety by addressing human factors. This 18-month project will start in fourth-quarter 2002. For more information, contact: www.maurertechnology.com.

Rowan’s Tarzans target offshore deep gas. Rowan Companies says it is forging ahead with plans for the first Tarzan-class jackup Scooter Yeargain. This rig is set for completion in March 2004 in LeTourneau’s, Vicksburg, Mississippi yard. It will perform drilling and production in water depths up to 250 ft in the Gulf of Mexico. It is designed for increased efficiency in drilling beyond 15,000 ft, with reduced environmental criteria. Rowan says Tarzan carries the power of a Gorilla-class rig in a much smaller jackup’s hull. One design challenge, however, is fitting the more powerful equipment onto the 16,000-ft² deck area, compared to the Gorillas’ 42,000-ft² decks.

The Gulf of Mexico newsletter says Rowan has ordered construction of three additional Tarzan-class jackups. Development of the new rigs was started in anticipation of greater emphasis on deeper drilling on the Gulf’s OCS, following implementation of deep gas royalty incentives by MMS. Of the more than 50,000 wells drilled to-date within this water depth in the GOM, less than 3,000 have reached a drilling depth greater than 15,000 ft. The company expects, after delivery of the first rig by mid-2004, the three other rigs should be delivered by year-end 2006.

New well-control CD-ROM. A new CD-ROM produced by Abderdeen Drilling Schools is now available at IADC. Titled "Well control for the rig-site drilling team," it provides a good understanding of well control and covers industry-recognized standards and practices, and basic well-control procedures, including API 59 and 53. IADC says it also includes: fundamental principles of well control; causes of kicks, and indicators; shut-in procedures; methods of well control; well-control equipment; inspection; testing and sealing components; surface and subsea BOP control systems; marine riser systems; plus formulas and conversion factors.

ADS’s kick sheets are also included and can be used to kill a deviated / vertical well with a surface / subsea BOP stack, using metric / oilfield units. For more information, contact Jason McFarland: +1 (281) 578-7171, ext. 214;email: jason.mcfarland@iadc.org.

First expandable corrosion-resistant alloy tubular. Nederlandse Aardolie Maatschappij (NAM) and Enventure Global Technology say they have successfully installed the world’s first corrosion-resistant alloy (CRA), solid-expandable tubular (SET) system in a well in the Netherlands. The cooperative effort between Shell, NAM, Vallourec Mannesmann (VAM) and Enventure resulted in expansion of a 6-in., 18.6 ppf, 13% chrome (Cr13) cased-hole liner (CHL) inside 7-5/8-in. casing. Proprietary gas-tight, CRA-expandable connections and tubulars, jointly developed by Shell and VAM, were also used for the first time.

The 710-ft system, installed in a gas well in Wanneperveen field, was expanded in the 7-5/8-in., 39/33.7/29.7 ppf casing, with elastomer seals in each section. Post-expansion liner ID was 5.92 in., compared to pre-expansion 5.39 in. Overall liner length was reduced to 710 ft from 730 ft. Enventure says, this proof-of-concept test is in preparation for installation of a 5,500-ft expandable CRA system.