ADVANCED TECHNOLOGY

Leonard LeBlanc
Houston

Reinforced fiber cement casing first step in single ID

Installing and cementing successive strings of smaller casing in a wellbore has been a time-consuming and costly, but very necessary, process. This telescoping arrangement, however, greatly increases the size of surface hole, limits the size of the bottom hole, and requires a much larger size variation in tools to work in each casing ID. A number of innovations have been proposed over the years to circumvent this telescoping process, including mold-in-place composite casing. Thus far, none of the processes have been acceptable because of higher cost, poor integrity, or inability to withstand drill string wear.

Shell, which five years ago developed a mud that could be converted into cement, has now developed a casing system that molds a slotted tube with fiber-reinforced cement to the formation to achieve a 1,000 psi fracture resistance. The process involves the installation of an expandable slotted tube into an under-reamed section to be cased. A mandrel is inserted and expands the screen to size. The fiber cement is then pumped and displaced. Shell says the system has been licensed for commercial use. [Ref: Stewart, R., Gill, D., Lohbeck, W., Baaijens, M., An Expandable Slotted tubing, Fibre-Cement Wellbore Lining System, SPE 36583, Annual Technical Conference, October, 1996, Denver, Colorado (USA).

3,000-ft-long floating runway concept returns

After being considered some years ago for commercial aircraft emergencies in mid-ocean locations, floating aircraft runways were put aside because of high cost. The concept has resurfaced, encouraged by the US government, which is facing the loss of military air bases in the Mideast and East Asia.

Brown & Root has designed a floating 3,000-ft-long runway for the US Office of Naval Research that can be towed or deployed in international waters. The concept's 300-ft wide deck is supported on semisubmersible pontoons large enough to keep the deck 100 ft above the waterline, but sufficiently ballasted to keep the deck steady in rough weather. The deck runway could support the takeoff of all combat aircraft, a C-130 cargo jet, or commercial aircraft in emergencies. One end of the runway or an accompany string of similar vessels would support hangers and work spaces, with aircraft storage below. The configuration would be variable, depending on the tasks. Tugs and rescue craft would be in attendance. The entire structure would be aligned by tugs with wind direction to assist takeoffs and landings. The cost of the structure was estimated at $2-4 billion.

Graphite-epoxy riser key to deep water for lighter rigs

Second and third generation rigs could begin drilling in 4,000-5,000 ft water depths if riser weight can be cut in half. That riser weight reduction is the target of Westinghouse Marine's effort to produce a riser prototype made of graphite-epoxy instead of steel. At present, rigs with less than fourth generation deckloading can drill in a maximum of 3,000 ft depths. The drilling riser diameter would be smaller, offering fewer problems for on-deck storage and mud volumes, but also reducing the hydrodynamic loads on the vessel when deployed. The manufactured riser joints for both drilling and production would be 75 ft in length.

Anti-matter warns of materials failure

Atomic scale positrons or positively charged anti-particles coming into contact with electrons, which are negatively charged, are annihilated. This annihilation process can be detected based on energy or gamma ray spectra lineshape. The lineshape narrows when annihilation occurs near tiny vacancies in metal molecular lattice. The vacancy region becomes negatively charged, attracting and trapping positrons, which in turn annihilate conduction electrons, which is then detectable.

AEA Technology of Didcot, (Oxfordshire) UK has developed a portable system to analyze lineshape, which detects the earliest sign of material degradation or failure - at the molecular level. The technology has been known for some time, but producing the equipment in a portable form has been a major challenge. The system uses a germanium gamma ray detector.

Use of superlattice coatings, metal ceramics in cutting materials

Much of a metal coating or ceramic materials durability and strength for use in cutting materials is a product of the type of inter-atomic bonding used to assemble the components. Scientists are paying attention now to the conditions that create superhard materials. Two recent findings are helping to boost the use of ceramics and metal coatings in cutting tools downhole:

• Nitride superlattice: Nanometer-scale physical vapor deposition of titanium nitride and vanadium nitride are providing a superlattice bilayer with a coating hardness of 50 GPa, compared with standard steel coating hardnesses of about 20 GPa. The process, which uses magnetron sputtering to built the coating, is being done at Northwestern University (Illinois, US) One of the interesting elements is the application of different partial pressures to the reactive gases and varying potentials to the anode and cathode elements in order to achieve proper stoichiometry and superlattice hardness. The differences in elastic modulus between the sputtered materials is what gives the superlattice its hardness, and makes it so difficult to apply.
• Metal ceramics: A better balance of hardness with workability, which is the key to ceramics' eventual use as a superhard cutting material, is being achieved by combining metals with ceramics. The metals act as a binder or adhesive which prevents crack spread. However, a problem occurs when undesirable microstresses resulting from the differing contraction rates of the sinter materials develop during cooling. As in metal coatings, scientists are working on the micro-conditions surrounding the assembly of the various materials, and resolving those to achieve ideal hardness and workability. One type of ceramic, titanium carbonitride ceramics or cermets, are 50% lighter than metal and provide an alternative to hard metals, while requiring a lower input of raw materials - titanium, nickel, and carbonitride. Although used for small machine tools now, research is underway to lower the cost for downhole tool use. [Ref: (1) Sproul, W. New routes in the Preparation of Mechanically Hard Films, Science, 16 August 1996.

Copyright 1997 Oil & Gas Journal. All Rights Reserved.