Markets for non-metallic materials in Oilfield Engineering

As oil exploration reaches new water depths and extremes of temperature, there is a need to validate high performance materials for key functions. The recent MERL Oilfield Engineering with Polymers conference, organised by Applied Market Information and held in London, 7-8 October, had record breaking numbers, reflecting the high level of interest in the use of non-metallics in this field. Garry Mahoney of Saipem outlined the urgent need for proper Design/Qualification/Validation (DQV) of polymer materials and manufacturing at an early stage of new deepwater projects. Typical applications are in flexible joints (laminated nitrile rubbers), reinforced hose (NBR/NR, SBR), flowline insulation (polypropylene, polyurethane (PU)), buoyancy modules (epoxy) and mooring and hawser ropes (polyamide, polyester). Buoyancy is now being used at depths of 2000m and offshore Brazil is expected to move to 2500m in the near future. New tests and standards are required, for example, non-destructive testing of rope to determine safety after handling and in-transit damage. Risk management is critical and Saipem aims to identify all potential risks in a new project at an early stage, to avoid failures such as disbonded pipe coatings and cracked buoyancy modules. Dr Bjorn Melve of Statoil Hydro is an expert in composites, pipeline insulation, flexible pipes and downhole polymer materials. His latest project was on composite free-fall life boats. There was an increase in drop heights of platforms and existing boats were suffering unacceptable damage on dropping into the water; now the design has been strengthened and replaced. MERL is working on materials qualification testing using NORSK M-710 Rev.2, which is being updated to incorporate the requirements of operators, service companies and suppliers. Kai Hostrup of ExxonMobil Development has investigated the failure of "wet" subsea insulation systems. Wet pipe insulation systems use epoxy, PP, PU or rubber. Glass syntactic insulation incorporates glass microspheres to improve thermal performance. All types have shown cracking in service. With PU, the pipe-contact surface is at a higher temperature and should not become wet as this will cause hydrolysis: in one case there were multiple cases of joint disbondment as the insulation expanded and pulled the anti-corrosion coating away from the pipe. The problem may have been due to poor preparation of adjacent casting surfaces prior to subsequent pours: a factor such as surface contamination with mould release agent could do this. DuPont has worked on a new downhole coating technology for oil and gas production tubes to withstand 10,000 psi, 200C operational temperature, salt water and more than 16% hydrogen sulphide. The result is the Streamax fluoropolymer coating. Abdullah Al-Dossary of Saudi Aramco has examined the failure of a gas compressor O-ring after less than 2 years in service, which caused a crude oil production loss of 110 MBD. The problem was incorrect materials in the seal material failing on exposure to hydrogen sulphide combined with operating temperatures of 171 C. Buc Slay of Halliburton has developed seal testing systems to simulate the field environment looking at factors such as: explosive decompression, fluid compatibility, seal force retention, high pressure and low temperature performance. NACE, NORSOK and Shell have all published qualification standards for seals. Most specifications are written for high temperature service. Daniel Herz of Seals Eastern has examined the effects of low temperatures on elastomer seals. The contact stress was related to the Tg and gave a rough guide to performance. The well environment is an aggressive environment both mechanically and chemically. Dr. Paul McElfresh of Baker Oil Tools has examined bonding of fluoro- and perfluoro-elastomers to metal and PEEK substrates downhole, using materials resistant to 200C and 100MPa (high temperature high pressure, HTHP). A proprietary bond enhancer improved the bond strength up to twice the control. Solvay Solexis has been developing new fluorelastomers to give good dynamic performance and fluid resistance at -40C. A new range of monomers has been used to lower the Tg: perfluoro methoxyvinyl ethers were particularly effective. Tecnoflon VPL 85540 also showed lower swell in hydrocarbons and methanol. Saint-Gobain has developed polymer spring-energized seals to meet low fugitive emission standards. The seal comprises a PTFE jacket around a metal spring. Daikin America and Evonik Degussa have also been working on high performance plastics, with work on multilayer tubing using new reactive fluoropolymers, which will bond to polyamides without a tie-layer or etching. One example is the Parker Polyflex Chemjec hose for metal replacement in umbilicals. Wellstream has worked with Evonik Degussa to obtain a Lloyds certificate for polyamide 12 non-bonded flexible pipes. Ticona is supplying polyphenylene sulphide (PPS) into this market as a barrier layer inside composite pipe gathering lines. Polyflow has manufactured these pipes and they have been tested in West Virginia. The installation cost was reduced by $5-6 per foot (33cm) compared to steel pipe. ERA Technology specialises in studies of long-term performance and has examined the behaviour of polyester mooring ropes. In ultra deep waters steel is too heavy to be efficient, however the current knowledge of alternative polymers is insufficient. ERA has tested polyester terephthalate (PET) and polyethylene naphthalate (PEN - double the stiffness of PET but more expensive). Part of the performance is related to the rope structure, but overall it is the polymer fibre that determines strength. Accelerate ageing testing and use of the Stepped Isothermal Method allowed creep data to be extrapolated to 30,000 years. PEN was shown to be a potential replacement for PET. Victrex has looked at the use of PEEK in applications such as seals and back-up rings, housings, cables, connectors (subsea and downhole), plugs and packers, compressors, bearings and bushings. With the more demanding service conditions, PEEK is also finding use in pipe (7-25mm) and liner for umbilical hose (PEEKline from Kutting UK). Fire is a key hazard in oilfields. Ole Bjorn Rasmussen of Trelleborg Viking has examined passive fire protection (PFP) methods aimed at continuous load bearing, integrity and insulation during a fire. One such structure is a rubber Fireshield that dampens, seals and protects. The company also has a new flexible Elastopipe that is flexible and corrosion-resistant: it has gained approval with major oilfield operators. Another innovation is a new water swelling rubber packer compound from Baker Hughes, which expands up to 150% in volume to achieve zonal isolation. Higher temperature accelerates swelling, whereas the presence of divalent ions reduces it. Lanxess Deutschland has developed cable materials for extreme conditions of -50C , oil resistant and flame retardant, such as those found on the Shtokman Gas Field in the Barents Sea. Ethylene-vinyl acetate and HNBR have been blended to meet international standards such as IEEE 1580, NEK 606 and BS 6883. Dr. Matthias Soddemann has been developing ultra high ACN HNBR (up to 50.5% nitrile content) elastomers to enhance performance in severe conditions. These materials have potential applications in stators and blow out preventers. Oil States Industries has tested elastomers for offshore riser bearings. It has developed a method to predict compression creep damage and service life of these laminated elastomeric structures. Dr Tibor Nagy is involved with hose R&D: one issue is that often hoses are specified last in a project and are not used properly, for example the minimum bend ratio (MBR) may be exceeded. As rigs get more crowded the space problem is increasing. Preformed curved hose manufacturing is one answer and a method has been developed by ContiTech Rubber Industrial in Hungary: the hose is preformed and then vulcanised. Tests have been carried out on a choke and kill line for a subsea blow out preventer stack. The use of the highest performing polymer materials is expanding in oilfield engineering and the recent MERL and AMI combined conference provided a vital forum to debate the latest developments.