Spoolable Composite Tubulars
A new generation of spoolable piping offers fatigue resistance and lower life cycle costs.
Several types of continuous spoolable composite piping are either on the market or under development for onshore, offshore and downhole applications, where jointed steel pipe has been the conventional solution. Spoolable composites are divided into two main families — bonded and unbonded. Bonded spoolables have a polymeric liner to contain the conveyed fluid and a structural composite layer or layers for hoop, collapse and tensile strength. The liner and structural layers are bonded together to form one unit. Unbonded pipe features discrete (unattached) structural layers that can slip in relation to each other and to the liner. Hybrids with both bonded and unbonded layers are also produced. Each has the ability to convey fluids at high pressures, ranging from 750 to 15,000 psi/50 to 1,050 bar — much higher than fluid pressures handled by non-reinforced thermoplastic piping.
Despite higher material costs, spoolable composite tubulars have found application in the oil industry for chemical injection and drilling fluid transport, in cases where installed and life-cycle costs can be shown to be lower than those for steel. Composite pipe offers better corrosion resistance and significantly lower weight. In addition, installation is easier because fewer joints are required and the lay rate is faster. It is an enabling product in the overall system used for extended reach drilling.
Proven onshore applications for spoolable composite pipe include water-alternating-gas (WAG) lines (lines that inject water and carbon dioxide into production zones), water injection lines, production gathering lines, gas lift injection lines, portable well test lines, and pipeline re-lining. Potential offshore applications of spoolable composite tubing could include injection strings, velocity strings, production tubing and hydrate blockage removal in pipelines. Bonded and unbonded flexible pipe have application as control umbilical lines, choke and kill lines, and catenary risers, although composite coiled pipe may also expand into those areas. “We see a real advantage in using spoolable composite piping in extended reach drilling, both onshore and offshore,” says Mark Kalman, technical excellence manager, composite applications, Halliburton Energy Services (Houston, Texas, U.S.A.).