HPHT downhole conditions are an increasing concern for operators in the North Sea, Gulf of Mexico and elsewhere. Analysts predict that by 2019, 11% of subsea wells will be HPHT (SLB 2008).
Schlumberger has classified HPHT downhole conditions as HPHT, Ultra-HPHT and HPHT-hc. HPHT begins at around 150°C at 10,000psi (69MPa), Ultra-HPHT at 205ºC at 20,000psi (138 MPa) and HPHT-hc at 260ºC and 35,000psi (241 MPa). The ability of downhole monitoring equipment to withstand reservoir temperatures above 150ºC and/or pressures above 20,000 psi, is defining the capability of new, high integrity, monitoring technologies. So heat shielding is essential.
Severn Subsea Technologies (SST) has developed industry leading heat shielding technologies to keep instrumentation electronics cool, below 90ºC, for an extended period, while preventing aggressive chemicals penetrating the tool under pressure. The combination of high temperature and pressure, and aggressive chemicals has a dramatic effect on reducing the tool’s ability to withstand HPHT conditions.
Severn Subsea Technologies has been successful in designing tools to meet the challenges of HPHT environments by finding the optimum balance of materials performance, and so minimising the trade-off in temperature, pressure and chemical resistance. Based on Dewar vacuum flask technology, the SST heat shielding reduces the electronics’ exposure to radiant heat, enabling tools to be deployed downhole at 150ºC for short periods of time, typically less than a day. Where a tool has to be deployed permanently downhole, the other option is to use a Dewar and re-design the electronics with high temperature resistant components – SST is able to offer both approaches.
Severn Subsea Technologies is the only company to have achieved thermal protection for electronics using Dewars at temperatures up to 400ºC at the relatively low pressure of 12,000psi in a recent geo-thermal project.