Challenges and Solutions
Deepwater high-pressure wells, thermal recovery techniques, and subsea completions are among the many applications that are increasing demand for equipment capable of operating successfully in HPHT conditions. These requirements push the limits of the metallurgy, corrosion resistance, sealing integrity, and chemical makeup of components and systems.
The SPE definition of HPHT wells includes all wells where
- the undisturbed bottomhole temperature is greater than 300 degF [150 degC]
- pressure control equipment rated in excess of 10,000 psi [69 MPa] is required.
API Technical Report 17TR8 provides HPHT equipment design guidelines and interprets the term to mean pressures greater than 15,000 psi [103 MPa] and temperatures above 350 degF [177 degC]. Cameron engineers played an active role in developing this report, a recognition of their unique expertise. These same engineers pioneered the multiyear development of a complete surface wellhead and production tree system rated 30,000 psi, 450 degF and qualified as per API 6A Appendix F, as well as the redesigned equipment needed to install the system.
Well control on high-pressure wells
The consequences of losing well control become more severe with increasing downhole pressures. As ratings increase, the equipment and connections become so massive that eventually a complete redesign becomes necessary, including new materials and manufacturing and qualification processes—a complex undertaking.
Cameron delivered the industry’s first 20,000-psi large-bore BOP stack, followed a year later by the first 25,000-psi one, with associated choke and kill manifold systems. Today, we are still the only providers of field-proven 25,000-psi BOPs, and are engineering a subsea BOP system rated 20,000 psi.
Equipment performance at high temperatures
Conventional elastomeric seals, lubricants, and other components can lose their effectiveness at high temperatures. Expansion of tubulars and other components must also be accounted for. High temperatures are often accompanied by corrosive gases or vapors, which exacerbate the challenge.
Cameron leverages years of experience with seal design in dedicated facilities and ongoing R&D across all Schlumberger to develop robust, technologically advanced seals. Specialized wellhead systems provide fluid control for virtually any type of geothermal reservoir, including vapor dominated, liquid dominated, dry hot rock, and geopressured. In addition, our wellhead systems can be used on waste disposal, hot water, and thermal recovery heavy oil wells.
Connection from surface to subsea well in deep water
As well pressures increase, in addition to the wellhead and BOP stack, the marine riser connecting the wellhead to the rig floor must also withstand higher pressures.
The innovative design of the 20K slim pin riser enables operators to drill in 20,000-psi environments, while keeping weight and footprint to a minimum.
Equipment integrity on the sea floor
Subsea Christmas tree assemblies must control production or injection from or into a subsea well, which can be located under thousands of feet of water. Access is difficult and expensive and loss of well integrity can have catastrophic consequences.
A long history of designing and delivering HPHT subsea tree systems worldwide includes the Gulf of Mexico, North Sea, and Caspian regions. Our current offering of HPHT subsea trees includes 10,000-psi and 15,000-psi systems rated up to 350 degF [177 degC], with horizontal and vertical monobore tree configurations, all tested under the most demanding conditions.
Reliability in high-pressure fracturing operations
A typical frac tree often needs to withstand more than 40 fracturing stages and 15 million pounds of abrasive proppant-laden fluids at very high velocities and pressures for considerable periods of time. Frac valves in the tree play a critical role in well control; issues with the valves can cause the entire fracturing spread to shut down, which is detrimental to project cost and efficiency. In the worst case, valve failure can lead to loss of well control.
Conventional Cameron frac trees are rated up to 20,000 psi—the highest pressure rating in the industry. Innovative frac tree designs streamline rig-up and rig-down and improve wellsite safety, and Cameron frac valves have provided three times more uptime than valves from other suppliers. In addition, specialized frac heads are available for high-volume CT fracturing jobs. Our FracServ enhanced valve-reliability program requires full disassembly, maintenance, and testing after each fracturing job, so that Cameron frac valves are delivered in “as new” condition for each job.