The severe environments of high temperature geothermal wells can pose a significant challenge in terms of well integrity, equipment performance, and reliability. Many of these challenges have also been faced by thermal oil recovery well operators in Western Canada; where high pressure steam (as hot as 350C) is injected into relatively shallow reservoirs to mobilize the highly viscous heavy oil.

 

Given the nature of thermal oil recovery operations, well integrity is of critical importance to operators. Many thermal wells are run into relatively shallow reservoirs (typically 150-600 m depth); thus, well barriers must be properly designed to prevent uncontrolled releases of reservoir fluids above the cap rock into potable aquifers and/or to surface. Cemented production casing strings are designed with the understanding that they will plastically deform under high temperature conditions as a result of axial confinement. Strain-based tubular design and the use of specially-designed premium connections for high temperature applications, in accordance with ISO/PAS 12835:2013, have become industry recommended practices in Western Canadian thermal operations.

 

Another key aspect of well performance for thermal well operators is the high temperature performance and reliability of the artificial lift equipment installed in thermal wells. Significant strides have been made in the development of improved technologies for producing fluids in thermal oil recovery environments. These efforts are still ongoing and have resulted in improved capabilities and reliability of thermal artificial lift equipment. Though technology gaps still exist, adapting thermal artificial lift equipment to the geothermal industry has the potential to advance geothermal power production.