An Industry-First, Unflasked Perforating Gun for Enhanced Geothermal, Ultra HPHT, and SAGD, Rated to 750 °F, 15-Kpsi
Authors: Roy Ting , Naceur Kamel Ben , Harrison Casey , Shelton James , Harrison Holden , Hall Aaron , Jones Kenny , Koyanagi Yoshihiko , Takahashi Mari , Wilkinson Christian , Ardic Hifzi , Roy Indranil 
Published: October 2023

Power generation, harnessing geothermal-energy is now attracting greater attention as one of decarbonization wedges required for a sustainable energy-transition. Recent innovations in drilling and completion have made it possible to harness ultra-deep HPHT wells (&gt;15,000 m), which will ultimately enable highly efficient power generation from Enhanced-Geothermal-Systems (EGS) with a much larger geographical scope. Many challenges to achieve this economically remain. To outline a few: first, hotter, deeper-wells require alloys with high-strength, creep, and corrosion-resistance; second, retaining system-enthalpy in EGS needs tubing with near- zero thermal conductivity; third, such Ultra-HPHT formations need perforating-systems to produce entry-holes large enough to enable effective formation-stimulation between an injector and the producer.

Here we present an economical, engineered-to-order, precipitate-hardened, thermally-stable, and grain-refined corrosion- resistant alloy with excellent elevated-temperature mechanical-properties as a metallic-skin on a nano-composite tube. This is the input- material for designing a perforating-gun body, enabling it survive a 15K-psi collapse at elevated operating temperatures. The nano- composite tubular gun-body with near-zero thermal conductivity allows the gun to operate at 750 °F, for fracturing Ultra-HPHT and hot granite formations.

The gun-body, designed from a nano-composite tube having a high-strength, thermally-stable, corrosion-resistant metallic-skin is designed to prevent supercritical-fluids and subcritical corrosive hydrothermal-brines from subjecting the gun to environmentally- assisted-cracking. The end of the gun is insulated with high-temperature reusable surface-insulation (HRSI) materials and equivalent- seals, including metal-to-metal seals. Passive electronics, the switch, and detonator, generates little to no heat and does not affect the internal temperature of the gun, requiring no refrigeration to dissipate internal-heat to cool the system.

Decades of completions experience drawn from the oil & gas industry and strategic partnerships amongst the advanced- materials world, played a pivotal role in solving these challenges associated with such Ultra-HPHT environments, expected in EGS. Our patent-pending embodiment, a concept, using a specially designed nano-composite tube with a near-zero thermal-conductivity of &lt;0.02 W/m-K to design a perforating gun, completely isolating the charges, switch, detonator and detonation chord from the external EGS environment. The tested and proven composite-insulation maintains the temperature of the gun internals below 150 °F, even when the external environment is in excess of 750 °F, for days.

For the very first time, an Ultra-HPHT perforating gun rated to 750 °F, 15K-psi for fracturing super-hot/granite formations to enable EGS and SAGD was conceived and designed. Key novelties of this industry-first design are (a) NO required flasking of the gun: avoiding multiple steel barriers that would limit the depth of penetration, and Entry-Hole-Diameter (b) Ability to deploy RDX-charges in a system rated to 750 °F (c) Reliable performance at extreme temperatures (d) Ability to deploy tracers via shaped-charges, field- tested and proven to survive T &gt; 750 °F, well suited for EGS (e) Unparalleled economics, not requiring the additional cost of a "Flasked- system".