High pressure high temperature (HPHT) Oil and Gas developments often require high density clear brines for well completion fluids used in the final stages of well construction. Formate and bromide brines are two which are commonly used. Heavy completion brines can, however, pose a corrosion and cracking threat, especially if the pH reduces or the brine degrades under high pressure/high temperature conditions. This latter threat can be problematic where the completion design permits brine to be trapped in the completion for an extended period, especially if further contaminated with formation treatment chemicals and formation fluids. Laboratory testing was conducted to explore the credibility of such a threat for two candidate completion brines. In the present work, a buffered mixed formate and a proprietary bromide brine were tested under 14Bar CO2 at 140°C. The materials tested were: super martensitic stainless steel (UNS(1) S41426) tubular, super duplex stainless steel UNS S39274 tubular, API 5CT/ ISO 11960 grade “C125” casing and nickel alloy (UNS N08825). The paper presents the specific corrosion and cracking threats introduced by the brines.
Key words: HPHT, Completion fluid, Formate brine, Bromide brine, Super martensitic stainless steel, super duplex stainless steel, 25Cr, Nickel alloy 825, Low alloy steel.