This paper introduces challenges faced in the exploration and development of high-pressure/extreme-temperature (HP/ET) wells and discusses how these challenges were successfully overcome through the development of materials and electronics capable of withstanding such harsh environments.
As HP/ET wells are produced, parts of the reservoir are differentially depleted by as much as 640 bar less than virgin pressure. When perforating wells, including virgin sands, this differential pressure has to be properly managed to reduce the risk of stuck guns. The safest method of perforation has been to complete as few runs as possible using high-strength (130 kpsi) coiled tubing (CT) to perforate a full interval of 230 m (755 ft) in one run. Gun weights of 3200 kg (7,055 lbm) have been deployed, fired, and retrieved under pressure without accident or incident.
Some HP/ET wells in the field have the additional challenge of scale formation throughout the completion. This scale cannot be dissolved in acid and is too heavy to be circulated out of the hole using CT. During a reperforation campaign, a cut of 25% Cr 125-kpsi tubing was correlated and completed successfully on CT in a high-angle well of 52° and a total depth (TD) of 7200 m measured depth (MD) (23,622 ft).