Avoiding Sustained Casing Pressure in Gas wells using Self Healing Cement

Abstract

U.S.A., Khuff gas reservoir is one of the most challenging gas fields in the Middle East; in the past several wells suffered from sustained casing pressure due to the downhole stresses and other contributing factors. The severity of the leaking annulus can range from the most hazardous blowouts, to less severe cases of residual gas pressure at the wellhead; recent zonal isolation solution consisted in using Flexible and Expanding cement system in the 12 ¼" open hole to case off the 9 ⅝" Liner, this system is good when the well operating envelope is well known, outside this envelope the Flexible and Expanding cement do not perform as well, this leads the cement to fail (A.S. Al-Suwaidi et al 2008).To further ensure a robust cement design and long term well integrity; Self Healing Cement is introduced in the 9 5/8" tie back section as an added assurance to provide a secondary barrier for the 12 ¼" open hole. Self healing cement is based on a responsive material with intrinsic self-healing properties automatically activated upon hydrocarbon exposure to rapidly seal by healing the damage; within hours the downhole well integrity is restored, reducing the health, safety and environmental risks and the extra costs associated to remedy to these problems including loss of production. This paper will cover the qualification and field implementation of the self-healing cement. It also includes case history covering Khuff gas wells.

Common attributes of hydraulically fractured oil and gas production and CO2 geological sequestration

“…Th ey will ultimately feed back into development of eff ective regulations for ensuring well integrity in class VI GS wells. For example, development and fi eld testing of 'self-healing' cements, 46,47 as well as development of best practices to prevent sustained casing-pressure and gas-migration issues [48][49][50] will benefi t development of eff ective cementing technologies for future GS projects. Progress made by HFO&G operators in ensuring robust surface casing and advances in cementing, both decreasing the risk of well failure, benefi t all sectors of subsurface industries.…”