One of the operator’s newly acquired ventures is in the North field offshore Qatar. Abnormal rise in Annuli C and D pressures during the last phase of drilling highlighted the need to investigate the condition of producing wells on other platforms. The chances of inner annuli becoming charged with shallow-gas pressure and possible communication to Annulus D was thought to be a well-integrity concern. Establishing safe access to the sealed and potentially gas-charged Annulus D thus posed a challenge.
The North field is offshore northeast of Qatar and is the world’s largest nonassociated-gas field. The wells are typically 7-in. monobore completed with a 26-in. conductor and three casing strings. Wells are completed with a liner-top isolation packer, tied back to the surface with 7-in. corrosion-resistant-alloy tubing.
The annuli between the well casings are labeled A (7×10¾ in.), B (10¾×13⅜ in.), C (13⅜×18⅝ in.), and D (18⅝×26 in.). Provisions were made for monitoring and bleeding off pressures in Annuli A, B, and C....
Method of Surface Interception To Access Annulus With Abnormal Gas Pressure
15 December 2015