SUBSIDENCE-INDUCED CASING DOGLEG (SICDOG) REMEDIATION WITH AN INNOVATIVE HYBRID MILLING SYSTEM

Subsidence Induced Casing Doglegs (SICDogs) occur in many oil reservoirs worldwide. Doglegging, at a minimum, leads to reduced mean time between failures of rod pumped wells. SICDog remediation techniques in the past have had limited success and are relatively expensive procedures. Most of these techniques have used various rotating mill assemblies and different strengths, sizes and connections of drill pipe. Some have been extreme such as destroying the dogleg with explosives. A multiphase, risk sharing, team effort over four years between Aera Energy LLC and Weatherford International Ltd led to the development by Weatherford of a hybrid broaching/milling tool. This hybrid milling system reliably and quickly remediates multiple doglegs in a single well bore. Seven Diatomite reservoir producers in the South Belridge Oil Field, Kern County, California were repaired and returned to production, with complete success in the latest four well phase. The work was routine in nature, requiring no special or extraordinary services. In this paper, we will discuss the geometry of SICDogs and the challenges they pose to rotational milling. Other topics will include the evolution of the hybrid tool from experiences in this and other projects, operational concerns such as well control and repair options of the remediated SICDog. Lessons learned during the evolution of this technique will be discussed at length.