RIASSUNTO
With the growing numbers of aging wellbores, recompletion programs help to reduce temporarily abandoned well counts, identify and prove future development potential, boost production and maximize return on investment. Typically base well completion programs have been composed of four main project types: recompletions, rework in the existing zone, sidetracks, and deepenings. This paper summarizes the lessons learned and recommendations from an active deepening campaign in the Permian Basin.
Deepening projects provide a cheaper and lower risk alternative to drilling new wellbores and can achieve the same objectives of zone testing and infill drilling potential evaluation. Once infill potential is proved up through deepening projects further value and scale can be exploited through infill drilling programs.
Two types of deepenings were executed, open hole and cased hole. Casedhole deepenings are more complex and costly, but must be attempted in the cases where openhole deepening is not feasible. Such cases may include deepening across water-bearing or depleted zones, deepening in prolonged pay intervals (>350ft), zones with poor hole stability or incompatible formation fluids. In a stacked pay carbonate rock the stimulation is an important part of the completion process. Therefore deepening projects may have different scopes which may include some isolation work in open or casedhole, single-stage or multi-stage acidizing and fracturing.
The three key pillars which must be in place to deliver a successful deepening program are sound wellbore conditions, reliable well history, and proper equipment selection. Given that deepening projects are implemented less frequently than other well intervention activities and new drilling activity, the equipment selection and the understanding of how to operate that equipment become critical success factors in these projects. It was observed that the time and cost associated with wellbore cleanouts before deepening may drastically change the project economics. The risks associated with poor well integrity and the presence of junk or fish in the wellbore need to be quantified in the candidate selection phase. Changing from roller-cone to PDC bits and adjusting drilling parameters increased the deepening ROP by 300%.
This paper compares the historical performance of 10 deepening projects. It contains a list of operational risks and follow-up plans needed to ensure cost effective and safe execution.