Lessons Learned from Drilling an Extended Open Hole Interval in a Marginal Field Environment

Abstract Drilling extended open hole sections which carries significant operational risks especially in pressured reservoirs has most times resulted to wellbore instability problems which could cause stuck pipe problems. However, drilling designs or operational challenges may lead to such risky decisions. When such a situation arise, precautionary strategies are normally put in place to ensure that potential wellbore instability does not cause loss of time or resources. The paper narrates the case of a well drilled in the Niger delta environment by one of the marginal field operators. The tophole was planned to be drilled with one hole section, but due to difficulties encountered while drilling to the planned depth, decision was made to sidetrack the well with a smaller 6-1/2"hole section. The well was finally landed successfully. The objective of this paper is to narrate the lessons learned in drilling an open hole interval, the challenges and the consequent decisions taken to land the well in the hydrocarbon interval. It discusses both the well design and actual subsurface challenges, with significant emphasis in the strategy adopted in having landing into the objective sand. Some of the key learnings are the need to get much information as possible when drilling into a compartmentalized reservoir. A thorough knowledge of a reservoir helps in adequate optimization during drilling and geosteering.