Most brown fields are now experiencing rapid decline in oil rate; also, the cost of drilling has escalated over the years, thus posing a challenge to drilling opportunities in brown fields. Over the years new field discoveries have been on the decreasing trend and this has prompted operators to start looking for ways to access reserves that were originally considered marginal and hence bypassed during the early stages of field development. As these bypassed reserves were not considered significant, most of the wells were completed leaving the "sub economic" potential above the packer. Accessing them now would typically require pulling the tubing through a major rig workover (MRWO). This is very expensive and as such, MRWO operations are challenged by the economics of the reserves in place.
The thru-tubing cement packer is an innovative and cost effective technique of accessing behind pipe opportunities in existing wells. So while not a new technology, it is new to Chevron Nigeria. The reason why it has not been implemented sooner is likely because until recently, we have been fortunate enough to have plenty of (MRWO) opportunities with solid economics. The combination of extremely high rig rates coupled with a significant drop in the price of crude oil has resulted in a need to look for other, less costly means to access additional reserves.
The cement packer operation achieves zonal isolation through rigless workover cementing. The use of Slickline perforation as opposed to the conventional E line further drives down the rigless operation cost thus improving the economics of marginal reserves. This low cost method of developing reserves is key in ensuring that operators extract as much value as they can from their assets.
This paper reviews two case studies in the Southern Offshore Area operations of Chevron Nigeria where the cement packer technology was deployed successfully. The cost savings realized is presented and further application of this technology to other areas is also discussed.