This paper will discuss a game-changing and innovative technology that enabled cementless annular isolation (liner to borehole) across the reservoir, removing the risk of previous experienced cost and time overrun from complex cement operations and securing the full economical return on the wells. The technology has been deployed in four Moho North Albian wells, drilled through a complex reservoir with highly laminated lithology requiring efficient zonal isolation for both acid treatment and water shut off. During the earlier field development, many cementing challenges were encountered that increased risk and cost and the ability to deliver effective isolation across the reservoir. Poor isolation leads to poor matrix acid stimulation, higher skin and a higher risk of water production. To address this the operator sponsored an industry challenge to achieve reservoir isolation with cost and risk reduction and to deliver overall efficiency gains. Through dialogue between the Operator and a leading service provider in Open Hole Zonal Isolation, a solution was identified that would effectively replace the cement across the reservoir with a metal expandable annular sealing system. Time for delivery was a key driver to meet the drilling schedule and materialize the cost and risk reductions on the remaining wells. A scope of work was completed that included extensive qualification, manufacture and field deployment. The solution has proven to deliver benefits that address several fundamental aspects which were associated with the cemented liners: Substantial reduction in risk and cost associated with drilling the extended rat hole (shoe track) into the highly pressurized water zone (+/- 100mMD)Removed the risk and cost for the additional run to under ream the 6 ½″ hole to 7 ¼″ (low-ROP)Provided more certainty for zonal isolation whilst delivering effective acid stimulation and maintaining the low skin values. The technology has many different applications within wells where conventional cement is challenged beyond its capabilities and inherently not fit for purpose, due to factors such as well trajectory, hole geometry, reservoir uncertainty, downhole environment (pressure, Temp, ECD) etc. Within these environments, the technology developed for Moho North adds a proven solution to the Operators toolbox, a technology that is already finding alternate applications and planned deployments.

It is well recognized that a failed isolation can have detrimental consequences on HSE, well productivity, and life of the well. This paper presents the case history of a metal expandable annular barrier used to provide cement assurance via a hydraulic seal in a challenging side-tracked well in West Africa. The initial well was shut in shortly after being brought on production due to excessive precipitation of scale. Investigations identified a shallow formation separated from the production zone by a thin shale section, and prompted questions on the effectiveness of the cement across the production casing. The metal expandable barrier was then selected to assure sealing in the side-tracked well. Two barriers were mounted on the 9-5/8" casing and deployed through the milled window. Following the cement operation, hydraulic pressure was applied to expand rapidly the sleeve bodies in wet cement and set against the 12 ¼" borehole thereby creating an impenetrable seal. The sealing was ultimately confirmed by the absence of scale during production compared to the previous experience of shut-in after only 18 hours of production. The barriers are seal backed stainless steel sleeves. The expansion process increases the differential pressure capabilities of the packers due to work hardening of the metal sleeves. This also provides a high degree of anchoring. The barriers are full-bore, highly customizable, and are tested ISO14310. The application was for cement assurance but this technology is also applied as zonal isolation in cement-less completions. The metallurgy allows the packer to shape fit into either an open hole with irregular geometry or inside a casing to preclude annular pressure build up by giving a life-of-well reliable seal. Stopping migrating fluids behind pipe has become a critical HSE issue to the industry. The application of this technology allows preventing loss of life and resources.