Managing Shallow Casing Leaks in Well Completions; Case Study of a Single Zonal Well in Niger Delta

Abstract

Abstract Re-entering old and mature wells is necessary to chase initially classified marginal hydrocarbon volumes. Many wells drilled in the 60s and 70s but suspended have become attractive to small players with relatively low overheads and tax regime. As a marginal field operator, such opportunities are classified as short term development opportunities establishing quick cash flow to further field development. Casing failure in an old well drilled through shallow faults can pose serious challenges to re-entry and workover operations. This paper presents the solution to a challenging casing leak interval across a shallow fault zone which could not be squeezed off with conventional cement squeeze technique. The failure of routine casing test prior to drill stem test during a re-entering and completion of a well drilled and suspended for 36 years necessitated the consideration of several isolation methods. Attempts made to squeeze off the leak interval across the fault zone using cement proved abortive due to the size and nature of the fault. Casing patch was considered but not available in-country as at the time of the operation. This led to a novel approach of isolating the leak interval with the completion packers and subsequently perforating the well through-tubing. The leak was successfully isolated and the well completed. The well has produced over 0.5 million barrels of oil and 4.5 billion standard cubic feet of gas and still contributing over 10% of daily field production. This method was also used in a dual completion in Niger Delta to manage two different pressure gradients.