With water production continuing to increase from mature reservoirs and the need to enhance hydrocarbon recovery from these reservoirs economically using existing wellbores, the requirement for innovative thru-tubing zonal isolation solutions has never been greater. Due to the complexity of the completion design and reservoir in mature fields, the benefits of high-expansion plugging devices and coiled tubing conveyance for chemical placement have become increasingly important.
Thru-tubing inflatable technology has, for some time now, been providing high-expansion devices to pass through the existing completion and isolate in the liner or casing below. However, as reservoirs deplete and remedial work such as re-perforation is performed, the conditions in which these tools are required to perform are becoming ever more challenging. This paper will focus on two coiled tubing water shutoff interventions using thru-tubing inflatable technology in conjunction with cement or chemical placement. In these interventions, the wellbore conditions were considered particularly challenging – sub-hydrostatic bottomhole pressure, multiple perforated intervals and an existing zonal isolation device in the form of a straddle. These case histories will be examined in detail, with emphasis on the pre-job planning, equipment selection, operational procedures, lessons learnt and post job results.