One of the most challenging coiled tubing (CT) operations is the inside cleaning of large-diameter casing at a low bottomhole pressure. In the West Seno field, offshore Indonesia, this type of work is basic with regards to recovering production, which is mostly from sanded-up and depleted horizontal wells. Deep wells and limited capacity of the tension leg platform (TLP) prohibit the use of large-sized CT, and this fact adds to the job’s complexity. However, with the integration of several methods, such as the special rotating jetting system, realt-time fiber-optic downhole telemetry, gas lift injection technique and a new clean-out, shear-thinning, oil-base gel fluid that has superior suspension ability, work that was almost impossible before is now viable. This article discusses two sand cleanout jobs in the West Seno field, one of which was successfully and the other a failure.