A Sustainable Drive in Well Intervention Operations with Case Studies

Abstract

Clean out using coiled tubing is the second largest application of coiled tubing after nitrogen kick-off. The advancements in coiled tubing metallurgies to intervene in complex wellbore geometries and precision of downhole simulators to predict on-site scenarios require more efficiencies from end tools that evolved from simple jetting tools to rotating jetting heads. The objective intended in the case studies performed in the Middle East and South Asia was to perform cleanout in scenarios where incumbent tools had failed in the past. The impact of jetting action in cleanout operations decreases with an increase in stand-off distance. It was confirmed from laboratory tests that a standoff of eight times the orifice diameter and fluid velocity of 200 ft/sec is required to remove moderate to hard deposits from wellbores. Conventional jetting tools have a standoff distance of more than 40 times and fluid velocities are below 200 ft/sec thus objectives are often compromised. A new type of fluidic oscillator was utilized in the case studies discussed in the paper. Unlike pulsating effects created by 1st generation of the fluidic oscillators, the SFO type oscillator had triple jetting action namely, Helix jetting, Pulses Jetting, and Cavitational jetting. The result of the clean-out with SFO technology was beyond expectations. It saved cost in all the case studies by an average of 35% if had been performed with incumbent technologies and increased production/injection from 30% - to 250% of the original value. Moreover, it reduced the operating times to two-thirds of conventional operations and increased the efficiency of treatment fluids which resulted in the reduction of waste of additives and extra additives to dispose of excess materials at wellsite. This is the first technology that used cavitational jetting in oilfield services and the first to use aforesaid jetting actions altogether in one tool. The technology adopted in the case studies doesn't have moving or rotating parts, thus eliminating the requirement to pull CT out of the hole for redressing and can perform long operations in one go. It doesn't depend on the centralization of the tool as the jetting effect is passed via kinetic energy through submersed fluids, thus can target deeper depth without limitations of the standoff. It allows a higher flow rate of liquid and gas, thus offering higher fluid velocities to perform an effective cleanout.