Abstract The objective of the paper is to outline the development of an innovative workflow that addresses the descaling operations in sour environment. The discussion will cover proven practices to remove iron sulfide scales while eliminating fluid losses and achieving production recovery from wells. Hydrogen sulfide (H2S) exposure to the personnel involved in this operation was also eliminated by careful risk management resulting in improvement of well site safety. A custom-fit enclosed flowback system for safe and efficient handling of liquid, gas, and solids, including H2S and naturally occurring high risk solids, was key to this new underbalanced (UB) approach. Real-time downhole telemetry from a CT string was also fundamental to understanding the dynamic bottomhole conditions, which included monitoring the equivalent circulation density, and making informed adjustments on rate of penetration, flow rates, and bottoms-up frequency. To address the triple challenge of heavy iron sulfide scale, H2S, and naturally occurring high risk solids, a custom-fit enclosed flowback system was engineered. This system brought proven concepts from CT drilling and well testing together to achieve the target objectives. The main components included a cyclone-type closed-loop solid handling station and a clean-phase fluid-handling system together with a hydraulically operated choke for pressure control. In addition, because of the continuous exposure to sour environment and to the abrasive fluids resulting from the scale cuttings, a tailored risk mitigation plan was implemented for CT pipe integrity. Building on the experience gained from UB CT drilling projects, concepts such as use of high pH working fluids, and real-time CT pipe inspection was deployed. To date, results have been encouraging, and UB mechanical descaling operations have been safely and efficiently completed, resulting in time savings exceeding 35 hours, as well as fluid savings and a total CO2 emission reduction of 20%. This innovative intervention approach brings production sustainability for strategic assets while extending their producing life as well. Experience gained from these innovative well interventions will benefit the intervention industry by improving well site safety and operational efficiency as well as contributing towards NetZero goals.
Hamid et al. (Mon,) studied this question.