Published: 06/29/2015
Published: 06/29/2015
Scale removal in sour gas wells has been one of the most challenging operations in Saudi Arabia during the last decade, due to the particularly demanding downhole environment with temperatures above 300 degF [149 degC], high concentrations of hydrogen sulfide (H2S) and carbon dioxide (CO2), presence of complex mixed-scale deposits with limited dissolution, and risk of H2S release and corrosion with chemical removal methods. These conditions have led the operator to use mechanical removal methods via CT as the preferred technique for descaling operations.
A scale diagnostic job confirmed the presence of scale across the production tubulars and perforated interval, and a steep production decline had been observed over six months, which prompted a mechanical descaling operation.
High-pressure jetting cleanout was conducted with a 2 7/8-in Jet Blaster engineered high-pressure jetting service tool and jetting sterling beads at 2.5 bbl/min while maintaining a differential pressure of 2,500 psi [17.2 MPa] across the downhole jetting nozzles and with full fluid circulation at the surface. This operation and subsequent cleanouts increased operational efficiency by 30%.
After the mechanical descaling operation, an abrasive perforating treatment was conducted to enhance injectivity for further stimulation treatment. Real-time gamma ray depth correlation enabled by the ACTive PTC tool saved an additional run. Abrasive perforating was performed at 3.75 bbl/min liquid rate and 600 ft3/min gas rate while keeping the optimum differential pressure across the ABRASIJET hydraulic pipe-cutting and perforating service tool. The operational capabilities for mechanical descaling and abrasive perforating operations were confirmed in sour gas wells with bottomhole temperatures up to 310 degF [154 degC] by using the ACTive PTC tool. The implementation of this technology reduced operational time by 40% for the operator compared with standard practices.
Challenge: Prevent gas influx or circulation losses during mechanical descaling operations in a sour gas well scaled up with iron sulfide (FeS) scale; use CT real-time downhole measurements for efficient mechanical descaling and abrasive perforating at bottomhole temperatures of more than 300 degF [149 degC]
Solution: Deploy 3 1/4-in ACTive PTC CT real-time pressure, temperature, and casing collar locator tool for real-time downhole readings and enable pumping rates up to 8 bbl/min using a rugged version of the fiber optic carrier
Results:
