Abstract

Scale deposition is one of the most common challenges encountered in oil and gas wells. Mature fields tend to have these issues, but tackling scale removal requires tedious diagnostic and intervention work due to uncertainty in determining the exact location and source of scale.

Production decline was observed in a High-Pressure High Temperature (HPHT) gas producer. Well testing was performed to assess and diagnose the production impairment. The preliminary well test data interpretation highlighted positive skin which needed to be characterized. Scale and even sand were considered as a possible cause of production impairment due to the nature of production chemistry and reservoir type, but the hypothesis lacked physical evidence in the wellbore.

A structured approach was adopted to identify, qualify and rectify the situation. High Pressure Coiled Tubing (HPCT) technology capable of providing real time down hole communication was utilized along with coiled tubing mounted downhole camera (DHC) to determine if the wellbore conditions were contributing towards the production decline resulting in a positive skin. The real time images acquired during the downhole camera run revealed astonishing details of the scale that was causing an impact in the production and the flowing wellhead pressure. The high-resolution images obtained during the well intervention clearly pin-pointed at the root cause of production loss and aided in designing a focused treatment for the challenge at hand. Given the sensitive nature of reservoir and possible interaction between the scale dissolving chemicals and reservoir, a customized treatment was formulated. The treatment design exploited the benefits of scale dissolution while preventing reservoir damage. The treatment was pumped using coiled tubing with a high-pressure jetting and rotating nozzle to ensure 360 degree wellbore coverage.

The well was opened to flow immediately after execution of the treatment. The post treatment flowback results indicated a resounding success with production almost quadrupling. A production log was subsequently performed to understand and gauge reservoir performance. The results of production logging further endorsed the fact that skin damage due to scale had been successfully removed and wellbore skin was reduced.

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