Sustaining Production in a Prolific Gas Well Using Storm Choke in Place of Failed TRSCSSV

Abstract

Well 1A is a prolific, big bore dry gas well that has been installed with storm choke due to failure of the well's hydraulic control line. Because of its pilot implementation, a one-year trial period was enforced as part of the valve's endurance and reliability test. The objective of this paper is to show findings from a root cause analysis on valve inadvertent closure (trip at FTHP above valve setting pressure) observed after the conclusion of the one-year trial period which had already indicated positive results with 98% reliability. Physical inspection of three separate sets of storm choke that had premature closure issues within a duration of five months were analyzed to find a common root cause. The well parameters were studied versus the known operating envelope to narrow down possibilities that were either naturally occurring or externally induced within the well that could have caused the inadvertent closures. Based on the available data, the root cause remained tentative triggering the need for downhole pressure and temperature data acquisition. Inspections of the retrieved valves revealed common damaged element; the piston O-ring. The O-rings were found to be either leaking, broken or flattened. When analyzing the well parameters, the only significant change detected since the valve installation was the wellhead temperature which had shown increase of 6 degrees Celsius. However, this increase in temperature should not have impacted O-ring's operating envelope. The well was designed to be completed with downhole gauge at approximately 2000 feet above top of perforations to eliminate need for wireline surveys. This limits the ability to verify predicted temperature profile in the tubing. Suspecting the inadvertent closures to be related to temperature, downhole temperature survey was launched to investigate its impact on the valve. Based on the survey, a much higher temperature was recorded at the storm choke valve depth compared to model estimation. This provided the key to provide a conclusive narrative to the storm chokes’ premature closure issues. The higher temperature had inadvertently increased the storm choke's dome charging pressure resulting in physical throttling of the valve when in operation and thus resulting in damaged seals. With the higher temperature being taken into consideration for new dome setting pressure, inadvertent closures of the same nature were no longer observed. This experience will be able to provide a guideline on best practices in managing wells with storm chokes in the future and outline recommendations for parameters to monitor, surveillance requirements, pressure setting determination practices, procedures for valve function testing and valve handling the well and at the yard.