Unlocking the Unseen: Advanced Approaches for Detecting Hidden High LEL Gas Pressure Sources in Annular Spaces
Authors: Qasida Fatema Abu , Uralsky Stanislav , Al Jahwari Suroor , Al-Nakhili Said , Mohammed Nofel , Petrova Irina , Fesina Yulia , Salmi Ammar 
Published: November 2024

This paper aims to introduce groundbreaking approaches for detecting unconventional phenomena related to identifying and controlling concealed annular pressure sources arising from gas-saturated formations with high Lower Explosive Limit (LEL) gases. Emphasizing safety and operational efficiency, it explores practical applications tailored to the challenges of high LEL gas environments. By providing novel strategies and insights, the paper seeks to contribute to improved risk management and productivity in such complex scenarios.

Effective methods for identifying pressure sources in the annular space are crucial in well operations. Spectral noise measurements, alongside conventional temperature measurements, are highly recommended. Properly organizing the logging procedure is essential for successful leak detection. Temperature and spectral noise measurements must be conducted in both static and bleed-off modes of the annulus, where sustained pressure is observed. Bleed-off mode is vital for activating the leak point by creating a pressure difference. Obtaining spectral noise data in both static and bleed-off modes is crucial, as data solely from the bleed-off mode may be insufficiently informative.

The SAP was observed in the A annulus of the horizontal water injector. Bleed-off analysis revealed the presence of high LEL gas, approximately 90%. Passive spectral acoustics and fast-response temperature measurements were performed in static mode, with the wellhead and all annuli closed and stabilized pressures therein.

In static mode, a low-frequency acoustic signal was detected opposite a gas-saturated formation, hypothesized as a probable pressure source. Subsequently, pressure bleed-off in the A annulus was executed, and spectral acoustics and temperature were measured again. The pressure drop was only 16%, indicating a significant pressure source.

During A-annulus bleed-off, a high-frequency, high-amplitude acoustic signal was detected across another gas-saturated formation, below the formation identified in the static regime. Remarkably, there was an absence of noise during bleed-off in the zone where noise was localized in static mode, and vice versa. This effect was attributed to the activation of formations under different pressure drawdowns.

Two gas pressure sources were identified in the A annulus, which could have gone unnoticed if only bleed-off mode were executed. This suggests the importance of conducting comprehensive measurements, including passive acoustics, to fully understand the dynamics of leak paths in such systems.

This methodology, paired with a meticulously created procedure, reveals hidden leaks and clarifies complex flow dynamics in annular spaces.

This method not only identifies leaks but also discerns their nuanced attributes, including clandestine and low-rate leaks, which might elude detection through alternative means.

Moreover, it plays a pivotal role in unraveling the intricacies of flow patterns, a critical aspect in assessing well integrity and formulating optimization strategies and remedial actions.