Abstract
Effective well control depends on the drilling teams’ knowledge of wellbore flow dynamics and their ability to predict and control influx. Unfortunately, detection of a gas influx in an offshore environment is particularly challenging, and there are no existing datasets that have been verified and validated for gas kick migration at full-scale annular conditions. This study bridges this gap and presents pioneering research in the application of fiber optic sensing for monitoring gas in riser. The proposed sensing paradigm was validated through well-scale experiments conducted at Petroleum Engineering Research & Technology Transfer lab (PERTT) facility at Louisiana State University (LSU), simulating an offshore marine riser environment with its larger than average annular space and mud circulation capability. The experimental setup instrumented with distributed fiber optic sensors and pressure/temperature gauges provides a physical model to study the dynamic gas migration in full-scale annular conditions. Current kick detection methods primarily utilize surface measurements and do not always reliably detect a gas influx. The proposed application of distributed fiber optic sensing overcomes this key limitation of conventional kick detection methods, by providing real-time distributed downhole data for accurate and reliable monitoring. The two-phase flow experiments conducted in this research provide critical insights for understanding the flow dynamics in offshore drilling riser conditions, and the results provide an indication of how quickly gas can migrate in a marine riser scenario, warranting further investigation for the sake of effective well control.
Highlights
Recent developments in offshore drilling technology and automation have made the mobile offshore drilling unit an engineering marvel
This section describes the results from the DTS, Distributed Acoustic Sensing (DAS), and pressure/temperature gauges obtained during the different stages of the experiment, described in the previous section
Stage-0, Baseline: Baseline data was established for the pressure and temperature in a static water column inside the test well
Summary
Recent developments in offshore drilling technology and automation have made the mobile offshore drilling unit an engineering marvel. In the face of these developments kick detection, which is relatively straightforward on land based units, has proven significantly more challenging to master on a marine vessel subject to currents and wave motion. A gas kick is a well control problem that results from an influx of gas (or kick) into the wellbore during drilling operation. It occurs when the pressure in the wellbore is lower than that of the formation fluids, causing flow. Factors such as inadequate equivalent circulating density (ECD), higher than expected formation pressures, mud losses during drilling, and swabbing can all trigger a gas kick [1]. The influx is removed by circulating the well by means of an adjustable surface choke [2]
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