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Abstract

Well control events are predominantly detected through surface measurements. Measuring an increase in the ‘closed loop’ mud circulation system, a standpipe pressure decrease or changes in a variety of drilling parameters provide identification of a kick. Especially in deepwater, where the riser comprises a substantial section of the wellbore, early kick detection is paramount to limiting the severity of a wellbore influx and improving the ability to regain well control.

  While downhole data is presently available from downhole tools near the bit, available data rates are sparse as mud pulse telemetry bandwidth is limited and wellbore measurements compete with transmission of other subsurface data. Further, data transfer is only in one-direction, latency is significant and conditions along the string are unknown.

This paper describes the use of a high-bandwidth downhole data transmission system via a wired or networked drillstring system that is uniquely equipped with real-time pressure and temperature measurement capability at many locations all along the drillstring. This system provides high-resolution downhole data available at a very high speed, eliminating latency and restrictions that typically limit the availability of downhole data.

The along-string data acquisition and broadband communication via the networked drillstring provides real-time downhole data independently from surface measurements which aid to identify, analyze, and control a wellbore influx. First, the system aids in identifyingpore pressure, fracture gradient and safe drilling margin. Second, the independent measurement capability provides early kick detection with distinction from ballooning and improves the ability to analyze and control an influx – even with heterogeneous mud column – through the ‘direct measurement method’. Third, during tripping operations that are associated with approximately 25% of all well control events, downhole data is now available to provide early kick detection.

Introduction

Prompt kick detection is critical in deepwater operations with a subsea blowout preventer (BOP), as it is imperative that the rig crew detect the influx since reaction times are shorter than with a stack at surface. Kick detection is crucial before the hydrocarbons rise above the BOP stack[i]becausewell control response options are severely limited and the risk of a blowout increase significantly.Especially in deepwater wells, it is paramount to detect a kick early to limitthe severity of wellbore influx andto improve the ability to regain well control. This is because in deepwater wells the marine riser comprises a substantial section ofthe wellbore and productive hydrocarbon zones can be found relatively shallow below the mud line and often the margin between pore pressure and fracture gradient is narrow.

While response times for early kick detection are crucial, traditionally, wellsite and operational personnel rely on surface measurements such as flow in and out, pumping pressures, and a number of mechanical measures to identify a wellbore influx. An increase in the ‘closed loop’ mud circulation system, a standpipe pressure decrease or changes in a variety of drilling parameters provide identification of a kick.