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Abstract
Novel systems such as the wired-pipe or networked drillstring telemetry system
have allowed broadband communication with downhole tools in various operating
areas around the world, including in deepwater. Two capabilities are vital to
offer operators and service companies with cost effective drilling and
completion in challenging scenarios:
1. High speed: real-time, bi-directional data transfer at a rate of 57,600 bits
per second (bps) enables downhole and subsurface conditions to be measured and
controlled,
2. Measurements all along the string: annular pressure and temperature
measurements distributed at network nodes beyond just at the drill bit enable
early warning of developing trouble events.
This paper describes cases where the broadband network provided downhole
information for identifying poor hole cleaning, determining sweep efficiency,
revealing cutting accumulation and recognizing pack offs early on.
Further, examples are described that improved drilling risk mitigation by the
capability to measure as many as 45 different drilling dynamics parameters that
are updated every few seconds revealing bit whirl, stick slip, lateral and
axial movement while drilling trouble zones.
The successful mitigation of downhole vibration resulted in a 68% increase in
time on bottom and a 58% increase in rate of penetration (ROP). Annular
pressure evaluation all along the drillstring ensured adequate hole cleaning in
challenging wellbores.
Introduction
Successfully drilling and completing wells in challenging environments, while
also keeping costs under control and risks at a minimum, has made the need for
fast and accurate decision-making while drilling increasingly imperative.
Deepwater reservoirs present several unique challenges that hinder data
collection and transmission, which require technology advances in transmission
speed and accurate measurement along the drillstring. These include:
• Deep, sub-salt reservoirs. The challenges of accurately characterizing
sub-salt reservoirs by seismic imaging force drillers to place greater reliance
on measurement while drilling (MWD) techniques to stay in zone and accurately
place the well for optimal productivity. This requires high-speed,
bi-directional data transmission and accurate measurement of string vibration,
to increase time on bottom and maximize the ROP, and help ensure improved
wellbore stability.
• Narrow pore pressure and fracture gradient (PPFG) margins. To quickly
mitigate the challenges associated with unknown pressure regimes in deep,
complex reservoirs that require many casing strings and have a high likelihood
for kick/loss events, drillers benefit from access to formation pressure
testing and high-resolution sonic data. They also need assurances that the data
is of good quality and verification from multiple sensors that the pressure
event is real.
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