American Oil and Gas Reporter - October 2015 - 86

SpecialReport: Drilling Fluids Technology
er Tertiary in the ultradeepwater Gulf of Mexico. No standard
NADF or high-performance WBM is completely acceptable at
those parameters today, but there is no doubt that the industry will
conquer the fluid stability challenges at these ultrahigh pressures
and temperatures.
Considerable research is being directed at automated mud testing, and work is in progress to measure the API drilling fluid properties on the rig using devices placed to continuously measure
mud weight and a single-point viscosity. There are devices that
can measure the rheology of the mud to some degree, but more
refinement is needed to be able to more accurately calculate the
ECD in the annulus. Devices also are available now to measure
solids content and particle size distribution, but they are not continuously automated. The industry continues to investigate continuous chemical analysis and fluid loss measurements.
Going hand-in-hand with testing automation is the ability to
continuously automate the varying surface system flow rates, the
drilling fluid volumes in the circulating and storage systems, and
mud dosages and mixing. Several companies are working on these
processes, some in conjunction with various managed pressure
drilling techniques and/or early kick detection. A complicating
factor is that NADFs have constantly varying viscosities and densities related to the changing temperatures and pressures encountered in the circulating system.
Ideally, it would be best to have downhole sensors, but it is
unlikely that these will be readily available or cost effective any
time soon. As an alternative, the industry is developing surface
or mud line techniques that show more immediate promise for
data collection.
From a drilling fluids system standpoint, Figure 9 shows an
example of the types of surface measurement and monitoring inFIGURE 8A
Schematic of Wellbore Ballooning

5,320

Depth (ft)

5,321

5,322

5,323
5,324

5,325

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0
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Radius (m)

86 THE AMERICAN OIL & GAS REPORTER

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strumentation available; in this case a system developed by Zaxxon Instruments LLC. The process uses a system of sensors and
programmable logic controller-based software covering the circulating system and all of the solids control equipment. Zaxxon
has developed several "drilling fluids data processing modules"
that utilize the flow rate, density, mass flow rate and temperature data from Coriolis meters to infer drilling performance characteristics and improve the diagnostic understanding of the system.
These enhanced diagnostic capabilities can be used to quantify the efficiencies of several key performance indicators in the
drilling process, including mud pump efficiency calculations, early kick detection, lost circulation severity, hole cleaning efficiency, and sweep efficiency evaluation. These data will enhance solids
removal equipment evaluation, dilution economics, hydraulics
modeling, wellbore stability, and waste management. Because
the new sensors are clamp-on devices, they make rig up very easy
compared with the Coriolis meter technology.
Even with all the technological and operational advancements
being introduced to drilling practices, arguably the single most
important element to ensuring a safe and successful drilling project is the basic competency of the personnel on the rig site. The
industry continues to focus on making certain that rigs are equipped
not only with the best available technologies, but also well-trained
and competent workers.
Verifying competency for all workers on a well location is a
difficult proposition, but it is moving forward, especially in well
control operations. Each operating and service company has difFIGURE 8B
Stress Cage Theory of Wellbore Strengthening

American Oil and Gas Reporter - October 2015

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