American Oil and Gas Reporter - November 2016 - 68

SpecialReport: Drilling Fluids Update
A mud system's per-barrel cost is not
necessarily the best measure. Choosing
a more complex fluid system matched to
a formation's specific geology will cost
more, but it also may eliminate formation
damage and minimize problems that
could turn into nonproductive-time events.
For these reasons, the "cheapest" fluid
may not have the lowest absolute cost
when all factors are considered.
The fluids industry is continuing to
maintain forward momentum by introducing
incremental advances in fluid products,
systems and applications. A cursory review
of technical presentations at this year's
American Association of Drilling Engineers'
Fluids Technical Conference & Exhibition,
and the International Association of Drilling
Contractors/Society of Petroleum Engineers
Drilling Conference & Exhibition, demonstrates several developments across a range
of areas, including WBMs, NAFs, lost circulation materials, on-site operations, and
automation.

makeup of high-performance WBMs.
Freshwater reacts with shale formations
and can accelerate wellbore collapse.
Brine-based systems and stabilizing additives slow the water-wetting of shales
to improve stability. Brine-based systems
typically eliminate the need to use bentonite for viscosity and fluid loss control,
with water-dispersible polymers added
to control API mud properties.
One of the more intriguing developments in WBMs is using polyamines as
shale stabilizers in high-performance systems. Polyamines disperse readily in
water and are known to stabilize clays
when drilling through water-sensitive
shales. At the AADE Conference, Newpark Drilling Fluids researchers presented
the results of a study examining the relationship between the inhibitive properties
of polyamine compounds and structural
changes to clay substrates.
Newpark used X-ray diffraction
(XRD), linear swell meter testing (LSMT),
and dynamic particle-size imaging to
study three types of polyamines:
* A linear, short-chain alkyl
polyamine;
* An angled, short-chain polyamine;
and
* A long-chain polyamine with modified functionality.
The focus of the work was to study
changes to the clay substrates after they
were treated with polyamines. The data

Water-Based Fluids
Water-based muds are the systems of
choice for onshore resource plays, and
several high-performance WBM products
for enhanced wellbore stability are now
available. The base fluids for these formulations range from freshwater with
very low chloride content to saturated
brines. Using brines for mud weight control and clay inhibition are part of the

collected included the effects of the
polyamine on the bentonite crystalline
structure and the effects on particle size
distribution and shape factors.
Looking at the results of XRD measurements on sodium montmorillonite
(Na-MMT) treated with different
polyamines, the researchers concluded
that the polyamines inserted themselves
within the interstitial layers of Na-MMT
in either a monolayer or dilayer arrangement, depending on their size.
XRD also demonstrated that structural
shifts occurred in the Na-MMT when
treated with polyamines. This structural
shift had a strong correlation with the
substrates' swelling and dispersive behaviors, as measured by LSMT and dynamic particle-size analysis.
This approach potentially can predict
the swelling inhibition capacity of a
polyamine. "The link between all these
techniques provides the potential to establish
a new screening approach for shale inhibitor
selection and a further understanding into
polyamines' inhibition mechanism," Newpark's Ezekeil Hudson II and Antoine
Thuriere state in an AADE paper.
Figure 1 shows some of the LSMT
results. A pellet press included with the
LSMT produces core plugs from ground
Na-MMT. The plugs were immersed in
3 percent volume/volume concentration
inhibitor solutions. The hydration of the
clay was monitored over 24 hours. The

FIGURE 2
Uniform Fluid Weight Before Trip (Left)
And Segregated Weight after 50-Hour Trip (Right)

FIGURE 1
LSMT Pellet Swelling Results
Using Polyamines as Shale Stabilizers
120

18.0
17.5

Total Swell (%)

100

17.0
16.5

16.0
15.5

Tripping ≈ 50 hr

40
20
0

Total Swell (%)

DI Water

3% w/v KCI

3% v/v
Glycol

3% v/v PA1

98.58

66.99

87.94

79.19

3% v/v PA2 3% v/v PA3
83.06

108.61

3% v/v KCI + 3% v/v PA1
10% v/v
+ 10% v/v
Glycol
Glycol
62.24

Source: Hudson and Thuriere, AADE 2016

68 THE AMERICAN OIL & GAS REPORTER

67.24

3% v/v PA2
+ 10% v/v
Glycol
65.74

3% v/v PA3
+ 10% v/v
Glycol
73.90

(a)

(b)

Source: Kulkarni, et. al., IADC/SPE 2016

American Oil and Gas Reporter - November 2016

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