American Oil and Gas Reporter - September 2024 - 69

SpecialReport: Pipeline Infrastructure
H2S Treatment Continues To Improve
By Paul Stephens
In many areas of the Permian Basin in
general and the Delaware Basin in particular,
hydrogen sulfide is becoming an increasingly
common concern. Through complex
geologic activity, many of the most promising
drilling opportunities that remain in
the Delaware Basin target formations that
contain relatively high concentrations of
the potentially deadly sour gas.
Because dealing with H2S adds extra
costs, operators prioritize sweet formations
when all other aspects are equal. However,
the sour formations in the Delaware Basin
contain so much oil that they increasingly
are competing for capital as operators develop
their acreage. One geologist estimated
that more than half of the Delaware Basin's
future wells will produce sour gas.
Meanwhile, pipeline operators are taking
a closer look at their corrosion risks
and tightening their standards for H2S
concentrations. Corrosion risk assessments
are mandated by the Pipeline and Hazardous
Materials Safety Administration's
Pipeline Safety Mega Rule, but I suspect
many of the changes would be happening
regardless. No one wants a pipeline rupture
to expose people or the environment to
H2S. Additionally, state and federal regulations
are becoming stricter regarding
flaring of sour natural gas.
Fortunately, the industry has gotten
much better at handling it. Long ago, operators
would use wood chips to absorb
H2S from sour gas, plug wells with high
H2S volumes or build expensive plants
to treat the gas. Today, most operators
rely on a far more economic solution,
the chemical scavenger MEA triazine.
Although it has been in use since the
1980s, triazine still is one of the best
scavengers in many applications.
Alternatives' Appeal
Unfortunately, triazine comes with a
significant downside. As it reacts with
H2S, it turns into sulfur-containing liquid
that must be hauled away for disposal.
Trucking and handling this spent triazine
can be costly. In some areas, disposal
well operators no longer accept it because
it's incompatible with the area's produced
water. They may be able to handle some
scavenger, but if the amount exceeds the
reaction stoichiometry threshold, plugging
solids will form.
As activity in the Delaware Basin increasingly
focuses on formations with
hydrogen sulfide challenges, bubble towers
like this one will become more common.
The inevitability of encountering
dangerous sour gas and oil is accelerating
interest in novel H2S scavengers
that can simplify operations and reduce
costs in many applications.
SEPTEMBER 2024 69
It does not help that spent triazine
stinks. Like most chemicals, it can be
handled safely with proper personal protective
equipment. But for some disposal
well operators, the extra revenue is not
worth the hassle or risk.
That is where an expanding suite of
MEA triazine alternatives steps in. In
many applications, spent material from
the right alternative can dissolve in produced
water without causing precipitates
to form. Instead of designating a separate
tank in the tank battery for spent scavengers,
the operator simply sends the
scavenger into the produced water.
This convenience adds up to significant
cost savings. Normally, a lease operator
needs to check the scavenger tank and
periodically call a water hauler to take
the scavenger away. This service frequently
costs $7-$30 a barrel, as well as compensation
for driving time. At sites that
process large volumes of sour gas, eliminating
scavenger-specific trips can save
thousands of dollars a month.
Affordable Options
With knowledge of certain chemical
reactions, it's possible to provide alternative
scavengers that are soluble in produced
water but still available at a cost comparable
to MEA triazine.
Even so, there are situations where
triazine continues to be the best solution.
Sometimes the alternatives are incompatible
with produced water or offer too
little benefit to warrant forgoing a familiar
workhorse.
In other applications, external factors
favor triazine. For example, triazine endures
condensate contamination more effectively
than many other scavengers.
Ideally, condensate will be removed before
the gas enters the treatment vessel. However,
pressure, temperature and volume
conditions complicate the situation. When
condensate persists despite the operator's
best efforts, triazine may prove to be the
most reliable and economic scavenger.
The industry standard also may cost
less on sites that must treat an especially
large volume of gas because it can be
run at higher concentrations. Higher
concentrations mean fewer gallons are
required at the site, thus reducing transportation
costs.
Yet in three out of four applications,
it's possible and worthwhile to switch to
an alternative. This is true whether the
scavenger is applied by bubble towers,
mixers or pipeline atomizers.
In pipeline atomizer applications, alternatives
can reduce chemical consumption.
Because alternatives often have a
lower molecular weight than triazine,
they disperse through a gas stream more
quickly and thoroughly. This dispersion
increases the chance each droplet of scavenger
will encounter H2S, allowing a
smaller volume to remove more.
American Oil and Gas Reporter - September 2024

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