Bentonite
Bentonite is an abundant, versatile
mineral found in many regions of the world. Its availability
and unique properties have led to this mineral becoming the
second most-commonly used industrial mineral in drilling fluids
- called muds - after barite. Water-based drilling mud also
commonly consists of additives such as calcium carbonate and
graphite.
Drilling fluids can be divided into
three primary types: water-based, oil-based and synthetic.
Bentonite is among the most popular of the water-based fluids,
and accounts for around 70-80% of the drilling grade bentonite
produced, and around 20% of overall bentonite demand.
Sodium bentonite has gained a
strong foothold in the oilfield market owing to its
viscosifying characteristics and effective sealing and
filtration properties. These properties come from
bentonite’s structure as colloidal clay, comprising mainly
of montmorillonite, meaning the mineral expands when added to
water.
Along with gel formation,
bentonite’s role in the oilfield is principally to seal
borehole walls and lubricate the cutting head. This is a small,
yet vital, part of the oil drilling process.
Bentonite’s popularity in the
oilfield sector is also supported by the fact that there are no
clear substitutes for this mineral in the drilling process.
Indeed, S&B Group, which dedicates 50% of its business to
bentonite, told IM that, bentonite might be
used as a substitute for other materials that have less
flexibility than that of bentonite.
Bentonite reserves
Bentonite deposits can be found in
abundance around the world, yet not all deposits are suitable
for use in the oilfield. Industry bodies such as the American
Petroleum Institute (API) and Oil Company Materials Association
(OCMA) specify stringent requirements for bentonite and other
oilfield minerals determining whether they exhibit the
necessary characteristics for this end-use.
Global bentonite reserves of more
than 10bn tonnes are mainly distributed between the US, China,
the CIS, Germany, Italy, Japan, Greece, Brazil, India and
Turkey. Most of this bentonite is of the calcium variety;
global sodium bentonite reserves are thought to be less than
500m tonnes.
Bentonite news
Bentonite Performance Minerals LLC,
part of the Halliburton group, announced that it is awaiting
approval for two new mines from the South Dakota Department of
Natural Resources (DENR), in late October.
The permits request development of
two sites located northwest of Belle Fourche in Butte County,
South Dakota, each with an estimated tonnage of 5-15,000 tpa
bentonite.
Application documents submitted
to the DENR indicate that both the Killinger Mine and Purple
Mine will cover an area of 2-10 acres
(0.008-0.04km2) at any one time during a seven-year
lifespan.
Bentonite mined at both sites
is expected to be transported from South Dakota to Bentonite
Performance Minerals’ processing plants in Wyoming,
US.
Once operations have concluded,
both mine sites will be reclaimed for use as livestock grazing
rangeland.
Leaking
concerns
Bentonite has also been causing
a stir this year in the US as several spills of the oilfield
mineral occurred as a result of other exploration
work.
One instance at the site of
Canadian mining company Mineral Mountain Resources Ltd, saw
bentonite seep into a creek in Keystone, South Dakota.
Work on site was suspended
until the leak was contained. The DENR confirmed it was
relatively small and non-hazardous.
Barite
The industrial mineral barite
is known by many names the most common being barite and barytes
all derived from the Greek word
βαρύς, meaning heavy.
The high atomic weight of
barite (molecular weight = 233.39 gm) is attributed to the
presence of barium in the compound. This gives barite an
extremely high specific gravity and it is this that makes it a
popular choice for use in oilfields.
Barite powder containing a
minimum 90% barium sulphate with 4.15 specific gravity is
recommended for drilling. For offshore drilling, the specific
gravity should be 4.2. At least 97% of ground barite should
pass through a 75-micron IS sieve and 95% through a 53-micron
IS sieve.
By adding barite to drilling
muds, oilfield companies are able to prevent blowouts of oil
and the collapse of the drilling-well wall. Barite is also used
to carry drill cuttings from the well bottom to the
surface.
The oilfield market accounts
for 84% of global barite production a figure that is expected
to increase with the growing amount of fracking taking place in
the US, Europe, China and other areas of the world.
Some fracking wells are a lot
deeper than those used in conventional drilling, meaning more
barite is needed (see fracking box below).
In the drilling mud market,
alternatives to barite include celestite, ilmenite, iron ore,
and synthetic hematite that is manufactured in Germany. None of
these substitutes, however, has had a major impact on the
barite drilling mud industry, according to the USGS.
Barite reserves
Barite manufacturers and processors
are located all over the world in countries such as Algeria,
Brazil, China, France, Gabon, Germany, India, Morocco,
Netherlands, Spain, Tunisia, Turkey, UAE, the UK and the US. In
fact, many of these countries have formed associations in
connection with the barite industry.
As is the case with many industrial
minerals markets, China leads the way in terms of barite
reserves, hosting approximately 100m tonnes and producing more
than 4m tonnes in 2012, according to USGS figures (see
table 1).
“For many years China has been
the dominant producer and exporter of drilling-grade barite
really dwarfing everybody else,” John Newcaster, VP
distribution and logistics at Baker Hughes, told
IM.
“China is still huge and still
very significant, but what’s great to see is [that] some
of the other markets in the world are now coming on stream.
Notably, Morocco has really stepped up its production and
exports; India has stepped up to some extent and now our
industry is looking at other sources around the world,” he
explained.
Algeria holds 29m tonnes, producing
only 60m tonnes in 2012 while India is the world’s third
largest country in terms of reserves, with 32m tonnes,
producing 1.4m tonnes in 2012.
The US is home to the
fourth-largest barite reserves with around 15m tonnes and
produced 654,000 tonnes barite last year. Of this total 95% was
used in the drilling mud market, the USGS states.
Newcaster told IM
that many producers are now looking at US-based barite reserves
in Nevada, for example, to overcome the potential supply issues
faced elsewhere in the world.
Barite
developments
The barite market has been more
active than that of bentonite in terms of news over the past 12
months, with several companies announcing new developments.
One that has been in the pipeline
for some time is Mabwe Minerals’ Dodge Mine, located in
Zimbabwe, Africa.
In late November 2013, the company
received its first purchase order from Steinbock Minerals
amounting to 2,000 tonnes barite.
Mabwe estimates Dodge Mine barite
production as being up to 165,000 tpa, and anticipates
shipments of 140,000 tpa bulk barite in 2014.
By integrating a crushing
processing facility in Q2 2014, the company aims to raise
revenues to between $14m and $16m.
Later, in December, a new barite
company was formed in Algeria, named National Company for
Barium Barytal.
The company will undertake
evaluation, development, and production of the Draissa barite
deposit in Bechar province, in western Algeria.
With a capitalisation of 200m
Algerian Dinar ($2.5m*), the company was formed on 2 December
as a joint venture between Sonatrach (60% split equally between
its subsidiaries NPHS, ENTP, and ENAFOR) and Manadjim El
Djazair (Manal), through its subsidiary Entreprise Nationale
des Produits Miniers Non-Ferreux et des Substances Utiles (ENOF
40%).
The Draissa resource amounts to
10.4m tonnes in total, with an average BaSO4 content
of 74.7% and at 4.2 SG.
Drilling fluid pricing
Speaking with IM
in June this year, Newcaster said that the price volatility of
both barite and bentonite has been dramatic.
“The two key industrial
minerals that go into drilling fluids are bentonite and barite
and price volatility in the last few years has been dramatic.
Starting in about 2011, the shortages that we’ve seen in
China in particular the main supplier globally really caused
significant pain,” Newcaster explained.
The reason behind this pain,
Newcaster said, was not the fact that the price of these
minerals going up, but the rate in which it increased.
“It really makes it difficult
for companies in our business who are in long-term contracts,
with very large exploration and production oil companies, to go
in and get recovery from that,” he added.
According to US-based sources,
bentonite prices are not expected to move before the end of
2013, but may alter in the first two months of 2014.
After fluctuating over the past 12
months, sources told IM that for now
“prices are stable”.
As we enter the first two months of
2014, prices could increase 3-4%, one source said, while others
suggested pricing will remain flat into this year.
Frac sand
Unlike barite and bentonite, which
are both used in the conventional and non-conventional drilling
process, frac sand, as the name suggests, is only used in
fracking. The sand is a proppant material, which is used to
‘prop’ open fractures made in shale rock during the
fracking process. These allow natural oil or gas trapped in the
rock to flow to the well surface.
There are three main types of
proppant used in the fracking process: raw silica sand, ceramic
beads (see below) and resin-coated versions of each of
these.
Like other oilfield minerals,
silica sand suitable for use as frac sand is specified by the
API. Some of these qualities include that the percentage of
quartz (SiO2) must be 99% or more and crush
resistance must be high so that the sand can withstand
compressive stresses of 4,000-6,000 psi max. fines wt.%: 14%
for 20-40, 14% 16-30 mesh, 10% 30-50 mesh, 6% 40-70 mesh, 20%
6-12 mesh.
Acid solubility must be low and
roundness and sphericity must meet API >0.6. Turbidity tests
also measure the amount of light that can pass through a
wetting fluid. The higher the measurement, the more suspended
particles are present. Turbidity is measured in Formazin
Turbidity Units (FTU) and the minimum threshold limit is
<250 FTU. Producers will look for a lower turbidity rating
as high turbidity readings can be an indication of poor
proppant manufacturing, transportation, or handling practices,
which can lead to interference with the fluid chemistry.
Frac sand
deposits
Frac sand has been the proppant
material of choice for many years as it remains in abundant
supply around the world and is a cheaper alternative to ceramic
proppant material.
The world’s largest producer
of frac sand is the US, where a fracking boom has been driving
demand for this mineral. Since fracking really took off in the
US 60 years ago, over 1m wells have been drilled using this
method.
High-purity quartz sands are common
in the US, and many of these deposits are currently being
exploited. The most notable deposits of API-grade frac sand can
be found in sandstone formations such as the St. Peter (or
Ottawa) sandstone (primarily mined in Illinois, Wisconsin,
Minnesota, and Missouri), the Jordan sandstone (Minnesota and
Wisconsin), and the Hickory sandstone (Brady, Texas).
Within the US, Wisconsin has become
the US’s top hub of frac sand activity, showing a 100%
increase in frac sand activity between 2011 and 2012, growing
from just a handful of facilities to more than 100 frac sand
sites.
Data from the USGS highlights that
Wisconsin ranked third in total US industrial silica sand
production in 2010 at 3.39m tonnes, accounting for 11.3%, after
Illinois (4.37m tonnes, 15%) and Texas (3.61m tonnes, 12.5%).
However, in terms of frac sand production, the state is leading
the way.
“The [new DNR] staff position
will speed up the process for frac sand oversight and
regulation of frac sand mining,” Walker explained.
The state’s largest frac sand
mining and processing facility, located in Trempealeau County,
was approved in April after a nine-hour public hearing and
meeting.
Other states in the US that are
abundant in API-grade frac sand include Illinois and Minnesota,
however these areas have experienced more limited success due
to government moratoria that have been put in place due to
health and environmental concerns surrounding silica sand.
The US Occupational Safety and
Health Administration (OSHA) is working to produce new safety
standards for industries that utilise silica sand, such as
fracking, in a bid to overcome these concerns.
In late August 2013, the OSHA
published proposals for two new crystalline silica safety
standards, suggesting, among other measures, a new permitted
exposure level (PEL) for respirable crystalline silica,
together with new provisions for measuring how much silica
workers are exposed to.
“Exposure to silica can be
deadly, and limiting that exposure is essential,” Dr David
Michaels, assistant secretary for labour at the OSHA, said.
“This proposal is expected to
prevent thousands of deaths from silicosis - an incurable and
progressive disease - as well as lung cancer, other respiratory
diseases and kidney disease. We’re looking forward to
public comment on the proposal,” he added.
At present, the OSHA enforces PELs
for crystalline silica that were originally adopted in
1971.
For industrial minerals markets,
such as construction and general sand industries, the current
PEL is 100 micrograms respirable crystalline silica per cubic
metre of air during an eight-hour period
(0.1mg/m3).
OSHA recommends that the PEL should
be reduced to 50 micrograms respirable crystalline silica per
cubic metre of air (0.05mg/m3 air) during an
eight-hour period and should apply to all industries - general,
maritime and construction.
While this move may be welcomed by
silica sand mining detractors, those working in the industry
have come out in opposition, stating that the PEL is
sufficient.
The National Industrial Sand
Association (NISA) said that it opposes the suggestion to lower
the PEL “because [the current PEL] has been proven
protective”.
“NISA companies have
demonstrated that silicosis can be prevented when exposures are
maintained consistently below the 0.1mg/m3 PEL.
Lowering the PEL is not justified,” the association
said.
Industrial Minerals Association -
North America (IMA-NA) told IM that its
position on the PEL is consistent with NISA’s
standpoint.
“A lower PEL will not
contribute to safer workplaces, and will have catastrophic
economic impacts across a broad spectrum of industries,” a
statement from IMA-NA said.
“In fact, an analysis by the
American Chemistry Council Crystalline Silica Panel indicates
that the total economic impact of halving the current PEL would
amount to $5.45bn/year,” it added.
Ceramic
proppants
While frac sand is by far the
market leader in terms of proppant consumption, ceramic
proppants have become the material of choice for those working
with deeper wells. The main reason for this is that ceramic
proppants, which most often contain sintered bauxite or kaolin,
are proven to be stronger, denser and more uniformly round than
frac sand, making the ceramic proppant pack more conductive
(meaning more hydrocarbons flow to the surface of the
well).
However, while these alternatives
may be more effective when used in high-pressure, deeper wells,
they are far more expensive and are less available at
present.
It is this large market value that
is driving development in the ceramic proppant market and
several companies are working in this space to increase the
overall volume of ceramic options used.
In late October 2013, halloysite
and iron oxide producer, Applied Minerals Inc., entered into an
agreement with OPF Enterprises LLC to develop a new range of
ceramic proppants.
The companies plan to utilise the
high-grade clay resource at Applied’s Dragon mine, located
in Utah, US, to manufacture proppants for use in the North
American fracking industry.
Preliminary development work
indicates that the alumina-rich clay at the Dragon Mine’s
Western Area meets the crush resistance, permeability and
specific gravity characteristics required for proppant use in
high pressure wells.
The mine’s location will also
aid the delivery of ceramic proppants to the Bakken Shale
formation, which utilises approximately $1bn ceramic proppants
a year, and the Niobrara shale basin in North America.
Another developer, Carbo Ceramics
Inc., introduced a new proppant grade in early October,
designed to maximise and sustain hydrocarbon flow at high
closure stresses for the life of a fracking well.
Named Kryptosphere, the proppant
solution has been developed in response to a request from a
major drilling operator working in the Gulf of Mexico.
According to Carbo, Kryptosphere is
able to deliver more than twice the baseline conductivity of
the more widely used bauxite-based, high strength ceramic
proppants available on the market and is able to work at 20,000
psi closure stresses, making it an ideal solution for deeper
wells.
Although Carbo was unavailable for
comment when approached by IM, the
company’s published technical specifications for
Kryptosphere indicate that this new proppant has “high
alumina” content, and is not bauxite-based.
Future oilfield mineral
potential
Unlike many industrial minerals
markets, the oilfield space is a safe one for many mineral
producers. While others have experienced a rough ride over the
past couple of years as the economic downturn significantly
impacted business, those working in the oilfield minerals
market have enjoyed fairly steady demand.
Despite some concerns over the
oilfield mineral supply situation especially for muds minerals
from China the supply and demand situation has not only
remained constant of late, it has actually risen.
This demand is expected to continue over the coming years as
developments, in unconventional drilling especially, take
off.
Fracking
The fracking process consists of both horizontal and vertical
drilling. First, a vertical hole will be drilled down to around
10,000ft (3,048 metres), which is where the shale bed can be
found. The second drilling stage is horizontal and takes place
at a ‘kick-off point’, which is where the shale
formation begins. This stage takes place at around 10,000ft and
can stretch from around 1,000-10,000ft (304-3,048 metres)
depending on the company’s requirements.
Once the hole has been drilled, a
perforating gun is lowered down to break the barrier between
the shale rock and the drill casing to create tiny fractures in
the rock. Fracking fluid is then pumped at high pressure into
the well in order to increase the size of the fractures in the
shale. This fluid is approximately 95-99% water, 2% proppants
and 0.5% different chemicals. Proppant consumption varies from
well to well but is usually in the range of 800-3,000 tonnes
per well.
The proppant material now props open the fractures in the
shale rock, allowing natural oil and gas to flow freely up to
the surface of the well.