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The Future of Drilling-Grade Barite Weight Material„A Case for a Substitute Specification Copyright 2006, Society of Petroleum Engineers

This paper was prepared for presentation at the 2006 SPE Annual Technical Conference and
Exhibition held in San Antonio, Texas, U.S.A., 2427 September 2006.

This paper was selected for presentation by an SPE Program Committee following review of
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Abstract
Drilling grade barite, the fundamental drilling fluids weight
material for over 8 decades, remains the primary source of
ore product to adjust drilling mud densities around the world.
However, quality, economically viable, and attainable supplies
of 4.2 specific gravity barite ore for oilfield use are rapidly
depleting. This is particularly true in the North American
market, where significant foreign imports of barite ore are
required to meet high demands from deepwater, Central US,
and Western Canada drilling regimes. Without significant
worldwide investments to locate and produce material to meet
current API 4.2 s.g. and contaminant specifications, it is
unlikely that producers of drilling grade barite will be able to
supply the industry with a low-cost product in just a few short
years. A viable alternative for less critical drilling applications
is to use 4.10 specific gravity ore that possesses all the quality
specifications of the current material.
Industry acceptance of this reduced specific gravity
material, co-existing with the current standard, could extend
barite supplies by 5 years, or more, with only modest
investment. The intent of this paper is to share results from a
strategy now being undertaken to introduce and demonstrate
the viability of the substitute specification ore in US
applications. Also presented are laboratory studies that show
that use of the 4.10-s.g. substitute will have minimal impact on
the performance of most drilling fluids.

Introduction
Barite (barium sulfate - BaSO
4
) is the most common and
widely consumed weight material additive for drilling fluids.
It is also used in many other applications including as a filler
and weight material for paints, rubbers and plastics. The
automobile industry uses barite for brake pads and as an
additive in paint primer for gloss and protection. Barite is
capable of blocking gamma and x-ray emissions and is
commonly used as an aggregate in high density concrete as a
shielding at nuclear power plants, hospitals, and research
facilities. By far, however, barite is most widely used in
drilling fluids as the primary density adjustment or weight-
up additive. Drilling grade barite is appealing over other
choices in weighting material due to its generally benign
characteristics.
In general, barite is not considered harmful when used in
accordance with recommended workplace precautions and is
usually deemed as safe. In almost all geographic areas,
drilling grade barites are environmentally acceptable from the
standpoint of disposal as part of the used drilling fluid. Barite
used in oilfield application is regulated for chemical purity as
it is recognized that some sources of barite may contain heavy
metals ranging from trace amounts to some exceeding 3% by
weight. The industry has recognized that discharges of heavy
metals may cause environmental damage and potentially
human health problems.
1
Due to the allowable and significant
discharge of barite-laden drilling fluids, most countries
regulatory bodies set maximum allowable levels of heavy
metals in barite such as a mercury (Hg) and cadmium (Cd),
2

and some are considering regulating lead (Pb) content. The
U.S. Environmental Protection Agency limits mercury at no
greater than 1 mg/kg and cadmium at no more than 3 mg/kg.
Mined and processed barite containing low trace heavy metal
content below these limits are currently considered not to
impose a significant environmental threat.
Barite consistency and quality allows its use as a density
increasing agent imparting minimal impact on most drilling
fluids. Fluid density adjustment using barite does not
normally affect the chemical properties of either water-based
or invert (oil-based) fluids. The physical characteristics of
barite weighted fluids are only slightly affected in most
drilling fluids. Viscosity adjustment of fluids to support the
4.2-s.g barite is required and depending on fluid type, some
fluids are limited to varying ranges of densities when weight
material is added, most notably in water-based systems with
high dispersible polymer concentrations. Recently and as
result of increasing numbers of high angle, extended reach
drilling projects, barite sag or settling, has been identified as a
serious issue. Understanding this phenomena and mitigating
its occurrence and further adjustments in drilling fluid
physical properties are being addressed.
3
In comparison to
other oilfield weighting additives, barite is less abrasive,
causing little damage to drillstrings, bottomhole assemblies,
drill bits, and circulating pump parts. Barite is non-magnetic

SPE 103135
The Future of Drilling-Grade Barite Weight MaterialA Case for a Substitute
Specification
J.R. Bruton, SPE, J. Bacho, SPE, and J.A. Newcaster, M-I S
WACO