Barite Sag is the settling of barite particles in the wellbore (or other weighting materials), which results in undesirable fluctuations in drilling fluid density. A variety of major drilling problems including lost circulation, well control difficulties, poor cement jobs, and stuck pipe can result from uncontrolled barite sag. Study of this phenomenon and how to mitigate its effects has long been of interest. This paper describes a fundamental mathematical approach to analyze the settling of barite particles in shear flow of Newtonian fluids. A set of four coupled partial differential equations to describe dynamic barite sag in Newtonian fluids in pipe flow is obtained by applying mass and momentum conservation for solid and liquid phase. Solid concentration in axial and radial directions as a function of time is calculated by using an explicit numerical method to solve these equations. A number of experiments in a flow loop were conducted to verify the mathematical model. Two mass flow meters were installed at the inlet and outlet of the flow loop’s test section. Differences in the density measurements over time were converted to the solid accumulation, which was compared with results from the modeling. In addition, based on the experimental results, three different stages of barite accumulation due to the settling and bed pickup of barite particles during circulation will be presented. The proposed methodology and results of this study will help drillers have a better understanding in terms of undesirable density fluctuations and barite bed characteristics.

References

References
1.
Bern
,
P. A.
,
Oort
,
E.
,
Neustadt
,
B.
,
Ebeltoft
,
H.
,
Zurdo
,
C.
,
Zamora
,
M.
, and
Slater
,
K. S.
, 1998, “
Barite Sag: Measurement, Modeling, and Management
Presented at the 1998 IADC/SPE Asia Pacific Drilling Technology Conference
,
Jakarta
, Sept. 1998, Paper SPE
47784
.
2.
Bern
,
P. A.
,
Zamora
,
M.
,
Slater
,
K. S.
, and
Hearn
,
P. J.
, 2008, “
The Influence of Drilling Variables on Barite Sag
Presented at the SPE Annual Technical Conference held in Denver
,
Colorado
, Oct. 2008, Paper SPE
36670
.
3.
Nunziato
,
J.
, 1983, “
A Multiphase Mixture Theory for Fluid-Particle Flows
,”
Theory of Dispersed Multiphase Flow
, edited by
Richard
E. Meyer
,
192
226
,
Academic Press
,
New York
.
4.
Richardson
,
J. F.
, and
Zaki
,
W. N.
, 1954, “
Sedimentation and Fluidisation: Part I
,”
Trans. Inst. Chem. Eng
.,
32
, pp.
33
52
.
5.
Scott
,
P.
,
Zamora
,
M.
, and
Aldea
,
C.
, 2004, “
Barite-Sag Management: Challenges, Strategies, Opportunities
,”
Presented at the IADC/SPE Drilling Conference
,
Dallas, Texas
, Mar. 2004, Paper SPE IADC/SPE 87136.
6.
Shook
,
A.
, and
Roco
,
C.
, 1991
Slurry Flow – Principles and Practice
,
Butterworth-Heinemann
,
Boston
.
You do not currently have access to this content.