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Practical Approaches For Solving Lost Circulation Problems While Drilling
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1.2 LITERATURE REVIEW
Lost
circulation is a broad subject and several studies and measures have
been introduced in the industry to combat it. For example, Moore, (1986)
noted that in shallow, unconsolidated formations where the drilling
fluid may flow easily into the formation, the most common method used to
combat lost circulation is to thicken the mud. This may be done in
fresh water muds by adding flocculating agents such as lime or cement.
He also stated that in areas such as below surface casing in
normal-pressure formations where natural fractures are common, the most
common method used to combat lost circulation is to drill without fluid
returns to the surface. The purpose is to remove the generated cuttings
from the hole and deposit them at the lost circulation zone. However,
this practice requires large volumes of water and close supervision as
there is the possibility of encountering high drill-string torque and
drag.
Current research on lost circulation has been focused on the
use of Lost Circulation Materials (LCMs), especially chemical
formulations which have been proven to be more effective. Hamburger et
al. (1983) of Exxon Production Research Company developed a
Shear-thickening Fluid (STF) which was tested successfully in 10
different wells that experienced severe lost circulation. A STF is a
multi-component system composed of water-swellable material (usually
clay) dispersed in an oil-external emulsion. The emulsion consists of
liquid oil, an oil-soluble surfactant, and aqueous-phase droplets
containing dissolved polymer. At the low shear rates encountered while
it is being pumped down the drill pipe, the fluid is a low-viscosity,
pumpable liquid. Yet as it passes through the drill-bit nozzles, the
resulting high shear rates cause the fluid to thicken irreversibly into a
high strength viscous paste.
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ABSRACT - [ Total Page(s): 1 ]As the demand for petroleum resources increases, drilling of oil and gas wells are often carried out in challenging and hostile environments. Among the top ten drilling challenges facing the oil and gas industry today is the problem of lost circulation. Major progress has been made to understand this problem and how to combat it. However, most of the products and guidelines available for combating lost circulation are often biased towards advertisement for a particular service company. The purpo ... Continue reading---
