BAKER HUGHES - Drilling Fluids Reference Manual

BOREHOLE PROBLEMS
deflocculant/dispersant. Alternatively substitute the existing product for one better suited
to the bottom hole temperature. Baker Hughes Drilling Fluids’ additives to improve the
thermal stability of water-base systems are MIL-TEMP ® , a low-molecular-weight copolymer,
and ALL-TEMP ® , a sulphonated synthetic inter-polymer. Additions of MIL-
TEMP or ALL-TEMP (0.3 to 3 lb m /bbl) to existing water-base fluids aid in stabilizing
rheological and filtration properties under severe temperature conditions. Laboratory and
field data indicate that these materials are effective at temperatures above 600°F. Care
must be exercised when increasing product concentration. Most chemicals will take up
free water and this can negate any beneficial affects of deflocculation.
• Increased Filtrate
• Add HTHP filtrate reducer – if it is apparent that the filtrate cannot be controlled
economically with existing products a more thermally stable product should be used.
Often this appears an expensive option but usually proves cost effective. Baker Hughes
Drilling Fluids’ additives for filtration control at high temperatures are:
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o
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PYRO-TROL ® , an AMPS/AM co-polymer. Has minimal effect on rheological
properties. Normal treatments are 0.75 – 2.0 lb m /bbl.
KEM-SEAL ® PLUS, an AMPS/AAM co-polymer. In fresh water will increase
viscosity. In brines effect on viscosity is appreciably less. Normal treatment
levels are 0.25 – 2.0 lb m /bbl.
CHEMTROL ® X, a lignite/polymer blend. Has a minimal effect on viscosity.
At temperatures greater than 400°F, caution should be exercised due to CO 2
from thermal degradation. Normal treatment levels are 1.0 to 10.0 lb m /bbl.
Remedial Action – Oil Based Drilling Fluid
• Increased Rheological Properties
• Add base oil – increased filtrate and surface evaporation reduces the total oil content of
the drilling fluid and, if not replaced, will in effect, “dehydrate” the system.
• Add oil wetting agents – by ensuring that all solids are oil wet the inter-particle
reactions between them are reduced. This results in reductions in viscosity and gel
strengths. Care must be taken when adding wetting agents. They are usually concentrated
products that prove very effective thinners for clay based rheological properties in oil
based drilling fluids. Over treatment can reduce suspension characteristics to levels that
will promote inefficient hole cleaning and may allow barite sag to occur.
• Increased HPHT filtrate
• Often increases in HPHT filtrate can be readily, and economically, remedied by the
addition of sufficient lime to restore a good (2 – 3 lb m /bbl) excess in the drilling fluid. If
this is not effective, increased levels of emulsifiers may be required. Ultimately the
addition of a dry powder filtrate reducer (MAGMA-TROL) may be required.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 7-50