BAKER HUGHES - Drilling Fluids Reference Manual

TABLE OF CONTENTS
• Logistics are normally more complex for invert emulsion fluids than for water based fluids.
For invert emulsion the base fluid has to be transported by boat to the rig, often over
considerable distances, whereas seawater can often be used as the base fluid in water based
systems.
Successful management of lost circulation in deepwater operations should include identification of
possible loss zones, optimization of drilling hydraulics, and a well thought out contingency plan for
the handling of possible lost circulation.
Loss of circulation in a production zone offers additional challenges. Normally, only acid soluble
materials should be added while the production zone is exposed. An engineering program is available
to take much of the guess work out of this process. Bridgewise is the new bridging technology
designed by Baker Hughes Drilling Fluids to maximize hydrocarbon recovery from reservoirs.
Bridgewise calculates the optimum blend of available calcium carbonate additives required to
effectively bridge reservoir pore openings of known size. The Bridgewise calculator is available
on BakerHughesDirect/DRILLING FLUIDS/Toolbox/OnLine Tools and Resources.
WELLBORE BREATHING
Wellbore breathing refers to the situation where losses are experienced while drilling ahead and then
fluid volume recovered when the pumps are turned off. This is often a problem in deepwater
operations where the difference in fracture gradient and pore pressure in any given hole section may
be relatively small. The magnitude of the losses and gains can vary from 25 to 250 barrels.
These loss and gain situations are caused by near-wellbore radial tensile and circumferential tensile
failures. Fractures are initiated when the ECD exceeds the fracture initiation pressure. These fractures
open and accept fluid. When the pumps are shut down, the fluid in the fractures returns to the
wellbore. Typically, fluid is steadily lost during circulation/drilling and is regained when flow is
static/during connections. Thermal stresses can also induce losses and gains in some cases.
Since loss and gain problems result from the initiation of fractures that do not continue to propagate,
mitigation steps will be the same as for lost circulation in general. It is recommended to pre-treat the
system with LCM if this sort of problem is expected. LC-LUBE is an ideal material for this
application as it is an effective LCM while neither detrimentally effecting viscosity nor filtration
control. It exhibits excellent sealing and bridging properties due to the deformable nature of the
material when particles are packed together under compression. It is able to effectively strengthen
fractured and porous formations by plugging fracture/pore throats and prevention of fracture
propagation and pore pressure penetration.DEA studies showed calcium carbonate to be an effective
lost circulation material. LC-LUBE and calcium carbonate, together with CHEK-LOSS FINE, or
CHEK-LOSS PLUS are the recommended materials for pre-treatment of the drilling fluid. The
recommended concentrations are 5 – 10 ppb LC-LUBE, 10 – 15 ppb calcium carbonate and 5 ppb
CHEK-LOSS FINE, giving a total LCM concentration of 20 – 25 ppb.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 13-10