BAKER HUGHES - Drilling Fluids Reference Manual

RESERVOIR APPLICATION FLUIDS
These pills may contain up to 50 lb m /bbl of the particular LCM material chosen and are usually
pumped directly across from the thief zone and allowed to sit for at least two hours before
circulation is attempted. This procedure is repeated until circulation is regained.
Both calcium chloride and calcium bromide are non-corrosive, but oxygen can dissolve in these
brines causing oxygen corrosion. Oxygen scavengers such as NOXYGEN TM will effectively
remove oxygen from these types of brines. Brines containing zinc will be acidic, thus they are
corrosive. Film forming inhibitors (such as AMI-TEC TM ) are the additives of preference for
combating this type of corrosion.
BRINE-PAC ® , because it is effective against corrosion by oxygen, carbon dioxide, and hydrogen
sulfide, is a convenient all-purpose corrosion additive. Corrosion will increase as greater
temperatures are encountered.
Mixing heavy brines can generate considerable heat and care must be taken to prevent the
inhalation of any dust particles from the dry products. The use of protective goggles, masks, rubber
gloves, and protective aprons should be mandatory for all rig personnel working with heavy brines.
These brines are hygroscopic and can dry out skin and irritate eyes. Emergency showers and eye
wash stations should be provided on the rig floor and pits. All personnel should be familiar with the
Material Safety Data Sheets (MSDS) of all products.
Other Workover Fluids
Alternative workover fluids to heavy brines that have been utilized in the past include acid soluble
carbonate materials such as calcium carbonate or iron carbonate (siderite) which are used as
weighting agents. When using calcium carbonate, densities up to 14 lb m /gal can be achieved while
densities of up to 18 lb m /gal (2.1 S.G.)can be obtained using iron carbonate as the weighting agent.
Advantages of these types of workover additives include lower cost, resistance to crystallization,
and greater fluid loss control.
Oil-base fluids can also be utilized as workover fluids in certain applications. The advantage of oilbase
fluids over water-base fluids is that the oil filtrate does not damage water-sensitive formations,
and low-density fluids can be formulated for depleted production zones. Conventional oil-base
fluid formulations for drilling applications have disadvantages for workover situations including
oil-wetting of producing zones caused by surfactants in the fluid, emulsion blockage, and solids
invasion.
WELLBORE DISPLACEMENT AND CLEAN-UP PRODUCTS AND
PROCEDURES
Introduction
Transfer of the completion/workover fluid to the wellbore by displacing the fluid already present is
one of the most important procedures of the completion/workover operation. The objective of the
displacement is to replace all of the fluid in the wellbore, usually drilling mud, so that a minimal
amount of displacing fluid is contaminated. Displacements typically follow a simple two step
procedure comprising the conditioning the current wellbore fluid and then displacing with
completion fluid (direct displacement) or by first displacing with water {sea or fresh) followed by
the completion fluid (indirect displacement). The purpose of conditioning the drilling fluid is to
disperse and evenly distribute into the wellbore fluid any solids that may be clinging to the casing
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 6-80