BAKER HUGHES - Drilling Fluids Reference Manual

RESERVOIR APPLICATION FLUIDS
Properties of 85% Calcium Nitrate Solutions (at 25°C) continued
Percent
Weight
Specific
Gravity
(g/cm 3 )
Density
(lb/gal)
85%
Ca(NO 3 ) 2
H 2 O Using
85%
Ca(NO 3 ) 2
(L/m 3 )
Ca(NO 3 ) 2
(mg/L)
Calcium
(mg/L)
Volume
Increase
Factor 85%
Ca(NO 3 ) 2
40 1.303 10.87 516 784 559159 107740 1.278 0.837
41 1.312 10.95 532 776 578038 111193 1.291 0.829
42 1.321 11.02 549 769 597197 114690 1.304 0.821
43 1.33 11.10 566 761 616640 118230 1.318 0.814
44 1.339 11.17 583 753 636370 121815 1.332 0.805
45 1.348 11.25 600 745 656389 125444 1.347 0.797
46 1.357 11.33 617 737 676701 129117 1.362 0.788
47 1.367 11.41 635 729 697308 132837 1.377 0.779
48 1.376 11.49 653 720 718214 136602 1.394 0.770
49 1.386 11.57 671 712 739421 140413 1.410 0.760
50 1.396 11.65 689 703 760933 144271 1.428 0.751
A w
WORKOVER FLUIDS
Many functions of a workover fluid are the same as functions of a drilling fluid. A workover fluid
must:
• Provide sufficient hydrostatic pressure to prevent formation fluids from entering the wellbore
• Be able to clean the hole with reasonable pump pressures and annular velocities
• Prevent excessive fluid (filtrate or whole workover fluid) losses to the formation
• Be stable at the maximum well temperature
• Provide maximum protection against formation damage.
The likelihood of a well being damaged can be much greater during workover operations than
during drilling operations. In the past it was a common practice to use drilling fluid materials
(barite, clays, filtration control agents, and chemicals) for preparing and maintaining workover
fluids. This practice has resulted in formation damage and loss of productivity in a significant
percentage of the wells worked over with these fluids.
Completion operations such as acidizing and fracturing, which are designed to open up a formation
and increase production, also increase the potential for invasion of the formation by the workover
fluid when remedial work is required.
Damage to the formation occurs when:
• solids contained in the workover fluid lost to the formation plug pores and reduce its effective
permeability
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 6-74