BAKER HUGHES - Drilling Fluids Reference Manual

BOREHOLE PROBLEMS
20 feet per minute with a 17½ inch bit and a flow rate of 500 gal/min could result in a fluid
density increase from 10.0 to 13.6 lb m /gal in the annulus. While this may be an extreme example
of a fluid density increase when drilling large diameter holes at a high penetration rate, it
effectively describes the situation. Remedial procedures for this problem would be (1) decrease
penetration rate, (2) increase pump rate, or (3) circulate several minutes after drilling each drill
pipe joint down. Real time annular pressure sensors have proven extremely useful in monitoring
these conditions.
Partial Loss
Partial loss (25–100 bbl/hr WBM or, 10–30 bbl/hr OBM) is generally associated with coarsely
permeable zones (gravel beds or vugular limestones), faulty cement jobs, and induced or existing
fracturing. As noted earlier, a defective cement job is normally solved by cement squeezes. Loose
to coarsely permeable and finely fractured zones may be cured by adding materials such as
medium MILPLUG ® , MIL-SEAL TM , MIL-CEDAR FIBER TM , Kwik-Seal, MIL-FIBER ® ,
MILFLAKE ® and SOLUFLAKE TM (acid soluble). If loss is severe, mix a concentration of lost
circulation material (30 to 40 lb m /bbl of MIL-SEAL, for example) into a portion of the system
and spot opposite the loss zone. After spotting this material, pull into the casing and wait six to
eight hours.
Another technique which has been successful with partial fluid loss is squeezing the loss zone
with high filter loss slurries such as SOLU-SQUEEZE or Diaseal M. The addition of 10 to 20
lb m /bbl of MIL-SEAL to this slurry will generally improve the chances of success. Mixing
procedures for Diaseal M are given in Table 7-1. When applying a high fluid loss slurry, squeeze
slowly (½ to 1½ bbl/min) with low squeeze pressures (50 to 100 psi). Normally, final squeeze
pressures should not exceed 0.1 psi per foot of depth. Obviously, for low squeeze pressures, it is
desirable to have an accurate, low-pressure gauge for reading annular pressures.
Density
Diaseal M
MIL-BAR ® Water
(lbm/gal) (lb) (sacks) (sacks)
(bbl)
9 50 1.00 0.0 0.87
10 50 1.00 0.6 0.84
11 47 0.94 1.2 0.80
12 42 0.84 1.8 0.77
13 38 0.76 2.3 0.74
14 34 0.68 2.9 0.70
15 31 0.62 3.5 0.67
16 28 0.56 4.0 0.63
17 25 0.50 4.6 0.60
18 22 0.44 5.2 0.56
Example: 100 bbl of 14 lb m /gal Diaseal M slurry required 68 sacks Diaseal M,
290 sacks MIL-BAR, 70 bbl water, and MIL-PLUG if desired
Table 7 - 1 Formula for Preparing One Barrel Diaseal M Weighted Slurry with Fresh Water,
Bay Water, or Sea Water
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 7-24