BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Seawater System
1. The seawater system should be pretreated with caustic soda and soda ash to precipitate
any magnesium and calcium. The pH of seawater should reach pH 10.5, using caustic
soda, to precipitate most of the magnesium. This will increase the performance of the
PHPA and eliminate pH decreases due to magnesium.
2. The ALPLEX should be mixed in fresh water (treated with caustic soda for pH 10.5) at a
high concentration (80 to 120 lbm/bbl) in the slug or separate pit and then fed slowly to
the active system (10 bbls/hour+ depending on the total circulating time).
Note:
Do not add ALPLEX directly to untreated seawater as it will not go into solution properly..
3. NEW-DRILL, MIL-PAC, or BIO-LOSE should be premixed in the pretreated brine water
and sheared adequately to enhance the performance of the polymers and prevent any
possible blinding of the shaker screens.
4. MIL-GEL should be pre-hydrated in fresh water to ensure good filter cake quality prior to
adding it to the seawater system.
5. NEW-DRILL should be well sheared prior to drilling to minimize blinding over shaker
screens.
6. MIL-PAC LV (0.75 to 1.0 lbm/bbl) can be substituted for BIO-LOSE (2 to 3 lbm/bbl).
7. XAN-PLEX should be used to increase yield point for better hole cleaning.
8. Use the FSE probe to measure the excess ALPLEX concentration.
Note:
Due to its strong inhibition characteristics, the initial ALPLEX treatment will depend on the
amount of solids in the initial fluid. In unweighted fluid (CEC < 10 meg/100 , less than 2%
LGS) the initial ALPLEX treatment should be about 1 lbm/bbl. The desired ALPLEX
concentration in the total system should be increased as drilling progresses. This measure
will prevent a sharp drop in rheological properties. Use the FSE probe (not mass balance)
to accurately determine the ALPLEX concentration.
Treatment and Maintenance
Maintenance of ALPLEX systems is generally dictated and directly proportional to the reactivity
of the shale being drilled. The following are maintenance guidelines for an ALPLEX system.
1. The pH of fluid should be maintained above 10.0 with small caustic soda or ALPLEX
additions. The pH typically varies between 10 and 11.5 depending on the ALPLEX ®
concentration.
2. Although the ALPLEX system is solids tolerant, the low gravity solids should be
maintained at less than 6%.
3. Use XAN-PLEX for sweeps instead of MIL-GEL.
4. Use caustic soda to raise the pH of ALPLEX fluids.
5. In seawater or high salt ALPLEX systems, use premixed lignite in freshwater for
additional filtration control. To avoid pH drop due to additional LIGCO (lignite),
compensate with caustic soda using a 4:1 (lignite: caustic) ratio.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 3-89