FORM-A-BLOK AS Acid-Soluble Lost Circulation Pill | SLB


Acid-soluble lost circulation pill

Schlumberger Oilfield Services

The FORM-A-BLOK AS acid-soluble lost circulation pill is a single-sack proprietary blend designed for wellbore strengthening applications and a wide variety of lost circulation scenarios, including fractures and matrix permeability. This product is applied in the form of a pill which, depending on the application, dewaters or deoils rapidly to form a high-strength plug.

The pill can be used in water-base or nonaqueous drilling fluids and at temperatures up to 350 degF [177 degC]. The recommended concentration of FORM-A-BLOK AS pill is 32-lbm/bbl [91-kg/m3] for all fluid densities in freshwater, seawater, or oil- or synthetic-base systems. Mixing a water-base pill will provide the maximum strength. The slurry is weighted with SAFE-CARB ground marble bridging agent. M-I SWACO recommends continuously agitating the pill until it is pumped and pulling the pump screens prior to pumping.

Water-Based Pill Formulation

Density, lbm/galUS [Relative Density] Freshwater Volume, bbl FORM-A-BLOK AS Pill Concentration, lbm/bbl SAFE-CARB 40 Agent Concentration, lbm/bbl
9 [1.08] 0.95 32 14
10 [1.20] 0.88 32 81
12 [1.40] 0.75 32 210
14 [1.60] 0.62 32 340

NAF-Based Pill Formulation (Based on 0.81-Relative-Density Oil)

Density, lbm/galUS [Relative Density] NAF Volume, bbl FORM-A-BLOK AS Pill Concentration, lbm/bbl SAFE-CARB 40 Agent Concentration, lbm/bbl
9 [1.08] 0.86 30 100
10 [1.20] 0.80 32 160
12 [1.44] 0.68 32 280
14 [1.68] 0.56 32 397


Physical Properties
Physical appearance Gray powder
Relative density 2.50–2.60
Solubility in water Insoluble
Solubility in 15% HCl <212 degF [100 degC] 92%–96%
Solubility in 5% HCl >212 degF [100 degC] 92%–96%

Toxicity and handling

Bioassay information is available upon request. Handle as an industrial chemical, wear protective equipment, and observe the precautions described in the material safety datasheet (SDS).

Packaging and storage

The FORM-A-BLOK AS pill is packaged in 32-lbm [14.5-kg] multiwell paper sacks. Store in a dry, well- ventilated area. Keep container closed when not in use. Store away from incompatibles. Follow safe warehousing practices regarding palletizing, banding, shrink-wrapping, and stacking.


  • Wellbore strengthening
  • Partial to wide-ranging severe lost circulation
  • Openhole remedial and preventive lost circulation squeezing
  • Improving casing shoe integrity
  • Cased hole squeezing for sealing perforations and casing leaks


  • Compatibility with freshwater, seawater, and nonaqueous drilling fluid (NAF)
  • Temperature stability up to 350 degF [177 degC]
  • Easy mixing in density up to 14.0 lbm/gal [1.68 relative density]
  • Simplified deployment that requires no activator or retarder
  • Temperature-independent plug formation
  • Premixable in advance of pumping if pill is continuously agitated