OBM Brine Calculator
Calculate brine specific gravity, density, and water phase volumes for CaCl&sub2;, CaBr&sub2;, NaCl, and KCl brines. Designed for oil-based mud water phase design.
Input Parameters
Results at 68°F (20°C)
Brine SG
--
at 68°F
Density
--
lb/gal
Salinity
--
wt%
Salinity
--
ppm
Density
--
lb/ft³
Density
--
kg/m³
Volume Expansion Factor
--
bbl brine / bbl water
Salt Required
--
lbs
Water Required
--
bbl
Total Brine Volume
--
bbl
Effective Salinity (mode 2)
--
wt%
--
Correlations from GPSA Engineering Data Book (14th ed.)
SG vs. Salinity Curve
Specific gravity at 68°F. Dashed line = crystallization limit. Dot = current operating point.
How this was calculated
CaCl&sub2; SG: SG = 1.0 + 0.007625×S + 0.0000638×S², S = wt%, valid 0–40% (GPSA 14th ed. tabular fit)
CaBr&sub2; SG: SG = 1.000168 + 0.007638×S + 0.00004698×S², S = wt%, valid 0–52% (least-squares fit to industry density tables)
NaCl SG: SG = 0.9982 + 0.007071×S + 0.00003018×S², S = wt%, valid 0–26% (API / GPSA 14th ed.)
KCl SG: SG = 0.9982 + 0.006327×S + 0.00001878×S², S = wt%, valid 0–26% (GPSA 14th ed.)
Density: ρ (ppg) = SG × 8.345 lb/gal (water density at 68°F)
Volume Expansion: Vbrine/Vwater = 1 / (SG × (1 − salinity_fraction)), from mass balance: Vbrine/Vwater = ρwater / (ρbrine × (1 − w))
Salt Mass (Mode 1): msalt = (salinity_wt / 100) × ρbrine × 42 × Vbrine lbs/bbl conversion
Reference: GPSA Engineering Data Book, 14th Edition. Brines chapter; SPE published density correlations.
Need help designing your water phase chemistry or OBM formulation?
Our team has optimized brine systems for HPHT wells, offshore operations, and shale inhibition across multiple basins.
Book a free strategy call →Related Tools
OBM Brine Design: Why It Matters
The water phase activity of an oil-based mud is controlled by the type and concentration of brine used. Matching the water activity of the brine to the formation water activity is critical for shale inhibition: too little salt and the formation swells; too much and the shale dehydrates. Calcium chloride (CaCl&sub2;) is the most common OBM brine, while calcium bromide (CaBr&sub2;) extends density reach above 11.6 ppg without solids. Sodium chloride and potassium chloride see use in specific shale inhibition applications.
This calculator implements published density correlations from the GPSA Engineering Data Book for CaCl&sub2;, NaCl, and KCl, and an exponential correlation for CaBr&sub2;. All computations run entirely in your browser — no data is sent to any server. Built by Groundwork Analytics, founded by Dr. Mehrdad Shirangi (Stanford PhD, Energy Systems).