OBM Mass Balance Calculator
Complete volumetric and mass balance for oil-based (invert emulsion) drilling fluid systems. Enter your mud recipe, compute mud weight, OWR, phase volumes, and treatment requirements.
Formulas from Bourgoyne et al., Applied Drilling Engineering (SPE Textbook Series, Vol. 2)
Mud Recipe — Components
| Component | Volume (bbl) | Mass (lbs) | SG | Category | Input Mode |
|---|
Mass Balance Results
Mud Weight
--
ppg
Mud Weight (SG)
--
g/cm³
Mud Weight
--
lb/ft³
Mud Weight
--
kg/m³
Oil/Water Ratio
--
% oil in liquid phase
Total Volume
--
bbl
Total Mass
--
lbs
Solids Content
--
vol%
Phase Volume Breakdown
Oil Phase
--
-- bbl
Water/Brine Phase
--
-- bbl
Solids + Additives
--
-- bbl
Per-Component Summary
| Component | Category | Volume (bbl) | Mass (lbs) | Vol% |
|---|
Volume Breakdown by Phase
Mass Breakdown by Component
Retort Back-Calculation (Field Retort Data)
Enter retort still readings to back-calculate high-gravity and low-gravity solids from field retort data.
Treatment Calculator
Calculate how much material to add to reach a target mud weight or oil/water ratio. Based on current balanced mud in the recipe above.
Weigh Up with Barite HGS = 4.20 SG
Auto-filled from recipe calculation
Barite to Add
--
lbs per bbl of current mud
Volume increase
--
bbl added per bbl of current mud
OWR Adjustment
Auto-filled from recipe calculation
Material to Add
--
per bbl of current mud
Download Full Report
Drilling Fluid Mass Balance Report with component table, phase breakdown, mud weight, OWR, and treatment recommendations — emailed as PDF.
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Understanding OBM Mass Balance
An oil-based mud (OBM) or invert emulsion is a drilling fluid where the continuous phase is oil (diesel, mineral oil, or synthetic base fluid) and water or brine is the dispersed (internal) phase. OBMs are preferred in shale-sensitive formations, high-temperature environments, and extended-reach wells due to their superior lubrication, shale inhibition, and thermal stability.
The oil/water ratio (OWR) defines the ratio of oil to total liquid and is the primary system identifier — typical OBMs run 70/30 to 90/10 (oil/water). Mud weight is controlled through the addition of high-gravity solids (HGS), predominantly barite (SG 4.20) or hematite (SG 5.05), and the volumetric balance must be maintained for each recipe change.
The mass balance approach converts all component masses to volumes using each component's specific gravity, then sums to compute mud weight. This is the standard approach in Bourgoyne et al., Applied Drilling Engineering (SPE Textbook Series, 1986) and the IADC Drilling Manual. All calculations run in your browser — no data is sent to any server.
Built by Groundwork Analytics, a petroleum engineering consulting firm founded by Dr. Mehrdad Shirangi (Stanford PhD, Energy Systems Optimization).