A bottle test gives you a dose in parts per million (ppm). To order chemical, size an injection pump, and budget, you need that as litres per day. The conversion has two steps — work out the total produced fluid from the oil rate and water cut, then take the ppm of it — and one thing people get wrong: demulsifier is dosed on the total produced fluid, oil plus water, not on the oil alone. This page shows the arithmetic and gives worked examples.
Water cut is the fraction of the produced liquid that is water. If you produce oil at a known rate and the water cut is WC(as a decimal), the total produced fluid is the oil rate divided by (1 − WC):
Example: 10,000 bbl/d of oil at 80% water cut → 10,000 ÷ (1 − 0.80) = 50,000 bbl/d of total fluid (that is 10,000 bbl oil + 40,000 bbl water). The demulsifier is dosed on all 50,000.
This is the step most often skipped. On a high-water-cut field the total fluid is several times the oil rate, so dosing on the oil alone would badly under-size the chemical.
Convert the fluid to litres, then take the ppm:
Continuing the example: 50,000 bbl/d × 158.99 = 7,949,500 L/day of fluid. At a bottle-test dose of 30 ppm: 7,949,000 × 30 ÷ 1,000,000 = ≈ 238 litres/day of neat demulsifier.
One caution: this assumes the dose refers to neat (undiluted) product, which is how bottle-test ppm is normally expressed. If the product is injected pre-diluted, scale the volume up by the dilution factor.
Total fluid, then neat chemical at the field dose, across three field sizes. Barrels converted at 158.99 L/bbl; monthly figure at 30 days.
| Oil rate | Water cut | Total fluid | Dose | Chemical / day | Chemical / month |
|---|---|---|---|---|---|
| 2,000 bbl/d | 70% | 6,667 bbl/d | 20 ppm | ≈ 21 L/d | ≈ 0.64 m³ (~3 drums) |
| 2,000 bbl/d | 70% | 6,667 bbl/d | 40 ppm | ≈ 42 L/d | ≈ 1.3 m³ (~6 drums) |
| 10,000 bbl/d | 80% | 50,000 bbl/d | 30 ppm | ≈ 238 L/d | ≈ 7.2 m³ (~36 drums) |
| 10,000 bbl/d | 80% | 50,000 bbl/d | 50 ppm | ≈ 398 L/d | ≈ 11.9 m³ (~60 drums) |
| 20,000 bbl/d | 90% | 200,000 bbl/d | 30 ppm | ≈ 954 L/d | ≈ 28.6 m³ (~143 drums) |
Drum counts use a 200-litre drum. The jump from the small field to the large one shows why water cut, not oil rate, drives the chemical bill: the 20,000 bbl/d field at 90% water cut makes four times the fluid of the 10,000 bbl/d field at 80%.
Once you have litres per day, the rest is straightforward. Multiply by the order period for the volume; divide by the drum or tote size for the count; and — since demulsifier is dosed at a few cents per barrel of oil — the chemical cost per barrel is small enough that the right question is almost never “which is cheapest per litre” but “which reaches spec at the lowest reliable dose.” A product that needs 50 ppm where another needs 25 ppm costs, at the same unit price, twice as much to run for the same result.
The dose itself comes from a bottle test on your crude at your treating temperature — this page turns that dose into volumes, it does not set the dose. Figures are rounded; confirm against your metered rates.