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Wellbore BioChemistry Root cause 4 of 7

Asphaltenes in Oil Wells: Causes, Costs and the Remedy

Asphaltenes are the heaviest part of crude oil. When pressure falls or the oil’s chemistry changes, they drop out as hard black solids that choke a well from the bottom up, and they are easy to mistake for wax.

What it is and what it costs

The heaviest part of the crude, knocked out by pressure

Asphaltene deposit: hard, brittle, glassy black chipsBlockage
From the oil
What it is
The heaviest, most polar part of the crude.
What causes it
Pressure falling toward the oil’s bubble point, or CO₂, acid, light solvents or a different crude changing its chemistry, knocks them out of the oil as hard, black, tar-like solids.
Lifting costs: the usual fixes and why they repeat
Xylene soaks, coiled-tubing cleanouts and inhibitors that don’t last long. Each new pressure drop brings more out of the oil.
Profitability
Deposits choke the well from the bottom up, where the oil enters the wellbore, and asphaltene-stabilized emulsions can be strong enough to plug production.
  • Billions of dollars a year across the industry, by ASTM International’s estimate.
  • 2.3 to 1.35 inches: how far asphaltene narrowed the tubing bore of one deep well, by model estimate, despite yearly coiled-tubing cleanouts. A solvent soak and a better inhibitor raised its production 16% over four months.

What this does to a well’s life: Lifting Costs and Well Life

ASTM International; Wylde and Punase, JPT (2020).

Asphaltene or paraffin?

Asphaltene or paraffin? How to tell them apart in the field

Both come from the oil, both can look black, and they are often found together. But they form for different reasons and need different treatments, and treating asphaltene as wax wastes the job and can make it worse.

What to checkParaffin (wax)Asphaltene
Looks likeSoft and waxy, light yellow to dark brown; you can dent it with a fingernailHard, brittle and shiny black, like broken glass or coal
Triggered byCooling below the wax appearance temperaturePressure falling toward the bubble point, or a change in the oil’s chemistry: CO₂, acid, light solvents, mixed crudes
Where in the wellUpper tubing, rods and flowlines, where the oil cools: mostly within about 3,000 ft of the surface in a survey of Texas, New Mexico and North Dakota wellsDeep, at the perforations and in the lower tubing, and at chokes and valves where pressure drops sharply
Heat testSoftens and melts in hot waterStays hard; it doesn’t melt
Solvent testDissolves in warm kerosene or condensateStays as black grains in kerosene, condensate or heptane, but dissolves in xylene or toluene
Watch outHot oiling can push melted wax into the formation, where it can damage permeabilityCondensate and other light solvents used on wax can knock more asphaltene out
Asphaltene deposit: hard, brittle, glassy black chips
An asphaltene deposit. Compare the soft, waxy paraffin in Paraffin impact.

Real deposits are often mixtures of wax, asphaltene, iron sulfide, scale and sand, so a lab analysis of the deposit and the oil is the surest guide. A Production Pilot starts with an oil lab test.

Solubility and triggers: SPE PetroWiki, Asphaltenes and waxes and Asphaltene problems in production. Depth and light solvents: Ivanhoe and Herman, Oil & Gas Journal (1999).

The remedy

What ChainBreaker does about asphaltenes

BioActive reports its microbes degrade asphaltenic sludge, and biosurfactants loosen the deposit from steel and rock. Hard deposits at the perforations may still need a solvent soak; the lab test above shows which.

Start with a Production Pilot How ChainBreaker works

Sources for this section