Stabilizing and dispersing asphaltenes to prevent plugging and related issues

FlOW ASSURANCE

AIs & ADs

Asphaltenes are soluble in crude oil at reservoir temperatures and pressure conditions. Physical and chemical factors contribute to destabilization of asphaltenes, leading to precipitation and possible flocculation of asphaltenes as the peptide layer is stripped (resins, e.g. maltenes)as a result of loss of aromaticity and increased linear alkane content.

Factors responsible for asphatene destabilization include:

• Depressurization

• Miscible flooding with CO₂ or natural gas

• Acidization

• Mixing fluids with different densities

• Gas lift

Asphaltenes can deposit in reservoirs wellbore tubing, flowlines, separators, and other parts of hydrocarbon production systems. These deposits can interrupt and potentially stop production due to the formation of plugs.

Other operational issues related to the precipitation of asphaltenes include stable crude oil emulsions, higher emulsion viscosity, and migration of asphaltenes into water phase leading to produced water treatment issues.

Treatment options

A range of mechanical and chemical options is available to treat asphaltene deposition issues. Mechanical cleaning methods include pigging, wireline cutting and coil tubing options, while chemical treatments include the injection of inhibitors, dispersants or solvents.

Asphaltene solvents usually include aromatics or aromatics-based blends, especially those containing bi-and tri-cyclic aromatics and reduced biphenyl content. The solvents work well with pigging and dissolve the asphaltene deposits.

Asphaltene inhibitors are polymeric compounds that stabilize the micelles and prevent the asphaltenes from flocculating.

The inhibitors have very similar properties to those of the resins and interact with the asphaltenes to stabilize the asphaltene micelles in the crude oil. The asphaltene inhibitors possess stronger association with the asphaltenes and are able to stabilize the asphaltenes through greater changes in pressure, temperature, shear and chemical environment. Asphaltene inhibitors can be squeezed into the formation or continuously injected downhole. Squeezing the inhibitor into the reservoir can prevent deposition of asphaltenes in the near-wellbore area. It is important that the inhibitors are added to the crude oil before the asphaltenes become destabilized and flocculation occurs.

Asphaltene dispersants do not prevent precipitation, but maintain precipitated asphaltenes in a dispersed state to prevent flocculation. The advantages of using asphaltene treatment chemicals include:

• Reduction in deposition of solids which helps to maintain production.

• Reduction in equipment plugging leading to reduced NPT.

• Reduction in produced water treatment problems leading to reduced oil-in-water carryover, which in turn results in environmentally safe water disposal.

• Lower pumping pressures due to reduced viscosities.

DESHI Group provides expertise in designing treatments to meet an operator’s particular asphaltene challenges. Based on specific field information about the issues, laboratory tests are designed and performed to evaluate potential solutions that will deliver the desired results. Factors considered include cost-effectiveness, environmental impact and safety issues.Product performance using various instrumental and chemical assay methods.