HPHT Reservoir Fluids with Focus on Scaling and thermodynamic Modeling

This PhD project is one of three PhD projects funded by the “NextOil” grant. The purpose of Nextoil is to add crucial knowledge to three aspects—rock mechanics, hydrocarbon reservoir fluids, and scaling—in the development of HP/HT petroleum reservoirs in order to reduce the related technical and economic risks and to convert the Danish HP/HT hydrocarbon resources into attractive commercial reserves.

This PhD project will deal with the description of mineral scaling and the inversion of the Joule-Thomson effect. In particular, the following areas will be investigated:

  • The Joule-Thomson inversion temperature in relevant brines
  • Experimental investigation of solid-liquid equilibrium at HP/HT conditions
  • Experimental investigation of the effect of pressure on crystal growth
  • Modeling of vapor-liquid-solid equilibrium at HP/HT conditions

The PhD student will be responsible for designing and requesting experimental equipment for measurement of crystallization and precipitation during oil production. A key parameter to be investigated is the Joule-Thomson effect. Autoclaves and possibly Differential Scanning Calorimetry will be used under high pressure. Experimental experiments with this equipment will be performed by the PhD student. Thermodynamic modeling will be carried out in order to describe solid-liquid equilibrium in HP/HT brines and the effect of brines on the Joule-Thomson coefficient of water.

Scaling in oil production occurs either directly due to precipitation from the naturally occurring water in reservoir rocks, or as a consequence of produced water becoming supersaturated with scaling components when two “incompatible” waters meet downhole. In HP/HT reservoirs, it is expected that the evaporation of water will be the main reason for super-saturation of scale minerals. The evaporation of water might be promoted by the Joule-Thomson effect.

The expected scale minerals that are relevant in this project are:

  • Halite scale, NaCl, due to evaporation of water
  • Sulfate scale, BaSO4, SrSO4, CaSO4, due to sulfate in injected water
  • Carbonate scale, CaCO3, FeCO3, BaCO3, SrCO3, MgCO3, ZnCO3, PbCO3, due to evaporation of CO2
  • Sulfide scale, PbS, ZnS, FeSx due to small amounts of H2S gas

The effect of pressure on the precipitation of many of these minerals has not been investigated previously. The measured solubility data for these salts will be used for improving and expanding an existing thermodynamic model for scaling minerals.

 Supervisor: Assoc. Prof. Kaj Thomsen: kth@kt.dtu.dk

Co-supervisor: Ass. Prof. Philip Loldrup Fosbøl, plf@kt.dtu.dk