During primary oil production, when the thermodynamic conditions within the well tubing lie inside the asphaltene-deposition envelope (ADE) of the produced fluid, flocculated asphaltene particles could start being deposited on the tubing wall, causing a restriction in the tubing inner diameter that results in loss of production. This paper presents a methodology that begins by determining the ADE in the laboratory. Moreover, asphaltene-deposition rates for the tubing conditions can be measured using high-pressure/high-temperature coaxial-cylinder technology.
At some thermodynamic states, asphaltenes exhibit a behavior called flocculation—that is, asphaltene particles or micelles aggregate or flocculate into larger particles or flocs. The locus of all thermodynamic points in a phase diagram at which flocculation occurs is called the ADE. Accurate measurement of asphaltene solubility at in-situ conditions inside the ADE is extremely difficult. Many asphaltenic reservoir fluids exhibit irreversible asphaltene flocculation. This means that, once the upper ADE boundary is crossed, some of the asphaltenes will not deflocculate and go back into stable suspension by simply reversing the thermodynamic path.
The spectrophotometric near-infrared (NIR) onset method uses the observation that there is a sharp increase in light absorption or attenuation in the NIR region of the electromagnetic spectrum at the onset of asphaltene flocculation....
Laboratory Testing and Prediction of Asphaltene Deposition in Production Wells
01 September 2017