ASPHALTENE DEPOSITS IN OIL PRODUCTION

摘要

Asphaltene deposit is a common problem encountered in reservoir as well as in pipeline transportation. It can cause production loss or even block up in the pipelines. The structure of asphaltene is very complex Even if the flocculation is well understood, the mechanisms involved in the deposit are quite unknown and therefore the risks cannot be assessed properly and the chosen treatment may not be efficient. First, a dynamic light-scattering method is used to measure the size of asphaltene aggregates as a function of concentration or as a function of time. Asphaltene aggregates are studied in their natural oil with the DL 135-45 apparatus from SEMATech. In this work, we determined the threshold concentration of n-heptane to obtain aggregation and it is possible to measure the kinetics of this aggregation. These information can be used to model the deposit in the tube. Then, we present a laboratory methodology where actual asphaltene deposit can be obtained. A flocculated asphaltenic tank oil is circulated in an open capillary loop. The variations of pressure drop with time are measured. At the end of the experiment, the deposit left in the tube is dissolved in toluene and is weighed after evaporation and filtration. In this apparatus, the influence of pressure, temperature, flow rate, tube material and concentration of n-heptane is estimated for various oils. Finally, understanding the mechanism of asphaltene deposit provides solutions to prevent it. Furthermore, the procedure developed here can be used to evaluate additives and eventually propose more efficient ones.