INFLUENCE OF ASPHALTENES - ON SOME PROPERTIES OF VENEZUELAN RESERVOIR ROCKS

Results obtained from the evaluation of the effect of asphaltenes and their occasional precipitation on wettability and permeability of some rocks found in Venezuelan oil reservoirs, are presented. Fluids and cores from six crude reservoirs with different asphaltene contents and Berea cores plugs were used. Wettability measurements were performed by using a variation of the Amott method evaluating the samples at different aging conditions. Similarly, measurements were carried out on cores in which precipitation was induced by n-pentane injection. Permeability and porosity reductions were evaluated by carrying out displacement tests before and after artificially induced-precipitation process. All cases verified the presence of changes in wettability. Asphaltene retention on samples reached values from 1.5 to 20.3% PV (porous volume). These reductions depend on the type of precipitation induction process, the rock nature, and the core properties: permeability, porosity and pore size distribution.