Abstract
Asphaltene precipitation can have profound effects on oil production during miscible flooding, heavy oil recovery, or even primary depletion. Even though asphaltene precipitation and eventual deposition have been known to have strong effects on permeability reduction (Turta et al., 1997; Minssieux et al., 1998), quantitative analysis of the process has not been studied extensively. This paper describes experimental work conducted to study the precipitation and deposition tendencies of asphaltenes within the rock material in the Marrat reservoir, South East Kuwait. Live asphaltenic reservoir fluids and carbonate cores of the Marrat reservoir were recovered and used at reservoir pressure and temperature conditions during core flood experiments. The live Marrat reservoir fluid was fully characterized, and subjected to pressure depletion tests to determine the asphaltene onset point at various temperatures.
The results reveal preferential deposition of the precipitated asphaltenes with respect to the rock material. The characterization of the rock materials by CT-Scans had indicated the presence of local occluded porosities. These occluded sites were found to be the main influence on the pattern of deposition seen in the core samples. The study shows clearly that although asphaltenes may precipitate and deposit from the Marrat reservoir fluid, the propensity for permeability damage is in fact determined by the nature of the rock material. In addition, the tendency of the precipitated asphaltenes to aggregate into larger flocs that are generally friable influences the rock damage potential.
Handling and treatment of asphaltenic fluids will continue to impact on reservoir operations, project costs and recovery efficiencies. Understanding the nature of asphaltenes and how they impact on the sub-surface behaviour of reservoir fluids will become more pertinent, as global oil demand forces a move towards heavy oils and / or highly asphlatenic fluids.
