Effect of Resins on Stability of Asphaltenes

Abstract

Abstract For deepwater operations involving crudes with risk of asphaltenes destabilization, knowledge of the properties and behavior of the effective resins could be useful for selection of additives. Hydrocarbon reservoir fluids can exhibit a tendency to deposit asphaltenes, typically depositing them in pressure drop locations down hole, in subsea trees, and/or surface separators. Asphaltenes phenomena remain challenging to accurately predict and control. The key to advances in technology are related to improved experimental definition of the fundamental characteristics and behavior of this complex system. Asphaltenes deposition in wells, valves and flowlines decreases throughput and blocks production. Asphaltenes are a class of macromolecules that are soluble in aromatic solvents. They are insoluble in aliphatic solvents, although they may appear solubilized in the presence of certain types of resins. Asphaltenes are usually solubilized in undisturbed samples at the reservoir pressure and temperature. As the reservoir fluid is produced and the pressure drops, apparent solubility of asphaltenes decreases until the oil reaches the bubble point. As the pressure continues to drop, asphaltenes become increasingly unstable and may precipitate. Precipitated asphaltenes are sticky amorphous pseudo-solids, which tend to deposit on surfaces of tubing and production equipment. Experimental results indicate that naturally-occuring resins isolated from Boscan crude oil have a stabilizing effect on asphaltenes in Hamaca crude oil, as well as in Boscan crude oil. Subsequent laboratory study indicates that resins isolated from Cerro Negro and Furrial crude oils stabilize asphaltenes in samples of Boscan, Hamaca, Furrial and Cerro Negro crude oil Resins of Type II were isolated from Boscan, Hamaca, El Furrial and Cerro Negro crude oil samples. Addition of extracted Resins II to samples of crude oil showed a stabilizing effect on asphaltenes. This study shows that resins isolated from one reservoir fluid could be useful for stabilizing asphaltenes in completely different crude oil systems having very different geologic origins. The Filter Drop Spreading Method is a simple experimental technique used to accurately detect the onset of flocculation for crude oils, crude oil mixtures, and for mixtures of crude oils plus additives. Background The focus of these experimental studies was to investigate the effect of adding naturally-occuring resins to crude oils that contain asphaltenes. For many years, there was an assumption that resins from a specified crude oil were incompatible in terms of asphaltenes stabilization with other crude oils. Yet, there is ample evidence that the resin/asphaltenes ratio is one indicator of asphaltenes stability in reservoir fluids. Would it be effective to extract resins from the crudes themselves and to use those resins as additives to increase the resins/asphaltenes ratio in crudes that exhibit asphaltenes instability problems in production? In this work, resins were extracted from fresh atmospheric samples of Boscan, Hamaca, Furrial and Cerro Negro crude oils. The extracted resins were used as additives to the crude oil samples. Their effect as asphaltenes stabilizers was determined by the flocculation point (asphaltenes appearance point) of asphaltenes in Boscan, Hamaca, Furrial and Cerro Negro crude oils.