Process of reducing viscosity of heavy crude oil by removal of asphaltene using a precipitating agent

Abstract

A process and system for reducing the viscosity of heavy and extra heavy crude oils, and more particularly to a process for reducing the viscosity of heavy and extra heavy crude oils by means of total or partial oil deasphalting using a precipitating agent in order to obtain an upgraded crude oil of lower viscosity that can be pumped without the use of diluents. The upgrading also includes a reduction in metals and sulfur associated with asphaltene removal. The process consists of relatively simple equipment such as static mixers and stirred tanks and operation temperature is low and pressure is moderate.

What is claimed is: 
     
         1 . A method of reducing a viscosity of heavy and extra heavy crude oils at an oilfield site by partially removing asphaltenes to produce a pumpable upgraded oil, the method comprising:
 combining a heavy or extra heavy crude oil and a feed precipitant, wherein a volumetric precipitant to crude oil ratio is in a range from about 1 to about 2;   precipitating and separating asphaltenes from the combination crude oil and precipitant;   separating the precipitated asphaltenes to form an oil slurry comprising the asphaltenes and precipitant, and a liquid stream comprising precipitant and a remaining volume of the crude oil; and   separating the liquid stream to produce the upgraded oil and a first precipitant stream, wherein a yield of upgraded oil is about 90% by weight or more with respect to the heavy or extra heavy crude oil.   
     
     
         2 . The method of  claim 1 , further comprising:
 washing the oil slurry with additional precipitant;   separating the washed oil slurry to produce an asphaltenes stream and a second precipitant stream; and   drying the asphaltenes stream to produce a solid asphaltene product, and a third precipitant stream.   
     
     
         3 . The method of  claim 2 , wherein at least one of the first, second, and third precipitant streams is recycled as feed precipitant. 
     
     
         4 . The method of  claim 2 , wherein at least one of the first, second, and third precipitant streams is recycled as additional precipitant to wash the oil slurry. 
     
     
         5 . The method of  claim 2 , wherein the second precipitant is combined with the liquid stream before separation of the liquid stream. 
     
     
         6 . The method of  claim 1 , wherein the heavy or extra heavy crude oil and precipitant is combined using static mixers. 
     
     
         7 . The method of  claim 6 , wherein the crude oil and precipitant are combined at temperatures of about 80° C. (176° F.) or below, and pressures between 40 and 60 psig to maximize asphaltene precipitation. 
     
     
         8 . The method of  claim 1 , wherein the step of precipitation utilizes one or more stirred or agitated tanks to induce asphaltene precipitation, or to remove crude oil occluded in the precipitated asphaltene particles. 
     
     
         9 . The method of  claim 1 , wherein the oil slurry and liquid stream are separated in a separation vessel comprising hydro-cyclones or centrifuges, wherein the precipitation of small solid asphaltene particles is induced by inertial forces many times the gravitational force, which operates to reduce residence time in the separation vessel. 
     
     
         10 . The method of  claim 2 , wherein the asphaltene stream is dried by dryers. 
     
     
         11 . The method of  claim 1 , wherein the first precipitant stream is separated from the upgraded oil using a flash separator or distillation tower. 
     
     
         12 . The method of  claim 1 , further comprising:
 stripping the upgraded oil by stream stripping to produce stripped upgraded oil and a fourth precipitant stream.   
     
     
         13 . The method of  claim 12 , wherein the fourth precipitant stream is recycled as feed precipitant. 
     
     
         14 . The method of  claim 12 , wherein the stripped upgraded oil has a higher viscosity than the unstripped upgraded oil due to the removal of precipitant. 
     
     
         15 . The method of  claim 1 , wherein a volumetric yield of the upgraded oil is greater than 92% with respect to the heavy or extra heavy crude oil. 
     
     
         16 . The method of  claim 1 , wherein the upgraded oil exiting the process has less than 5% by weight of light component depending on a target viscosity of the upgraded oil. 
     
     
         17 . The method of  claim 1 , wherein the upgraded oil has a higher API gravity compared to heavy or extra heavy crude oil, wherein a difference in API gravity comprises at least 3 API gravity units. 
     
     
         18 . The method of  claim 1 , wherein the upgraded oil comprises a significant reduction of metals and sulfur from crude oil. 
     
     
         19 . The method of  claim 2 , wherein a precipitant loss in the dried, solid asphaltene product is less than 1% by weight. 
     
     
         20 . The method of  claim 1 , wherein the feed precipitant comprises a light gasoline or natural gasoline. 
     
     
         21 . The method of  claim 1 , wherein the feed precipitant comprises a solvent and one or more additives formulated according to a chemical makeup of the heavy or extra heavy crude oil. 
     
     
         22 . The method of  claim 21 , wherein the one or more additives are selected from the group consisting of light paraffinic hydrocarbons or oxygenated hydrocarbons.