The American Petroleum Institute classifies crude oils as “light”, “medium”, “heavy”, and “extra-heavy”, according to their API gravity:                Light crude oil: has API gravity greater than 31.1° API;        Medium crude oil: has API gravity between 22.3 and 31.1° API;        Heavy crude oil: has API gravity between 10 and 22.3° API; and        Extra-heavy crude oil: has API gravity lower than 10° API.        
The depletion of light and medium crude oil reserves has forced the production and refining of increasingly heavier crude oil. Among other economic and technological types of implications, this problem has grown making it progressively difficult not only for the extraction of this crude oil but its transportation from platforms to maritime terminals or to existing refineries, since a crude oil is considered transportable as long as it meets the required specifications of API gravity and viscosity essentially.
Hence, platforms and maritime receiving and distributing terminals of crude oil will be in the need for applying efficient and affordable technologies of heavy crude oil upgrading to accomplish the demands of current and future refineries.
Nowadays, various process technologies for upgrading of heavy crude oils and residues are available to overcome their transportation problems. However, most of these technologies are inappropriate to be installed on platforms that require a lot of space, therefore a conscious evaluation must be applied to fulfill important criteria such as: investment, adaptation of compact versions for platforms and maritime terminals, capacity, feedstock, byproducts disposal, etc.
Current technologies for upgrading heavy crude oils and residues such as delayed coking, catalytic cracking of residue, solvent deasphalting, catalytic hydrocracking, among others, are mainly designed to operate at reaction conditions, reactor configuration, type of reaction system, catalysts, etc. such as to obtain the maximum conversion and required quality of products, so that their application to operate at low severity conditions are inefficient, impractical and uneconomical.
The state-of-the-art related to the present invention, by referring to the use of processes for partial upgrading of the properties of the heavy and extra-heavy crude oils, is here represented by the following patent documents:                U.S. Pat. No. 7,381,320, issued on Jun. 3, 2008, relates to a process of upgrading and demetallizing heavy crude oils and bitumen. The process involves mainly the following stages: (1) Feedstock is supplied to a solvent extraction process to separate asphaltenes, and obtain a deasphalted oil with reduced content of metals, (2) The deasphalted oil is processed in a fluid catalytic cracking unit (FCC) with a catalyst of low activity for the removal of metals, (3) The demetallized fraction is hydrotreated to improve the properties and obtain a synthetic crude oil. Hydrotreating is carried out at pressure of 35 kg/cm2 to 105 kg/cm2 and 350-400° C., (4) The fraction containing asphaltenes can be sent to a gasification process for generating power, steam and hydrogen, which can be used in the hydrotreating process, (5) The excess of asphaltenes and/or decanted oil can be processed in a coker unit for producing naphtha, middle distillates and gasoil, which can be sent to hydrotreating units.        U.S. Patent Publication No. 2008/0083653, published on Apr. 10, 2008, relates to a process of partial upgrading of heavy crude oil, which is processed first in a solvent deasphalting unit, where two fractions are obtained, a free of asphaltenes light fraction and a heavy fraction concentrated in asphaltenes.        The deasphalted fraction is processed in a fluid catalytic cracking unit loaded with a catalyst of low activity and low conversion, to produce a light distillate fraction of a hydrocarbon (generally naphtha) that can be used as a diluent for the end users. The intermediate fractions can be sent to a hydrotreating unit to be further combined with the produced diluent to form synthetic crude oil that can be delivered to a refinery. The heavy fraction can be processed in a gasifier that allows for the generation of electricity, steam and hydrogen.        U.S. Patent Publication No. 2007/0267327, published on Nov. 22, 2007, relates to a process for upgrading of heavy crude oil to synthetic crude oil with acceptable properties as refinery feedstock. The method includes solvent deasphalting for separating asphaltene fraction of heavy oil and contacting the deasphalted oil with biological and chemical reagents to reduce pollutant concentrations through oxidation. The recommended solvent for the deasphalting process is composed of a mixture of paraffinic, iso-paraffinic and aromatic hydrocarbons ranging from C4 to C10. Then the deasphalted oil is submitted to biochemical oxidation to remove nickel, vanadium, sulfur, nitrogen and unsaturated compounds present in high concentrations in the heavy oil.        U.S. Pat. No. 6,355,159, issued on Mar. 12, 2002, relates to a moderate hydroconversion of heavy crude oil followed by addition of a specific diluent to stabilize the synthetic crude oil against phase separation and asphaltenes. In this process, a product with lower viscosity and API gravity suitable for pipeline transportation is obtained. The product needs to be stabilized, because the hydrotreating alters the solubility of asphaltenes, which can be separated into pipelines during transportation or when the product comes into contact with other oils. As mild hydroconversion it relates to a catalytic process in the presence of hydrogen, in which around 40-60% of the 525° C. fraction of the heavy oil is converted to lower viscosity oil. The hydroconversion is carried out at temperatures ranging between 400-450° C. and pressures ranging from 49-105 kg/cm2 for sufficient time to reduce the viscosity of the oil.        