Abstract: A process for the joint production of middle distillates and oil bases (viscosity index between 95 and 150) particularly from vacuum distillates and/or deasphalted oils, comprises a first step in which the feedstock is brought into contact with an amorphous catalyst containing at least one metal or metallic compound with a hydro-dehydrogenating function, such as Ni, Mo, W or Co, at a temperature of between 350.degree. C. and 430.degree. C., a pressure of between 5 and 20 MPa, a space velocity of between 0.1 and 5 h.sup.-1 in the presence of hydrogen in a ratio H.sub.2 /HC of 150 to 2,000 by volume. The product from the first step is brought into contact in a second step with a second catalyst comprising a support, a Y zeolite, at least one group VIB element and at least one group VIII metal at a temperature of between 350.degree. C. and 430.degree. C., a pressure of between 5 and 20 MPa and a space velocity of between 0.1 and 5 h.sup.-1.

Abstract: A treatment of highly viscous and very dense oils at the oil field to effect their desalting, and resulting in the production of an easily transportable hydrocarbon mixture of reduced viscosity, comprising the steps of:(a) diluting the crude oil with a hydrocarbon cut obtained in step (d);(b) subjecting the effluent from step (a) to a desalting-dehydration treatment;(c) subjecting the effluent from step (b) to hydrovisbreaking; and(d) distilling the effluent from step (c), and recycling a hydrocarbon cut to step (a), the remaining part forming a synthetic crude oil of reduced viscosity.

Abstract: A process for conversion of an asphaltenes-containing heavy oil or heavy oil fraction to lighter fractions comprises 3 steps of: catalytic hydrodemetallation, hydrovisbreaking and catalytic hydrodesulfuration.

Abstract: An asphaltene-containing heavy oil or heavy oil fraction is converted to lighter fractions in a process comprising three steps: a hydrovisbreaking, a catalytic hydrodemetallation and catalytic hydrodesulfuration.

Abstract: Process for reducing the viscosity of a highly viscous hydrocarbon charge containing 10-30% b.w. of constituents distilling above 375.degree. C., said treatment comprising hydrovisbreaking said charge to such an extent as to convert 10 to 30% of the 375.degree. C..sup.+ fraction to a 375.degree. C..sup.- fraction, fractionating the hydrovisbreaked product to separate a fraction comprising at least 90% of the constituents boiling below 375.degree. C. from a distillation residue, deasphalting said distillation residue and admixing at least a portion of the deasphalted distillation residue with at least a portion of said fraction comprising at least 90% of the constituents boiling below 375.degree. C.

Abstract: Heavy asphaltenic oils are converted to lighter fractions by(a) Deasphalting the asphaltenic oil with an aliphatic C.sub.5 -C.sub.7 hydrocarbon,(b) Maintaining the oil with hydrogen at 440.degree.-530.degree. C. and 40-140 bars in a non-catalytic conversion zone, and(c) Feeding the product of step (b) to a catalytic conversion zone at 320.degree.-430.degree. C. and 40-140 bars, the catalyst in said zone comprising at least one molybdenum and/or tungsten compound and at least one nickel and/or cobalt compound.