Process for Pre-Refining Crude Oil with Moderate Multi-Step Hydroconversion of Virgin Asphalt in the Presence of Diluent

A process for pre-refining at least one crude oil P, comprising:

• at least one first step F1 comprising initial fractionation by distillation, (PRE-DIST), to produce a first asphaltenic residue R1 and at least one first non-asphaltenic stream E1;
• at least one second step F2 comprising fractionation of at least a portion or fraction derived from R1 by deasphalting (SDA) with a hydrocarbon solvent with a mean molecular weight of more than 50, to produce at least:
• firstly, a second non-asphaltenic stream E2 comprising at least 50% by weight of virgin deasphalted oil included in the residue R1, and secondly a virgin asphalt AS;
• and
• passing a heavy asphaltenic stream ASF to a unit RHDC for ebullated bed hydroconversion of residues, the ASF comprising at least 50% by weight of virgin asphalt AS and at least one diluent DIL which is liquid at ambient temperature and comprise at least 30% by weight of compounds derived from P boiling below 340° C., in which said diluent represents 3% to 40% by weight with respect to the asphalt included in the ASF, and conducting said ebullated bed residue hydroconversion unit RHDC in at least two hydroconversion steps in series in at least two ebullated bed reactors in series, the flow rate of the heavy asphaltenic stream being sufficiently high, and the dimensions of said two reactors being selected in relation with said flow rate so that conversion of the feed ASF into products boiling below 524° C. is over 30% by weight but less than 56% by weight, so as to obtain an asphaltenic hydroconversion effluent HAS with a sulphur content in the fraction which is non distillable at 524° C. and which is reduced with respect to the ASF, so as to produce at least one pre-refined asphaltenic oil Pc comprising at least the major portion of residual asphaltenes included in the HAS.