Process for the downhole upgrading of extra heavy crude oil

In a well formation comprising crude oil, methane and a mineral formation, a down hole hydroconversion process for improving the crude oil viscosity comprising the steps of:

• analyzing a well in order to determine:
• (1) the concentration of crude oil in the well with respect to the mineral formation, and (2) the amount of CH.sub.4 present in the well;
• comparing the amount of CH.sub.4 in the well with the concentration of crude oil in order to determine the sufficiency of CH.sub.4 for carrying out the hydroconversion of the crude down hole in the well;
• feeding down hole to the well a mixture comprising steam, hydrogen donor, and, if necessary, CH.sub.4 so as to obtain down hole in the well a concentration of hydrogen in an amount of at least about 0.15 moles per Kg of crude oil, a concentration of methane in an amount of at least about 0.06 moles per Kg of crude oil, and sufficient steam to raise the temperature down hole of the well to at least about 250.degree. C. such that the crude oil is subjected to hydroconversion in the presence of the hydrogen donor, the methane, the steam and the mineral formation so as to produce an upgraded crude oil;
• and
• recovering the upgraded crude oil from the well wherein the viscosity of the crude oil is decreased and the API.degree. is increased.