Downhole Upgrading of Extra-heavy Crude Oil Using Hydrogen Donors and Methane Under Steam Injection Conditions

• Published in: Petroleum science and technology Vol. 21; no. 1-2; pp. 255 - 274
• Main Authors: Ovalles, César, Vallejos, Carlos, Vasquez, Tito, Rojas, Iraima, Ehrman, Ursula, Benitez, Jose Luis, Martinez, Ronald
• Format: Journal Article
• Language: English
• Published: Colchester Taylor & Francis Group 01.02.2003; Taylor & Francis
• Subjects: Applied sciences; Catalysis; Catalysts; Crude oil; Crude oil, natural gas and petroleum products; Crude oil, natural gas, oil shales producing equipements and methods; Energy; Enhanced oil recovery methods; Exact sciences and technology; Fuels; Methane; Naphthalene; Natural gas; Prospecting and production of crude oil, natural gas, oil shales and tar sands; Silicon carbide; Upgrading; Methane; Viscosity; Hydrogen; Enhanced recovery; Oil field; Steam injection; Density; Heavy oil
• ISSN: 1091-6466; 1532-2459
• DOI: 10.1081/LFT-120016947

An extra-heavy crude oil underground upgrading process is described which involves the downhole addition of a hydrogen donor additive under steam injection conditions (280-315°C and residence times of at least 24-h). Laboratory experiments showed a 4° increase in the API gravity (from 9 to 12°) of the upgraded product, a two-fold reduction in the viscosity and, an approximately 8% decrease in the asphaltene content with respect to the original crude. Further increases on the temperature led to products with improved properties reaching 15°API at 315°C. It was found that the presence of the natural formation (catalysts) and methane (natural gas) is necessary to enhance the properties of the upgraded crude oil. From GC and GC-MS results a reaction pathway is proposed that involves hydrogen transfers from tetralin to the extra-heavy crude oil resulting in the formation of 1,2-dihydronaphthalene. This compound is then transformed into naphthalene, further upgrading of crude oil through hydrogen donation. The results of the experiments carried out in the presence and absence of the mineral formation and with an inert solid (SiC) strongly indicate that the former acts as a catalyst and not as a heat transfer matrix. Isotopic labeling studies (CD 4 and 13 CH 4 ) give evidences that, most probably, methane is involved in the upgrading reactions.