Extra-Heavy Crude Oil Downhole Upgrading Process Using Hydrogen Donors under Steam Injection Conditions

Abstract

An extra-heavy crude oil underground upgrading process is described which involves the downhole addition of a hydrogen donor additive (tetralin) under steam injection conditions. Using a batch laboratory reactor or a continuous bench scale plant (280–315°C and residence times between 24–64 h), physical simulation experiments showed an increase of at least 3° in API gravity of the treated Extra-Heavy Crude Oil, three-fold viscosity reduction and, approximately, 8% decrease in the asphaltene content with respect to the original crude. It was found that the presence of the natural formation (catalyst) and methane (natural gas) is necessary to enhance the properties of the upgraded crude oil. Compositional-thermal numerical simulations were carried out and the results showed a good match between the calculated and experimental °API gravities of the upgraded crude oil (average relative error 1–4%) for all conditions studied. Similar results were obtained with the asphaltene contents (14–23%), percentage of conversion of the >500°C fraction (12%) and tetralin (16–23%). Introduction Downhole extra-heavy crude oil upgrading processes have high potential value due to the possibility of improving crude oil quality with the concomitant higher benefits obtained by their exploitation. Underground processes leads to several advantages in comparison with aboveground counterparts. First at all, enhanced oil recovery could be obtained by adding additional oil reserves. Also, increase in the volumetric production of wells and lower lifting and transportation costs from the underground to the refining centers could be generated. Finally, the use of porous media (mineral formation) as natural chemical "catalytic reactor" will improve the upgraded crude oil properties with further reductions in expenses during down stream refining operations. Several routes for underground extra-heavy crude oil upgrading have been reported. These concepts involve the following: Physical separations (steam distillation1 or deasphalting2), underground cracking or hydrocracking (visbreaking3–4, hydrogen6 or hydrogen precursor injection6–7) and in situ combustion8–9. In this work, a different concept10 is presented (Fig. 1) involving the underground addition of a hydrogen donor additive (tetralin), which in the presence of steam, natural formation (catalyst) and methane (natural gas), leads to extra-heavy crude oil upgrading. This concept is coupled to a steam stimulation process11 with 70–80% hydrogen donor recycled as depicted in Fig. 1. Specifically, batch reactor and continuous bench scale plant physical simulations are presented under steam injection conditions (280°C, 1600 psi), and crude oil upgrading is measured in terms of its API gravity, viscosity and percentages of asphaltenes. Different extra-heavy crude oils were studied and compositional thermal simulations were carried out in order to model the upgrading process under steam stimulation conditions. Experimental Part The extra-heavy crude oils came from the Orinoco Belt (Hamaca and Cerro Negro) and their properties are listed in Table 1. The percentages of asphaltenes were measured using the ASTM D-3279 and crude oil viscosities in a Brookfield apparatus, model RVTDV-II.

Downhole Upgrading of Orinoco Basin Extra-Heavy Crude Oil Using Hydrogen Donors under Steam Injection Conditions. Effect of the Presence of Iron Nanocatalysts

“…These results clearly indicate that the presence of a catalyst is necessary to yield upgraded products with higher quality. Consistent with these and previous results, naphthalene was detected in the reaction media as determined by GC-MS analysis [3][4][5][6].…”

“…As reported previously [3][4][5][6], the main sulfur-containing product detected was H2S in the gas formed (lower than 5% w/w) during the upgrading experiments.…”

“…Even though the changes in the product properties were small and sometimes within the experimental error of the techniques used, the results presented in Table 1 indicates a general trend, which allows concluding that effective crude oil upgrading can be achieved in the presence of hydrogen donor (tetralin) at steam injection conditions (315 °C, 24 h) [5]. As mentioned, these results have been reported before in our previous publications [3][4][5][6].…”

“…In our previous publications [3][4][5][6], we reported a concept that involves the addition of a hydrogen donor additive (tetralin or other distillate fractions having at least 40 wt.% naphthenic aromatic compounds) and, in the presence of steam, natural formation (catalyst) and methane (natural gas), leads to extra-heavy crude oil upgrading (from 9 to 14° API) at lab conditions [5,6]. This concept could be coupled to a steam stimulation process with 70-80% hydrogen donor recycled [5,6].…”

Enhanced Oil Recovery: An Update Review

“…Some examples of recent steam injection projects reported in the literature are the steamfloods in the Crude E Field in Trinidad [43], Schoonebeek oil field in Netherlands [44] and Alto do Rodrigues in Brazil [45]. Although attempts to optimize steam injection processes by using solvents [46], gases [47], chemical additives [48] and foams [49] have been proposed, few of these methods have been tested in the field [38,50]). One example is the LASER (for Liquid Addition to Steam for Enhancing Recovery) process, which consist in the injection of C5+ liquids as a steam additive in cyclic steam injection processes.…”