Comparing Venezuelan and Canadian Heavy Oil and Tar Sands

Abstract The world's two largest oil deposits are the heavy and extra heavy oil deposits of Venezuela and Canada. These deposits have many similarities and some differences; however, the general similarity in geological disposition and history, in reservoir and fluid parameters, and in other factors, is striking. Extensive technological developments in Canada in the period 1985–2000 have resulted in several new heavy oil exploitation technologies, and new ideas continue to be generated. This innovative thrust has developed in part because of the great exploitation difficulties experienced in Canada and the greater maturity of the sedimentary basin: to maintain oil production, it was necessary to move toward heavy oil and oil sand development sooner than in Venezuela. The technologies of SAGD, CHOPS and PPT have been the major directions of technical activity in Canada, whereas in Venezuela, more favorable reservoir conditions allowed the use of multilateral horizontal wells. The article reviews technical developments and deposit properties in the two countries, and points to a vast potential in the application of technologies developed and perfected in Canada to the vast resources in Venezuela. Not only will this be of value in specific projects and areas, it will also benefit and stabilize world oil supplies in the long term. Introduction There are vast heavy oil deposits (defined herein to be all the liquid petroleum resource less than 20 °API gravity) in Venezuela and Canada. In both cases, these resources are found largely in unconsolidated sandstones with roughly similar geomechanical and petrophysical properties. This article will attempt a comparison of the Faja del Orinoco deposits in Venezuela (Figure 1) with the Heavy Oil Belt and Oil Sands deposits in Alberta and Saskatchewan (Figure 2). The term "unconsolidated" is used to describe the high porosity sandstone reservoirs in both Canada and Venezuela. It is analogous to the term "cohesionless" in the soils or rock mechanics sense: it is meant to convey the fact that these sandstones have no significant grain-tograin cementation, and that the tensile strength is close to zero. This turns out to be an important attribute in technology assessments. The magnitude of the resources in the two countries is vast, probably on the order of 3.5–4 trillion barrels of oil in place (bbl OOIP), but its scale deserves a few comments. Conservation authorities, through the use of geophysical logs and cores to analyze and examine the oil-bearing strata, determine a "total resource in place". This depends substantially upon a choice of "lower cutoff" criteria, below which an individual stratum is not included in the resource base. For example, any bed less than 1.0 m thick may be excluded from resource calculations, no matter where it is found. If a thin bed (e.g. 1.5 m) is separated by more than several m from superjacent or subjacent oil saturated beds, i.e. if it is "iolated", it may be excluded from the resource base, no matter what value of oil saturation (So) it possesses. Furthermore, any bed with a low oil saturation, such as So< 0.4, may be excluded.