Evolution of In Situ Oil Sands Recovery Technology: What Happened and What’s New?

Abstract

Over the past 50 years, in-situ recovery methods for oil sands reservoirs have evolved and the patent literature is rich with different well designs, operating conditions, and recovery mechanisms. Here, the patent and literature has been analyzed to understand those features of in-situ recovery technologies that persisted through time. Over 250 hundred patents covering different well designs and injectants have been examined. A simple example of a persistent technology is the horizontal well: Steam-Assisted Gravity Drainage (SAGD) is enabled by horizontal well technology; the vertical equivalent of SAGD is not feasible as an economic recovery process. Cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) are now over two decades old since invention and at this point there are few new technologies on the table which are being researched or evaluated. Most new technologies, for example, thermal-solvent, electrical heating with solvents, and toe-toheel combustion are incremental adds on existing technology ideas proposed in the patent literature years to decades ago. Here, an analysis has been done to understand the evolution of in-situ oil sands recovery technology and what features have enabled economic recovery oil sands resources. The results reveal that a small number of features arising from the oil sands recovery process ideas dreamed, proposed, and developed over the past 50 years account for the success of current commercial oil sands recovery methods.

Interfacial Chemistry in Steam-Based Thermal Recovery of Oil Sands Bitumen with Emphasis on Steam-Assisted Gravity Drainage and the Role of Chemical Additives

“…Currently, there are two main steam-based thermal methods commercially used for recovering heavy oil/bitumen from oil sand reservoirs: cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) [1]. In SAGD, two parallel horizontal wells are used.…”

“…Normally, steam at a sub-fracture pressure is injected via the injection well which is typically 5-10 m above the production well which is located close to the bottom of the reservoir (Figure 2) [2]. The major drive mechanism of SAGD is gravity drainage [1]. In practice, the SAGD process starts at a high steam pressure, which is reduced as the process evolves [2].…”

“…These then collect below the steam inlet level where they are extracted via a second horizontal production well a few meters below the injection well. Early work indicated that recovery rates of 79-159 m 3 /day can be achieved, with bitumen recoveries of the order of 50% [1,55,56]. SAGD is deemed suitable for unconsolidated reservoirs with high vertical permeability, and is therefore relevant to oil sand deposits for which it is a more environmentally acceptable alternative than mining.…”

“…It is estimated that there are about 6 trillion barrels of oil stored in the form of heavy oil and bitumen [1]. One of the key characteristics of these unconventional crude oils is their very high viscosity at reservoir conditions.…”

“…For example, typical Athabasca reservoir temperatures are about 7-11 • C [2], and a typical Lloydminster reservoir temperature is about 25 • C [3]. At these temperatures, the mobility of the oils is poor, with heavy oil viscosity being in the range of tens of Pa·s, whereas bitumen viscosity is in the range of hundreds of Pa·s [1]. Therefore, the recovery of these petroleum resources requires radically different strategies than those used for the more familiar conventional crude oils.…”