An Assessment of In Situ Oil Sands Recovery Processes

Abstract

Development of Alberta's 1.7 trillion barrels of oil sands resources has been growing rapidly. Significant factors in this growth include conventional oil production declines, oil price and spread improvements, increasing pipeline access to markets, a favorable fiscal regime and imminent lease expires. The recent successes with in situ processes including cold flow, cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) have increased in situ production from Alberta oil sands by 65 % in just two years to over 34,000 m3/d. The growing successes of SAGD and cold flow have created an energy to implement these processes that is reminiscent of CSS in the late 70s and early 80s. Oil sands reservoirs are complex. Coupled with high bitumen viscosities, a commercial development must address a range of reservoir properties including variable bitumen saturations, ranges of reservoir thickness and sand qualities, the presence of shale interbeds and diagenetic clays and the impacts of gas and water thief zones. In the process of evaluating the three aforementioned processes it is important to gauge the type and amount of resource that each can develop. The purpose of this overview is to summarize key success factors and the applicabilities of the CSS, SAGD and cold flow processes at accessing the bitumen resource. Before providing the comparison, a background understanding of the evolution of Cold Lake CSS and the mechanisms controlling its performance are provided. Cold Lake Technology Development Imperial's Cold Lake operations are an example of successful in situ oil sands technology development. When Imperial started at Cold Lake in 1964, there was no recovery process and no assurance that economic development was possible. As shown in Figure 1, it took approximately 20 years of piloting a number of processes before commercial production could occur. Since 1985, volumes have grown to the current 100,000 b/d. Over time, many processes were examined and even field tested. The most successful has been CSS. However, before describing CSS further, it is worth mentioning a few of the other field tested processes. The most obvious was steam drive. In the 60s steam drive was being successfully developed in California so that it appeared to be just a matter of translating the California successes to Cold Lake. This meant that CSS would simply be a precursor to steam drive. The initial purpose of CSS was thus to obtain early production and develop communication between the CSS wells. Continuous steam drive processes of various types were initiated in the early stages, at mid-life and during late stages of CSS. None were commercially feasible. A second alternative to CSS, SAGD, was invented and patented. Testing started in 1979. Disappointed again with the constant pressure performance, the horizontal well pilots now operate in a cyclic steam stimulation mode. Another process, Hydraulic Borehole Mining, to jet the sands and produce a slurry to surface proved technically impossible due to the collapse of bounding shales. Finally, cold flow was attempted but rates were low and unsustainable.