Currently, pilot project on heavy oil production by SAGD technology is being implemented in Tatarstan fields. An essential factor complicating heavy oil production is presence of oil-water transition zones penetrated by production wells. Other adverse factors include presence of gas and water zones, lack of distinct reservoir continuity, mudded interlayers, high variability of OWC depth over short intervals in new fields and uplifts. All these factors result in either man-induced or natural migration of underlying mineral waters into the overlying fresh water aquifers. At the same time, a number of issues should be addressed prior to production operations, including selection of optimal composition based on rock mineralogy in the interwell space, and calculation of the required injected amount and concentration of chemicals, which will depend on reservoir rocks (clay and carbonate content). On the one hand, the amount of the injected composition should be sufficient for efficient treatment of the interwell space; on the other hand, it is necessary to prevent channeling between parallel horizontal wells (injector and producer), which will eventually result in steam breakthrough. It is critical to solve the problem of minimizing the adverse impact on the tubing string and the screen pipe by selecting an optimal composition and stimulation option. Some engineering aspects must also be addressed concerning treating either the entire horizontal wellbore or the selected borehole sections. This will require application of emulsion compositions.
To date, due to concerted efforts of engineers from scientific and production units of Tatneft PJSC, a suite of technology has been developed to significantly mitigate the negative effect of the above-mentioned factors when producing heavy oil by SAGD method.
References
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