Особенности разработки залежей сверхвязкой нефти западного склона Южно-Татарского свода

Thermal methods of heavy oil reserves development in Tatarstan are associated with two fields-the Mordovo-Karmalskoye and the Ashalchinskoye fields. The paper presents analysis of pilot production using steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) technologies. For the first time thermal flooding production methods including steam and steam-gas injection into vertical wells were attempted in 1989-2002 in the Ashalchinskoye field, however with little, if any, success. In 2006, pilot production using SAGD technology was launched. Pairs of parallel horizontal wells were drilled at a vertical distance of 5 m, with steam injected into the upper well and oil produced from the lower well. In single horizontal wells, cyclic steam stimulation method is used to produce oil-the wells are put through cycles of steam injection, soak, and oil production. The practices and the experience gained by the Company during pilot production of the Ashalchinskoye field was used to proceed to another pilot project, involving four heavy oil fields southeast of the Ashalchinskoye field. It is evident that the performance of SAGD-wells is much higher than the CSS-wells. The authors recommend a development scenario providing for SAGD-wells drilled in the areas with a net pay thickness more than 10 m and CSS-wells in thin productive zones (with a net pay thickness not less than 5 m). In the Karmalinskoye field, oil is mainly produced by SAGD-wells; the reservoir is characterized by better performance compared to neighboring fields, with higher average annual oil production and lower steam-oil ratio (SOR). To improve performance of CSS-wells in thin productive intervals, the steam stimulation technology must be matured to meet the reservoirs' conditions.