A fishtail well design for cyclic steam injection—A case study from Yarega heavy oil field in Russia

Abstract

Yarega heavy oil field (YHOF) is a naturally fractured heavy oil field where only recently steam‐assisted gravity drainage (SAGD) technology has been introduced. SAGD employed in this field has so far resulted in early steam breakthrough leading to producer well abandonment and recurrent drilling procedures invariably increasing costs. Therefore, as opposed to SAGD, we propose the joint application of cyclic steam injection (CSS) technology with fishtail wells. The advantages of CSS are well documented. The addition of fishtail wells to this strategy assists in reducing the travel time the mobilized oil takes to arrive at a well perforation. Our results demonstrate that the synergy between these two strategies can further improve recoveries in heavy oil reservoirs. A reservoir simulation model of a sector in the YHOF is employed to understand heat/mass transfer mechanisms and for production enhancement recommendations. Different well configuration strategies were tested on this model. Results from the three‐dimensional sector in the YHOF model suggest that in addition to the thermal development technologies employed in this reservoir, CSS coupled with fishtail wells provided favorable steam‐oil ratios, cumulative energy‐oil ratios, and enhanced cumulative oil recovery for a naturally fractured reservoir. Well abandonment issues arising from SAGD approach currently being applied can therefore be eliminated. Based on results from this research, we recommend the testing of a fishtail well development plan with CSS that includes a 10‐day steam injection, 10‐day soaking period, and 10‐day production period. In comparison with continuous steam injection recovery (4.5% over 3 years), our simulation results showed an improved recovery of 7% over the same period with this concept. In addition to the technical advantage of this strategy, favorable steam‐oil and energy‐oil ratios imply that minimal economic costs are achieved and carbon footprints are lessened.

Experimental Investigation of Steam Conformance Evolution in Vertical-CSS and Optimization of Profile Improvement Agents

“…The well configuration and well pattern can be modified to change the streamline of injected fluid [19,20], while the systematic workover requires a substantial operational cost and the valid period is unknown. Parameters can be optimized for integral wells' management [21,22], but for wells in harsh reservoir conditions or those with severe steam channeling problems, the alteration of operational parameters can hardly take effect due to the preferential streamlines of steam in porous media.…”