A comprehensive investigation of SAGD steam chamber in dual horizontal well pairs: Expansion angel and connection characteristics

Abstract

The expansion behaviors of the steam chamber play a significant role in the stability of steam-assisted gravity drainage (SAGD). For Long Lake extra-heavy oil reservoir, the 3D SAGD physical model based on similarity criteria is established in this work to investigate the expansion angel and connection characteristics of the steam chamber at varying well-pairs spacing and vertical distance. The results show that expansion angles of the well spacing of 50 m, 75 m, and 100 m are 16.5° and 17.6°, 22.5° and 23.0°, 25.4° and 24.8°, and the sweep efficiency is 96.7%, 90.8%, 78.6%, respectively. The smaller the well spacing between the dual well-pairs, the smaller the final expansion angle of the steam chamber, and the greater development effects. The vertical distances of 3 m have the maximum expansion angles (24.0° and 16.7°), and the highest sweep efficiency (81.6%). The smaller vertical distance of the dual well pair is accompanied by the larger expansion angle, which is beneficial to the development and propagation of steam chambers. The vertical expansion of the steam chamber is concentrated in the early stage of development, and the lateral expansion speed increases after the steam chamber contacts the top of the reservoir. The lateral expansion velocity and width of the steam chamber are the largest (0.36 cm/min and 0.4 cm/min, 20 cm) at the well-pairs spacing of 100 m. The heavy oil recovery factors at varying well-pairs spacing are in turn, 39.4% (50 m), 37.1% (75 m), and 33.7% (100 m). Compared to 6 m and 9 m, the vertical distances of 3 m have the highest ultimate oil recovery, 35.4%. Considering the economy and exploitation effect, the dual well-pairs with 50–75 m spacing and no vertical distance is recommended to promote the successful application of the SAGD technique in heavy oil reservoirs with 20–30 m thickness.