Development characteristics and enlightenment of Eagle Ford deep shale gas reservoirs in North America

The large-scale development of shale gas with a buried depth of less than 3 500 m within the overpressure Wufeng-Longmaxi Formation has been realized in Sichuan Basin, and the effective development of shale gas resources with a buried depth of 3 500-4 000 m is being explored currently. Eagle Ford is an emerging deep shale oil & gas reservoir, which is comparable to the domestic medium-deep development regions and deep exploration regions, and its development technology policy and learning curve are available for reference. The parameters of drilling, fracturing, production and cost of 6 223 wells are analyzed in the dry gas production region of Eagle Ford from 2009 to 2019 based on the Shale Gas Cloud Data Intelligent Platform. The research indicates that the medium-shallow shale gas development shows a better performance than that of deep shale gas in the Eagle Ford dry gas production region. The medium-shallow shale gas well has an average measured depth of 6 013 m, a lateral length of 2 558 m, a drilling cycle of 25.3 d, a stage-spacing of 50.0 m, a sanding intensity of 3.81 t/m, a fracturing fluid intensity of 24.2 m³/m, a EUR per 100-meter lateral length of 677×10⁴ m³, the single-well drilling-fracturing cost of 617×10⁴ USD, and the fracturing cost per 100-meter lateral length of 13.4×10⁴ USD. The deep shale gas well has an average measured depth of 6 394 m, a lateral length of 2 423 m, a drilling cycle of 33.3 d, a stage-spacing of 50.0 m, a sanding intensity of 4.03 t/m, a fracturing fluid intensity of 26.9 m³/m, a EUR per 100-meter lateral length of 520×10⁴ m³, the single-well drilling-fracturing cost of 697×10⁴ USD, and the fracturing cost per 100-meter lateral length of 16.1×10⁴ USD. The Eagle Ford dry gas production region is highly efficient in the engineering organization and construction, with the main horizontal well construction circle of 100-150 d and the current single-well construction cycle of 100 d. The relation between lateral length and cumulative gas production per unit drilling-fracturing cost shows a triangular distribution. The reasonable lateral lengths for the medium-shallow and deep wells are 2 300 m and 1 600 m respectively. It is recommended to explore a reasonable lateral length to maximum benefit for domestic medium-shallow scale-development zones, and control the lateral length of deep shale gas wells in the early stage of deep exploration zones.