ABSTRACT
Shale gas extraction in China often faces inadequate reservoir stimulation after initial fracturing of the wells, leading to production challenges despite abundant residual gas. Refracturing is an effective approach to enhance gas recovery; however, its impact on water consumption remains understudied. This study analyzes two refracturing techniques employed in China's largest shale production field, Fuling: temporary plugging and diverting refracturing (TPD) and wellbore reconstruction refracturing (WR), focusing on fracturing efficiency and water consumption. The results demonstrate that WR refracturing exhibits superior fracturing performance but consumes 1.3 times more water than initial fracturing. Considering 315 wells that required refracturing from 2013 to 2017, this study reveals, for the first time, that the lifecycle water consumption for shale gas production with refracturing is more than twice that without refracturing. The estimated total water consumption for the Fuling shale gas field over the next decade, incorporating refracturing, is approximately 7594.53 × 104 m3. By including the water consumption of refracturing, this study provides a more comprehensive evaluation of water usage throughout the entire lifecycle of shale gas development. The findings offer new insights for assessing water consumption in global shale gas development and highlight the importance of considering refracturing when evaluating the environmental impacts and resource management strategies associated with shale gas extraction.
ABSTRACT
Block H, located in western Hubei-eastern Chongqing, remains at a low exploration degree. Characterized by its complex structural attributes, the area presents adverse conditions such as a thin thickness of high-quality shale reservoir, rapid lateral formation occurrence, and poor stratigraphic correlation, challenging conventional geosteering methods. The primary shale gas reservoir in Block H corresponds to the Upper Permian Wujiaping Formation. To ensure that the shale gas horizontal wells in this block effectively penetrate high-quality gas reservoirs, this study delves into the geological characteristics of this stratigraphic unit, identifies principal challenges faced by current geosteering techniques, and introduces a tailored technical solution. This solution encompasses the application of real-time 3D geological modeling to track while drilling, identification of steering marker layers, optimization of steerable tools, and optimization of the steering trajectory while drilling. In the technology of optimization of the steering trajectory while drilling, a trajectory control calculation model based on the average angle technique was established for the first time. Additionally, a sectional control chart for marker layers and well inclination under different deflecting constraints was established. These methods have solved the problems of large error in target prediction and poor trajectory control effects by using the equal thickness method alone. The findings from this study can significantly enhance target prediction and trajectory control accuracy in complex structural areas, offering pivotal insights for the proficient development of analogous shale gas reservoirs in the future.