Assessment of tight-oil and tight-gas resources in the Junggar and Santanghu Basins of Northwestern China, 2018

In 2018, the U.S. Geological Survey (USGS) quantitatively assessed the unconventional (continuous) oil and gas resources in two previously unassessed formations in northwestern China. These include an assessment of tight-oil resources in the lower Permian Lucaogou Formation (Yang and others, 2010) of the Santanghu Basin (Altay-Sayan Folded Region Province) and tight gas in the Lower Jurassic Badaowan Formation (Guo and others, 2014; Yang and others, 2015) in the southern part of the Junggar Basin (Junggar Basin Province) (fig. 1). Lacustrine mudstones of the Lucaogou Formation are present in several basins and intervening uplifts in northwestern China (Carroll and Wartes, 2003). Tight oil is produced from this formation in the Junggar Basin, and in 2016, the USGS completed an assessment of tight-oil and tight-gas resources in the Lucaogou of the Junggar Basin (Potter and others, 2017). Over the past 15 years in the Santanghu Basin, oil has been discovered and produced from several types of tight reservoirs in the Lucaogou Formation; this oil has apparently undergone short-distance vertical migration from interbedded organic-rich mudstone (Hackley and others, 2016). The thick Lower Jurassic Badaowan Formation in the southern Junggar Basin represents a fluvial and shallow lacustrine system containing low-permeability channel sandstones interbedded with coal and carbonaceous shale. Guo and others (2014) indicate that the tight sandstone layers and lenses contain a significant gas resource sourced mainly from the coals—a geologic framework that is very similar to that of major tight-gas fields in the western United States. In the southern Junggar Basin, natural gas has been discovered in coal and shale within the Badaowan (Petromin Resources, 2009); possible resource exploration concepts include tight gas, shale gas, and coalbed gas (Guo and others, 2014). This 2018 USGS assessment focused on tight-gas resources in sandstone that are analogous to tight-gas sandstones in the Upper Cretaceous Mesaverde Group in the Piceance Basin, Colorado (Johnson and Roberts, 2003; Cumella, 2009).