Sedimentary facies and reservoir characteristics of the Lower Jurassic Sangonghe Formation in the Shixi–Mobei Uplift of the Junggar Basin, NW China

The Junggar Basin, a major hydrocarbon province in China, contains more than 3 Bt of petroleum and 150 Bcm of natural gas. Within its Central Depression, the Shixi–Mobei Uplift is a key area for oil and gas exploration. This study examines the geological and depositional characteristics of the Sangonghe Formation using cores, microscopy, mineral analysis and seismic profiles. The Sangonghe Formation represents the peak of lacustrine transgression, transitioning to regression in the overlying Xishanyao and Toutunhe formations. It features diverse sedimentary facies, including braided river deltas and lacustrine fans, reflecting a progression from shallow- to deep-lake environments. Palaeogeomorphology, controlled by secondary structural slope-break zones, influenced facies distribution, with braided river deltas above and delta front/lacustrine fans below these zones. Provenance analysis has identified two main sediment sources: a northwestern source affecting the Shixi region's west and north, and a northeastern source impacting the Mobei region's east and NE. Reservoirs are characterized by residual, secondary and primary intergranular pores, with porosity positively correlated with permeability. The diagenetic stage of mesogenetic A2–B is observed, particularly in the Mobei region's east and SE. 2D seismic profiles and well-logging data estimate the areal extent of the lacustrine-fan reservoirs at 25–30 km 2 , with a gross rock volume of 15–20 km 3 and hydrocarbon volumes of 50–100 MMbbl of oil equivalent. Exploration should focus on areas near wells QS and M171 with significant potential identified around wells QS1, QS404, QS403, QS204, QS9, M14, M20, M27, F003 and M171 as priority targets.