Hydrocarbon exploration has been carried out in the lower assemblage (P and F formations) of the western Bongor Basin for many years without breakthrough. Through in-depth studies of the hydrocarbon accumulation patterns in western Bongor Basin

Well D-2 was deployed and drilled by China National Petroleum Corporation in 2024; oil reservoirs were encountered during drilling in the lower assemblage of Bongor Basin

and the well production during well testing exceeded 200 tons per day

thus determining the exploration potential in the study area. To better summarize this discovery and guide further exploration

a systematic study

which is based on analysis of regional geological setting and exploration history

has been conducted on the tectonic evolution

stratigraphy

sedimentation

and source-reservoir-seal assemblages of the western Bongor Basin. On this basis

the hydrocarbon accumulation models and exploration deployment strategies have been clarified. The results show as follows. (1) The lower assemblage of Bongor Basin developed in the fault depression period. Thick lacustrine mudstones and near-source deltaic sand bodies were developed in the deep depression area

forming favorable lithological combinations. (2) The thick lacustrine mudstones of P and M formations

with high total organic carbon content and good organic matter type

have already entered into the oil generation window. They served as not only the excellent source rocks but also regional seals in western Bongor Basin. (3) Due to tectonic inversion

uplift and denudation during late stages

the deltaic sand bodies of P Formation had a certain porosity despite large burial depths

thus being considered as good reservoirs. The underlying buried hills experienced long-term structural fracture

weathering and denudation

and formed composite reservoirs with the sandstones of P Formation. (4) The Bongor Basin underwent multiple stages of tectonic evolution and inversion

leading to extensive fault development

which allowed oil and gas to migrate along the faults and accumulate in both upper and lower assemblages and buried hills. (5) Based on the characteristics of reservoirs in the lower assemblage

a comprehensive three-dimensional exploration deployment strategy was recommended to explore both shallow and deep formations

structural and non-structural traps

which can achieve breakthroughs in exploration of new strata and new fields. (6) The quartz sandstone above the basement is speculated to be a set of older formation than P Formation

and widely developed in western Bongor Basin

indicating good hydrocarbon accumulation conditions. The exploration breakthrough of Well D-2 has confirmed the resource potential in western Bongor Basin and exploited new reservoirs in Bongor Basin. Moreover

the three-dimensional exploration deployment strategy can provide guidance for oversea risk exploration in the future.