After more than 60 years of exploration and development

Huanghua depression in Bohai Bay Basin has the accumulative proven oil geological reserves exceeding 13×10

8

t

where the proven conventional oil reservoirs exceed 50 %

facing great difficulty in increasing reserves on a large scale. Shale oil-gas and intra-source tight oil-gas resources have emerged as crucial exploration

fields for future reserve growth and production increase in Dagang oilfield. Based on the drilling

geophysical

and analytical testing data obtained in recent years

a study has been conducted on the favorable conditions and enrichment characteristics for the formation of shale oil-gas and intra-source tight oil-gas resources in Huanghua depression

establishing theoretical insights into the intra-source hydrocarbon accumulation in faulted lake basin. The findings reveal that faulted lake basins possess geological conditions conducive to large-scale shale oil accumulation. Despite diverse lacustrine basin development environments

the organic matter abundance generally remains high in the study area. The lacustrine basin is characterized by small size with multiple sediment sources

and high brittle mineral contents; the high-frequency laminae develop

ensuring good source-reservoir matching at the microscopic scale. Additionally

the organic matter thermal evolution level is moderate

resulting in high retained oil content in shale. Shale oil in faulted lake basin possesses the enrichment characteristics of favorable fabric facies and hydrocarbon retention exceeding effect. The deep sag zones in faulted lake basin

located at the deposition/subsidence centers

have substantial accommodation space

and provide favorable conditions for intra-source tight oil enrichment

i.e.

basin-mountain coupling

source-channel-sink matching

and two sand-rich accumulation modes developed in the deep sag zones. Effective reservoirs are developed under the control of both sedimentary facies and diagenetic facies. Moreover

source-reservoir coexistence and source-proximal charging result in the stable large-area distribution of reservoirs in the deep sag zones. Essentially

intra-source tight oil and shale oil in faulted lake basin correspond to source-reservoir combinations at different scales

exhibiting the orderly distribution of oil reservoirs and large-area continuous petroleum accumulation

which enable the integrated ex

ploration and development. The theory of intra-source hydrocarbon accumulation in faulted lake basin has effectively guided exploration practices

providing an alternative field for the high-quality and sustainable development of mature oilfields.