Liupanshan Basin

a Cretaceous fault basin

shares similar hydrocarbon accumulation conditions with Jiuquan Basin and Hetao Basin

which have already seen breakthroughs in oil and gas exploration. It is considered one of the important basins with exploration breakthrough potential in the periphery of Ordos Basin

and Hexi Corridor structural belt. This study systematically evaluates the Cretaceous hydrocarbon accumulation conditions in the basin by integrating field outcrops observations

drilling data

analytical testing results

as well as the latest geophysical data including seismic framework profiles

time-frequency electromagnetic data

and two-dimensional seismic reprocessing data. The research results show as follows. (1)The Lower Cretaceous Madongshan Formation develops high-quality source rocks of semi-deep lake to deep lake facies

with thickness ranging from 100 m to 600 m

total organic carbon (TOC) content of 0.08 % to 6.46 % (with an average of 1.57 % )

and vitrinite reflectance (R

o

) between 0.56 % and 1.12 % (with an average of 0.88 % ). The organic matter is primarily of Type Ⅰ to Type Ⅱ

1

exhibiting rich oil and gas reserves and significant oil generation potential. (2)The reservoirs can be divided into two types

i.e.

sandstone from Liwaxia Formation and Sikouzi Formation

and shale-mudstone from Madongshan Formation. The regional cap rocks include thick mudstone interbedded with gypsum from Qingshuiying Formation and evaporites from Naijiahe Formation. These strata form two types of accumulation assemblage models. One is the self-generating

self-reserving and self-sealing model

the other is the generation in lower part and reservoir in upper part model. The structural

structural-lithological

and lithological traps are mainly developed in the study area. (3)Madongshan Formation in the four major hydrocarbon-generation sags of Liupanshan Basin

i.e.

Haiyuan sag

Guyuan sag

Shagou fault terrace

and Longde sag

covering a total area of 5 800 km

2

has an in-situ petroleum resource of approximately 1.7×10

8

t. (4)An innovative exploration approach of "hydrocarbon accumulation under the control of source rocks with matching between fault and cap rock" was proposed to identify structural trap groups near the hydrocarbon generation center

focusing on areas wi

th well-developed faults and cap rocks. The primary target is to achieve a breakthrough in the exploration of medium- to high-quality reservoirs in the upper strata of source rocks. Four favorable target zones were identified

including Lijun

Zhangyi

Yanglangnan

and Chengmengou areas

with a total area of 1 700 km

2

which provides crucial geological evidence for achieving breakthroughs in the next phase of oil and gas exploration in the basin.