Jizhong depression is the main crude oil production base in Bohai Bay Basin

boasting of rich and diversified oil and gas resources. After more than 50 years of exploration and development

the proved reserves of conventional oil and gas are

very considerable. However

there is an increasing difficulty in hydrocarbon exploration. As a result

the unconventional oil and gas resources will become the key target for the next large-scale discovery. Through systematically summarizing the geological conditions for the formation of tight oil and gas in the faulted lacustrine basin of Jizhong depression

it has been determined that there are a number of sedimentary and subsidence centers and oil-generating sags and troughs in the depression

where the high-quality hydrocarbon source rocks together with fan sedimentary sands of the adjacent delta front

fan delta

and nearshore subaqueous fan or lacustrine facies carbonate reservoirs form a dominant configuration

thus providing favorable conditions for the efficient charging and accumulation of tight oil. According to the source-reservoir configuration

the tight oil and gas reservoirs in Jizhong depression can be divided into two types

i.e.

extra-source and intra-source hydrocarbon reservoirs

generally showing the characteristics of large-area continuous distribution

complex lithology

non-homogeneity and near-source reservoirs. The study suggests that three types of tight oil and gas reservoirs are mainly developed in the Paleocene of Jizhong depression

including tight oil and gas conglomerate reservoirs in nearshore subaqueous fan of the steep belt (Type 1)

and in fan delta of the slope belt (Type 2)

as well as delta-front and shore-shallow lake facies tight oil and gas reservoirs at the peripheral of sags and troughs (Type 3)

which have superior hydrocarbon accumulation conditions

demonstrating a large resources potential and a broad exploration prospect. Among them

Type 1 is mainly developed in single-faulted dustpan-like sags such as Langgu sag

Wuqing sag

Jinxian sag

and Shulu sag

with the distribution area of 476 km

2

the predicted oil resource of 0.53×10

8

t

and the estimated natural gas resource of 1 460×10

8

m

3

. It is the main zone where brea

kthroughs have been made in hydrocarbon exploration of deep sags in the steep belt of Jizhong depression. Type 2 is mainly developed in Shuolu sag

Jinxian sag

and Baxian sag with narrow and steep slopes in Jizhong depression

with the distribution area of 700 km

2

and the predicted resources of 2.6×10

8

t. It demonstrates a realistic battleground for the realization of large-scale efficient discovery. Type 3 is mainly distributed in the lower member of the first Member of Shahejie Formation of Raoyang sag

with the distribution area of 1 214 km

2

and the predicted resources of 1.8×10

8

t

indicating a favorable direction for the strategic succession.