In recent years

Sinopec has used the unconventional natural gas idea to strengthen the Permian natural gas e

xplorationin eastern Sichuan and obtained industrial gas flow in the first member of Maokou Formation of several wells in Jiaoshiba of Fulingand its adjacent area

revealing a good prospect for natural gas exploration.In this paper

the sequence stratigraphy

sedimentarycharacteristics

hydrocarbon generation conditions

micro pore structure characteristics and gas bearing property of Mao-1 Memberin Jiaoshiba area are systematically analyzed.The results show that:（1） Mao-1 member can be divided into two fourth-ordersedimentary cycles and eight small layers

which mainly develops four kinds of lithology such as Limestone

micritic limestone

nodular limestone and nodular micritic limestone.（2） The average TOC of the Mao-1 Member ranges from 0.75%to 0.87%

whichon the whole

belongs to carbonate source rock with medium organic matter abundance.The organic matter abundance of micriticlimestone and nodular micritic limestone is relatively low

while the organic matter abundance of limestone and nodular limestoneis relatively high.The type of organic matter is mainly type I and supplemented by typeⅡ.R

o

ranges from 1.71%to 2.18%

withan average of 1.97%.（3） The Mao-1 Member is an ultra-low porosity and permeability reservoir

and the local layers show thecharacteristics of fractured reservoir.The reservoir space is mainly composed of organic pores

diagenetic contraction fissures ofclay minerals

and grain margin fractures of mineral particles

followed by dissolution pores of carbonate minerals.Moreover

thepore size distribution is mainly mesoporous and macroporous.（4） The natural gas of Mao-1 member is mainly composed of methanewith low heavy hydrocarbon content

which is typical dry gas;δ

13

C

1

ranged from-31.25‰to-31.12‰

δ

13

C

2

is between-35.28‰and-31.23‰

δ

13

C

3

is between-34.87‰and-34.66‰

which is a typical oil type gas.The carbon isotope of alkane series isreversed

showing a trend of changeδ

13

C

1

>δ

13

C

2

>δ

13

C

3.

According to the characteristics

the natural gas from Mao-1 Member is themixture of kerogen cracking gas and liquid hydrocarbon cracking gas.（5） Mao-1 Member has the characteristics of self-generatedand self-reservoired

which is a set of special carbonate reservoir between shale reservoir and fractured reservoir.It is necessary tolearn from shale gas exploration experience

strengthen sweet spot interval evaluation and adaptive engineering technologyresearch

and promote the large scale production and benefit development of natural gas.