There is no significant breakthrough in the exploration and development of the Xujiahe Formation in Shunan area in recent years compared with that of lithologic gas reservoir of the Xujiahe Formation in the central Sichuan Basin.Thus the lithologic gas reservoir forming conditions and exploration potential of the Xujiahe Formation in gently structured zones of Shunan area have always been the focus of attention.With the integrated analysis of outcrop

core and logging data

and the investigation of various accumulating conditions and major controlling factors

such as tectonic setting

sedimentary sandbody development

source rock presence

reservoir characteristics and etc.of the Xujiiahe Formation in this area

we believe that:(1) a large area of flat laying strata in the tectonically quiescent area is favorable for forming lithologic gas reservoirs;(2) the source rocks capable of large area hydrocarbon generation are distributed widely in the 1

st

3

rd

5

th

member and the 2

nd

submember of the 6

th

member of the Xujiahe Formation

providing the gas source for lithologic accumulation;(3) the 2

nd

4

th

member and the 1

st

6

th

submember of the 6

th

member of the Xujiahe Formation in the large-scale open flow lacustrine basin mainly are sandstones that are widespread and present in multiple zones

favorable for reservoir formation;(4) source beds and reservoirs interbeddedly deposit

resulting in similar accumulating features to the Xujiahe Formations in the central Sichuan Basin

i.e.large area continuous source kitchen hydrocarbon supply and efficient near-source charge.We believe that the Xujiahe Formation in the Shunan area has the conditions favorable for lithologic gas accumulating and may have formed a large-scale gas accumulation area.The understanding provides the geological basis for the exploration deployment of the Xujiahe Formation in tectonically quiescent zones

and indicates that the gently structured area between the low structures will be a focus for further exploration.