The deep oil and gas pools develop mainly in the lower third member of Hetaoyuan Formation in the deep sag in southeastern Biyang Depression. There are two reservoiring patterns: Anpeng-Zhaowa type and Xia'ermen type. The former is characterized by three charging periods and the reservoirs have mainly been formed in the middle and late stages. The latter type of oil and gas pools have undergone the processes of formation-destruction-reformation. The early anticlinal oil and gas pools were formed during the deposition of the first member of Hetaoyuan formation and Liaozhuang formation

the pattern of the present oil and gas pools was not formed till the later stage of deposition of Shangsi formation

due to the reformation and destruction

caused by the tectonic movement in the later stage of Liaozhuang formation deposition. Except the above-mentioned two reservoiring patterns

probably there are also lithologic oil & gas pools in lenticular sandstones

as well as deep basin reservoirs.