Identifying shallow natural gas by time-lapse neutron-gamma logging in casing well

Xinglongtai and Huangjindai oilfield in Liaohe basin are rich in shallow gas resources. By using time lapse radioactive logging technology, the un- interpreted gas layers missed by old wells in old oilfield can be discovered, the status of the interpreted gas layers which is blow -down or water - flooded can be determined, and the missed gas layer for drilling - contamination can be detected. Through the application of neutron - gamma logging in Xinglongtai Oilfield, a great deal of shallow natural gas has been found out. The effective application provides useful guidance for potential direction of natural gas in old oilfield.