Abstract: Langgu Depression is an old oil and gas exploration area with industrial oil and gas flow confirmed in oil testing. Large-scale reserves are found in the area. Those results help accumulate the rich experience for discovery of gas formations, assessment of gas formations and emancipation of gas formations, namely looking for gas and testing gas. Based on the practices, it is realized that various data can be comprehensively used to interpret gas formation and substantially improve the conformity rate of interpretation. Organic combination of various methods, such as conventional well log, gas-inspecting well log and logging, is the most effective method to find and identify gas formations. Neutron gamma time lapse logging remains as the effective applicable technology for identification of gas formations. APR-TCP combination and point method to calculate AOF are now the applicable technologies for testing of gas wells. The factor of natural gas volume is big and more seriously damaged by filtration of drilling fluid as compared to oil formations. Use of high-quality and light drilling fluid is an important precondition for looking for gas and testing gas. Meanwhile, a lot of problems still need to be brought under study and consideration