Single control factor analyses of the palaeogeomorphology unit

structural feature

and mudstone compaction characteristics of Jingbian gas field show that these three factors individually have some impacts upon the gas enrichment in the field.However

a comprehensive and accurate understanding of gas enrichment pattern and recognition of prospect need further analyses of the combinations of the influential factors.Taking the karst paleogeomorphology and the present structures as the predominant control factors

four types of combinations are recognized:1)structural high combinations;2)combinations of platform edge slope and structural nose uplift with different parts of palaeostructure;3)combinations of platform edge slope and structural nose flank with different parts of palaeostructure;and 4) combinations of lowland and structural nose hollow combined with different parts of palaeostructure.Among the four types

the first one is considered to be the most favorable.By integrating various factors that control or affect the natural gas enrichment with geological characteristics of high productivity wells

five necessary conditions for gas accumulation in Jingbian oilfield are proposed to reveal the pattern of gas enrichment.