Distribution of ancient ditches in Leikoupo Formation and its control over gas accumulations in Yuanba Gas Field

Based on the analyses of generation condition, identification method and distribution feature of the ancient ditches in the Leikoupo Formation in the Yuanba Gas Field, the influences of ancient ditches on reservoir, trap, flow and hydrocarbon enrichment were discussed, and several favorable exploration targets were pointed out. Erosion, early fracture and hot and humid climate controlled the generation of ancient ditches. The ditch area was featured by thin residue formation, thickening overlying formation and underflow development. "Concave" and "bidirectional onlap" were identified on seismic sections. There are four main ditch areas in the study area, usually 2-3 km wide for a single ditch, and the cutting depth is 30-60 m. Karst residual hills, which were well-preserved and favorable for reservoir, are potential targets for exploration.