Abstract: In Oilfield A there are many seismic reflection anomalies which is concave or broken seismic event. At present, there is a lack of in-depth research and clear understanding of identification and origin of seismic anomalies, which has affected the oil and gas exploration process. Coherence, variance and likelihood seismic attributes are used to identify seismic reflection anomaly. The results indicate seismic anomaly extends shortly laterally but extends from dozens of meters to a kilometer vertically, and they are of subcircular shape in plan view, most of which are irregular distribution and few of which is linear or echelon distribution. A comprehensive analysis of the origin of seismic anomaly is made based on structural evolution, stress and core data of target formation. The results indicate that seismic reflection anomalies are the combined result of dissolution and compression. Dissolution develops in target formation but development intensity is uneven horizontally and vertically. Because late compression is weak, fault is generated in fragile area of target formation. Some seismic anomalies are the vertical path of oil migration and some seismic anomalies destroy trap of lower formation.

Key words: carbonate rock, seismic reflection anomaly, origin analysis, dissolution, compression