Minimising Image Distortion by Depth Modelling: A Case Study for Arthit Field, Gulf of Thailand

Abstract

Seismic imaging distortions in South Arthit area are mainly fault shadows and reflection horizon push downs (saggings) in PSTM volumes. Target reservoirs in the area are located near fault planes and therefore accurate fault imaging is essential for well planning and operation safety. Incorrect seismic images from PSTM method could lead to high uncertainty during interpretation and volume estimation. It's well known that PSTM technique has limited capability in handling image distortion beneath shallow anamalies and large-scale faults and therefore PSDM is required. Using more advanced depth imaging technique, including high resolution 3D reflection tomographic inversion, channel calibration, fault shadow correction, and by collaborating with South Arthit Asset Interpretors, DPC team successfully constructed a depth velocity model that minimizes saggings, and other imaging distortions in the legacy PSTM volume. Comparing with the PSTM volume, the new PSDM volume shows significant imaging improvement: eliminated sagging on deeper reflections below the shallow anomalies (channels and localized geological bodies), minimized fault shadow effects along major faults, and restored seismic amplitude in the fault zone. Fault planes can be interpreted with higher confidence, allowing better well path design with more accurate safety distances. In conclusion, advanced depth velocity modelling and PSDM imaging have proven to be a useful tool in minimizing seismic image distortions and reducing risks and uncertainties for South Arthit field development.