A New Subtle Fault Modeling Technique Based on OBN Seismic Data and Production Performance and its Application in X Oilfield, Central Asia

Abstract With the deepening of field development, subtle faults have an increasing impact on reservoir production. However, limited by the resolution of seismic data, the interpretation accuracy of subtle faults is difficult to meet the needs of oilfield development adjustment, which brings great challenges to fault modeling in the middle and late stages of development. Subtle faults can lead to problems such as complex oil-water relationship in reservoirs, poor water injection connectivity, and quite differences in production and pressure drop between nearby wells. In order to improve the accuracy of fault modeling in the middle and late stages of development, this paper proposes a method of subtle fault interpretation and modeling based on production performance driven, integrated of fault cut, FMI and azimuth Ocean Bottom Nodes (OBN) data. The X oilfield is located in the strike-slip fault zone in Central Asia, its fault system is very complex, after nearly 50 years of production, the distribution of remaining oil is scattered. The conventional small fault identification and modeling methods are difficult to meet the requirement of oilfield development adjustment research, therefore, the technique proposed in this paper is based on production driven and dived into 4 steps: 1) The inter-well connectivity was analyzed by using the reservoir PVT data, pressure and production data, and the distribution of subtle faults between wells was preliminarily speculated;2) Through well correlation study, the subtle fault cut and fault type of the wells were identified, combined with the regional tectonic stress and FMI data to analyze the dip angle and orientation of subtle faults;3) Based on possible faults’ dip and orientation, the seismic attributes and azimuth OBN data were combined to identify subtle faults, and a three-dimensional complex fault model was established to accurately describe the geometric shape and properties of subtle faults; 4) The rationality of subtle fault distribution is verified by fluid contact analysis and production data. The application of this technology in Central Asia X oilfield is good, and the fault model is consistent with the results of fluid contact analysis and production performance analysis results, which proves that this technology can improve the accuracy of the fault model and lay a solid foundation for efficient adjustment in the later stage. The subtle fault modeling technique proposes a new workflow of fault characteristics. It can better integrate dynamic data into subtle fault interpretation and modeling, improving the rationality and accuracy of subtle fault model, and meet the requirement of remaining oil study in field development.