--> Reviving a Mature Field: Fluid Detection in Frequency-Broadened Seismic Data Through Rock Property De-Trending

2018 AAPG International Conference and Exhibition

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Reviving a Mature Field: Fluid Detection in Frequency-Broadened Seismic Data Through Rock Property De-Trending

Abstract

The initial development of a conventional salt dome field and identifying the associated infill wells can be achieved through proven and robust workflows. As DHIs and obvious AVO prospects are drilled, options for further development become increasingly challenging to identify. Pinpointing remaining hydrocarbon accumulations and analyzing their economic viability can be significantly hindered by their capability to have a recognizable seismic signature, resolution limitations, and useful well control. This study of an ultra-mature salt field in the shallow-water US Gulf of Mexico employs a series of high-grading methods to identify remaining hydrocarbon deposits. Two main components drive this study; seismic with its derived attributes, and logs from well control. Targeted seismic reprocessing focused on salt flanks aided in sharpening salt-sediment traps. Increasing seismic resolution through well-driven frequency broadening, and the subsequent derivation of pre-stack simultaneous inversion rock properties, helped reveal hydrocarbon-bearing sands below the original seismic resolution. Well control was used to relate seismic and reservoir characteristics to the production success of completed zones. Logged acoustic impedance shale values were averaged between sequence boundaries, and a corresponding frequency-broadened seismic acoustic impedance shale model was generated. The acoustic impedance volume was divided by the shale model, resulting in a shale de-trended impedance or pseudo litho/fluid volume. The de-trended property volume was used to isolate shales, water saturated sands, and oil saturated sands using the corresponding properties of logged wells and their petrophysical interpretation. These seismic-derived observations were confirmed with quantified correlation of log-defined vs. seismic-defined shale, wet sand, and pay sands intervals. The imaged drilled and undrilled hydrocarbon accumulations were then used to estimate volumetrics, economics, and were also risked for continuous development of the soon to be revitalized field.This set of techniques was especially effective in an industry environment of high cost and low capital spending.