Velocity model estimation of karstic fault reservoirs using full-waveform inversion accelerated on graphics processing unit

Abstract

The karstic fault reservoir is a type of hydrocarbon-enriched carbonate reservoirs. It is a combination of small-scale caves, vugs and fractures developing near deep-seated faults, which makes it difficult to delineate using traditional seismic imaging methods. Recent researches on geological characteristics of paleokarst reservoirs facilitate hydrocarbon exploration and exploitation in western China. To interpret karstic fault systems and reservoirs, the seismic image is an effective tool. A high-quality velocity model is essential for high-resolution migration. These seismic results contain crucial information to interpret reservoirs. Full waveform inversion (FWI) is a powerful method to obtain high-precision velocity models since it makes use of both kinematic and dynamic information in the seismic full wavefield. In order to image such complicated and irregular fractured-cavity reservoirs accurately, we applied multi-scale FWI method accelerated on graphics processing unit (GPU) devices to fault-controlled paleokarst reservoir models. According to model test results, FWI shows high performance of delineating boundaries of fault-controlled karstic reservoirs. The proposed method also has the potential to characterize inner structures. Based on the high-precision velocity model provided by FWI, the seismic image obtained by reverse time migration (RTM) is also improved. These seismic results will show the location, width and shape of the fault-karst structure, which gives detailed information for fault-controlled paleokarst reservoir interpretation.

Application of a model-driven simultaneous prestack inversion of rock physical properties in ultra-deep Ordovician carbonate reservoirs in the Shunbei area

“…The complexity of the deep Cambrian-Ordovician oil and gas transport systems makes geophysical predictions challenging (Ding et al, 2020;Wang et al, 2020;Mu et al, 2021). Prestack synchronous inversion can simultaneously obtain the P-wave impedance, S-wave impedance, and density from the CRP gather.…”