Rock physics studies based on laboratory core velocity measurement

Abstract

Reservoir characterization using seismic data serves large contributions to oil and gas development projects and CO₂ sequestration projects. Rock physics analysis has been one of pivotal disciplines in such reservoir characterization because it plays a role in connecting physical properties of rocks and reservoir properties. Laboratory experiment is the central part in a rock physics analysis because it reveals various physical properties on a single rock sample. In this paper, we introduce two rock physics case studies using results of core velocity measurements conducted at Japan Organization for Metals and Energy Security （JOGMEC） Technology and Research Center （TRC）’s lab. The first study is the estimation of velocity anisotropy at a gas field offshore Australia. We measured elastic propagation velocities of rock samples from the field with a tri-axial compression test apparatus and estimated both intrinsic anisotropy and stress-induced anisotropy. With synthesized CMP gathers, it was revealed that the estimated stress-induced anisotropy would affect seismic inversion and subsequent reservoir characterization. The second case is the interpretation of time-lapse walkaway VSP （Vertical Seismic Profile） conducted in a CO₂-EOR pilot at an oil field onshore Abu Dhabi. Based on the results of velocity measurements performed on rock samples from carbonate reservoirs and dynamic reservoir models, we modeled changes in elastic properties associated with the CO₂-EOR pilot between the time of the baseline and monitoring VSP. The modeling of elastic property changes allowed us to deepen the understanding about 4D response obtained through time-lapse full waveform inversion applied to the walkaway VSP data. JOGMEC TRC offers continuous supports for improving reservoir characterization in E&P and CCS projects.