Elastic wave velocities of hydrate-bearing sands containing methane gas bubbles: Insights from CT-acoustic observation and theoretical analysis

Elastic wave velocities of hydrate-bearing sands containing methane gas bubbles: Insights from CT-acoustic observation and theoretical analysis

Gas hydrates

Methane

Wave propagation

Seismic waves

Petroleum reservoir engineering

Hydration

Petroleum prospecting

Gases

Computerized tomography

Acoustics

Acoustic wave velocity

Natural gas well logging

Acoustic wave velocity measurement

The elastic wave velocities of hydrate-bearing sediments (HBS) are considerably affected by the content of free gas and hydrate. Although several existing models relate the free gas and hydrate saturation to acoustic velocities, the accuracy of these models is still uncertain because of the difficulty in determining the gas content. In this study, we acquired the gas volume fraction and acoustic velocity data of the hydrate-bearing sands through a X-ray computed micro-tomography (CT) and an ultrasonic apparatus, respectively. The acoustic velocities increase slowly at low hydrate saturation (Shp) when the hydrate saturation varies from 15% to 55%. The value of Vp calculated by the STPE model, without considering the effects of gas on velocity, is higher than the experimental value. We further applied a new method combining the Wood and Domenico equations to calculate the bulk modulus of HBS containing methane gas, which can improve the precision and applicability of the STPE model. Compared with the EMT and BGTL models, the modified STPE model is more suitable for predicting Vp of unconsolidated reservoirs with high porosity and permeability. These results provide a new method for further experimental research and a theoretical reference for accurately estimating hydrate saturation through logging data during natural gas exploration and development. 2021 Elsevier B.V.

88

Journal of Natural Gas Science and Engineering

2021

Chen, Jie

Hu, Gaowei

Bu, Qingtao

Liu, Changling

Dong, Lin

Wan, Yizhao

Mao, Peixiao

Guo, Yang

Wang, Zihao

journalArticle

18755100

10.1016/j.jngse.2021.103844