Variation characteristics of dynamic stress of cap rock during gas storage multicycle injectionproduction process
Author of the article:WANG Chen1, JIA Shanpo2, YANG Junwei1, ZHONG Guosheng3, CHEN Zhenlong3, CHANG Yongsong3
Author's Workplace:1. College of Civil Engineering & Architecture, Northeast Petroleum University, Daqing, Heilongjiang, 163318, China; 2. Institute of Unconventional Oil & Gas, Northeast Petroleum University, Daqing, Heilongjiang, 163318, China; 3. PetroChina Jilin Oilfield Branch, Songyuan, Jilin, 138000, China
Key Words:Multi-cycle; Cap rock; Dynamic stress evolution; Gas reservoir storage; Flow-solid coupling
Abstract:
The deep understanding of the dynamic stress evolution
law and influencing factors of the cap rock under the multi-cycle injection-production
cycle is helpful to scientifically and effectively predict the setting of the
upper limit pressure in the process of gas reservoir injection and production.
According to the operation mechanism of the gas storage injection and production
and the rock mechanics theory, the formation deformation and pore pressure
change are the main factors affecting the disturbance of the cap rock stress
field, that is, the change of the stress field of the gas reservoir cap rock is
caused by the deformation of the reservoir and the change of the cap rock
seepage field. The size of the influence of the reservoir is not accurately
evaluated in the traditional cap rock stress analysis theory. In order to
supplement the above theory, this study takes the S gas reservoir in Songliao
Plain as the research object, and conducts corresponding research on the cap
rock through different working conditions. Based on the rock fluid-solid coupling theory, the supracrustal rock is
regarded as a porous medium, and the geological mechanics model that considers
the cap rock, reservoir and the bottom layer is established. The above two
factors are numerically simulated by ignoring the deformation effect of the
reservoir, the impermeability of the cap rock and the actual formation
conditions. Meanwhile, the gas storage full life cycle (three stages as gas
reservoir depletion, injection and multi-cycle
injection and production) is taken into account as well. The research results
show that the change of the seepage field of the cap rock has the most
significant effect on the stress field of the cap rock, and the most sensitive
part of the stress change is located at the junction of the cap rock and the
reservoir. This research not only has important practical significance, but
also has important scientific research value. It will enrich the evaluation
theory of gas storage cap rock sealing and provide reference for engineering
practice.