Journal
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
Volume 207, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.petrol.2021.109082
Keywords
Coalbed methane; Relative permeability model; Interface effect; Unconventional gas
Categories
Funding
- Key Project of the Na-tional Science & Technology, China [2016ZX05042-002]
- National Natural Science Foundation Project, China [U1703126]
- Fundamental Research Funds for the Central Uni-versities, China
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This study conducted unsteady displacement experiments using coal samples based on nuclear magnetic resonance technology to monitor the interface effect between gas and water, establishing and verifying a new relative permeability model that considers the interface effect. The results show that in two-phase flow, the interface effect plays a dominant role, with the gas phase driving the water phase, resulting in a relative permeability of the water phase greater than 1.
During the process of gas and water production in coal reservoirs, the interface effect between gas and water should not be ignored. In this study, based on nuclear magnetic resonance technology, the unsteady displacement experiment was carried out with coal samples to monitor the interface effect, and a new relative permeability model (with a specific benchmark) is established and verified which considering the interface effect. The results show that the NMR method can be used to monitor the interface effect effectively, and in the experiment movable water controlled by the pressure difference is limited (11% and 20%), and that controlled by the interface effect is dominant (89% and 80%), which means the interface effect plays a dominant role in the two-phase flow. In the flow, the gas phase drives the water phase, and this additional driving effect results in that the relative permeability of water phase is greater than 1. The verified results show that the new model can effectively describe the driving effect which can not be achieved by the capillary force model.
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