Online NMR displacement experiment on gas-water mutual displacement during multi-cycle injection-production in a water-invaded gas reservoir

doi:10.3969/j.issn.1006-6535.2026.01.008

Abstract

Abstract: Due to the complex gas-water mutual displacement flow mechanisms and insufficient understanding of the evolution of effective storage space during multi-cycle injection-production in water-invaded gas reservoirs,this study selected the core from Well 5 of Wen 96 Gas Storage as research object and carried out online nuclear magnetic resonance(NMR)displacement experiments under multi-cycle gas-water mutual displacement.By real-time monitoring of T₂ spectra and signal distribution characteristics,the effects of reservoir physical properties,displacement pressure,and injection-production rates on gas-water mutual displacement efficiency were systematically analyzed.The results indicate that reservoir properties have a significant impact:in low-permeability reservoirs with permeability below 5.00 mD,the recoverable gas pore volume decreases by about 15% after multi-cycle injection-production,whereas in high-permeability reservoirs with permeability above 80.00 mD,it decreases by only about 2%,with most of the pore volume reduction occurring in the first three cycles.Displacement pressure correlates logarithmically with recoverable space,and a critical pressure of around 17 MPa is identified.Below this threshold,displacement efficiency declines significantly,while above it,fluid distribution tends to become homogeneous.When the injection-production rate is increased to 2.0 mL/min,the movable space increases by about 7%,indicating that high-rate injection-production can reduce fluid entrapment by enhancing drive forces.The cumulative seepage hysteresis effect induced by multi-cycle injection-production continues to reduce effective storage space,a phenomenon calling for special attention in long-term operation.This study provides theoretical guidance and technical support for site selection optimization,injection-production parameter optimization,and operational efficiency improvement in water-invaded gas storage reservoirs.

Key words: water-invaded gas storage, multi-cycle injection-production, gas-water mutual displacement, online NMR, displacement experiment

CLC Number:

TE349

YANG Xiaosong, ZENG Daqian, PANG Jin, ZHANG Guangquan, ZHOU Chunxi, ZHU Sinan, WU Tongtong, ZHANG Ming. Online NMR displacement experiment on gas-water mutual displacement during multi-cycle injection-production in a water-invaded gas reservoir[J]. Special Oil & Gas Reservoirs, 2026, 33(1): 66-74.

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