Experiment on development of multilayer unconsolidated sandstone gas reservoir with edge water invasion in Qaidam Basin, China

The Quaternary unconsolidated sandstone gas reservoir in the Qaidam Basin is characterized by multiple layers, strong heterogeneity, and active edge water. Based on these characteristics, a physical simulation experiment method for production from multi-layer edge-water gas reservoirs was proposed. In this method, the experimental models were established by using natural cores in series and parallel connection to show the geological characteristics of multi-layer gas reservoirs, and according to the results of the indoor simulation of the whole depletion production process, an experimental study on four layers of commingled production in one well was conducted under three scenarios of gas reservoirs: without the water invasion, with the water invasion without flow, and with the water invasion with flow. In this study, by visually monitoring the water invasion process of a constant-pressure edge water body along layers with different permeability and quantitatively analyzing the influence of gas well production allocation on the water invasion path and advancing speed of the water invasion front, the influence of non-uniform edge water invasion on gas reservoir productivity, recovery factors, and residual gas occurrence characteristics was clarified, and the mechanism of non-uniform edge water invasion along high permeability layers and the formation of water-sealed gas were revealed. The findings of this study can provide a basis for reasonable water control for this type of gas field.