To deeply understand the dynamics of gas–water displacement in fractured porous media, especially under extreme high-pressure conditions, is essential to prevent water invasion in natural gas reservoirs. To this end, we presented an experimental study on the interfacial dynamics of gas–water displacement in a microfluidic device with fractured porous media, in which the displacement pressure could reach as high as 25 MPa. We found that, under the condition of quasi-static imbibition (i.e., at quite low differential pressure), water preferentially invaded the matrix instead of the fracture. In contrast, invasive water tended to permeate the fracture under high differential pressure; as a consequence, a conical front edge was formed at the gas–water displacing interface. More importantly, the interfacial front in different fractures contacted at the cross junctions and led to the formation of trapped gas in the matrix, due to the velocity of gas–water interface in the fracture being higher than that in the matrix. Besides, with increase in differential pressure and fracture number, the difference in the interfacial velocity between fractures and the matrix increased and hence the gas in the matrix was more easily trapped. Finally, we established a theoretical model to predict the interfacial velocity of gas–water displacement in fractured porous media under high pressure, which was able to well reproduce experimental data.
High permeability zones in the water-drive gas reservoir tend to act as dominant channels for formation water to invade into gas reservoir from the aquifer. The presence of high permeability zones results in uneven water flow front in reservoir and early water breakthrough in gas well, which seriously affects the gas field development. In this paper, conventional logging and production logging data are used to identify and characterize high permeability zones, so as to guide the optimization of development plan of Kela 2 gas field. A method to determine the lower limit of high permeability zones by using cumulative frequency curve of permeability distribution is proposed, and high permeability zones of 21 wells are identified. These high permeability zones account for 10–15% of the effective reservoir thickness in single wells, and they are mainly distributed in the middle of the Bashijiqike (K1bs) Formation (i.e., K1bs12, K1bs21 and K1bs22). The analysis of production logging data shows that the effective gas producing intervals only account for 29.2% of the total number of test intervals, most of which are related to high permeability zones. Further study shows that the high gas flow from the high permeability zones dominates the wellbore production profile, and the gas in low permeability zones flows vertically to the high permeability zones and horizontally to wellbore through these zones. Through the analysis of production profiles over the years and computer modelling, it is confirmed that water channelling occurred in some gas wells at the depth where the high permeability zones are located, which leads to a significant decline in production of these wells. Based on the study of distribution and behaviour characteristics of the high permeability zones, two suggestions on controlling inhomogeneous water invasion are put forward to realize the sustainable and stable production of the gas field.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.