A series of experiments is performed to determine the damage behaviour and energy evolution of red-bed sandstones subjected to drying–wetting (D–W) cycles. The experimental results reveal that accompanied by the strain increases, the input energy density gradually increases, the elastic energy density increases slowly first, then increases linearly, and reaches the maximum value at the peak strength, then gradually decreases. The dissipated energy density continuously increases and then maintains a steady-state level before it finally increases rapidly. Furthermore, with the increase in the number of D–W cycles, all three energy densities of specimens present a linear downward trend. According to the damage variable defined by the energy principle, the damage evolution models of the uniaxial compression strength (UCS) and peak strain of the D–W specimen are established, which can well characterise the evolution of the UCS and peak strain of rocks after different numbers of D–W cycles.
a b s t r a c tAiming at the large error in productivity predication and incomplete consideration in completion parameters design of perforated horizontal well, a model which coupled the relationship of pressure and flow rate in reservoir seepage, near-wellbore inflow and wellbore flow was established. The impact of near-wellbore heterogeneity, wellbore flow pressure drop and completion parameters on the inflow profile of horizontal well is analysed. Studies showed that with a stronger near-wellbore heterogeneity, the inflow profile would fluctuate more seriously. Perforation density had a great influence on the inflow profile and local changes of it would bring a shunt effect. Completion design of variable density perforated horizontal well with an optimized inflow profile which was close to a standard profile would improve the horizontal well development effect. The achievement can provide directive meanings to productivity predication and completion parameters design of horizontal wells in oilfield.
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