Mechanism Of Fluid Pressure On Detrital Particles And Pore Retention In Clastic Reservoir

Overpressure in clastic reservoir can generally reduce the effective stress on the particles,which is beneficial to the preservation of primary pores and delay the breakages of clastic particles.Studying the influence of fluid pressure on reservoir debris and pore retention is of great significance for understanding the development mechanism of deep reservoirs.Taking the southern margin of the Junggar Basin as an example,the diagenetic physical simulation experiments of different fluid pressures are used to study the effects of fluid pressure on the face rate,particle contact relationship and micro-crack formation of clastic reservoirs.The comparison of sample analysis results summarizes the mechanism of fluid pressure on reservoir debris and pore retention.The experimental results show that the fluid pressure can delay the mechanical compaction and decrease the rate of primary pore degradation.The higher the fluid pressure coefficient,the slower the reduction of the native face rate.During the burial of clastic rocks,there is a significant critical depth point for the influence of fluid pressure on mechanical compaction.Before this depth,the fluid pressure can effectively suppress the mechanical compaction;after this depth,the fluid pressure is mechanically pressed.The actual inhibition effect is significantly weakened.In the background of hydrostatic pressure,the length of microcracks in rock particles formed by mechanical compaction increases rapidly over a certain depth range,and the microfracture partially heals beyond this depth.Under the background of high fluid pressure,the micro-cracks of the particles develop in multiple stages.Before reaching the main development depth of micro-cracks,the length of micro-cracks tends to increase gradually.The length curve of the micro-crack development has a corresponding relationship with the pressure coefficient curve.The minimum value of the micro-crack length corresponds to the inflection point of the fluid pressure coefficient curve,that is,the depth point at which the rate of change of the pressure coefficient changes.