Study On Variable Mass Flow Law In Multi-hole Injection Of Horizontal Wellbore

In the real situation of the horizontal well development,the flow is actually variable flow due to radial influx along the flow direction in the perforating horizontal wellbore and the law of pressure distribution in the wellbore cannot be calculated as in the ordinary horizontal tubes using simple calculation.Aiming at the complex distribution and constitute of pressure in the perforating horizontal wellbore,firstly,a large number of documents are investigated and surveyed,and the experimental and mathematical methods of previous researchers are,then,summarized,and the difference of experimental methods and each mathematical models are compared,the advantages and disadvantages of each other are elaborated and the imperfections among them are also pointed out.Secondly,the pressure drop mathematical models of single(one perforation unit),double holes and triple holes injection under the isothermal conditions with no heat transfer to and from the fluid to the environment are derived,according to the mass and momentum balance formulas and also under several reasonable assumptions.And then,the numerical simulation experiments about single hole and multi-hole are done by the Fluent of Computational Fluid Dynamics(CFD)software.Comparing the result with the existing conclusion,the numerical simulation of single hole injection can achieve the same conclusion done by other researchers.And fitting the data of mix pressure drop of variable mass flow of single hole injection,so the correlation of equivalent mix fraction factor can be got.The pressure drop that consists of accelerated,fractional and mix ingredients in the perforation horizontal wellbore by the result of numerical simulation can also be achieved.And the total,accelerated,fractional and mix pressure drop increase when the ratio of hole velocity and main velocity increases.When the hole velocity is relatively high,the mix pressure drop of total pressure drop is dominant,and fractional pressure drop increase with the main velocity increasing.The increase amplitude of accelerated pressure drop is apparent with the number of perforation holes increasing when the hole velocity is relatively high.Qualitative analysis of variable mass flow with hole influx by the simulation result of postprocessor in the software are also done in this paper,aiming at solo perforation unit.The mechanism of mix pressure drop are: the arisen backflow,viscous flow and rotational flow at the aria of perforation hole nearby due to the difference between the main and hole velocities,and the disturbance of main flow in the wellbore due to perforation hole injection.The last,the sensitivity analysis of the pressure distribution of perforation horizontal well is done through the case under the real situation.The result shows that the total,accelerated,fractional and mix pressure drop of horizontal wellbore increase with the increasing of the length,the density of perforation and the flow rate of the perforation hole of horizontal wellbore,and the pressure drop decreased obviously with the increasing of the inner diameter of horizontal wellbore.The distribution law of flow rate along the horizontal wellbore is also calculated through the case,and the result can be used for the suggestion of optimized design for horizontal well so that the maximum commercial benefit can be achieved.