Full-hole critical liquid carrying flow model of shale-gas horizontal well

None of current critical liquid carrying flow rate models can completely reflect the complex casing programs of shale gas wells and the change characteristics of flowback rate or accurately predict the liquid loading in shale-gas horizontal wells. In this paper, a full-hole critical liquid carrying flow rate model of shale gas well was established by analyzing droplet dynamics and energy and comprehensively considering the droplet energy loss caused by the liquid production rate, droplet deformation and build-up rate change in the wellbore. The long axial length of the droplet with maximum stable deformation was determined according to the energy balance relationship of the droplet with the maximum stable deformation. The drag coefficient and surface tension formula applicable to shale-gas horizontal wells were selected. Based on the error analysis, Mukherjee-Brill two-phase flow model was adopted to calculate the distribution of wellbore pressure in shale-gas horizontal well. The case analysis shows that compared with existing critical liquid carrying flow rate models, the new model is higher in the prediction coincidence rate of liquid loading in shale-gas horizontal well and its prediction accuracy is high up to 92.3%. The new model can accurately predict liquid loading wells and approximate liquid loading wells and its liquid loading prediction accuracy for the wells without liquid loading can meet the requirement of field application, so it can provide an effective guidance for judging liquid loading in shale-gas horizontal wells and selecting proper production technologies.