A Simple Analytical Model for Predicting Gas Productivity of Horizontal Drain Holes with High-Friction

摘要

It has been recognized that horizontal-wellbore friction significantly affects deliverability of gas wells in highly productive reservoirs. But there is lack of a simple and rigorous flow model for prediction and evaluation of such type of gas wells. This paper fills the gap. Starting from the first law of thermodynamics and Darcy's law, the reservoir-horizontal wellbore cross-flow was modeled analytically in this study. Pressure and flow rate variations in the horizontal wellbore were formulated analytically. A simple closed-form equation for the total gas production rate from the well was derived. This newly developed mathematical model was compared with Joshi’s model and Furui’s model in a field-case study. The result shows that the error of the new model is 11.04%, which is much accurate than the other two models. Sensitivity analyses indicated that use of the new model is more beneficial in situations of high-permeability reservoirs, long horizontal wellbores, and small flow paths in the horizontal sections. This paper provides reservoir engineers an accurate and easy-to-use tool for prediction and evaluation of horizontal gas wells.^