Abstract
Use of horizontal and multilateral wells for oil and gas recovery has become a common practice in the petroleum industry. It is generally recognized that most horizontal wells do not produce oil and gas at the expected production rate. The discrepancy is mainly due to the fact that it is unclear as what constitutes the "expected production rate." The expected production rate is usually the production rate predicted by the mathematical models that were derived on the basis of the assumption of infinite-conductivity drain hole. Although a number of mathematical models are available for predicting the productivity of horizontal wells, they are not easy to use due to their common nature of mathematical complication and numerical treatments. This paper presents a simple and rigorous mathematical model for estimating the productivity of horizontal wells.
By rigorously coupling reservoir inflow and drain hole hydraulics we derived an equation for pressure distribution in the horizontal drain hole in this study. A simple function for fluid flow rate distribution in the drain hole was then developed. An equation for deliverability of the horizontal drain hole was obtained by evaluating the flow rate function at heel. This new model was compared with three existing mathematical models and field data. The comparison shows that the new model has two advantages over other models: 1) it is more accurate than other models, and 2) it is very easy to use. This paper provides petroleum engineers a simple tool for accurately predicting productivity of horizontal drain holes.
