A New Method for Earlier and More Accurate EUR Prediction of Haynesville Shale Gas Wells

Abstract

Haynesville shale gas wells are operated over a wide range of back pressures, varying from 8000 psi or higher at early time to 1000 psi or lower at late time. Traditional Arps Decline Curve Analysis (DCA) presumes constant back pressure, and therefore over-predicts Estimated Ultimate Recovery (EUR) for Haynesville wells when applied at early time, prior to reaching line pressure. A new method has been developed to forecast well EUR earlier and more accurately by using pressure normalized rate instead of actual rate. In this method, the actual rate is normalized to the rate corresponding to a constant operating pressure. DCA methodology may then be applied to this normalized rate to forecast EUR. This new method yields consistent EUR predictions from much earlier time than traditional DCA methods, and converges to the same EUR as the traditional DCA method once constant flowing pressure is reached. Both field data and simulation results confirm the advantages of this method. The new method is practical to use and it reduces the uncertainty range of well performance predictions, thus providing better and earlier well performance comparisons, a quicker assessment of completion trial results, and more accurate booking of reserves and resources.