Abstract
Pressure transient theory for a water-injection well in the presence of a closing fracture and a discontinuity in fluid mobility is developed in elliptical coordinates. Solutions are obtained using the Laplace transform and numerical inversion. From the results it is concluded that a pressure fall-off test with a closing fracture, in principle provides three different methods for determining the fracture length. The first method is based on rock mechanical principles only. The second method makes use of formation linear flow. The third method analyses the transition of the pressure transient from the inner fluid region to the outer region in conjunction with a heat or volume balance. If more than one method is applicable consistent results should give a reliable estimate of the fracture length. The in-situ horizontal rock stress can also be determined from the test. It is equal to the pressure at which the closing of the fracture is observed.
