Well Pressure Behavior of a Finite-Conductivity Fracture Intersecting a Finite Sealing-Fault

Hydraulic fracturing is important to the development of low permeability reservoirs. Recent advances in the technology of hydraulic fracturing, coupled with its economic success, have led to its application in high permeability reservoirs. Consequently, fracturing is now applied in all types of formations including highly faulted systems. The existence of a fault near a well may impede or contribute to the fracture extension process. Various models and techniques have been introduced in the literature for the interpretation of transient pressure behavior of vertically fractured wells. However, none of the current models and techniques has taken into account the case of a fracture intersecting a fault. This paper presents a theoretical model for analyzing the pressure behavior of a finite-conductivity vertical hydraulic fracture intersected by a sealing-finite fault, considering different angles of intersection and neglecting in all cases wellbore and fracture storage effects. The point at which fracture and fault conjoint has also been a matter of analysis in this study. The model was solved numerically using PEBI grids. For the case where the fracture-fault system form an angle of 90 or 75°, the pressure response is characterized by a maximum point or "hump" in the pressure derivative which takes place once the transient response of the fracture has vanished. This is because the fault delays the development of the pseudoradial flow regime. For smaller angles, a peak is not observed; however, there is a transition period that causes an apparent pseudoradial flow to develop earlier. This is because the hump tries to develop but the fault is not long enough for that to happen. When the fault is very long (LD > re), pseudoradial flow does not develop because the fault acts as a boundary. A horizontal line on the pressure derivative curve is observed which can be easily confused with that of the actual pseudoradial flow regime. Correlations to estimate both fault length and fracture-fault angles are presented. A simulated example is presented to illustrate the proposed step-by-step procedure for interpreting a post-fracture pressure test of well near a sealing-fault.