AN OFTEN OVERLOOKED DETAIL IN WELL TREATMENT DESIGN
When fracture stimulating a well, maximum wellhead pressure can be reached seconds after the high-pressure pumps are stopped following a rapid pressure increase during a "screenout" or other sudden flow stoppage. This maximum pressure is caused by a water-hammer effect. When this effect is ignored, maximum allowable wellhead and downhole pressures can be exceeded, even if pumping stops before reaching the maximum allowable pressure. This paper provides a method to calculate the water-hammer pressure. Data from several case study wells demonstrating the water hammer effect are compared to the calculated values obtained from the methods described in this paper. For tight formation screenouts, the predictions are within 12% of the maximum pressure recorded. Methods to help minimize the pressure surge are also presented. Use of these methods can minimize the risk to people, the environment, and equipment caused by the potential water-hammer pressure surge often overlooked in well treatment designs.