Well Control: Hard or Soft Shut-In, The Onshore Experience

This paper investigates the effect of pressure surge referred to as "water hammer" on the formation as a result of shut - in procedure. Two methods are generally used to shut – in the well when kick is experienced: a soft shut – in or a hard shut – in. It is generally believed that when a well is hard shut – in, the additional surge pressure is capable of fracturing the formation creating a big issue in well pressure control. Hence, most operators advise against the use of this procedure. Drill sim 50 was used to simulate various kick sizes ranging from 2bbls to 20bbls and the resultant pressure surge due to water hammer was calculated and added. The result obtained indicated that soft shut – in procedure allows additional influx that increases the pressure on the formation while hard shut – in reduces the additional influx thereby reduces the possibility of formation breakdown. For all the kick sizes considered, the BHP for hard shut – in with additional pressure surge due to water hammer effect was not up to formation fracture pressure of the various depths considered. The paper concludes that more time will be saved to prevent additional influx if hard shut – in procedure is adopted especially in an onshore location of Niger Delta on which the simulation studies was carried out.