Physical Concept Validation Testing Performed for a Pore and Fracture Pressure Margin Prediction System during Offshore MPD Operations

Abstract

Abstract A pressure determination system (PDS) was field tested to progress Managed Pressure Drilling (MPD) from a reactive system to one that prevents well control events from initiating. Physical testing performed on an offshore drilling operation successfully demonstrated the capability of the PDS to detect a simulated, unsafe change in fracture margin without incurring significant losses in August 2014. A summarized overview of the test method, conclusions, and results will be discussed as well. The PDS Pressure Control Valve (PCV) is designed to oscillate its position size in a repeatable and gradual fashion and analyze the behavior of Applied Surface Back Pressure (ASBP), Bottom Hole Pressure (BHP), and Flow Out indicators over time. In the event that average BHP begins to near a drilling margin, the behavior of the above indicators at the crest or trough of a wave cycle will momentarily deform indicating an unsafe change in a drilling margin trend that will eventually lead to a recordable well control event if wellbore pressure is not proactively adjusted. Since, average BHP has continuously remained within drilling margins during this process, any resultant gain or loss is negligible. Once the threat of a well control event is detected, the MPD PCV will adjust wellbore pressure to a safer value to prevent the occurrence of a well control event. During field testing, the PDS concept was verified with two assessments, signal transmission reliability and simulated fracture detection. Both tests were performed in open hole of a medium depth well with a rotating and reciprocating drill string and the mud pumps running. The signal transmission reliability test validated that the PDS can oscillate PCV position in a controlled and consistent fashion as well as create highly repeatable behaviors in ASBP, BHP, and flow rate waves over time. The simulated fracture margin test demonstrated that the PDS has the sensitivity to detect a fracture margin at 20 psi above the driller's intended wellbore pressure with a negligible volume of losses while the PDS PCV oscillated wellbore pressure as described above. Prior to field testing, a SIT (System Integrity Test) was performed on the PDS equipment installed on MPO's MPD Pressure Control Manifold (PCM) to ensure the system was prepared for concept testing. The SIT was performed with the MPD PCM isolated from well bore riser returns in August 2014. The field tests performed offshore, were previously performed as an initial test, at the MPO Dubai Training Center Flow Loop where the PDS concept was also successfully validated in a laboratory environment. During those tests, the sensitivity of the PDS system was also demonstrated by validating that a 4 inch Coriolis meter in a small, closed loop system was able to detect less than a 1 gallon difference in flow.