Successful System Integration Test of Real-Time Drillstem Test String for Deepwater Using Fully Acoustic Telemetry Monitoring and Control of the Well Across Electrohydraulic Subsea Disconnect Tool

Abstract

Depletion of shallow water oil reserves and growing energy demands have required exploration and development to extend into deepwater resources. Ever-changing environments in deepwater offshore locations present new challenges and require cutting-edge well-testing technology as well as advancements in cost optimization and operational safety. This paper introduces a successful system integration test (SIT) in preparation for the first deepwater well test in Vietnam on a dynamic positioning vessel in 1117 m water depth for a 3764 m deep well. It was the first time both a real-time acoustic controlled well-testing system and an electrohydraulic (EH) controlled subsea safety system were to be deployed. The acoustically controlled well-testing system eliminated the use of electric lines to obtain real-time accurate reservoir information and minimized the use of annulus pressure to operate downhole tools. The EH-controlled subsea safety system introduced superior safety measures for emergency situations requiring less rig time. The full system included the following: EH-controlled subsea safety system that uses the speed of EH actuation to perform emergency well shut-in and landing string secure disconnectAcoustically operated combined tester valve and circulating valveAcoustically triggered downhole samplersReal-time acquisition of reservoir pressure and temperature dataReal-time monitoring of downhole valve statusReal-time monitoring of seabed pressure and temperature data During the SIT, the EH-controlled subsea safety system demonstrated an emergency shut-in including disconnecting the landing string in 8 seconds. Additionally, the acoustically controlled well-testing system demonstrated real-time acquisition of downhole pressure and temperature data, operated and monitored the status of downhole valves, and acoustically activated bottomhole samplers. Although the tool string was not deployed offshore because of dry holes, the success of the SIT validated the ability of this combined system to provide high performance, high safety levels, and high quality standards. This combined system would not only allow the operator to make immediate and accurate decisions to achieve intended well-test objectives, but also would provide effective safety measures in emergency situations in less rig time. The successful SIT should encourage exploration expansion in deepwater environments in the near future when solutions are available for additional challenges facing operators.