First Real-Time Drill-Stem Test in Deepwater Using Fully Acoustic Telemetry Monitoring and Control of the Well

Abstract

Abstract As exploration has moved into deeper, more hostile environments, drill-stem testing (DST) has had to address new challenges related to testing in these ever-changing, more demanding environments. These new scenarios have required continuous technology innovations to enable DSTs to meet the additional needs inherent to the deeper offshore environments. Testing technology has had to find solutions for these conditions, while maintaining cost optimization and operational safety, both of which present continuous concerns. One strategy has been to reduce the use of electrical cables in the well and minimize the application of pressure to the annulus. This paper presents the industry's first fully acoustic telemetry controlled and monitored real-time drill-stem testing (DST) operation performed in a deepwater environment. The fully acoustic controlled operations included: Opening tester valve for flowClosing tester valve for build upOpening circulation portsActuating downhole samplersAcquiring real-time pressure and temperature data. This job was performed in the pre-salt region of southeast Brazil from a semi-submersible rig at 7,053-ft water depth in a well that was17,600 feet deep. In this DST, a completely wireless acoustic system was used to control the downhole tools, and as such, had to actuate the tester valve, the circulation valve, and the bottomhole fluid sampler, while acquiring real-time bottomhole pressure and temperature data. This was the first time that this type of operation had been attempted in deep-water conditions. Acoustic telemetry systems usually can help optimize operational cost because of their capability to access quickly real-time data pertinent to the reservoir evaluation; because of this capability, immediate well-timed decisions or changes to operations can be made. The fully wireless system (acoustic wireless transmission across the subsea safety tree and its components) provided the operator with acoustic feed-through response, which enabled troubleshooting from the surface and capability to change the "next steps" for the DST quickly. This paper also discusses how the use of these tools elevated testing operations to a higher performance level and improved quality standards.