Fully Acoustic Telemetry System Improves Cost Efficiency and Safety in DSTs for Deepwater

Abstract

The Drillstem Test (DST) is an important process used to gain knowledge and understanding about a reservoir, from identifying the characteristics of its oil and gas, to production planning, extending as well to the commercial viability of the entire reservoir. Since 1920, the need to better understand reservoir conditions has driven numerous technology developments throughout different generations. These technologies have helped define reservoirs in harsh conditions. Through the continued search for innovative DST solutions for the challenging deepwater scenario, a new generation of DST tools was successfully achieved. This technological package of downhole tools were influenced mainly by the communication method applied. The acoustic telemetry system is the backbone of the downhole tool network system, providing an efficient and effective bi-directional communication link between the data acquisition computer in the rig control cabin and the tools located down hole. This paper presents how wireless acoustic control of drill-stem test tools can improve cost efficiency and safety in DST operations by: Reducing risks associated with the use of annulus pressure to actuate downhole toolsReducing casing-pressure limitations by using lower applied annulus pressureReducing and, in some cases, eliminating the use of wireline operations in the wellAcoustic signal not affected by mud weightAllowing optimization of the operations by providing real time data monitoringAllowing accurate status feedback and diagnostic from the down hole tools, reducing uncertaintiesReducing the duration of each period of the operation can potentially reduce rig timeAdding redundancy capabilities (tools can operate with means other than acoustic as backup)Comparing with wireline based systems in allowing real-time data acquisition during all the periods of the operationReducing number of personnel necessary in the rig by allowing remote access and analysis of the data The system was first-time deployed in a semi-submersible rig in a pre-salt region of southeast Brazil. The fully controlled operations included: Opening tester valve for flowClosing tester valve for buildupOpening circulation portsActuating downhole samplersAcquiring real-time pressure and temperature dataTransmitting real-time data to customer officeAnalyzing data in real-time This paper will discuss how this new full telemetry acoustic system elevated testing operations to a higher performance level, improving cost efficiency and safety in DSTs for deepwater application.