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 tools
Reducing casing-pressure limitations by using lower applied annulus pressure
Reducing and, in some cases, eliminating the use of wireline operations in the well
Acoustic signal not affected by mud weight
Allowing optimization of the operations by providing real time data monitoring
Allowing accurate status feedback and diagnostic from the down hole tools, reducing uncertainties
Reducing the duration of each period of the operation can potentially reduce rig time
Adding 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 operation
Reducing 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 flow
Closing tester valve for buildup
Opening circulation ports
Actuating downhole samplers
Acquiring real-time pressure and temperature data
Transmitting real-time data to customer office
Analyzing 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.
