First Multi-Zone Drill-Stem Test in the UAE Improves Operational Efficiency and Enhances Value of Information

Abstract Well testing is a critical stage of reservoir characterization. If not optimized, drill-stem tests (DST) can be time consuming when testing multiple formations in a well. This paper presents a case study for the first dual-zone DST performed in the UAE, to test 2 different zones individually in one single DST run. Significant operational efficiency gains, DST string design with multiple pressure gauges, multiple packers and wirelessly activated downhole tools will be explained. In standard DSTs, non-value-added time such as running in hole, pulling out of hole, pressure testing the DST string and others can take 50% of the total test duration and cost. Operator companies may also test wells with simple completion strings to save time, but such tests come with limitations such as difficult downhole sampling operation (if possible) and challenging well kill operations. A dual-zone DST with wirelessly controlled downhole tools enabled to test 2 different zones individually. Multiple pressure gauges with real-time data transmission were used to monitor operations. Wireless downhole valves have controlled flow from different zones individually and enabled commingled flow. Significant efficiency gains were achieved, and multiple operations were enabled with this first dual-zone DST performed in the UAE. Two zones were tested successfully in one DST run using the dual-zone DST string. A combination of 2 different packers were set in the well to isolate two zones from each other. Each zone was opened to flow through the DST string individually by two wirelessly controlled downhole valves. Pressure and temperature responses from each zone were recorded by multiple pressure gauges for pressure transient analysis. Downhole fluid samples were also collected with the built-in samplers on the DST string. Compared to two separate standard DSTs, 21 rig days and associated cost were saved with the use of the dual-zone DST string. In addition, compared to well testing with a completion string, downhole shut-in for accurate reservoir characterization was enabled. Despite high wellhead pressures that sometimes prevent wireline entry in the wellbore, wireline runs were performed without having to kill the well, enabled by the DST tools. Well kill operations were carried out smoothly by placing the kill fluid in the tubing with the use of downhole circulation valve. The first dual-zone DST performed in the UAE has changed the well test philosophy from testing wells with a completion string to testing with DST. Efficiency gains and new practices are explained in this paper and can be applied to all well tests with multiple zones to test and enable new well test methods to enhance the value of information from well tests.