Drill-Stem Test with Real-Time Reservoir Data Monitoring Improves Operational Efficiency — Case Study, Senoro-6

Abstract

Well testing generates essential reservoir data, and although it can impact initial operating expenditures significantly in oil or gas upstream projects, the data generated can be essential to the efficiency of the completion operation ultimately designed. While having proven its value, data-gathering methods still must be balanced with operational and economic strategies, if the completion goals are to be economically feasible. Drill-Stem Test (DST) tools with downhole shut in and memory gauges are commonly used in well testing operations to provide reliable data and enhance operational efficiency of the completion. However, DST tools alone cannot monitor reservoir pressure response in real-time for justifying the subsequent operational objective changes during the data acquisition, because the recorded data cannot be retrieved at surface until the well test operation is completed, and the workstring is pulled out of hole. To overcome this problem, surface read-out (SRO) systems can be used with DST for retrieving downhole memory-gauge data in real time; thus, the pressure response can be monitored directly, and operational changes can be made immediately, based on actual reservoir conditions. An SRO system was used in Senoro-6 well to aid in justifying a shut-in duration to reach reservoir boundary and attain information that indicated the need for a stimulation treatment. Based on the real-time SRO data, it was found out that the permeability was lower than expected, and shut-in should be terminated earlier than planned, since the required shut-in time to reach boundary would be much longer than anticipated. Prolonging testing time would not be reasonable when reviewing operational and economic considerations. In addition, pressure transient analysis from real time SRO data indicated that the well had severe wellbore damage. Thus, the decision was made to conduct matrix acid stimulation based on the SRO data and to continue with post-stimulation well testing without pulling the DST string out of the hole. Post-test results showed a 22% production improvement, while the operation itself saved more than US$150,000 from daily rig cost. This approach in using the SRO system proved to be effective in helping to determine an efficient testing operation and completion strategy.