Novel Analyses and Design of Relief Well Considering 3-D Vector Effect of Kill Fluid

Abstract

Abstract A novel approach that considers the three-dimensional flow effects while designing kill well strategies has been developed. This type of analysis helps to accurately model the flow behaviour downhole at the interception point and offers game-changing safety and environmental benefits for well kill design and operations. In planning a relief well contingency, the current industry standard is the 1-D multiphase model which is used to determine the requirement of pump rate and mud weight to kill the blowout well. Using 3-D Computational Fluid Dynamics (CFD) helps to capture the physics of the flow better and provides more accurate representation of the mixing and multiphase interaction occurring. Both 1-D and CFD modeling were compared to analyze well kill design conditions. In one field case, the 1-D analysis returned results where even with a 19.0 ppg mud pumped at 100 bpm, the worst-case discharge rate from the well (680 MMSCF/D) could not be killed. Another case using the 1-D analysis showed that planning a relief well kill for a 1.0 BCF/D gas blowout rate, required three to four relief wells with a kill rate of 200 bpm simultaneously to kill the well. CFD modeling was used to model the same two conditions, in addition, the CFD model also captured the jetting effect from the relief well. CFD model also iterated on a design that included pumping down a smaller string to analyze/understand the detailed fluid flow behavior at the intercept. This allowed for two successful designs of a kill with lighter muds for the 680 MMSCF/D case. For the 1.0 BCF/D rate case, the CFD analysis indicated that the well could be killed at a much lower pump rate compared to the 1-D model. A test apparatus was designed and created to verify which of the two methods was more accurate. Physical experiments indicate that results from the proposed method match the test results closer than the standard approach. This approach can reduce the equipment required and the time to drill a relief well (which can take two to three months to drill) and more effectively terminate a blowout event earlier, thereby minimizing the negative impact on environment, economics and human life.