Abstract

Hydrate formation/blockage causes serious flow assurance issues during deepwater operations (e.g. well testing). Current dominant method is total prevention of hydrate formation with massive thermodynamics inhibitors (THIs), which render this method economically infeasible. Moreover, the required inhibitor storage and injection capacity may be far beyond the facility limits when the water production rate is high. In this work, aimed at addressing hydrate associated problems at reduced cost, a method is developed to prevent hydrate blockage with lower inhibitor consumption. Based on hydrate formation and deposition dynamics, a method is developed to prevent hydrate blockage during deepwater gas well testing. Implementation procedure of the proposed method is developed and further illustrated through case studies. We recommend that testing operations should be run within the Hydrate Blockage Free Window, HBFW. The HBFW refers to the period from the beginning of testing operations to the moment when a significant pressure drop increase is encountered. Case study work is conducted on a deepwater gas well in the South China Sea. The case study suggests that hydrate inhibitor can postpone the occurrence of conduit blockage. When the scheduled operation time (SOT) is shorter than the HBFW, the testing operation can be completed within the HBFW and no hydrate inhibitor is needed. If the SOT is longer than the HBFW, a small amount of inhibitor is required to extend the HBFW, thus the testing operation can be completed within the HBFW. The inhibitor consumption is much lower compared with the current over-inhibition method. With the proposed HBFW-based method, the inhibitor storage/injection capacity requirement can also be relaxed. The study suggests that with lower inhibitor consumption and inhibitor storage/injection capacity requirement, the HBFW-based method can address hydrate associated problems during deepwater gas well testing at reduced cost. In addition, the reduced inhibitor storage/injection capacity requirement makes this method more feasible especially when high water production is encountered during testing operations.

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