メタンハイドレート資源開発における坑井内流動解析

–メタンハイドレート生産システム流動解析シミュレータの開発および坑底圧自動制御手法の検討–

抄録

A numerical simulator is developed as a part of a Japanese National hydrate research program (MH21, funded by METI) to examine performance of methane gas production system from methane hydrate layer under deep seabed. The simulator solves mass and momentum equations of gas-water two-phase flow using one-dimensional drift flux model to trace velocities and volumetric fractions in each phase along a gas production well with various diameters. An automatic control system is devised in the simulator to control methane gas production rate by keeping the bottom pressure constant. Numerical simulations are conducted to examine characteristics of the system by changing pipe dimensions as parameters based on the real system in the field test. Also, in order to increase performance of the automatic control system, an additional component related to estimated water production rate under designed gas production rate is considered in the system. The new control method is tested as well as a standard feedback control system. As the result, it was verified that the simulator could estimate the flow characteristics during operation in the production well. Also, it was clarified the proposed control method is useful to get the designed gas production. One could get useful information by adding necessary functions and further information by doing more parametric studies with it.