The Effect of Reaction Heat by Acid Injection for Enhanced Gas Recovery From Methane Hydrate Reservoir

Kaneko, Fuyuki (Tohoku University) | Nakamura, Kengo (Tohoku University) | Sakamoto, Yasuhide (National Institute of Advanced Industrial Science and Technology (AIST)) | Watanabe, Noriaki (Tohoku University) | Komai, Takeshi (Tohoku University)

OnePetro 

Abstract

Natural gas production from methane hydrate reservoir requires supplying heat. However, it is necessary to decrease energy consumption, and some new ways for enhanced gas production are investigated. One of them is partial-oxidation and heating process, which is proposed newly by us. This process is injecting acid or oxidant into the reservoir, which makes several effects for enhanced gas production. One of them is heat effect which comes from mineral dissolution by acid injection. In this study, we evaluated this with simulation.

In order to carry out this calculation, we extended conventional numerical simulation model, and some parameters were needed. These parameters were about the dissolution rate and the heat. Therefore, we made the flow experiment with a column and measured the heat of mineral dissolution with a differential scanning calorimetry. In this experiment, Toyoura sand as a sediment and hydrochloric acid were used. In based on those experimental results, we determined constants.

We carried out three types of numerical analyses about injecting acid into the reservoir. The first of them was the calculation about the reservoir which has no methane hydrate. The next was about the methane hydrate reservoir. The last was also about the methane hydrate reservoir, but injected acid temperatures were changed. In these calculations about the methane hydrate reservoir, the initial saturation of methane hydrate is 20 % on the assumption that this process as the secondary recovery follows the depressurization.

The results show that injecting acid whose concentration is 0.50mol/L heats the reservoir by approximately 30℃ from the initial temperature of methane hydrate reservoir. Hence, the total gas production in that case is comparable with that in hot water injection at 50℃. Additionally, the lower the temperature of injected acid is, the higher the effect of reaction heat of mineral dissolution is. In conclusion, acid injection to methane hydrate reservoir will be the effective way of enhanced natural gas production.