Challenging the Presence of Natural Gas Hydrate in the Messoyakha Pool

The Messoyakha gas field with a pool in Cenomanian sediments lies in north Siberia. Some authors consider it a gas hydrate field mainly because initial pressure and temperature in a part of the pool fit hydrate stability. Other hydrate indications are also reported: characteristic features of logging records, intricate distribution of gas and water in the pool, low productivity of some wells, amount and composition of produced water, gas reservoir drive, and thermodynamic behavior of some beds. However, al the above could be due to specific geology of the pool and inadequate development rather than to the presence of hydrate in the reservoir. Long-term observations have been conducted on the alteration of gas composition using a special technique based on the measurement of helium concentration. The latter highly varied, showing and amplitude of more than three orders of magnitude. The data obtained prove that there are no natural hydrates in the upper part of the pool, which is reported as hydrate bearing. Technogenic hydrates are forming in this part in bottom-hole zones of idle wells as a result of gas cross flow, while natural hydrates are likely to exist in the lower part of the pool. This research is tomore » be continued. Actual gas reserves of the pool cannot be determined without evaluated hydrate content. A solution to this problem is important for the evaluation of gas reserves elsewhere in the cold regions.« less