Dynamic reserves calculation is an important basis in the process of abnormally high-pressured offshore gas fields development. Based on the early stage development experience in abnormally high-pressured gas fields, the calculated dynamic reserves will be larger than the actual value. And the number of development wells in offshore gas fields is relatively small, which makes it more difficult to accurately calculate dynamic reserves. If the gas fields development dynamic was not acquired in time, the gas fields development adjustment would not be made effectively. Therefore, how to calculate the dynamic reserves accurately in the early stage is the key for this type gas fields development.

In this paper, a new method of calculating the dynamic reserves for abnormally high-pressured offshore gas fields early stage development has been put forward. First of all, the complete dynamic reserves prediction model was established with the use of material balance method. Secondly, in the process of model solving, the calculation model of effective compressibility coefficient was modified for the first time without laboratory experiment. Moreover, in order to improve the calculating precision of the early stage development dynamic reserves, the quality control model was established and the R factor was introduced.

The accuracy of dynamic reserves calculation is determined by the production data, pressure data, R value, etc. The greater R value is, the higher the accuracy is. When the R factor is between 0.9 and 1.0, the result of dynamic reserves calculation is right. Otherwise, we need to recalculate the input data. This new method has been applied in the early stage development of X abnormally high-pressured offshore gas field, and the calculated dynamic reserve is 186.66Bcf. If using traditional method, the dynamic reserve is 293.20Bcf, which is 36% larger than the new calculated dynamic reserve. The reservoir dynamic test data and geological static data have shown that the result of using this new method is more reasonable.

This paper provides a quantitative and operational new method to accurately calculate the dynamic reserves in abnormally high-pressured gas fields, and can guide the early stage development adjustment effectively.

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