Analysis on tubing-casing annular gas production

Gas-oil rate is an important to optimize mechanical recovery. The currently used calculating method of gas-oil rate is only based on the partial gas measured in the metering room, which neglects the casing gas. As a result, bigger error is caused by the calculating results. In view of the production oil wells generating casing gas, the casing gas is measured in several wells. The difference between the calculating results of gas-oil rate considering or neglecting casing gas is compared. It is demonstrated that bigger error will be caused without considering casing gas. When the pressure at the casing shoe is lower than the bubble point pressure, there is a certain proportion relation between the casing gas production and the submergence pressure as well as the casing-tubing sectional area ratio. It is proposed that the casing gas be taken into account to determine the gas-oil rate during the optimization of mechanical recovery. The methods such as the calculating method and the practical measurement method can be applied to estimate the casing gas production and then add it into the calculation of gas-oil rate. 