Operators of large well count oil fields often experience a production difference between the sum of all individual well test quantities and the total sales quantities. This paper demonstrates a case in which limitations in the surface facilities’ capacity increasingly act as a constraint for production from the reservoir and ultimately impact future production predictions.

A method is presented to improve these predictions using a real field example of a South-American operator. The periodic observed production difference at this operator is far beyond values commonly seen in the industry. It affects the predictions on future reservoir performance and required improvement. The method unlocks the true reservoir potential by leveraging identified surface constraints and plotting valuable rate-time well test data on a set of dimensionless type curves to establish a more representative decline exponent.

The method has been successfully implemented at an operator that is responsible for over 700 wells. It improved the oil rate’s prediction and increased the expected future reservoir performance. It simultaneously firmed-up the estimated reserves, extended the reservoir’s lifetime and effectively upgraded its value without additional costs. Accordingly, it enabled the operator to report more than 200% for the Reserves-Replacement Ratio in its latest audited reserves reporting.


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