Drainage area average reservoir pressure , , is an important reservoir parameter needed to define reservoir potential and also to plan and evaluate performance of various flooding processes. In certain countries and states, Alaska for one, the state oil and gas department requires the measurement of annually on designated wells. Typically, is estimated by shutting in a well and performing either a conventional pressure build-up test or taking static pressure measurements at designated intervals. In both the scenarios, test times can be days to weeks depending on the formation permeability. In the case of static pressure test, error bounds can be significant.
In this paper we present an alternate technique that allow the estimation of without shutting in the well and performed in a relatively short period of time. The technique was developed in conjunction with BP Exploration in Alaska by modifying Schlumberger’s existing Transient Rate and Pressure (TRAP) testing analysis. The technique involves imposing a transient on the formation; and the rate convolved pressure is used in conjunction with the Mathews-Brons- Hazenbroek (MBH) method to calculate.
The project described in the paper consist of developing the technique and applying to six wells. In several cases long term build-up data was available for comparison. The comparison was very good and following a review by the State of Alaska regulatory board the technique was approved as a replacement for long term shut-in tests.