Revisiting Inplace Volumes of Matured Field Using Material Balance Assisted SIMEX Approach

Shrivastava, Pranshu (ONGC Ltd.) | Muraleedharan, Ranjith (ONGC Ltd.) | Srivastava, Pratibha (ONGC Ltd.) | Ram, Binay (ONGC Ltd.) | Mekap, Saroj (ONGC Ltd.) | Nautiyal, Dilip (ONGC Ltd.)



The paper presents a case of applying classical reservoir engineering technique of material balance to one of the major carbonate reservoir in the western offshore basin in India that eventually led to establishment of more hydrocarbon volumes.

During Material Balance calculation, multiple runs were performed to match the pressure performance with a balance between the aquifer strength and hydrocarbon volume that was in agreement with geological understanding and performance of the field. The analysis indicated extra energy support that may be in the form of aquifer or higher in-place volumes. Following the in-house developed SIMEX (Simultaneous Exploration) approach a vertical well was identified for testing below assumed lowest known oil (LKO) limit.

The material balance study formed the basis for revisiting the geological understanding. The establishment of oil through the testing of well necessitated the revision of geological maps and re-estimation of hydrocarbon in-place volumes. Accordingly property maps have been prepared and volumes are revised. The revised volumes are about 14% more than the previous estimation. Similar approach was successfully applied to another reservoir in the Mumbai High field. Presence of more established oil will help in planning future strategies for field development.

Especially in fields where enough pressure production history is available, it is important to reassess the field's potential from time to time through simple and classical techniques available. Fields with multiple reservoirs have added advantage of developing the established hydrocarbons through zone transfer and in turn saving significant cost of drilling new well. This being a proven and classical technique, can be applied to other analogous reservoirs.