An Innovative Method of Integrating Geo-Cellular and Dynamic Models for Secondary Oil Recovery
Authors: Rajput Sanjeev , Roy Amit , Hassan Siti Normaizan , Bin Salleh Fairus Azwardy , BT Hashim Nur Hazwani , Kumar Sanjeev , Khalil Ashraf 
Published: October 2019

Injecting energy into the reservoir is a suite of injection techniques used by the oil and gas industry for producing more oil. Injecting a large amount of water is called ‘waterflooding’ which improves oil production by sweeping the hydrocarbon fluids towards the producer well and by increasing the reservoir pressure. Waterflooding imposes a new set of challenges to understand the connectivity between wells, fault compartments, and reservoirs.

Water flooding in mature fields offers a significant increase in secondary oil recovery and enhances the economic life of a field. However, to optimize the waterflood program, the level of detailed understanding of reservoir architecture has always been a challenge in complex structural regime field. This study presents innovative methods of integrating the seismically derived geo-cellular model into the dynamic model of closing the loop for improved understanding of the reservoir. The example presented here is from an offshore field, Sarawak Malaysia. The study area lies in the North West Balingian sub-province in Malaysia where the main reservoirs are of Oligocene to Lower Miocene age.

Target reservoir consists of stacks of lower coastal plain sandstones interbedded with shale and coal that were deposited in an overall transgressive setting. The field consists of a very complex structural regime with multiple stacked reservoirs. There were more than 1200 faults captured in the structural interpretation of seismic data. Capturing the features of the fault compartments and defining the communications between blocks are important for predicting the water pathway, breakthrough time, and identifying beneficial wells.

Due to the complex structural configuration with more than 250 fault compartments, it was challenging to design a fully integrated simulation model to examine in detail all aspects of the historical and planned development. This being the most challenging case a model was constructed which aimed to identify the location of the remaining oil for infill drilling, likely future production, and establish reservoir connectivity between the injectors and oil producers. In the constructed model seismic data was utilized in a unique way by integrating very detailed reservoir probabilities from stochastic inversion into rock physics modeled logs, sedimentological information, and geo-cellular model. At this stage, dynamic properties were integrated into the geo-cellular model to study the fault block communication.

In the end, four unswept zones have been identified for future development. The necessity of optimizing secondary recovery in re-development campaign with fit-for-purpose seismically assisted simulation models designed in the ongoing brownfield development program. The integrated interpretation of detailed reservoir probabilities together with geo-cellular and dynamic modeling helped in understanding reservoir architecture. The study offers substantial benefits in order to plan the waterflood program for secondary oil recovery.