Improved Prediction of Fluid Contacts using Calibrated Material Balance Models

Abstract

The demand for oil has been on the high in the recent past and will continue as search for sustainable alternative energy sources intensifies. The exploration and exploitation of oil from subsurface reservoirs have posed several environmental challenges which include flaring and improper water disposal to name a few, caused by excessive production of gas and water. Hence, it is important to establish a reservoir performance monitoring scheme that will ensure that appropriate fluids are produced from the reservoir within the economic producing life of each well-draining a given reservoir by monitoring the fluid contact levels. Furthermore, appropriate reservoir monitoring will help to improve productivity and recovery of old wells, calibrate predictive reservoir models and identify opportunities for optimum reservoir development. A key tool used in reservoir performance monitoring is the post production log, particularly the Pulsed Neutron Capture (PNC) and Pulsed Neutron Spectroscopy (PNS) logs which make use of high energy neutrons to determine the fluid contacts in the reservoir. This campaign however is very expensive; hence an alternative and less expensive method of determining and predicting the present and future fluid contacts will be discussed. This involves using calibrated material balance models to predict the fluid contacts based on the pore volume (voidage) replacement by the displacing fluid. This will help in generating fluid contacts on a more frequent time interval.

Keywords: Fluid contacts, Reservoir, Material balance models