Oil and gas reserves are the most important assets for oil companies. An accurate estimation of reserves not only helps listed oil companies prepare solid annual reserves reports required by SEC, but also guarantees the good reward from divesting assets or reasonable price to farm-in asset. A precise reserves calculation is the fundamentality for production forecast, which is vital to the sale contract, thus the feasibility of project. It controls the cash flow and most of all the sustainable development of the company. The importance of reserve estimation cannot be overemphasized whatsoever.

We know that in the practice of exploration and production, all efforts are to obtain fluid and rock properties such as porosity, permeability, saturation, rock and fluid compressibility, viscosity, fluid gravity, gas z-factor, saturation pressure, reservoir pressure and temperature. Due to the instrument sensitivity, limitation, measurement error, environmental effect, sample interval, location, the representative of sample, and Mother Nature of these properties, there is always uncertainty. In this research, a systematic study on the effects of fluid and rock properties on reserves estimation had been conducted. Effect of each property on reserves estimation is quantified through sensitivity analysis. As a result of this study, a comprehensive picture of how fluid and rock properties affect the reserves was brought to engineers. Reserves evaluator can use this to estimate the range of reserves as a consequence of uncertainty. With this study, we realized their different impacts on reserves. Therefore main efforts should go to the variables that affect the reserves most.

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