Abstract
The material balance is one of the fundamental practice in reservoir engineering and is considered as a reliable estimation of hydrocarbons-in-place. A good knowledge of average reservoir pressure is essential to determine original gas-in-place. To have such reservoir pressure, the well needs to be shut-in for few days to months, resulting in loss of production. In the current economic environment, this production loss is often unexpected. In a previous study, Matter and McNeil showed that material balance calculation could be done without shut-in well, which uses flowing well pressure instead of static pressure and constant flow rates. However, a constant production rate for an extended period of time is very challenging production criterion for the majority gas fields. The dynamic material balance is an extension of the flowing material balance that allows either constant or variable flow rate. This study describes the practical application of a method known as Dynamic Material Balance for average reservoir pressure determination using flowing pressures and variable production rates and thus to estimate the original gas-in-place of new gas sand of Kailashtila Gas Field. The main purpose of this study is to apply the method in field cases and to make a comparison with other standard methods of reserve estimation such as volumetric, type curve analysis to see the result and validate the efficiency of its application. These comparisons show a fairly good agreement in gas in place obtained from the dynamic material balance method and that of type curve analysis in this field.
Highlights
Material balance has long been used as a simple yet powerful tool, which uses actual production performance data to determine the original-gas-in-place [1]
A straight line is drawn through flowing pressure data and a parallel line is drawn through initial reservoir pressure gives original gas in place
As dynamic material balance is only applicable in boundary pseudo steady state condition, production data on the transient condition are ignored for further calculations
Summary
Material balance has long been used as a simple yet powerful tool, which uses actual production performance data to determine the original-gas-in-place [1]. The conventional material balance for a gas reservoir relies on obtaining a straight line on P/z versus cumulative production graph to estimate original gas in place. This method requires average reservoir pressure, which is obtained from buildup test. Instead of shut-in pressure, the flowing well pressure data along with the constant rate production are analyzed In this method, a straight line is drawn through flowing pressure data and a parallel line is drawn through initial reservoir pressure gives original gas in place. ∫ t ca t 0 dt μcg the main objective of this study is the application of dynamic material balance in field cases to calculate the average reservoir pressures and to estimate the original gas-in-place
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