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物质平衡方法是计算气藏储量常用的方法之一。应用该方法确定气藏储量必须准确测定气藏的静态平衡压力，然而对于低渗透气藏，气井关井复压到气藏平衡压力需要很长的关井时间，这对实际生产来说是很不实际的。针对此问题，文章给出一种瞬态物质平衡法，即在物质平衡方程中用关井复压时的某一瞬态压力代替静态平衡压力，从而大大减少了测压带来的停工关井时间。以定产量生产为例阐述了该方法的原理、最短测试关井时间的确定，并通过实例说明了该方法的应用。

Estimating Gas Reserves in a Reservoir by use of Transient Material Balance Method

Material balance method is one of the methods used commonly in estimating gas reserves in a reservoir.In order to determine the gas reserves in a reservoir by applying this method,it is necessary to measure accurately the static balancing pressure in the reservoir.For a low permeability gas reservoir,however,a very long closed in time well need for making the gas well shut in pressures building up to the gas reservoir balancing pressure,which is unrealistic in practice.For this reason,a transient material balance method,in which the static balancing pressure in the material balance equation is replaced by a certain transient pressure,is put forward in the paper,thus greatly reducing the closed in time caused by pressure measurement.By taking constant rate production as an example,the principle of this method and the determination of the shortest testing closed in time are expounded and the application of this method is explained with an example in the paper.