煤层灰分对其储集性能的影响

INFLUENCE OF COAL ASH CONTENT ON COAL RESERVOIR BEHAVIOUR

在煤层气勘探开发中,煤层储集性能的评价对煤层气储量、产能的预测至关重要,将直接影响钻探成 功率和勘探开发成本。以往对煤层储集性能的评价主要依靠其孔隙度和渗透率的直接测定。但由于煤层易碎,完 好的在钻井中很难得到。因此对井下煤层储集性能的评价比较困难。此外,孔隙度和渗透率测定的费用也较高。 根据扫描电子显微镜观察和统计分析,灰分充填煤层中的孔隙,影响煤层的储集性能,而且煤层灰分产率与孔隙度 之间存在线性关系,当灰分产率增高时孔隙度降低。因此,可以根据灰分产率预测煤层储集性能和非均质性。灰 分产率的测定用样少,极易获得,而且费用很低。因此,这种方法在煤层储集性能的评价中是十分有用的。

The coal reservoir behaviour evaluation is of great importance to predicting the reserves and productivity of coalbed methane, which will directly affect the success ratio of drilling and the coat of exploration and development. In the past, such an evaluation was mainly based upon the actual measurement of the porosity and permeability of coal samples, it was difficult, however, to obtain the good samples from borehole to carry out the evaluation because of the fragility of coal. In addition, the measurement of the porosity and permeability of coal samples would cost a lot of money. According to the SEM observation and statistic analysis of coal samples, it was concluded that the coal reservoir be haviour could be influenced by the coal ash filling the pores in coal beds, and there existed a linear, relation between ash content and porosity, the porosity decreasing along with the increase in ash content. The coal reservoir behaviour and heterogeneity, hence, can be predicted according to the ash content. Because the measurement of coal ash content requires a few samples only and they are easy to be obtained, this method is very useful to coal reservoir behaviour evaluation.