胜利油区疏松砂岩低电阻率气层测井评价技术

Log Evaluation Technology of Unconsolidated Sand Low Resistivity Gas Layer in Shengli Oilfield

针对胜利油区疏松砂岩低电阻率气层、低气/水电阻率对比度气层测井评价工作中存在的难点,分析其形成的主要原因,优化确定适用于低电阻率气层含水饱和度计算的黏土阳离子交换饱和度模型;利用中子、密度、声波三孔隙度测井在气层响应的差异性,计算储层的三孔隙度差值和比值,提取三孔隙度测井所蕴含的储层含气信息,用于指示含气储层。提出利用含水饱和度、三孔隙度差值和比值等3个参数对储层含气信息进行组合放大、构建气层判别指标的技术思路,以达到提高低电阻率气层识别灵敏度的目的。阐述气层判别指标的计算方法,结合区块试气数据统计气层、气水同层的气层判别指标下限值,形成储层含气性分级解释的判别规则,实现储层含气性计算机数据处理的自动分级判别并提高低电阻率气层的评价能力。该技术在胜利油区2个区块19口井的实际应用,效果良好。

There are low resistivity gas layers and low gas/water resistivity contrast payzones in unconsolidated sand in Shengli oilfield. After analyzing their major genesises, Waxman-Smits model based on the principle of clay cation exchange action is determined to calculate water saturation for low resistivity gas layer by optimizing. According to the different responses of triple porosity logging （i. e. neutron, density and acoustic） in the gas layer, the difference value and the ratio value of them are calculated, and the gas bearing information is extracted to identify the gas layer. The technical idea is proposed, which uses three parameters to assemble and amplify the reservoir gas bearing information. In order to enhance the identification sensitivity of the low resistivity gas layer, the discriminant index of gas layer is created. The discriminant index calculation method of gas layer is expounded. And the discriminant index＇s lower limit value in gas and gas-water layers is obtained from the statistic result of combining discriminant index with gas testing data in the block. Summarized is the discriminant rule of reservoir gas bearing classification of interpretation. Finally, the reservoir gas bearing grade automatic identification is realized by the computer data processing, so enhancing the evaluation ability of low resistivity gas layer. This technique has been applied to practical reservoir evaluation of 19 wells in two blocks in Shengli oilfield, and the effect is fine.