川东北部飞仙关组鲕滩储层含气性识别方法

GAS POTENTIAL IDENTIFICATION OF THE OOLITIC BEACH RESERVOIRS IN FEIXIANGUAN FORMATION IN THE NORTH PART OF EAST SICHUAN

碳酸盐岩鲕滩储层作为地层中的特殊岩性 ,是岩相及岩性变化形成的岩性圈闭 ,地层不仅结构复杂 ,非均质性强 ,而且具有层薄、横向变化快及穿时迁移等特点 ,使得长期以来 ,有关鲕滩储层分布的预测及其气水关系识别仍然没有建立一种比较有效的地震预测方法。文章利用测井资料对鲕滩储层含气、含水及非储层的各种地球物理参数做综合分析和对比 ,确定鲕滩气藏主要的敏感参数 ,分析不同敏感性参数的地球物理响应特征及其影响因素 ;在此基础上 ,结合工区储层地质特点 ,进行地震反演预测方法研究 ,提出适合于该区鲕滩储层和气水关系预测的地震反演方法 ,并根据气层AVO特征 ,对储层含气性进行综合预测解释。通过研究表明 ,速度是鲕滩储层含气性预测最为敏感参数之一 ,通过精细的速度反演可以有效地识别鲕滩储层气藏和水层的分布 ,此外通过AVO模型分析、实际资料AVO属性参数处理、解释 ,总结出该区鲕滩气藏主要以两种AVO特征为主 ,一种是裂缝型气藏 ,其AVO特征为P·G强波峰 ,道集上振幅随炮检距增大明显增强 ;另一种是裂缝不发育型气藏 ,其AVO特征为P·G值近似于零 ,道集上振幅随炮检距增加几乎没有变化。

As a special lithology in stratigraphy,the carbonate oolitic beach reservoir is a lithologic trap formed by the change in petrofacies and lithology and it is of these characteristics,such as complicated structure,strong heterogeneity,thin bed ,large lateral change and diachronous migration,etc.For this reason,an effective seismis method of predicting oolitic beach reservoir distribution and identifying water-gas relation hasn′t set up yet for a long time past.Through comprehensively analyzing and contrasting various geophysical parameters of gas-bearing oolitic beach reservoirs,water-bearing oolitic beach reservoirs and non-reservoirs by use of log data,the principal sensible parameters of the oolitic beach reservoirs were determined;and the geophysical response features of different sensible parameters and their influence factors were analyzed.On the basis of this,a research on seismic inversion prediction methods was carried out and some seismic methods suitable for predicting the oolitic beach reservoir distribution and water-gas relation were proposed in combination with the characters of reservoir geology in the region.The comprehensive prediction and interpretation of the hydrocarbon potential of the reservoirs were finished according to the AVO (amplitude versus offset) property of gas-bearing layer.Through investigation,it was indicated that the velocity is one of the most sensible parameters of predicting the hydrocarbon potential of the oolitic beach reservoirs;and the oolitic beach reservoir distribution and water-gas relation may be effectively identified through a fine velocity inversion.In addition,on the basis of analyzing the AVO model and processing and interpreting the AVO attribution parameters of the practical data,two main AVO properties were summarized for the oolitic beach reservoirs in the region: one is the fractured gas reservoir which AVO property is of strong P·G wave crests,the amplitude on trace assemblage being obviously strengthened with the increase in the offset;the other one is the fracture-undeveloped gas reservoir which AVO property is that the P·G value is close to zero,the amplitude on trace assemblage being constant with the increase in the offset.