鄂尔多斯盆地中部气田断层发现及其意义

Discovery and significance of faults in the Mid Gasfield,Ordos Basin

以往研究中对鄂尔多斯盆地中部气田是否存在断层一直未有定论。随着开发的深入和资料的完善,在地层对比和地震资料解释工作中,发现气田内部存在北东和北西向2组小断距剪切断层,其组合模式有4种,即正逆断层共存断阶式组合、相同倾向正逆断层组合、同倾向正断层系列组合及背向式逆断层组合。研究表明这2组小断距剪切断层是燕山期、喜马拉雅期构造强烈改造的结果,其性质和分布特征与区域构造应力场相吻合。断层周边伴生的微裂缝对储集层渗透性有极大改善作用,并对低渗气藏的开发具有重要意义,与气井产能对应分析表明,80%高产井位于断块圈闭范围内,表明断块区对油气富集控制作用明显。

In the past,researchers could not make sure whether there were faults in the Mid Gasfield in Ordos Basin.With the progress in development and more available data,two groups of shear faults with NE direction and NW direction in the gasfield were found during the formation comparison and seismic data interpretation.There are four kinds of combination forms,namely,faulted-steps combination with co-existence of normal and reverse faults,same-dip normal and reverse faults combination,same-dip normal faults combination,and back-folding reverse faults combination.These two groups of faults were generated due to the strong tectonic movement during the Yanshan and Himalayan periods.Their properties and distribution features are consistent with the regional structural field.The associated micro-fractures around the faults greatly improve the permeability of the reservoir and have a great significance for developing the gas reservoir with low permeability.Production capacity analysis of relevant gas producers indicates that 80% of the productive gas producers are located in the faulted-block trap,showing the obvious effect of faulted-block on gas/oil accumulation.