高邮凹陷东部阜宁组薄储层测井评价方法及其应用效果

阜宁组沉积时期,苏北盆地高邮凹陷经历过两次大规模湖侵,并发育一套北东-南西向的大型三角洲沉积体系,高邮凹陷东部位于该三角洲翼部。该区阜宁组发育有大量的厚度小于2m的薄砂层。由于这类薄砂层厚度小、泥质含量高,以及早期的测井系列纵向分辨率低等原因,使得其在测井响应上常表现为微电极正差异小、自然电位曲线异常幅度小、电阻率低等特征,早期大多被解释为干层或未解释。对岩心的"四性"关系研究表明,这些薄砂层的岩性主要为粉砂岩、泥质粉砂岩,大部分薄砂层都有油迹、油斑级别的油气显示。物性分析资料证实,部分薄砂层的储层物性在所在区块的储量计算界限值以上,可以成为好的油气储集层。通过对深感应电阻率的球形响应进行小层分割、反演计算,对老的测井资料进行提高纵向分辨率处理后,有效解决了早期测井资料因为层薄而造成的数值失真,使相当部分原来的未解释层以及原来解释为干层、油水同层的薄砂层提升了解释级别,起到了挖潜增储效果。

Study on Log Evaluation Method of Thin Reservoir of Funing Formation and Its Application Effect in the East of Gaoyou Sag

Large-scale delta sedimentary system at northeast to southwest developed after twice macro-scale lake transgression during the Funing formation deposits in Gaoyou sag of Subei basin.Eastern Gaoyou sag locates at the limb of this delta.A large amount of thin sand layers with the thickness less than 2m developed in Funing formation of this area.The reservoir log responses are characterized by small positive separation in microelectrode curves,small anomaly magnitude and low resistivity of spontaneous potential curve,which resulted from small thickness,high clay content and low vertical resolution of early logging tools.Research on ＂four properties＂ correlations of the cores shows that most of these thin sand layers are composed of siltstone and pelitic siltstone with varying degrees of oil and gas show,such as oil trace and oil patch.Physical property data proves that if the physical property of thin sand reservoir is above the threshold value of reserve calculation in its block,it will be good oil-gas reservoir.Globular response of deep induction resistivity is separated by sublayers and calculated through inversion.Old logging data is processed for improving vertical resolution.After that,numerical distortion because of thin bed among early logging curves is effectively solved.It improves the log interpretation level of those thin sand layers that interpreted as a dry layer or oil-water layer.It will result in tapping the potential and increasing reserves.