塔中隆起西北部中奥陶统一间房组地层识别对比及地质意义

塔中隆起西北部中古15井区奥陶系的油气突破促进了对中奥陶统一间房组的新认识,因此该套地层在塔中隆起区—斜坡区的分布特征备受地质勘探者的关注。基于旋回地层学、生物地层学、同位素地层学、层序地层学理论与技术,结合地层岩电特征、沉积特征、暴露溶蚀特征,从不同角度论证了塔中隆起西北部一间房组的存在;进而,通过钻井地层对比,阐述了一间房组的空间分布;并基于精细地震层位追踪与解释,厘定了一间房组尖灭线的范围。认为INPEFA测井旋回分析和小波分析技术是识别塔中隆起西北部一间房组地层界面的有效手段;一间房组主要分布在顺西地区和中古15井区,厚度为110~190 m,自北向南依次减薄并上倾尖灭。一间房组及其尖灭线的厘定对于区域性地层分布、中—下奥陶统构造演化过程、岩溶储层分区评价等方面的认识具有重要意义。

Stratigraphic recognition and correlation of Middle Ordovician Yijianfang Formation in northwestern Tazhong uplift and its geological significances

Because of the breakthrough in Ordovician hydrocarbon exploitation in well block ZG15, northwestern Tazhong uplift, the new understanding of the Middle Ordovician Yijianfang Formation has been promoted. As a result, widespread attentions from geological prospectors are paid to the distribution characteristics of the Ordovician strata in Tazhong uplift zone and slope zone. Based on the techniques and theories of cyclostratigraphy, biostratigraphy, isotopic stratigraphy and sequence stratigraphy, the existence of Yijianfang Formation in northwestern Tazhong uplift was demonstrated from various aspects in combination with lithologic and electronic features, sedimentary characteristics and exposed karstification symbols of Ordovician strata. Furthermore, the spatial distribution of Yijianfang Formation was displayed by drilling stratigraphic correlation. Moreover, the range of pinchout line in the Yijianfang Formation was determined according to the precise tracking and interpretation of seismic horizons. It is believed that INPEFA logging cycle and wavelet analysis techniques are effective methods for identifying the stratigraphic interfaces of Yijianfang Formation in northwestern Tazhong uplift. Yijianfang Formation is mainly distributed in Shunxi area and well block ZG15, which has a thickness of 110-190m reduced from north to south till upward pinchout. The delineation of Yijianfang Formation and its pinchout line has critical geological significances to the understanding of regional stratigraphic distribution, the Middle-Lower Ordovician tectonic evolution process and the zoning evaluation of karst reservoirs.