Palaeogeomorphology Restoring of Ordovician weathering crust in Yan’an area, Ordos Basin
-
摘要: 鄂尔多斯盆地东南部延安地区奥陶系马家沟组顶部发育风化壳岩溶储层，因古地貌代表了地层沉积和成岩作用的背景，因而在储层的形成和演化过程中具有重要意义。在区域构造背景和地层展布的基础上，综合利用残余厚度法和印模法，并结合铝土岩厚度分布和古沟槽识别结果，准确恢复出延安地区奥陶系风化壳古地貌分布格局。结果显示，延安地区西南部表现为古岩溶高地，中部大部分地区表现为古岩溶斜坡，东部属岩溶斜坡与岩溶盆地之间的过渡带。古地貌格局和古沟槽的分布影响了储层的形成、发育和天然气的富集。延安地区岩溶古高地、靠近侵蚀古沟槽的斜坡位置含气性较好，可能与大气水淋滤等因素导致的储层发育程度、物性好坏、不整合面之上盖层的封盖性等因素有关。Abstract: The karst reservoir rock of Ordovician weathering crust is developed on the top of Majiagou Formation, Ordovician system, in Yan′an area, southeastern Ordos Basin. Because of the palaeogeomorphology stand for background of sedimentation and diagenesis in formations, so it is important in formation and evolutionary process of reservoir rocks. On the basis of regional tectonic setting and formation distribution, utilizing comprehensively "methods of residual thickness" and "methods of moulage", combining with thickness distribution of bauxite and identifing results of ancient erosion grooves, the spatial pattern of palaeogeomorphic features from Ordovician weathering crust in Yan'an area is restored correctly. It is showed from the results that it displays for karst highland in southwest, mostly of karst slope in middle parts, and intermediate zone between karst slope and karst basin in east of Yan'an area.The formation and development of reservoir rocks and accumulation of gas are influenced by the spatial pattern of palaeogeomorphic features and distribution of ancient erosion grooves. There are better gas display in karst paleo-highland, as well as in slope adjacent to eroded ancient erosion grooves, responsible for development degree of reservoir rock, physical property and sealing nature of caprock upon unconformity surface, caused probably by learching of meteoric water.
-
Key words:
- Ordos Basin /
- Yan&prime /
- an area /
- palaeogeomorphic feature /
- the method of remnant thickness /
- thickness of bauxite
-
点击查看大图
计量
- 文章访问数: 2132
- HTML全文浏览量: 23
- PDF下载量: 1129
- 被引次数: 0
下载:
