塔中地区鹰山组古岩溶潜水面及控储模式

Paleokarstic water tables and their control on reservoirs in Ordovician Yingshan Formation, Tazhong Area, Tarim Basin, NW China

综合岩心、测井、岩溶古地貌等资料,研究塔中北斜坡鹰山组古岩溶多期次潜水面的识别方法、分布及控储模式。研究区鹰山组自下而上可识别出第1、2、3等3期潜水面,相应水平潜流带的典型判识特征分别为:囊状溶蚀孔洞层或近水平溶缝等单一岩溶组构,出现小型洞穴及不同岩溶组构之间的叠置组合,多层洞穴及孔径更大的不同岩溶组构的叠置组合。平面上,阶段上升的海平面使得岩溶洼地、斜坡、高地分别发育第1期、第1、2期、第1、2、3期潜水面,受控于岩溶期鹰山组近水平的地层产状,3期岩溶潜水面及之下水平潜流带内的缝洞体与各亚段地层夹角极小,导致岩溶储集层呈"区域穿层、局部顺层"的展布特征。各期的潜水面与不整合面之间距离、水平潜流带厚度、储集层平均厚度等参数均具有随着岩溶地貌升高而变大的趋势,具有2~3期潜水面及更大厚度水平潜流带的岩溶高地和斜坡,储集层套数更多、厚度更大,Ⅰ、Ⅱ类储集层更发育,是有利的勘探区域。

Based on cores,well logging and karstic paleogeomorphology,the identification method of multi-period paleokarstic water tables and their distribution and control on reservoirs were researched of Yingshan Formation in Tazhong Area,Tarim Basin.Three periods’water tables numbered 1 to 3 have been identified from bottom to top of Yingshan Formation in Tazhong Area.The corresponding typical horizontal undercurrent zones are characterized by single karst fabrics such as sack-like dissolved vugs or subhorizontal channels,combination of various karst fabrics like pre-existing high-angle fractures intersected by small caves and subhorizontal channels,and combination of multi-layered caves and different karst fabrics of large pores.On the plane,periodical rising sea levels caused the development of No.1,No.1 and 2,No.1,2 and 3 water tables in karst depressions,slopes and highlands respectively.As the result of the nearly horizontal occurrence of Yingshan Formation,submembers of Yingshan Formation had tiny angles with fracture-cave bodies of each period’s water table,so the karst reservoirs are characterized by“crossed strata regionally and developed along the stratum locally”.The distance between water table and unconformity,thickness of horizontal undercurrent zone and average thickness of reservoir all tended to increase with the rise of karst landforms.The karst highland and slope had 2-3 periods’water tables and thicker horizontal undercurrent zones,so they had thicker and better quality reservoirs,making them favorable exploration areas.