塔北哈拉哈塘加里东期多期岩溶古地貌恢复与洞穴储层分布预测

Restoration of multistage paleogeomorphology during Caledonian Period and paleokarst cavernous reservoir prediction in Halahatang area,northern Tarim Basin

为了认识塔里木盆地北部哈拉哈塘加里东期多期岩溶作用对奥陶系碳酸盐岩储层发育的控制机理，选择不同方法对各期古地貌进行恢复。结果表明良里塔格岩溶期古地貌以丘丛洼地、谷地为主，由北向南发育了多条深切河流，地震剖面证实河流常切穿至一间房组；前志留纪岩溶期，由北向南可划分为潜山岩溶区、碎屑岩浅覆盖岩溶区和厚层覆盖岩溶区，地势北高南低，北部潜山区以微岩溶地貌为主，未发育深切河谷，南部厚层覆盖区为碎屑岩山地，由北向南的水系，汇入碎屑岩尖灭线附近岩溶湖。通过钻录井、岩心、测井解释等资料统计，总结浅覆盖区洞穴型储层主要发育在两个带：一间房组顶面以下0—30m及50～110m，对应层位分别为一间房组和鹰山组，厚层覆盖区洞穴型储层主要发育在一间房组顶面以下0—40m，分带性不明显。结合断裂、古地貌、古水系等因素，认为浅覆盖区下部洞穴型储层及厚层覆盖区洞穴储层主要受控于良里塔格岩溶期径流带岩溶作用，该期南部深切河流为排泄点，控制了储层发育规模及走向。而浅覆盖区上部洞穴型储层受控于前志留纪岩溶期径流带岩溶作用，岩溶湖为径流排泄区，控制了上部洞穴储层发育。

This paper studied the controlling mechanism of multi-stage Caledonian karstification on the development of the Ordovician carbonate reservoirs through reconstruction of the Palaeogeomorphology with different methods in Halahatang area, northern Tarim Basin. It shows that the karst geomorphology is dominated by mound-cluster depression and mound- cluster valley during the Lianglitage period. Several deep incised-rivers are developed from north to south and seismic sections reveal that they often cut through the Yijianfang Formation. The pre-Silurian paleokarst can be divided into three zones from north to south, namely buried hill karst zone, shallow coverage karst zone and thick coverage karst zone. The terrain is high in north and low in south. The northern buried hill karst zone is dominated by mini-karst physiognomy without deep incised-rivers. In contrast, the southern thick coverage karst zone is in clastic rock mountain landform where a drainage system flowing from north to south and finally into the karst lake near the pinchout line of clastic rock. Based on the statistics of logging, drilling and cores, the cavernous reservoirs in the shallow coverage karst zone mainly occur in two intervals. One is 0 to 30 m below the top Yijianfang Formation （ corresponding to the horizon of the Yijianfang Forma- tion） and the other is 50 to 110 m below the top Yijianfang Formation （ corresponding to the horizon of the Yingshan Formation）. In contrast, the cavernous reservoirs in the thick coverage karst zone mainly occur in an interval of 0 to 40 m below the top Yijianfang Formation without obvious zonation. A comprehensive analyses of the geomorphology, ancient drainage system, tectonic fault and other factors shows development of the cavernous reservoirs in the lower part of the shallow coverage zone and thick coverage zone was mainly controlled by paleokarstification in runoff zone during Lianglitage period when the deeply incised-rivers in the southern part acted as the runoff drainage points controling the size and direction of cavernous reservoirs. In contrast, the development of cavernous reservoirs in the upper part of the shallow coverage zone was mainly controlled by paleokarstification in runoff zone during the pre-Silurian period when the karst lakes were karst runoff drainage areas.