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 Formation) 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.