塔里木板块古城墟隆起奥陶系油气成藏分析

CONFIGURATION OF THE LOWER PALAEOZOIC SOURCE AND RESERVOIR UNITS IN THE GUCHENGXU HIGH,TARIM BLOCK

塔里木板块中央隆起带东段古城墟区块受多期构造活动影响形成了单斜隆起,具有烃源岩和储集单元在沉积和构造上的良好配置。该区北临满加尔凹陷寒武系—中、下奥陶统烃源岩分布区,向西与塔中低凸起逐渐过渡,油气成藏条件优越。奥陶系序列具备3类碳酸盐岩型和1类砂岩型的优质储集体,分别为中奥陶统一间房组台地边缘礁滩相、一间房组风化壳岩溶层、下—中奥陶统内幕型岩溶储集体以及中—上奥陶统却尔却克组陆棚—盆地相的浊积扇体,一间房组风化壳型储层最有利于储油。良好的储盖组合自上而下分别为却尔却克组自储自盖型、一间房组碳酸盐岩与其上恰尔巴克组泥灰岩或却尔却克组泥岩构成的正常式储盖组合、鹰山组自储自盖型及突尔沙克塔格组泥灰岩与其上黑土凹组泥岩构成的正常式储盖组合。

Multiple tectonic deformations result in a monoctine structure in the Guchengxu Well Block, eastern Central High of the Tarim Block. Sequences throughout the Cambrian to Middle Ordovician along the northward Mangaer Depression are considered as source rocks. Potential region for hydrocarbon accumulation shows a transitional distribution adjacent to the Tazhong Lower Uplift to the west. Sedimentary as well as tectonic patterns show optial spatial configurations of the source rocks and reservoirs. Three types of carbonates and one type of sandstone are considered as ideal Ordovician reservoirs. These are the reef complexes of the platform margin from the Middle Ordovician Yijianfang Formation; karst crusts of the Yijianfang Formation; Lower-Middle Ordovician inner karst units; turbidite fans of the out-shelf and basin facies of the Querquek Formation. Of these rock types, the first is considered the best. Reservoir- cap associations occur in the Querquek and Yishan formations; in the Yijianfang Formation limestone capped by the overlying Qiaerbaq Formation limestone or Querquek Formation mudstone; and the Tursaq Formation muddy limestone overlain by the Heituao Formation mudstone.