塔河地区加里东中期古岩溶作用及分布模式

地震资料解释、地层古生物、钻井地质及地球化学等方面的证据证实塔北地区存在加里东期运动及该期岩溶作用。本文探讨了原岩性质、断裂裂缝发育程度、古地貌形态、古气候等岩溶发育的控制因素,从岩石学、锶同位素、包裹体特征等方面建立了识别加里东期大气水作用的标志,指出早期断裂及伴生裂缝发育程度是加里东中期岩溶作用的主控因素,总结了该期岩溶具有以下特征:①层控性:岩溶发育具有发育面积广,深度浅,在不整合面以下0～35m发育;②断控性:较大溶洞发育在断裂附近;③有效储层具较强非均质性。由此预测该储层发育区位于古风化壳剥蚀区和加里东期断裂发育区的叠合部位,主要位于阿克库勒凸起的轴部倾没端和塔河西南部、东南部的北东向、近南北向断裂发育区。该期岩溶的存在与发现,对塔河油田南部的油气勘探具有重要意义。

Caledonian Paleo-Karstification and Its Characteristics in Tahe Area, Tarim Basin

The data of seismic interpretation,paleontology,drilling-geology,geochemistry and etc adequately prove the existence of Caledonian Movement and corresponding paleo-karstification in the north area of the Tarim Basin.This paper discusses the control factors such as paleo-karstification,property of primary rock,grade of fracture,paleo-physiognomy,palaeoclimate,paleo-hydrology and so on.Lithology,Sr isotope and inclusions all helped us figure out the characteristics of Caledonian atmosphere fresh water eluviation.Early fault and accompanying fractures are the main control factors in the mid-Caledonian karstification and their distinctive features are as follows:1) strata-bound with extensive area and a low depth,and well-developed 0 to 35 meters below p unconformity;2) fault-controlled,with bigger dissolved cavern near the fault;3) greater heterogeneity of effective reservoir.Thus it is predicted that the areas of favorable reservoir rocks would be distributed around stacked sites of erosional areas of paleoweathering crust and areas of Caledonian faulting e.g.the plunging crown of the axial zone of the Akekule anticline and the NE-and nearly N-Striking fault zones in the southwest and southeast parts of the Tahe oilfield.Discovery and occurrence of paleo-karstification is of great significance to the oil exploration in the sourthern aprt of the Tahe oild field.