新疆北部吉木乃坳陷下二叠统卡拉岗组页岩气地质特征初探

An approach to the geology of the shale gas in the Lower Permian Kalagang Formation,Jimunai depression,northern Xinjiang

为评价新疆北部吉木乃坳陷页岩气勘探潜力，通过对吉木乃坳陷下二叠统卡拉岗组暗色页岩段有机地球化学以及储层特征分析，初步探讨其页岩气地质特征。卡拉岗组下段暗色页岩段烃源岩以碳质泥页岩为主，TOC最小值为0．3％，最大值为4．32％，平均值为1．01％。有机质丰度中等，有机质类型为Ⅲ型，Ro值介于1．43％-2．87％之间，平均值为2．12％。热演化程度为成熟-过成熟度阶段，具较好天然气生成能力。暗色页岩矿物成分以石英、长石等脆性矿物为主，粘土质矿物次之，具较好可裂性及吸附性。页岩孔隙以宏孔、细小孔以及小孔为主，储集空间主要为粒内及粒间溶孔、矿物间的微孔隙与微缝隙、矿物微裂缝。孔隙度为0．97％～1．52％，平均为1．36％。渗透率为0．0097—0．0197mD，平均为0．0139mD，具较好天然气储集能力。

The geological characteristics of the shale gas in the Lower Permian Kalagang Formation, Jimunai depression, northern Xinjiang are approached on the basis of organic geochemical signatures and reservoir characteristics. The dark shales from the lower member of the Lower Permian Kalagang Formation consist mainly of carbonaceous shales with the total organic carbon contents ranging between 0. 3% and 4. 32%, indicating a moderate organic carbon abundance and type III of organic matter types. Ro values ranging between 1.43% and 2.87% suggest the mature to overmature stages of thermal evolution of kerogens with good hydrocarbon potential. The mineral compositions include quartz, feldspar and clay minerals. The pore types are composed of macropores, mesopores and micropores. The reservoir spaces are represented by intragranular and intergranular solution openings. The porosity values vary from 0.97% to 1.52% ,and the permeability values from 0.0097 to 0. 0197mD with an average of 0. 0139mD ,implying that the black shales in the study area have good reservoir potential.