湘西北地区寒武系牛蹄塘组页岩气资源前景

湘西北地区牛蹄塘组黑色页岩展布广泛，为寒武纪纽芬兰世—第二世滞留还原条件的沉积产物，适中的埋深和较大的厚度为其提供了良好的气藏条件。对其有机地化参数进行试验分析:TOC值为0.59%～13.05%，均值3.75%，有机质丰富;R_o值为1.87%～4.00%，均值3.05%，成熟度高;干酪根类型以Ⅰ型为主，少量为Ⅱ型，具有良好的生气潜力;矿物组成中脆性矿物含量为33%～87%，平均含量为68%，而黏土总量为13%～43%，平均为26%，脆性矿物/黏土矿物值高，有利于储层改造;页岩孔隙度为0.3%~8.0%，平均为3.3%，渗透率均小于0.04×10^-3μm²，为低孔低渗类型。综合研究表明，牛蹄塘组具有良好的页岩气生储潜力，同时运用条件概率体积法对其资源量进行评估计算，资源量十分可观。在此基础上对湘西北地区牛蹄塘组划分出6个页岩气有利区，为进一步实施页岩气勘查提供依据。

Exploration Prospect of the Cambrian Niutitang Formation Shale Gas in Northwestern Hunan

Niutitang formation black shales are widely distributed in northwestern Hunan, which are the deposition products of reduction environment during Early Cambrian (Terreneuvian-Epoch 2), where the moderate buried depth and large thickness provide good gas reservoir conditions. Physical and chemical analysis shows the black shales are characterized by abundant organic matter (TOC: 0.59%~13.05%, average 3.75%), high maturity (Ro: 1.87%~4.00%, average 3.05%), good hydrocarbon generation potential (the kerogen is dominated by I type with minor II type), favorable reservoir reconstruction (brittle mineral content: 33%~87%, average 68%, clay mineral content:13%~43%, average 26%, and a high ratio of brittle mineral/ clay mineral), and low porosity and low permeability (porosity:0.3%~8.0%, average 3.3%, permeability less than 0.04×10^-3 μm²). Comprehensive studies show that Niutitang formation has good potential for shale gas reserves, and the method of conditional probability volume was used to assess resources, which shows abundant shale gas reserves. In addition, six favorable prospecting areas for shale gas are divided in northwestern Hunan, which provides evidence for the further research of shale gas.