滇东北木杆向斜奥陶系五峰组—志留系龙马溪组页岩气资源潜力评价

基于Xd2井和Ydd3井奥陶系五峰组—志留系龙马溪组岩心测试结果，结合邻区资料，总结滇东北地区木杆向斜黑色页岩岩性、分布规律、有机地球化学、储层及含气性特征，评价木杆向斜页岩气资源潜力。木杆向斜五峰组—龙马溪组一段主要为深水陆棚相黑色碳质泥页岩和粉砂质泥岩，其中龙马溪组一段可以分为1亚段、2亚段和3亚段，页岩优质段（总有机碳含量大于2.0%）厚40～70 m，平均有机碳含量为3.00%～3.61%，干酪根碳同位素值-30.21‰～-27.01‰，有机质含量高、类型好，等效镜质体反射率（VR_o）为2.73%～2.79%。矿物组成具有较低含量的石英和长石，较高含量的碳酸盐岩和黄铁矿，由下至上，石英、碳酸盐岩和黄铁矿含量降低，长石和黏土含量增加。页岩孔隙度为2.39%～8.53%，横向渗透率（0.000 01～15.0）×10^-3 μm²，以中等孔隙为主，低—特低渗透率，孔隙类型主要为有机质演化形成的介孔和微孔。木杆向斜五峰组—龙马溪组页岩埋深约1 500～2 300 m，含气面积125.55 km²，资源量999.93×10⁸ m³，主力含气层段位于五峰组上段—龙一段1亚段，厚度38～43 m，平均总含气量2.95～4.31 m³/t。木杆向斜五峰组—龙马溪组页岩厚度大，横向上和纵向上连续分布，埋藏适中，具有良好的页岩气资源潜力。

Evaluation of shale gas potential in Ordovician Wufeng-Silurian Longmaxi formations,Mugan syncline,northeastern Yunnan

Shale gas potential was evaluated according to wells Xd2 and Ydd3 in the Ordovician Wufeng-Silurian Longmaxi formations in the Mugan syncline of the northeastern Yunnan, using core test results, data from the neighboring area, black shale lithology, distribution, organic geochemistry, reservoir and gas bearing characteristics. The Wufeng Formation to the first member of Longmaxi Formation is mainly composed of deep-water shelf black carbonaceous shale and silty mudstones. The first member of Longmaxi Formation can be divided into the 1st, 2nd and 3rd submembers. The high-quality shale section with a total organic carbon content greater than 2.0% is 40-70 m thick, and the average organic carbon content is 3.00%-3.61%. The kerogen carbon isotope is -30.21‰ to -27.01‰. The higher the organic matter content, the better organic matter type is. The equivalent vitrinite reflectance (VR_o) is 2.73%-2.79%. The shale has limited quartz and feldspar, but more carbonate and pyrite. From bottom to top, quartz, carbonate and pyrite contents decrease, while feldspar and clay contents increase. The shale porosity is 2.38%-8.53%, and the transverse permeability is (0.000 01-15.0)×10-3 μm2, indicating medium porosity and low to extra low permeability. Mesopores and micropores formed by organic matter evolution are dominant. The Wufeng-Longmaxi shale is 1 500-2 300 m deep in the Mugan syncline. The gas-bearing area is 125.55 km2, and the resource is 100×109 m3. The main gas-bearing interval is located in the upper member of Wufeng Formation to the first member of Longmaxi Formation, with a thickness of 38-43 m and an average total gas content of 2.95-4.31 m3/t. The Wufeng-Longmaxi shale in the Mugan syncline has a large thickness, a continuous distribution in the horizontal and vertical directions, and a moderate burial depth, which show a great resource potential.