川南古叙地区LD1井龙潭组海陆过渡相泥页岩地质特征及其含气性

Geological characteristics and gas bearing capacity of shale from transitional marine-continental facies of Longtan Formation: A case study from the Well LD1 in Gulin-Xuyong, southern Sichuan

关键词:  龙潭组  页岩气  海陆过渡相  川南古叙地区

Key words:  Longtan Formation  shale gas  marine-continental transitional facies  Gulin-Xuyong area in South Sichuan

摘要:

扬子地区二叠系龙潭组海陆过渡相煤系泥页岩广泛发育。本文以川南古蔺-叙永地区页岩气调查井LD1井为例，利用测录井、岩心样品测试等资料评价其页岩气地质条件。LD1井龙潭组富有机质泥页岩与盆内JY1、N203等高产井五峰-龙马溪组海相页岩相比较，主要地质参数差异明显。LD1井龙潭组优质泥页岩单层厚度一般小于5m，累计厚度可达40m以上。龙潭组泥页岩有机碳含量总体较高，干酪根类型以Ⅱ₂型为主，有机质成熟度达到过成熟阶段（R_O平均值为3.21%），黏土矿物组分含量相对较高，脆性矿物组分含量相对较低，孔隙度普遍大于3%。龙潭组泥页岩气测异常值偏高，共计5.9m/13层气测异常层，最高异常值可达背景值的8倍，龙潭组上段标态总含气量平均可达4.08m³/t。

Abstract:

The transitional marine-continental coal-measure shale of Permian Longtan Formation is widely developed in Yangtze Block. Taking the shale gas investigation Well LD1 in Gulin-Xuyong area of southern Sichuan as an example, the geological conditions of shale gas of Longtan Formation are evaluated by using data of logging well and core sample testing.Compared with marine shales of Wufeng-Longmaxi Formations, which are of high-yield shale gas wells such as JY1 and N203 of in Sichuan Basin, the Longtan Formation has a smaller shale thickness of single layer,generally less than 5m, but the total cumulative shale thickness is more than 40 meters. Shale of Longtan Formation has a higher organic carbon content, its kerogen is mainly type Ⅱ₂, and its maturity of organic matter has already reached the over-mature stage (the average value of R_O is 3.21%).In Longtan Formation, the contents of clay minerals are relatively high, the contents of brittle minerals are relatively low, and the porosity is generally greater than 3%.The abnormal value of shale gas in Longtan Formation is high, reaching 5.9m/13 layers.The value of highest anomaly is more than 8 times the background value, and the average total gas content in the upper part of Longtan Formation can reach 4.08 m³/t.