五峰-龙马溪组页岩有机质赋存特征及其对孔隙结构的影响

Characteristics of Organic Matter and Its Implications for Pore Structure of Wufeng-Longmaxi Formation

有机质是页岩气富集成藏的物质基础,是选区评价的重要参数。选择上扬子地台东南缘的YY-1井五峰-龙马溪组为研究对象,基于岩心观察、扫描电镜观测(自然断面及氩离子剖光面)、低温氮气吸附等测试手段,研究了五峰-龙马溪组有机质赋存特征(显微组分、形态、孔隙)及其对页岩气储层储集能力(孔隙度、孔隙结构参数)的影响。结果表明:五峰-龙马溪组有机质以菌藻体和固体沥青为主,呈现四种形态,发育四种类型的有机质孔隙。有机质丰度是影响页岩储层储集能力的关键因素。在适宜的有机质丰度范围内,孔隙度随着有机碳含量的增加而逐渐增大,孔隙结构的非均质性逐渐增强。

Organic matter is the material basis of shale gas accumulation,and an important parameter for selected-area evaluation.Taking Wufeng-Longmaxi Formation of well YY-1 in the Upper Yangtze Platform as the research object,based on core observation,scanning electron microscope(SEM)observation(natural section and argon-ion cross-section polishing),low-temperature nitrogen adsorption and other test methods,the organic matter occurrence(macerals,morphology,pores)of Wufeng-Longmaxi Formation and its influence on shale gas reservoir capacity(porosity,pore structure parameters)were discussed.The results show that organic matter of Wufeng-Longmaxi Formation in the northern Guizhou is mainly composed of algae and solid bitumen,showing four forms and developing four types of organic matter pores.Organic matter abundance is a key factor affecting shale reservoir capacity.Within the appropriate organic matter abundance range,porosity increases with the increase of total organic carbon content,and the heterogeneity of pore structure increases gradually.