高煤级煤储层成岩特征及其力学响应间关系研究

RELATIONSHIP BETWEEN DIAGENESIS CHARACTERISTICS OF HIGH COAL RANK COAL RESERVOIR AND ITS MECHANICAL RESPONSE

利用沁水东北地区高煤级烟煤物性、力学、声学及薄片等分析资料对煤储层成岩作用特征与力学响应间关系进行了探讨,主要包括:压实作用与应力加载间关系;溶蚀作用及裂缝与力学响应间关系;脉体—蚀变矿物与有效应力系数α、屈服应力及动力学参数间关系。结果表明:该区煤层经历了较强压实及变质作用,压实作用对煤储层纵向物性及强度变化具有一定影响;区内煤岩发育的微裂缝往往伴随一定溶蚀,未充填溶蚀孔缝及张性缝往往导致煤岩三轴强度及弹性模量降低,泊松比升高;有效应力系数α、屈服应力及部分动态力学参数与煤岩中方解石脉体及蚀变矿物含量或填充程度具有较好对应关系。随着煤岩中脉体及蚀变矿物填充程度的增加,煤岩非均质性加强,有效应力增加,渗透性降低,由此可以利用力学参数响应特征对煤岩孔、渗、成岩、裂缝等方面进行综合研究,从而制定合理煤层气储改、排采开发方案。

Based on the analysis of physical property, mechanics, acoustics, and thin sections of high coal rank bituminous coal in northeast Qinshui Basin,the relationship between the coal reservoir diagenesis and its mechanical response is discussed. The focus is placed on the study on the relationship between compaction and stress load; relationship between dissolution, fracture and the mechanical response ; relationship between effective stress coefficient a, yield stress, some dynamic mechanical parameters and vein body-alteration minerals. It shows that this kind of coal experienced strong compaction and metamorphism and compaction has a certain influence on the lon- gitudinal physical properties and intensity of the coal reservoir. The micro cracks in coal can often be associated with certain dissolution, unfilled dissolution opening and tensile seam can often result in the decreasing of triaxial strength and elastic modulus, and in the increasing of Poisson＇s ratio. There is a good correlation between effective stress coefficient α,yield stress,some dynamic mechanical parameters and the content of calcite vein and alteration mineral or filling degree of mineral. At the same time, with the filling degree increasing of vein body and alteration mineral in coal, the heterogeneity of coal increases, and the permeability decreases sharply. Therefore, it is possible to make a comprehensive study of coal physical properties, diagenetic, cracks etc by use of the response characteristics of mechanical parameter,so as to formulate reasonable CBM reservoir stimulation,drainage and development project.