冀中坳陷东北部石炭-二叠系裂缝发育特征研究

Study on Permo-Carboniferous Fissure Development Features in Northeastern Central Hebei Depression

岩心裂缝观测是目前研究裂缝的一个最重要、最基本,也是最有效的方法,它是根据岩心裂缝发育情况对地层中的裂缝进行最直观的描述,是进行裂缝研究的最直接的手段,是裂缝测井和地震研究的基础,也是对后者研究精度的最直接的检验。通过对冀中坳陷东北部钻遇石炭-二叠系井的岩心观察,发现研究区的裂缝主要是天然裂缝,人工裂缝较少。天然裂缝的主要特征为裂缝间距较小,裂缝开启程度小或者是在地下为闭合缝,高角度缝和低角度缝均较为发育。其中,开启裂缝大部分未被充填,缝面干净,有镜面擦痕。影响天然裂缝发育的地质影响因素主要有岩性、埋藏深度和构造应力的关系。在冀中坳陷石炭-二叠系中裂缝发育段主要集中在泥质粉砂岩和含砾砂岩中;裂缝发育程度在同一期构造应力场下是随着深度的增加而减少的。

The core fissure observation is an above all, essential and most effective way to study fissures at present. It carries out most intuitive description for fissures in strata based on fissure development in cores, thus a direct means of fissure study, the fundamental work for fissure well logging and seismic studies; and can directly inspect research accuracy. Through observation on cores from borehole intersected Permo-Carboniferous strata in the northeastern Central Hebei depression, has found out the fissures in study area are mainly intrinsic fissures, less artificial fissures. Main features of intrinsic fissures have small interval and opening or closing underground, high-angle and low-angle fissures are all rather developed. Open fissures have mostly unfilled clean surfaces with scratches.Intrinsic fissure development geological impacting factors have mainly lithology, buried depth and relation with tectonic stress. Fissure developed zones are mainly concentrated upon argillaceous siltstone and pebbly sandstone. Under identical stage tectonic stress field,the degree of fissure development is decreasing along with depth increasing in Central Hebei depression Permo-Carboniferous strata.