The lower Silurian Qusaiba Shale is one of the major source rocks for Paleozoic oil/gas reservoirs in Saudi Arabia and recently considered a potential unconventional shale gas resource. The study aims to evaluate the reservoir heterogeneity and production potential of Qusaiba Shale through the integration of geological, geomechanical and fractures characteristics. Three lithofacies were identified in Qusaiba shale. Mineralogical composition resulted in variable amounts of quartz ranging from 39 to 40, 45–55 and 60–78% for Lithofacies-I, II and III, respectively. Inter-granular porosity of these lithofacies is very low; however, fractures along laminations, at angle with laminations, and few micro-faults enhance porosity up to 5–6, 2–3, and < 1% in Lithofacies-I, II and III, respectively. The Lithofacies-I hosts the lowest fracture density (1.2 fractures/foot), likely due to the relatively lower quartz content (39%) as compared to other lithofacies. The fracture densities in Lithofacies-II and III are 2.1 and 3.2 fractures/foot, respectively. Lithofacies-I exhibits low stiffness in terms of low Young’s modulus (average 26 GPa) and high Poisson’s ratio (average 0.34). Mineralogy- and elastic parameters-based brittleness indices exhibited ductile behavior of this lithofacies. The brittleness index exhibited brittle behavior for silica-rich Lithofacies-III and has highest intensity of natural fractures. Hence, it is concluded that mineralogy and geological characteristics are the main controlling factors on shale brittleness, mechanical properties and fractures characteristics. The integration of geology, mineralogy and geomechanics plays the key role to better evaluate the prospectivity of shale reservoirs.

Silurian Qusaiba页岩下部是沙特阿拉伯古生代油气储层的主要烃源岩之一，最近被认为是潜在的非常规页岩气资源。该研究旨在通过整合地质，地质力学和裂缝特征来评价库赛巴页岩的储层非均质性和生产潜力。在库赛巴页岩中发现了三个岩相。矿物学组成导致岩相I，II和III的石英量分别为39％至40％，45-55％和60-78％。这些岩相的粒间孔隙度非常低。但是，沿着叠层的角度，与叠层成一定角度的裂缝以及极少的微断层将岩相I，II和III的孔隙率分别提高至5–6、2–3和<1％。Lithofacies-I的裂缝密度最低（1。每英尺2个裂缝），可能是由于与其他岩相相比石英含量相对较低（39％）。Lithofacies-II和III的裂缝密度分别为每英尺2.1和3.2裂缝。Lithofacies-I在低杨氏模量（平均26 GPa）和高泊松比（平均0.34）方面表现出较低的刚度。基于矿物学和弹性参数的脆性指数表现出该岩相的延性。脆性指数对于富含二氧化硅的Lithofacies-III表现出脆性，并且具有最高的天然裂缝强度。因此，可以得出结论，矿物学和地质特征是影响页岩脆性，力学性能和裂缝特征的主要控制因素。地质一体化