论文部分内容阅读
鄂西渝东地区蕴藏着丰富的油气资源,纵向主要分布有侏罗系和志留系两套泥岩盖层,区域经历的抬升剥蚀过程会导致盖层破裂,影响油气保存。选取沉积于侏罗系沙溪庙组、桐竹园组以及志留系龙马溪组的3个典型区块泥岩,开展10~50MPa 5种围压下的三轴卸荷力学试验,探索卸荷对泥岩力学特性影响。研究表明:随卸荷围压增大,3类泥岩的卸荷效应均增强,侏罗系泥岩体现在卸荷变形增大,志留系泥岩主要体现在沿卸荷方向的侧向膨胀;对比常规三轴压缩试验中岩石破裂时的应力状态,卸荷得到的泥岩强度均上升,内摩擦角更大,泥岩侧压破裂系数呈负指数分布,随围压增大而减小,并且沉积时间短浅的泥岩在抬升剥蚀过程中更容易产生破坏;岩石破裂形态由岩石组构与应力环境共同决定,沙溪庙组泥岩的裂纹形态为单一剪切断面破坏,并且断口平缓,而桐竹园组泥岩与龙马溪组泥岩则随围压升高,由单一剪切断面向共轭剪切破坏过渡,其中桐竹园组泥岩断口平滑,龙马溪组泥岩断口则呈现锯齿状。
There are abundant oil and gas resources in the eastern Hubei and western Chongqing areas. There are two sets of mudstone caprocks of Jurassic and Silurian in the longitudinal direction. The regional uplifting and erosion process will cause the cap rock to rupture and affect the preservation of oil and gas. Three typical block mudstones deposited in the Jurassic Shaximian Formation, Tongzhuyuan Formation and Silurian Longmaxi Formation were selected to carry out uniaxial unloading mechanical tests under 5 confining pressure of 10 ~ 50MPa to investigate the unloading Effect on Mudstone Mechanical Properties. The results show that with the increase of the unloading confining pressure, the unloading effects of all three kinds of mudstone are enhanced, and the deformation of the Jurassic mudstone is larger than that of the unconfined one. Silurian mudstone mainly manifests in lateral expansion along unloading direction. In the conventional triaxial compression tests, the stress state during rock rupture, the strength of unloaded mudstone all increase, the internal friction angle is larger, and the lateral pressure rupture coefficient of mudstone shows a negative exponential distribution, decreases with the increase of confining pressure, and the deposition time Shallow mudstone is more likely to cause damage in the process of uplifting and denudation. The shape of rock rupture is determined by the rock structure and stress environment. The shale cracks in Shaximiao Formation are single shear failure and the fracture is gentle. Mudstone in the mudstone and Longmaxi Formation transitioned from a single shear section to a conjugate shear failure with the increase of confining pressure, in which mudstone fracture of Tongzhuyuan Formation was smooth and shale fracture of Longmaxi Formation was jagged.