鄂尔多斯盆地南缘长8储层岩石力学特征及影响因素

鄂尔多斯盆地南缘中生界长8是进行油气开发的重点层位,针对长8储层砂泥岩交互,低孔低渗的特点,对其岩心样品开展了模拟地层下的岩石力学实验研究。实验研究表明：三轴条件下,岩心样品均随着围压的增大,破坏强度变大,即弹性极限显著增加;随着围压的增大,岩石的抗压强度显著增加;随着围压的增大,岩石的变形显著增大。利用测井资料,计算出了动态岩石力学参数并结合实验结果进行了动静态参数拟合,结果表明在进行GR加权的情况下拟合情况较好,因此构建了较可靠的岩石力学参数剖面。在岩石力学参数剖面的基础上,对岩石力学参数空间分布的影响因素进行分析,表明影响泊松比、杨氏模量和抗压强度空间分布的主要因素为岩性、泥质含量和深度。研究成果对鄂南地区长8储层的压裂优化设计提供了重要的依据。

Rock Mechanics Characteristics and Influence Factors Analysis of Chang 8 Reservoir in the Southern Margin of Ordos Basin

The Mesozoic Chang 8 is the key area for oil and gas development in the southern margin of the Ordos Basin. According to the characteristics of sandstone-mudstone interaction, low porosity and low permeability in Chang 8 reservoir, rock samples were subjected to experimental study of rock mechanics under simulated strata. The experimental results show that the failure strength of core samples increases with the increase of confining pressure under triaxial condition, indicating that the elastic limit increases significantly. With the increase of confining pressure, the compressive strength of rock increases significantly and the deformation increases significantly. Using logging data, dynamic rock mechanics parameters are calculated and the static and dynamic parameters are fitted according to the experimental results. The results show that the fitted condition is better under the condition of weighted gamma value, so a more reliable rock mechanics parameter profile is obtained. Based on this study, the factors affecting the spatial distribution of rock mechanical parameters are analyzed. Lithology, shale content and burial depth are the main factors affecting the spatial distribution of Poisson"s ratio, elastic modulus and compressive strength. The research results provide an important basis for fracturing optimization design of Chang 8 reservoir in southern Ordos.