构造裂缝是碳酸盐岩的主要储集空间之一,能为致密灰岩提供油气运移的良好通道和储集空间。构造裂缝的发育受构造位置、岩性、地层厚度、温度、围压和构造破裂等多种因素的影响,其中区域构造应力场的局部构造应力导致的构造破裂是控制构造裂缝发育的主导因素。针对碳酸盐岩储层的特点与裂缝发育特征,采用在单井动态岩石力学参数标定下,基于三维地震数据体的岩石力学参数反演功能获取非均质岩石力学模型,以提升应力场模拟中模型力学参数的真实性和准确性;引入自适应边界条件约束方法,以自动获取模拟结果与实测结果误差最小时的最优边界条件,从而显著提升应力场模拟的精度与可靠性。并在此基础上,通过储层张破裂率、剪破裂率、综合破裂率、水平两向应力差、应力非均质系数和断裂面滑动趋势系数等参数,定量表征了SHB16号断裂带及邻区的储层裂缝发育特征与活动性。储层裂缝的发育特征与断裂的活动关系密切,故定性或定量研究了水平两向应力差、距断裂的距离和断裂的垂向活动强度等参数对储层裂缝发育特征的控制作用,用斯皮尔曼等级相关系数定量研究变量之间的相关性。在明确储层裂缝发育的控制因素的基础上,构建奥陶系碳酸盐岩储层规模储集体发育指标,将奥陶系碳酸盐岩储层划分为从最优至最差的I~IV类储集体,并明确了走滑断裂的变形方式和规模储集体发育程度的相关性,进一步建立了不同类型储集体中钻井奥陶系碳酸盐岩储集体发育的地质模式。该地质模式不仅提升了基于应力场模拟的裂缝发育特征及多参数分布定量预测的准确性和可靠性,而且对碳酸盐岩储层裂缝发育的控制因素的定性或定量研究、规模储集体发育指标的构建以及单井储集体发育的地质模式的建立、对碳酸盐岩储集体的勘探与开发进程的加快,具有重要的参考价值。

Tectonic fractures are one of main reservoir spaces in carbonate rocks, which can provide a good conduit for oil and gas transportation and reservoir space in tight limestone. The development of tectonic fractures is affected by various factors such as tectonic location, lithology, reservoir thickness, temperature, peripheral pressure and tectonic faulting, among which tectonic faulting caused by local tectonic stress in the regional tectonic stress field is an important factor controlling the development of tectonic fractures. In view of the characteristics of carbonate reservoirs and fracture development, we use the inversion function of rock mechanical parameters based on 3D seismic data volume, calibrated using dynamic rock mechanical parameters for a single well, to obtain a non-homogeneous rock mechanical model to improve the authenticity and accuracy of mechanical parameters in the model in the simulation of the stress field. Using the method of self-adaptive boundary condition constraint the optimal boundary conditions are automatically obtained when the error between the simulation and measured results is minimized, significantly improving the accuracy and reliability of the stress field simulation. On this basis, the fracture development characteristics and fracture activity in reserviors in the SHB16 fault zone and adjacent areas are quantitatively characterized using parameters including reservoir tensile rupture rate, shear rupture rate, comprehensive rupture rate, horizontal stress difference, stress difference coefficient, and sliding trend coefficient for the fault plane. We carried out qualitative and quantitative investigation into the effect of controlling parameters, such as horizontal stress difference, distance from faults and fault activity intensity in the vertical direction, on the fracture development characteristics; the correlations between variables were quatified using Spearman’s rank correlation coefficient. On the basis of clarifying the controlling factors of reservoir fracture development, we constructed the reservior development indexes for Ordovician carbonate reservoirs to classify the Ordovician carbonate reservoirs into categories I-IV from the best to the worst, and clarified the correlation between the deformation modes of the strike-slip faults and the degree of fracture development in sizable reserviors, further establishing the geologic model under different reservoir categories. The above results not only improve the accuracy and reliability of quantitative prediction of fracture development characteristics and multiparameter distribution rules based on stress field simulation, but also have significant importance for speeding up the exploration and development process of carbonate reservoirs.