论文详情
受复杂地质因素的影响,地质工程一体化一直是页岩气提产增效的关键,其中,多尺度裂缝建模是一体化建模的关键环节之一,直接影响着综合地学模型的准确度和适用性。为了预测天然裂缝对南方海相页岩气水平井钻井和压裂工程的影响,从地球物理、地质、测井和地质力学等多学科的角度对天然裂缝空间分布及其受力状态进行了精细刻画,具体如下:①对叠前地震道集进行精细化针对性的处理,提高地震资料的分辨率和保真保幅性,而后进行蚂蚁追踪和多尺度裂缝预测,并结合成像测井、录井和钻井数据进行验证,准确预测天然裂缝的空间分布;②结合成像测井揭示的天然裂缝产状,建立分尺度离散裂缝模型;③由于不同尺度裂缝的力学参数对钻完井工程存在不同程度的影响,故以分尺度的方式对裂缝模型进行粗化;④采用等效原理对裂缝的地质力学参数进行分尺度赋值,合理刻画天然裂缝对地应力场的扰动,预测天然裂缝应力状态,为研究天然裂缝对钻完井工程的影响奠定基础。利用上述方法有效预测了钻井过程中的泥浆漏失,方法应用结果表明,包含天然裂缝影响的地质力学模型更能反映真实原场应力,可用于研究压裂过程中水力裂缝与天然裂缝的相互作用,优化水平井压裂设计。
Geology and engineering integration is essential to improve shale gas productivity and efficiency because of the complex geological settings in shale reservoirs.Moreover,the multi-scale natural fracture network is a key component in the integrated geoscience model.To predict the impact of natural fractures on the drilling and fracturing of marine shale gas horizontal wells in southern China,the spatial distribution and stress status of natural fractures were analyzed from the perspective of multiple disciplines including geophysics,geology,petrophysics,and geomechanics.First,seismic pre-stack gathers were conditioned,such as denoising,flattening,and frequency raising gathers,and the partial gathers with a high signal-to-noise ratio in the target layer were selected to stack the ant tracking input.Strict quality control of the ant tracking results was conducted through the manual interpretation of the fracture system,drilling complex events,and horizontal well image log interpretation.The large-,meso-,and small-scale natural fracture predictions of the Longmaxi/Wufeng formation obtained by ant tracking were analyzed,and the discrete fracture model was established by incorporating imaging log interpretation and the multi-scale fracture intensity predicted by ant tracking.According to the different rock stiffness levels with different scales of fractures,the equivalent principle was used to analyze and test the influence of fractures of different scales on mechanical parameters,and geomechanical modeling was used to predict the in-situ stress state of natural fractures.The results indicate that the impact of natural fractures on drilling is not only related to their scale but also to the slip tolerance of the fracture surface,that is,the stability of the fracture.The higher the slip tolerance,the worse the stability of the fracture and the more likely it is to generate mud loss when a horizontal well is drilled.The case study proved that the geomechanical model incorporated the influence of natural fractures and was suitable for hydraulic fracture simulation,allowing the investigation of the interaction between hydraulic fractures and natural fractures during the fracturing process,and optimization of the fracturing design of horizontal wells.
国家科技重大专项(2017ZX05063)和中国石油天然气集团有限公司重大现场试验项目(2019F-31)共同资助。