L2M NSERC - Fibre Optic Technology Innovation for Subsurface Fracture Characterization

在资源勘探过程中，通常使用检波器进行诱发微震活动监测和地下成像。最近，光纤技术（例如，分布式声学传感（DAS），分布式温度传感（DTS））已经显示出优于检波器的优势，例如能够监测整个光纤（增强空间分辨率）和宽频率。因此，DAS/DTS提供了一种有效的地下成像解决方案，使用相同的仪器检测微震活动和慢滑。在大多数情况下，光纤电缆安装在单口水平井中，与多口井相邻。单个光纤可以探测微地震事件，但与多分量检波器不同，它不能明确地确定震源位置，因为它只记录一个方向的地面运动。事件位置的确定对于裂缝作图和表征、作业成功与否和风险管理至关重要。我们创造了新的方法，利用光纤电缆上记录的反射波来更好地确定微地震事件的位置，并表征裂缝孔径和支撑剂的分布。使用选择直接波到达的标准做法，用单个光纤电缆定位微地震事件缺乏深度分辨率。就像扫描条形码一样，我们的方法基于从水平层边界检测到的反射模式来解码事件深度，这些模式通常被丢弃。我们还利用垂直水力裂缝反射的细微振幅变化来确定裂缝孔径和支撑剂等其他未知的关键特征。将这些计算整合到专注于识别和定位微震活动的工作流程中，将是一种变革，使行业能够更好地了解地下裂缝的范围和特征。我们的目标是提高我们的技术，以满足不断变化的需求，允许许多不同客户集成我们的技术。

During resource exploration, monitoring induced microseismicity and imaging the subsurface has typically been undertaken using geophones. Recently, fibre optic technology (e.g., Distributed Acoustic Sensing (DAS), Distributed Temperature Sensing (DTS)) has shown advantages over geophones, such as the ability to monitor the entire fibre (enhanced spatial resolution) and over broad frequencies. DAS/DTS therefore provides an effective solution for subsurface imaging, detecting microseismicity and slow slip using the same instrumentation. In most instances, a fibre optic cable is installed into a single horizontal well adjacent to others at a multi-well pad. A single fibre can detect microseismic events but, unlike multicomponent geophones, it cannot unambiguously determine source locations since it records only one direction of ground motion. Determination of event locations is essential for fracture mapping and characterization as well as determining operational success and for risk management. We have created novel methods that use recorded reflected waves on fibre optic cables to better determine locations of microseismic events, and to characterize fracture aperture and proppant distribution. Using the standard practice of picking the direct wave arrivals, locating microseismic events with a single fibre optic cable lacks depth resolution. Like scanning a bar code, our approach decodes event depth based on the detected pattern of reflections from horizontal layer boundaries, which are typically discarded. We also use subtle amplitude variations of reflections from vertical hydraulic fractures to determine critical characteristics such as fracture aperture and proppant, which are otherwise unknown. Integrating these calculations into a workflow focusing on the identification and location of microseismicity would be transformative, enabling industry to gain a better understanding of the extent and characteristics of fractures in the subsurface. We aim to enhance our technology to account for evolving demands, allowing integration of our technology by many different clients.