Abstract

Distributed temperature sensing (DTS) is an enabling technology for fracture diagnosis and multiphase flow measurement in unconventional areas. Fracture characterization and flow profiling are crucial to evaluate the performance of hydraulic fractures. The objective of our DTS data analysis approach is to provide a high-resolution quantitative diagnosis of hydraulic and natural fractures with the full-physics model, which will benefit the fracturing operation design and decision-making process in the unconventional reservoir. In this work, we developed a comprehensive numerical forward model for DTS data analysis. Our model includes reservoir and wellbore models. Also, the flow and thermal models are fully coupled. A thermal embedded discrete fracture model (TEDFM) is developed to handle the thermal modeling of complex fracture networks. Subsequently, we developed ensemble smoother with multiple data assimilation (ESMDA) as the inverse model to match field data and characterize fractures. ESMDA can handle large volume of data and model parameter sets with acceptable computational time. The DTS analysis with our model provides a high-resolution solution since the fracture diagnosis and flow profiling are performed for each fracture. The hydraulic and natural fracture properties and geometry such as fracture half-length, height, and fracture conductivity are evaluated. With this analysis, we obtain a deeper understanding of the effectiveness of the field hydraulic fracturing operation. Although numerous simulators are developed for DTS data analysis, relatively few existing models can handle the full-physics such as complex fracture geometry and multiphase flow. Our inverse model provides an improved DTS data match result. Our model is more rigorous than the prior models to simulate and match the field DTS data.

Introduction

The key technology for shale gas reservoir is hydraulic fracturing: pressurized fracturing fluid containing water, sand, and other proppants is injected into a wellbore to create cracks in the formation. The high contact area of the fracture surface enables high oil and gas production. However, in the field applications, usually, 20 percent of fractures contribute 80 percent of production. The reason behind this is a lack of understanding of fracture geometry and fracture property. Due to the pre-existing natural fractures, the complex fracture network may be generated during the hydraulic fracturing operations. (Maxwell et al. 2002; Fisher et al. 2004; Cipolla et al. 2010; Cipolla et al 2011)

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