Fracture-Stimulation Diagnostics in Horizontal Wells Through Use of Distributed-Temperature-Sensing Technology
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SummaryHorizontal wells with hydraulic-fracture treatments have proved to be an effective method for developing unconventional oil and gas reservoirs. During the past several years, fracturing methods have evolved and improved rapidly; however, there still exist many uncertainties in fracture design. Several fracture-diagnostic techniques have been developed to improve the understanding of the fracturing process. In this study, after reviewing the application and limitations of the current fracture-diagnostic techniques, we describe the application of distributed-temperature-sensing (DTS) technology as a complementary tool for real-time fracture diagnostics. DTS technology has enabled us to observe the dynamic-temperature profile along the wellbore during the treatment. However, quantitative interpretation of dynamic-temperature data is very challenging and requires in-depth mathematical modeling of heat and mass transfer during the treatment.We have developed a thermal model to simulate the temperature behavior along the wellbore during the treatment, as well as during the shut-in period. This model takes into account the effect of all significant thermal processes involved, including conduction and convection.Examples are presented to illustrate how this model can be applied for fracture-stimulation diagnostics. Estimation of the fracture-initiation points, number of created fractures, and distribution of stimulation fluid along each isolated zone are the problems for which DTS technology can help obtain answers. The effectiveness of isolation can also be diagnosed by DTS technology because the heat-transfer mechanism changes when convection caused by leaking in isolation occurs. This information can be used for more-accurate fracture modeling and better estimation of fracture conductivity and fracture geometry and, therefore, to optimize future treatments and also to evaluate the well performance.
