Horizontal wells with hydraulic fracture treatments have been proven to be an effective method for developing unconventional oil and gas reservoirs. During the last several years, fracturing methods have evolved and improved rapidly, however, there still exists 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 technology (DTS) as a complementary tool for real-time fracture diagnostics. DTS 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, distribution of stimulation fluid along each isolated zone, effectiveness of isolation are the problems that DTS can help us to obtain the answers. This information can be used for more accurate fracture modeling and better estimation of fracture conductivity and fracture geometry, and therefore to optimize the future treatments and also evaluate the well performance.

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