A relative injection profile identification method based on distributed temperature sensing

To overcome the strong dependence of conventional fine-scale inversion on prior parameters while reducing computational complexity, this study proposes a relative injection profile identification method based on distributed temperature sensing (DTS). Constrained by a wellbore temperature response model, the method integrates temperature propagation characteristics during water injection with post-shut-in thermal recovery features, and establishes a set of characteristic parameters, including cumulative cooling, threshold arrival time, and residual cooling, for the automatic identification of the boundaries of the main injection interval and the key contributing interval. Uncertainty analysis of model parameters indicates that both global and local parameter perturbations have only limited effects on the identification results, demonstrating good overall robustness of the proposed method. Field applications show that, for Well HD01, the lower limit of effective injection is approximately 2,129.0 m, the main injection interval extends from 1843.0 to 2075.5 m, and the key contributing interval is located near 1969.0 m. Moreover, when the standard deviation of temperature noise is no greater than 1.0 °C, the interpreted relative injection profile remains stable. Compared with the conventional inversion method, the proposed method shows good consistency in the macroscopic delineation of the main injection interval, while providing more refined identification of the key contributing interval. Further application to Well HD02 demonstrates that the main injection interval can still be identified using only injection-period DTS data, even in the absence of stable post-shut-in thermal recovery observations, indicating good cross-well applicability and promising engineering potential.