| dc.description.abstract | The ideal outcomes of multistage hydraulic fracturing in horizontal wells are to create a controlled fracture distribution along the horizontal well with maximum contact with the reservoir which can provide the sufficient production after stimulation. Downhole temperature sensing is one of the valuable tools to monitor hydraulic fracture treatment process and diagnose fracture performance during production. Today, there are still many challenges in quantitative interpretations of distributed downhole temperature measurements for flow profiling. These challenges come from the following aspects: the uncertainties of the parameters ranging from the reservoir properties, well completion, to fracture geometry; the need of a fast and robust forward model to simulate temperature behavior from injection, shut-in and production accurately; the need of an inversion methodology that can converge fast, reduce the uncertainties and lead to a practically meaningful solution.
In this study, an integrated multiphase black-oil thermal and flow model is presented. This model is developed to simulate the transient temperature and flow behavior during injection, shut-in, and production for multistage hydraulic fractured horizontal wells. The model consists of a reservoir model and a wellbore model, which are coupled interactively through boundary conditions to each other. It is assumed that the oil and water components are immiscible, and the gas component is only soluble in oil. Comparing with the compositional model, this model has an improved computational efficiency while still maintains the maximum robustness. This study gives guidance on when and how to apply this black-oil thermal model to fulfill its full advantages.
This study also proposed a new temperature interpretation methodology which incorporates the black-oil thermal model as the forward model for temperature simulation and the inversion model for inverting the flow rate profile along the wellbore by matching the simulated temperature with the measured temperature. The sensitivity study is first performed to determine the impact of parameters on temperature behavior such as fracture half-length, fracture permeability, matrix permeability, and matrix porosity. The inversion model uses the initial analysis on temperature gradient to identify the initial guess of fluid distribution which leads to a faster convergence as well as a sensible solution. The Levenberg-Marquart algorithm is adopted to update the inversion parameters during each iteration. A synthetic example with multiple fractures is presented to test the interpretation procedure’s accuracy and speed.
The interpretation methodology is further applied to two different filed cases. One is a single-phase gas producing horizontal well with multiple hydraulic fractures; the other one is a two-phase water-oil producing horizontal well with multiple hydraulic fractures. This study illustrates how to adjust the methodologies and perform the analysis for each particular case and explains how to reduce the uncertainties and increase the interpretation efficiency. The results reveal that this temperature interpretation methodology is efficient and effective to translate temperature measurements to flow profile quantitatively with reasonable assumptions. | en |
