Evaluation of multi-fractures geometry based on water hammer signals: A new comprehensive model and field application

Abstract

• A new factor, the stress interference between the various fractures, was considered in the water hammer model. • Based on the conservation of the total volume of fractures, the rationality of the volume equivalent relationship of multiple fractures was proved. • A new method was proposed to allow the new factor to be added to the model reasonably, under the premise of ensuring the conservation of volume. Hydraulic fracturing is an important means to develop unconventional resources. Fracture diagnosis techniques have been emerged in recent years, which can evaluate hydraulic stimulated fractures after stimulation treatment. Fracture geometry evaluation is an important part of hydraulic fracturing diagnosis. The fracture geometry evaluation techniques based on water hammer signal has the advantages of high economic efficiency, easy implementation and high timeliness. Previously, a model that couples the wellbore and the fracture ( RCI model) had been proposed, which could calculate the fracture geometry. However, this model was mainly based on the assumption of a single fracture with a pair of double wings, and there was no research on the calculation of the geometry of multi-fractures. In this paper, a new model for calculating the geometry of multi-fractures was proposed. First, a new factor, the stress interference between the various fractures, was considered in the model. Second, based on the conservation of the total volume of fractures, the rationality of the volume equivalent relationship of multiple fractures was proved. Third, a new method was proposed to allow the new factor to be added to the model reasonably base on volume conservation. Additionally, our model was validated with the model in the previously published research. The effect of different parameters (number of fractures, fracture spacing, fracture volume) on the water hammer was analyzed. At last, the fracture geometry evaluation of micro-seismic and our model in field cases were compared. This paper provides a new model for evaluating the geometric characteristics of multiple fractures of water hammer signals.