A study to assess the stress interaction of propped hydraulic fracture on the geometry of sequential fractures in a horizontal well

Abstract

The sequential fracturing in a horizontal well has been widely used in developing the unconventional oil and gas resources. The stress interactions among the sequential fractures have significant impacts on the fracture geometry (width, length and shape). One of the interacting stresses is the stress induced by the propped fracture. The stress interaction will decrease drastically, if the hydraulic fracture (HF) is fully closed by the confining stress. The proppant inside the HF retains the residual fracture width after the pumping is stopped, which remains poorly understood. This paper presents a HF model, which couples the fracturing fluid flow and the HF opening, to simulate the sequential fracture propagation in the horizontal well. In addition, a linear joint element is used to evaluate the closure when the previously created fractures are elastically propped by the compressible proppant. The closure of the propped HF on the stress field and the fracture geometry are evaluated numerically using this HF model. It is found that a stiffer proppant used in previously created fracture results in a wider HF after the pumping is stopped. A stiffer propped fracture causes a higher interacting stress on the subsequent HF which becomes more curved with a narrower width and a higher injection pressure. The subsequently created HF has little influence on the width of previously created HF. All the HFs are curved except the first HF in sequential fracturing. This paper is helpful to understand the geometry of the sequential fractures and the stress interaction among them, and to design the stiffness or size of the proppant for the hydraulic fracturing technique.