Interwell interference has been widely observed in the development of unconventional reservoirs. It describes the phenomenon that legacy production of parent wells impact the completion quality of child wells, which in return changes production performance of both parent and child wells. This work models pressure and stress evolutions caused by parent well depletion and the corresponding asymmetric child well hydraulic fracture growth. The study presents a 3D finite-element-based fully coupled flow and geomechanics model that simulates the poroelastic behaviors of pressure and in-situ stress evolutions, and a hydraulic fracture model. Based on the simulated pressure and stress heterogeneities at and around child wells, the complex and asymmetric fracture patterns for the child well can be quantified. In the study, with several candidate child-well locations placed away from the parent well, the stress and pressure evolutions along the child well are observed to be asymmetric. Numerical investigations show that production timing of parent wells, in-situ stress contrast, well spacing, parent well fracture geometry, and the design of perforation clusters along the child wellbore are key parameters affecting the asymmetric fracturing of child wells. Specifically, prolonged parent well production, small in-situ stress contrast and close parent-child well spacing lead to significant asymmetric stress and pressure evolutions along the child well, and consequently contribute to the asymmetric fracture wing growth during child well completion. Effects of the parent-well fracture geometry on asymmetric child-well fracture wing growth are only noticeable when the well spacing is small. This work identifies key parameters in a typical interwell interference case and studies their effects on asymmetric child well fracturing. The work serves as a reference for the avoidance of child-well underperformance, which is widely observed in many major shale plays.

No abstract

The sandy conglomerate reservoirs in the Mahu oilfield located in the Junggar Basin of Northwest China are featured by a significant horizontal stress difference between two directions, making formations easy to form double-wing fractures upon hydraulic fracturing instead of creating a complex fracture network. In addition, as the well spacing or interval cluster spacing decreases, the stress interferences between hydraulic fractures strengthen accordingly, leading to more difficulties in the prediction of fracture propagation patterns. Given the geological characteristics in the study area, an extended finite element method (XFEM) based hydraulic fracture model that can handle fracturing fluid flow distribution was proposed to evaluate the seepage, stress, and damage of the formation under hydraulic fracturing. The influences of the initial stress difference, cluster spacing, and fracturing stage sequence on the hydraulic fracture stress interference and the fracture propagation were investigated, producing discoveries that include: (1) as the fractures propagate, the stress difference between two fractures changes as well, and such change is also affected by the initial stress difference and the fracture distance; (2) the postfracturing stress difference first decreases but then increases with the increase in cluster spacing; (3) as the cluster spacing increases, the interfracture stress interference decreases. In addition, the outer fractures suppress the length of the middle fractures, thus limiting the stimulated reservoir area (SRA); (4) for the cases of creating multistage fractures, the later fracturing stage experiences both the interfracture and the interstage stress interferences from the prefracturing stage. As the fracture width changes with time, the nonplanar fracture feature of the later fracturing stage becomes more evident while the corresponding SRA decreases.

The low-permeability reservoir is mainly featured by small reservoir pore, tight, fine throat, high filtration resistance, and low oil productivity. After several years of working to recover hydrocarbons from these reservoirs effectively, it has been proven that creating complex fracture networks by multi-stage fracturing is one of the most efficient ways to enhance production. However, several factors affect the development of the complex fracture networks, and the in-situ stress is the most significant one. Low in-situ stress anisotropy [1] increases the possibility of creating complex fracture networks with hydraulic fracturing. In order to compensate for the in-situ stress anisotropy, based on the application of a numerical model coupled flow and geomechanics, this research analyzes the variation of in-situ stress and suggests arranging a sequence of horizontal well deployment. In addition, the research predicts the dynamic productivity coupled flow and geomechanics. From the results, this research concludes the dynamic change regularity of in-situ stress and the impact of difference well deployment, which is beneficial to optimize horizontal well deployment and fracturing design [2].

This paper provides a novel three-dimensional meshless Galerkin for horizontal well reservoir simulation. The pressure function is approached by moving least-square method which consists of weight function, basic function and coefficient.Based on Galerkin principle and use penalty function method, the paper deduces the meshless Galerkin numerical linear equations. Cut off the pressure distribution of the horizontal section from the simulation database of horizontal well reservoir. It demonstrates that meshless Galerkin is a feasible numerical method for the horizontal well reservoir simulation. It is useful to research complex reservoir.