Parent-Child Fracture Interference: Explanation and Mitigation of Child Well Underperformance

Abstract

In the last few years, several operators in unconventional plays have seen fracture interference between existing production wells (parent wells) and newly fractured infill wells (child wells). This interference usually has a negative impact on the production from both the parent and child wells. In this work, a mechanistic explanation of the parent-child interaction is provided using results from poro-elastic simulations. Child well underperformance is studied in detail and mitigation strategies are discussed. Results shown in this work quantify the impact of depletion and refracturing on child well fracturing. In this work, a 3D reservoir-scale poro-elastic geomechanics software (Multi-Frac) was used to model the depletion of the parent well region and calculate its impact on pressure, total stress and effective stress. Refracturing simulations of the parent well were conducted to showcase the importance of a good refracturing operation in reducing the probability of fracture hits from the child well to the parent well. The poro-elastic capabilities of Multi-Frac help in analyzing the stress changes in the reservoir induced by depletion and re-fracturing. These stress changes explain the observed fracture hits from child wells. The stress changes and the depletion patterns also explain the underperformance of the child well fractures. Implications of depletion on both total stress and effective stress are analyzed. Decrease in the total stress near the parent well creates a zone of attraction for the child well fracture, thus, causing the child well fracture to be created in a region of extensive depletion. Depletion induced increase in the effective stress was observed from the simulation. This increase in the effective stress makes fracture network creation harder and thus reduces the productivity of the child well fractures. Re-fracturing of the parent well showed an increase in the stress in the reservoir and can help avoid fracture hits from neighboring child wells. Thus, re-fracturing a parent well and subsequently fracturing a child well can be a possible strategy to mitigate the impact of fracture hits and thereby improve the EUR of the pad. The three main factors that induce interference between parent wells and child wells are reservoir depletion, reservoir total stress changes and reservoir effective stress changes. All of these factors have been studied and quantified in this work. Modifications to parent well fracturing treatment design, refracturing treatment design and child well fracturing treatment design are suggested to improve productivity.

Numerical Investigation of Major Impact Factors Influencing Fracture-Driven Interactions in Tight Oil Reservoirs: A Case Study of Mahu Sug, Xinjiang, China

“…sin θ 2 cos θ 2 cos 3θ 2 (13) where σ H and σ h are the horizontal maximum and minimum in-situ stresses, respectively, and K I is the model I intensity factor. It should be noted that Equation ( 13) is not in the inelastic deformation zone (r < r c (θ)).…”

“…In some cases, a large amount of fluid is injected into the dominant fractures, which results in an excessive extension to adjacent wells. Furthermore, the pressure-depleted region around the production well lowers the stress level, which causes HFs in adjacent wells to expand into this region [12][13][14]. In general, HFs tend to intercept aged production wells or their vicinity, and the probability of this appearance primarily depends on the depth of the horizontal well, its location, and the extent of HFs [15].…”

How will treatment parameters impact the optimization of hydraulic fracturing process in unconventional reservoirs?

“…In Manchanda et al [30], a 3D reservoir-scale poro-elastic geomechanics software (Multi-Frac) was utilized to model the production decline of the parent well and calculate its impact on the pressure, total stress and effective stress. Similarly, a fully coupled flow and geomechanics model was developed [31,32] to the identify the poro-elastic behavior of multiphase-fluid diffusivity and rock deformation of interwell fracturing interference in Eagle Ford unconventional reservoirs, using finite-element method (FEM) and multifracture propagation using the displacement discontinuity method.…”

Effects of parent well spacing on the poroelastic behaviors in the infill zone in shale oil reservoirs: A case study in Jimsar Shale Oil, China

“…Typically, tightly spaced horizontal wells that are hydraulically fractured are placed in shale oil reservoirs for better production performance. In consequence, hydrocarbons in the infill zones between the tightly spaced wells are not efficiently produced and infill well drilling and completion can help to produce the infill zones 8 . Based on poromechanics, depletion caused by the production of tightly spaced fractured wells alters the poroelastic parameters in the producing wells and in the infill zones, which indicates that the pore pressure and in situ stress are also changed.…”

“…hydrocarbons in the infill zones between the tightly spaced wells are not efficiently produced and infill well drilling and completion can help to produce the infill zones. 8 Based on poromechanics, depletion caused by the production of tightly spaced fractured wells alters the poroelastic parameters in the producing wells and in the infill zones, which indicates that the pore pressure and in situ stress are also changed. Such poroelastic changes directly affect the hydraulic fracturing performance and the hydrocarbon production potential in the infill zones.…”