Surfactant-Based Treatment Fluids Mitigate Fracture Hits in Parent Wells
Authors: Carpenter Chris 
Published: November 2020

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 197097, “Fracture-Hit Mitigation Through Surfactant-Based Treatment Fluids in Parent Wells,” by Liang Xu, James Ogle, and Todd Collier, SPE, Halliburton, prepared for the 2019 SPE Liquids-Rich Basins Conference - North America, Odessa, Texas, 11-12 September. The paper has not been peer reviewed.

Preloading parent wells with surfactant-based treatment fluids for fracture-hit mitigation has been applied extensively in liquids-rich shale plays. However, why specific chemical packages help improve parent-well production remains unclear. The complete paper presents a strategy for selecting a surfactant/solvent package for parent wells. Oil recovery and associated water saturation in the microfluidic-based device, with or without surfactant, are quantified and reveal that the oil recovery is enhanced with surfactant. Water saturation in the parent well could be reduced, thereby mitigating water blocks from primary fracturing-fluid invasion from child wells.

Introduction

During child-well completions in development of liquids-rich shale plays, fracturing fluids and proppants are likely to infiltrate the parent-well fracture net-work and wellbore through hydraulically connected flow paths. Parent wells, after producing for a period, serve as a pressure sink that attracts new fracture propagation and extension initiated from a child-well fracture. As a result, parent wells could lose production because of a potentially plugged fracture network filled with new sand from child wells. The production of child wells also could suffer because of unwanted fracture extension and loss of reservoir pressure.

The technique of reloading parent wells with surfactant-based treatment fluids for fracture-hit mitigation has been applied recently in environments where intense infill drilling and tighter well spacings are prerequisites for improved production and economic return. Preloads can provide a significant temporary increase in fracture network pressure if performed properly and are most effective with a surfactant and solvent package. However, why specific chemical packages help improve the parent-well production remains unclear, although the notion of capillary force resistance reduction for further treatment-fluid leakoff into fractures and rock- wettability alteration by surfactant has been proposed in the literature. Recent residual surfactant analysis in produced water from both parent and child wells indicates that hydraulic communication exists after fracture hits; additionally, field trials in the Wolfcamp suggest that the same surfactant package in primary fracture fluids in child wells can migrate gradually to parent wells, potentially activating various secondary oil-recovery mechanisms.

This study provides an evidence-based strategy for selecting a surfactant solvent package by a commercial microfluidic device (MD) and spontaneous imbibition (SpI), thus eliminating unnecessary testing that does not involve formation rocks. Surfactant optimization permits further leakoff into secondary fractures, potentially increasing fracture network pressure. Surfactant migration from child wells presents a unique enhanced-oil-recovery mechanism for parent wells. Field trials in different liquids-rich shale plays, including the Wolfcamp, appear to support this finding.