Water-Jet Fracturing a Horizontal Openhole Completion
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 134855, ’Effectiveness of Water-Jet Fracturing on a Horizontal Openhole Completion: Case Study,’ by Sigifredo J. Rosales, SPE, Chevron, and Rafael A. Hernandez, Cynthia Yuen Lynch, and Ernesto Bustamante, SPE, Halliburton, prepared for the 2010 SPE Annual Technical Conference and Exhibition, Florence, Italy, 19-22 September. The paper has not been peer reviewed.

Without proper isolation methods, the use of openhole horizontal-well fracturing is limited. During many fracturing processes, fracture or acid placement often occurs where fluid first contacts the borehole, usually at the heel of a horizontal well. A method that combines hydrajetting and fracturing techniques enables positioning a jetting tool at the precise point where the fracture is required, without the use of sealing elements. Multiple fractures can be placed in the well, spaced evenly or unevenly as prescribed by the fracture-design program.

Introduction

Water-jetting is a cold-cutting process that can be used for cutting or perforating holes in stone, glass, and metal. There are two basic types of water-jetting techniques: water-only jetting (hydrojetting) and abrasive water jetting (hydrajetting). Common applications for hydrajetting in the oil industry are cutting and perforating. Recent improvements in hydrajetting tools have made them more resistant to abrasive materials, significantly increasing tool life. With more-reliable tools, this technology can be used for well stimulation. The full-length paper details results from a stimulation treatment performed with the hydrajet fracture-stimulation technology in a horizontal openhole completion, executed in a low-permeability, high-porosity reservoir in the Antelope formation of the Monterey shales in the San Joaquin Valley of central California.

Horizontal Openhole Stimulations

Low-permeability zones often contain multiple layers with varying porosity and permeability. Unexpected vertical-permeability barriers that are too thin to detect with conventional well logs often exist. In low-permeability environments, horizontal openhole completions enhance reservoir contact, but there are challenges when designing stimulation treatments for this type of completion.

Uncontrolled generation of hydraulically induced fractures normally results in poorly distributed fractures along an openhole lateral, of any length. For optimum production enhancement, a fracturing-stimulation program should produce a limited number of discrete fractures that are widely separated and well distributed along the horizontal section. The width and length of each fracture are reduced as the number of fractures increases.

Another objective is to create fractures only where they are needed. Multiple close-proximity fractures will improve the initial stimulation response, but only for a short time following the treatment. High-rate large-volume open-hole fracturing-stimulation attempts in which fluid is bullheaded into the open hole typically result in extreme multiple fracturing that causes most of the treating fluid to be placed in one small part of the reservoir near the heel section, leaving the rest of the interval essentially untreated.