Study Summarizes 20 Years of Horizontal Multistage Completions

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 207698, “Twenty Years of Horizontal Multistage Completions: A Summary of Industry Evolution in Unconventional and Conventional Plays,” by Alberto Casero, SPE, BP. The paper has not been peer reviewed. The innovative idea behind the shale gas revolution was the combination of horizontal well drilling and hydraulic fracturing, which allowed for an increase in the surface area available for hydrocarbon flow and overcame the slow, shallow hydrocarbon release from the source rock. To achieve the high number of hydraulic fractures needed for economical production, different execution techniques evolved in what became known as horizontal multistage fracturing (HMSF) completions. The complete paper covers the most-common types of HMSF completion systems and includes a section about the use of these completions in conventional plays. This synopsis focuses on HMSF use in unconventionals. Well Architecture as a Function of Location and Reservoir Properties As hydraulic fracturing and horizontal wells became popular, many preconceptions associated with hydraulic fracturing had to be reimagined. The concept of stimulated reservoir volume (SRV) was introduced; contacting as much rock as possible was the new priority of hydraulic fracturing, while more-conventional fracturing concepts such as fracture conductivity and planar fractures became secondary or irrelevant. Fracture-production interference and fracture complexity became an aim rather than representing a risk. Very high fracture count and reduced well spacing became a necessity, and, inevitably, a mass-production approach had to be applied rather than an individual fit-for-purpose design for each well or fracture. These changes brought a substantial shift in primary well-construction costs, with completion costs in many cases surpassing the drilling cost by a factor of 40–50%. Multistage fracturing with complex and developed fracture networks or SRV, which is at the basis of unconventional developments, requires a robust infrastructure and resource availability to allow easily moving large amounts of proppant (typically natural sands) and water. This can be challenging for remote locations. When permeability decreases, cased and perforated completions with hydraulic fracturing or acid stimulations become the norm. When permeability decreases even further, multistage fractures and horizontal wells are applied; finally, in ultratight gas and shale gas, horizontal multistage fracturing represents the only option.