A Multientry, Multistage Fracturing-Sleeve System in Bakken Shale Wells
Authors: Carpenter Chris 
Published: August 2016

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 171629, “Does a Multientry, Multistage Fracturing-Sleeve System Improve Production in Bakken Shale Wells Over Other Completion Methods?,” by Ben Wellhoefer, Andy Eis, and Geoffrey Gullickson, Halliburton, prepared for the 2014 SPE/CSUR Unconventional Resources Conference—Canada, Calgary, 30 September–2 October. The paper has not been peer reviewed.

This paper evaluates dominant and currently applied completion methods by comparing wells in the Middle Bakken continuous resource play that have used all identified systems. The authors discuss these completion designs and methods and fracturing operations that are often executed. Assessment of viability and production efficiency of multiple-entry-point fracturing-sleeve-system (MEFSS) completions as compared with other completion methods is the primary focus of the complete paper.

Introduction

The three most common completion techniques in the Middle Bakken are plug and perforation (P&P), single-entry- point fracturing-sleeve systems (SEFSSs), and MEFSSs. Traditional P&P techniques were developed initially for vertical-well applications and then adapted to horizontal wellbores. As a result, composite-fracturing-plug design had to evolve for horizontal-well deployment and pumpdown capabilities. Cementing, typically the isolation method for P&P-completed wellbores, is also difficult in horizontal wellbores. Because of the need for an interventionless completion system to facilitate compartmentalized stimulation designs, development and use of SEFSS technologies to overcome many of these challenges came into accepted practice.

SEFSS technologies use specifically sized balls that are dropped from surface to actuate sleeves that are preinstalled with the completion liner string. These actuation balls also provide progressive downstream isolation as the treatment is pumped sequentially from toe to heel. Fracturing-sleeve systems can be used in conjunction with openhole annular isolation packers or cemented in place. These systems do not require millout to ensure that a target zone can produce, although the ball seats are typically milled in the Bakken system. Fracturing-sleeve technologies also help eliminate the use of water and chemicals because the isolation balls do not have to be pumped to depth postflush as in a P&P technique. Because the actuation balls can be launched and landed on the fly, hundreds of barrels of water are typically saved on each individual treatment.

With fracturing-sleeve technology, many tools must be deployed to depth as part of the completion liner string. This increases the complexity of running the completion casing after the wellbore has been drilled when compared with a conventional liner-running operation. While steps can be taken to overcome these installation challenges, fracturing-sleeve systems are often limited in the number of fracturing stages that can be targeted because of the use of actuation balls and ball seats of graduated size against the completion tubular geometry. The use of graduated balls and ball seats can also have an effect on the rate at which fracturing stages can be pumped, especially for smaller- sized ball seats toward the toe of the completion.