Advances in OH Multistage Fracturing Systems - A Return to Good Frac-Treatment Practices?

Abstract

Technology Update New developments in fracturing systems have returned focus to good fracturing practices that have been all but abandoned with the advent of horizontal wells. In major plays, such as the Barnett Shale of east Texas, operators have employed fracturing practices that are often inefficient and ineffective. Examples would include the massive overdisplacement of prop-pant and extended shut-in periods during a well’s completion phase, instead of initiating immediate flowback and load recovery. One of the problems with resource plays is that field development moves at a very rapid pace. In addition, most of the work is designed to simulate a manufacturing assembly-line process, i.e., use the minimum number of technical people to complete the maximum number of wells. Much of the engineering used in completion design has been replaced with a one-size-fits-all process. In our view, good fracturing practices developed over some 40 years are being ignored in the field-development strategies of many of today’s resource plays. Fortunately, there are now major developments in multistage fracturing technology that address many of these problems. One example is a new series of high-density, openhole (OH) fracturing systems that allow more than 20 fracture treatments to be performed in a single, seamless operation (JPT 2009). High-Density Fracturing Technologies The first OH multistage fracturing systems were installed in late 2001. At that time, it was believed that four to five stages would be sufficient to drain most horizontal wells. It would have been unimaginable to think that a few years later, the industry would be installing fracture liners with more than 40 OH packers. Key developments have taken place across a number of venues to make this possible. One item that was in question in the early days, but has now been clarified, is the ability to push long, high-density frac liners into a well. The industry now has the ability to accurately model installations of frac liners with OH packers with a high degree of certainty. In addition, hardware developments have taken place to allow higher-density fracturing. Issues such as abrasion and erosion encountered in massive hydraulic fractures, with millions of pounds of proppant, had to be addressed. The primary activating method for these OH systems is a ball-actuated port mechanism. Continued advancement in the systems, including 8 years of R&D into materials and the mechanics of the process, has greatly enhanced industry capabilities. More than 10 types of ball materials now are offered, as well as numerous port-design options. The net effect is that capabilities have increased from four or five fracture stages per well to more than 20 stages, using this mechanism. Engineering work is under way to increase these numbers to more than 60 fractures in a single horizontal. (The current record for number of stages is 47, installed in a ~10,000-ft lateral in the Bakken Shale of North Dakota [Slawson Exploration/Packers Plus Energy Services, 2010].)