Time for a step change...

Multi-stage fracturing challenges
April 30, 2019 by
Time for a step change...
Entech Solutions AS, Anthony Kent

The past, present and... future?

For decades, plug & perf ("PNP") was the only generally accepted method to achieve multistage fracturing. At the turn of the century, ball operated sliding sleeves ("BOSS") were introduced. BOSS opened sequentially from toe to heel. The ball served two functions: 1. To open the sleeve and 2. To isolate previously treated sleeves. To selectively open the sleeves, ball and seat sizes were varied, starting with the smallest in the toe and gradually increasing towards the heel.

The number of sleeves that could be operated was increased through the invention of 'multi-sleeves,' where a single ball could open a set of sleeves with matching seat dimensions. BOSS was essentially emulating PNP stages with multiple entry points, except that they were typically uncemented due to the inability to pump a cement wiper dart through dozens of tiny restrictions. The BOSS technique worked great for wells with limited lateral length and wide fracture spacing and as such, use of BOSS saw a significant increase from 2010 through 2015.

A third technique called coiled tubing annular frac ("CTAF") was introduced almost ten years ago. This was a game-changer in terms of proppant placement. Coiled tubing shifts open one sliding sleeve at a time and directs proppant down the CT annulus into the single entry point. While this proved excellent at propping 100% of the fractures, most operators in the lower 48 states ("L48") struggle to accept the added risk of pumping enormous volumes of proppant at high rate down the CT annulus. CTAF remains a popular treatment method in Canada but has not gained traction in L48.

"When we start to see a drop in production for each dollar spent, we need to stop what we're doing  and reevaluate our options!"
George E. King  PE
Viking Engineering

While BOSS is still relatively popular in Bakken and Western Canada, most operators in L48 have reverted to PNP as they drill longer laterals and increase fracture concentration. To improve the efficiency of pumping a much higher volume of fluids and proppant in each well with narrow cluster spacing, PNP variations called the Texas two-step (Jo, 2012) and zipper frac (Jacobs, 2014) were introduced. Today, horizontal reach continues to increase and the primary method of improving efficiency is adding more clusters per stage and pumping faster, with more horsepower and higher pressure at surface. Operators are increasing liner sizes to 6" to reduce fluid friction and pumping as high as 120 bbl/min. Increasing liner size and horsepower have obvious cost implications, yet production per cluster is evidently decreasing due to poor diversion in the toe-half and single-frac dominance (Wheaton, Haustveit, Deeg, & Miskimins, 2016).

So where do we go from here? This much is clear:

1. The industry will continue to drill farther.

2. Existing stimulation techniques are not optimized for the ERD wells.

3. Operators are seeing a reduction in production per dollars spent.

 4. Pumping higher volumes faster exhibits diminished returns as clusters per stage increases.

Superstage® Pinpoint Stimulation ("SPS") offers the fracture concentration of PNP, the efficiency of BOSS and the diversion control of CTAF. Contact Entech for an opportunity to pilot the technology in your field.

Odoo CMS - a big picture


Jo, H. (2012, January 1). Optimizing Fracture Spacing to Induce Complex Fractures in a Hydraulically Fractured Horizontal Wellbore. Society of Petroleum Engineers. doi:10.2118/154930-MS

Jacobs, T. (2016, June 1). EOR-For-Shale Ideas to Boost Output Gain Traction. Society of Petroleum Engineers. doi:10.2118/0616-0028-JPT

Wheaton, B., Haustveit, K., Deeg, W., Miskimins, J., & Barree, R. (2016, February 1). A Case Study of Completion Effectiveness in the Eagle Ford Shale Using DAS/DTS Observations and Hydraulic Fracture Modeling. Society of Petroleum Engineers. doi:10.2118/179149-MS

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Time for a step change...
Entech Solutions AS, Anthony Kent April 30, 2019
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