What's new in production: Welcome diversion?

LEONARD KALFAYAN, CONTRIBUTING EDITOR 

We all need a diversion every so often. For example, a hobby or an interest that allows one to forget the pressures of a job, would be a welcome diversion. That’s one type of diversion. Another type is diversion in well stimulation treatments, such as in hydraulic fracturing of long horizontal intervals or acidizing in formation intervals with significant permeability contrasts throughout.  

For years, there have essentially been the same diversion options, mechanical, solid or particulate, or chemical (e.g., gels, foams). All have their limitations. So, what would be welcome in the world of well stimulation would be a new diverting agent, especially a solid or particulate diverter, that would outperform the existing options.  

Diversion in well stimulation. Fluid diversion, in hydraulic fracturing or acidizing applications, is necessary and crucial in most modern well stimulation treatments. In long zones or even shorter zones with heterogeneous permeability, diverters direct stimulation fluids to desired portions of a zone to be stimulated, such that the entire zone is uniformly treated, or at least given the best chance to be uniformly treated. Diversion must be temporary, though, so that the entire production zone, post-stimulation, is effectively open to flow.  

Not quite ideal solid diverters. The ideal diverter in the category of solid or particulate diverters would be one that can be sized according to perforation diameter, is swellable, and has elasticity enabling deformation, such that it greatly reduces or eliminates fluid leakage, and is fully degradable with time and temperature or in contact with water or hydrocarbons during post-stimulation production.  

 However, current commercial solid/particulate diverters do not satisfy all of these desirable characteristics. Without detailing all of the different types and offshoots of various diverting agents, the most popular diverters lack one of the characteristics. There are those that can be sized according to perforation diameter and are degradable, at least to a significant extent, such as biodegradable ball sealers. But even biodegradable ball sealers have not caught on all that much, despite being available for many years now. Ball sealers of any type are not expandable or swellable.  

Benzoic acid flakes, a common diverting agent, can be reasonably effective at bridging off fractures, and reducing injectivity to perforations in matrix stimulation treatments. They do degrade with temperature (above 248^oF, at which point they melt). But benzoic acid flakes are not fully reliable with regard to leakage. They are, of course, inelastic, and non-conformable. Under many downhole circumstances of temperature and produced fluid rates and fluid entry locations, the rate of degradation can be slow.  

Polylactic acid (PLA)-based diverters have gained popularity in both acidizing and fracturing operations because of their versatile properties. PLA diverters may be the closest to ideal in the category of solid diverters, but they are just not quite there. PLA is bio-based and eco-friendly, can withstand high temperatures, and degrades in the presence of heat and water, leaving essentially no residue, a common issue with other degradable diverters. What PLA lacks is the ability to swell, which is not always necessary, but having that property would make PLA ideal, or even closer to it, at least relative to other solid diverters.  

The ideal solid diverter (potentially). As mentioned, an ideal solid or particulate diverter would be one that can be sized according to perforation diameter, is readily degradable post-treatment and does not leave a residue. In addition, the ideal case would include elastic properties, enabling conformation to the perforation or fracture that the diverter is intended to temporarily seal under stimulation fluid injection pressure conditions.   

A recent publication, in which the development of a new solid diverting agent was discussed, caught my attention.¹ While certainly in the early, very much pre-commercial stage, the potential is intriguing. Per the authors: 

“To address the challenge, a new generation of diverter has been developed, using elastic polymeric particles with good expandability and degradability, based on polyurethane chemistry. By adjusting the synthesis conditions, the particle size of the synthesized polymeric diverter can be easily tuned in the range of 0.2 – 8.0 mm. Characterization results confirm the presence of both polyurea and polyurethane structures, as well as good thermal stability for subsurface wellbore operations. Compression experiments demonstrate the excellent elasticity of the materials, showing that the diverter can quickly return to its original shape and size, once the compression stress is released. 

“In the plugging performance tests, the diverter material completely blocked fluid flow at a slot size of 2 mm and 4 mm. As the slot size gradually increased from 0.3 mm to 3.0 mm, no drop in differential pressure was observed, indicating continuous sealing during multiple fracture initiation and propagation processes. The dynamic temporary plugging performance evaluation clearly shows the efficiency of the newly developed diverter, thus enhancing well productivity. The newly developed diverter material shows great promise for diversion applications. It can improve the efficiency of multi-staged fracturing, thereby reducing the total number of stages, and ultimately the associated operational time and costs.”  

In 1948, my father did his PhD thesis on polyurethane chemistry. So, that is another reason this stood out, and I may have a biased interest. But apart from that, I encourage interested readers to explore this and other new, potential diverter materials, as they can make a significant difference in stimulation efficiency, as well as in cost savings. There are the default diverters, and stimulation treatments more often than not meet economic targets. But there is always room for improvement. This particular polyurethane-based diverter cited, which is not the only one being developed and studied, has the type of potential that should be pursued further. Also, for consideration is that such materials may also have application in water control/water shutoff applications, which can be combined with stimulation operations.  

REFERENCE 

1. Wang, et al., “New Generation of Expandable Diverter for Well Stimulation: Preparation, Properties and Performance Evaluation,” SPE paper 226958, presented at the Middle East Oil, Gas and Geosciences Show, Manama, Bahrain, September 2025.