What's the cost v. regular fracking? Is it something that can be generally applied or is it a speciality tech?
This is really a completely different stimulation technique than the more recently termed 'hydraulic stage fraccing' that is the basis for the huge boom in unconventionals.
What is generally done when one does hydraulic stage fraccing is to open up new fractures by high injection (or frac pressures) in stages that are mechanically separated by packers outside the casing in an openhole or by plugs inside the casing in a cemented hole. These fractures will close after the pressure is let off, so sand in large quantities are introduced to 'prop' them open so formation fluids can then produce through them to the wellbore.
This application is best for very tight(or tite or low permeability formations). These formations must be in friable formations or rock which can be shattered easily. Think of breaking glass which is easily broken vs breaking chocolate pudding which does not.
The procedure this article entails is quite different. It is only for very calcified formations such as limestone or dolomite, as the fractures are not created by high pressures as much as dissolving via acid action the actual formation. They do not require the sand as a propping agent after pressure is removed as they were not created by pressures that move the rock apart but by dissolving rock.
The stages described in this article are not mechanical separation, but simply placing within the injected fluids what they call a diverting 'agent' periodically which just fill up the fractures created to 'divert' the injection fluids to a new interval that can be fracced. This diversion agent breaks down over time to allow the fractures to reopen, and may be as simple as rock salt which is more than capable of plugging up a fracture then dissolving after time as water is passed through it.
There are certain formations that respond extremely well to acid fracs, and some are just simply fabulous. That is a key on their application.
And acid fracs, since they do not require generally as high a pressure to inject, no sand or propping, and much less volumes, as well as a cheaper way to create stages, are much cheaper.
When they are correctly applied to a formation, they can be much more prolific than even hydraulic fracturing.
I worked a tight formation in California in which hydraulic fraccing was tried for several years with lukewarm success. When someone decided to apply an acid frac, the results were many times better than the hydraulic fracs. That field became one of the largest consumers of acid in the world due to its astounding success.
