June 2024

What's new in production

There is more about oolitic aragonite than one might imagine

Maybe the above subject title isn’t something that crosses your mind. Probably not, but it has crossed mine, since writing about oolitic aragonite in the August 2023 column, specifically as a replacement for sand as a proppant in hydraulic fracturing (as EnviroProp, from Pisa Carolina, for example).  

Oolitic aragonite

What was not specifically mentioned was how this fascinating, naturally occurring material could be applied optionally in fracturing operations, if not as a full replacement, which will take time with respect to availability of sufficiently massive quantities. But in sufficiently available quantities, it can be added as a tail-in or lead-in to fracturing with sand to provide greater conductivity, especially at or near the wellbore. It could be mixed with sand in a specific weight percentage throughout, given its applicable size range, smoothness, and roundness, to provide greater overall conductivity. It could be included fully in some, but not all, fracturing stages in long horizontal completions. And with its capacity to absorb water and its naturally high crush strength, along with its absence of fines, even with crushing (at very high closure pressure), it can add proppant pack strength to a sand proppant pack as an additive.  

Sand is often applied in wells at its crush strength limit in certain unconventional reservoirs, after all, with no association made to the rapid productivity declines of such wells. There is also the potential to replace intermediate and even high-strength ceramic proppants commonly used in deepwater fracturing or frac pack operations, at a lower cost. Also, as was mentioned last August, its high porosity enables infusion of production chemistries, such as scale inhibitor and surfactant, to enable longer-term production enhancement.  

Furthermore, what was not mentioned at all in August 2023 were the many other applications of oolitic aragonite, some of which would be of use in the oil and gas industry, apart from fracturing, and which would not automatically come to mind.  

But first, some background, courtesy of Pisa Carolina, the highlighted supplier of oolitic aragonite for fracturing, as well as a supplier for many other applications outside of the energy industry. 

Material origin Aragonite is a naturally occurring form of calcium carbonate with unique chemical properties. It is deposited continuously in vast quantities throughout the Bahamas. Chemically, aragonite is identical to its more common polymorph, calcite. The differences between the two materials are the result of their different crystalline structures. As a result, the characteristics of Bahamian aragonite are compared to calcite (terrestrial limestone).

Sustainability: An additional benefit of Bahamian aragonite is that since it is continuously forming, the resource can be considered sustainable/renewable. Tests completed on aragonite by the USDA Bio-based Testing Laboratory at Iowa State University indicated that 62% of the carbon in the sample was fixed in the last three to five years. 

Purity: Since it comes from the ocean, the chemical composition of oolitic aragonite reflects that of the ocean waters around the Bahamas. It is exceptionally high in calcium (typically >37%) and low in magnesium (<1%), when compared to dolomite or limestone. It is also relatively free of impurities, with no other metals greater than 1%. Oolitic aragonite is 96% to 99.6% calcium carbonate (CaCO3).  

So, what are other applications of oolitic aragonite, and specifically in the oil field, as they relate to production? There are actually a multitude of oolitic aragonite applications, far too many to list and discuss. Many can be found with online investigation, and one is encouraged to do so, as interested. Applications generally include agriculture, in livestock feed (as chicken feed), along with plastics, adhesives, pharmaceuticals, food, cosmetics, soil remediation (pH control), reef management, multiple water filtration uses (including wastewater treatment), heavy metal removal, and also flue gas CO2 and SO2 removal, in disease control, as an aquarium substrate, and on and on.  

Oil and gas industry applications. Beyond fracturing as a proppant technology, oolitic aragonite physical properties lend themselves to filtration, such as in waterflood applications, as a potentially lower-cost filtration medium. Perhaps even sulfate removal in seawater flood applications offshore.  

Certainly, oolitic aragonite as a cement additive makes sense and is a current use case. Its purity, high surface area, and stability are important characteristics for cementing applications. It is why oolitic aragonite has application outside the oil field in concrete applications. It’s imaginable that with its high porosity, oolitic aragonite could carry nano-sensors, enabling long-term monitoring of wellbore cement integrity. The same could be imagined with sensor application in fracturing (via oolitic aragonite proppant). 

Oolitic aragonite also makes good sense as fluid loss control additive in well drilling and completion/workover operations. The very high calcium carbonate purity means it is essentially fully acid soluble, which is an advantage in establishing a non-damaged (low-to-no skin) well, post-completion, with acid treatment for removal.  

Oolitic aragonite is an excellent example of a material, which finds its uses almost exclusively outside of the oil and gas industry, which has been used in many industries for a long time, but offers potential advancements in well and production applications. Not only that, but applications in the oil field can ultimately be at potentially lower costs, and would be more environmentally favorable, as oolitic aragonite is naturally occurring and sustainable, from non-land surface mining sources. It’s an intriguing material with unique properties. It is worth exploring further, and imagining the greater possibilities in our industry, which would be in addition to use as a proppant in hydraulic fracturing, which is (and should be) the primary focus, presently.  

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