Abstract
Mineral scale formation in the wellbore represents a widespread and serious threat to flow assurance and ultimately to well productivity. Scale formation is generally attributable to the incompatibility between reservoir and injection waters and the main mineral scale types include carbonate, sulfate and sulfide salts of divalent cations. Currently available scale dissolvers for the latter two types are often based on chelating ligand chemistry, restricted by a kinetically sluggish process of displacing the cations plus near static scale-fluid interface at the scale surface area in downhole scenarios.
We wish to report two newly generated material developments aimed at accelerating downhole scale dissolution treatment performance by using either or both:
Discrete surfactants able to encapsulate entrained gases in the form of micro- and nano-bubbles that migrate in the fluid body along the pressure differential.
Gas generating reactions catalyzed by freshly produced divalent cations at the scale-fluid interface.
It has been demonstrated through systematic, lab-based proof of concept tests that these minor additives can promote interfacial mass transfer of both reactant and products as such that some of the current physical and engineering challenges of downhole mineral scale treatment can be circumvented, resulting in remarkably enhanced scale dissolution rates. Further increase of scale dissolution rates can also be achieved by the inclusion of a genuinely sustainable biosurfactant which, at certain concentration range, can effectively remove any hydrocarbon coatings that might have saturated the mineral scale surface, hence eliminate the often-hazardous organic solvent based preflush.
In addition to the aforementioned example, it is believed that the methodology reported in this manuscript can also be applicable to enhance other chemistry oriented downhole treatments where mechanic agitation is not viable.
