New Insights on the Impact of Mass to Volume and Volume to Volume as it Relates to Barium Sulphate Dissolver Performance

Abstract

Dissolver technology has been developed and applied with varying degrees of success over the past few years to clean carbonate and the more challenging sulphate/sulphide scales from production tubing and process equipment. A common question that is often raised but which has no published experimental work to provide an answer is "under what liquid to solid ratio would a sulphate dissolver not be effective to clean production tubing?" A set of experiments were conducted at a range of temperatures to review the impact of surface area/mass to fluid volume ratio for barium sulphate scale. The surface area/mass to fluid volume ratio were measured from 13 examples of scaled or partially scaled production tubing in an attempt to understand why in some laboratory tests dissolvers used to remove sulphate scale appear to show better performance than is observed in the field. This paper shows that simple dissolver tests, when performed with high volume/volume ratio (1 part scale to 45 chemical) which equates to a mass to liquid volume ratio of 1:10 which is most commonly used in screening studies, can give misleadingly high performance information as they show enhanced dissolution rates and mass of scale dissolved. In fact, from the 13 scaled pipe sections examined in this work, a much higher ratio of solid mass to liquid volume (10:1 to 1:1) (equating to a volume/volume ratio of 1:4.5 to 2:1) is more typical and with these ratios dissolver performance is greatly reduced. The results from these experiments are used to give a guide as to the measured liquid to solid ratio where sulphate dissolvers have the potential to work for barium and calcium sulphate scales and to where mechanical removal of the deposit would be the better treatment option.

A Technical Playbook for Chemicals and Additives Used in the Hydraulic Fracturing of Shales

“…142 Chemical formulations that can dissolve sulfate scale are now an emerging field of interest led by base-assisted polyaminocarboxylic acid chemistry, such as diethylenetriamine pentaacetate (DTPA) 146 and green inhibitor 3,141 additives. 147 Sulfides of iron (e.g., FeS, Fe 3 S 4 , etc.) are often encountered in wells exposed to sulfate-reducing microbes, sour gas from the reservoir, or high-sulfur-content hydrocarbons (e.g., thiols and thiophenes).…”

“…Historically, the only available options for removing barium and strontium sulfate scales were the costly measures of mechanical milling or impact hammer . Chemical formulations that can dissolve sulfate scale are now an emerging field of interest led by base-assisted polyaminocarboxylic acid chemistry, such as diethylenetriamine pentaacetate (DTPA) and green inhibitor , additives …”

The Impact of Thermodynamic Hydrate Inhibitors (MEG and Methanol) on Scale Dissolver Performance

“…Scale removal methods via scale dissolvers (chelants/acids) have been extensively published in literature (Carrel 1987;De Vries and Arnaud 1993;Clemmit et al 1985;Bakken and Schoffel 1996;Putnis et al 1995;Klepaker et al 2002;Kelly et al 2005;Jordan et al 2002;Jordan et al 2012;Sutherland et al 2012). Mechanical scale removal has focused on two methods for removal of the scale with such methods (1) jetting, milling and blasting the deposits on the surface of pipes and tubulars or (2) penetration of the rock/scale using perforation or fracturing to break through scale-induced formation damage to undamaged zones within the reservoir.…”