Laboratory and Field Studies of Long-term Release Rates for a Solid Scale Inhibitor

Abstract

Mineral scale build-up decreases permeability of the formation, reduces well productivity and shortens the lifetime of production equipment. Chemical scale inhibitors are commonly used in production wells to prevent scaling in the formation and/or in the production lines downhole and at the surface. An ideal scale inhibition treatment will last as long as possible and minimize the production interruption for treatment. In the art for introducing scale inhibitors into production wells, adding a solid scale inhibitor into the producing formation in conjunction with a hydraulic fracturing operation is often preferred to extend scale inhibition lifetime.This study quantified release rates of a solid scale inhibitor for use in fracturing treatment. Tests were conducted under dynamic conditions with various loading rates as a percentage of sand proppant. Results show that this solid derivative of a phosphonate inhibitor has a sustained long-term release profile. Inhibitor release rate gradually increases with solid inhibitor loading. However, this effect slows when the loading exceeds 5% (wt/wt).Based on the test results, a mathematical model was developed to describe the release rate profile and thereby predict the long-term behavior of inhibitor returns from initial solid inhibitor loading. Actual data collected from treated wells were compared to the mathematical model. The earliest wells treated with this type of product have achieved 5 years of production with continued effective residual chemical measured in the produced water. Other wells treated have achieved greater than 1 million barrels of produced water with continued effective residual chemical measured in the produced fluid. The data from this laboratory release study have verified that additional long-term protection can be achieved by increasing initial loading rates. IntroductionTraditionally, liquid chemical inhibitors were primarily used to control the formation of scale in oil and gas production. These chemicals can be administered through batch, continuous or squeezed applications (Szymczak et al., 2006). A main drawback of conventional squeeze treatments in a carbonate formation is that most of the acidic phosphonate inhibitor is precipitated near the formation face because the reaction of acid with carbonate and the formation of Ca-phosphonate precipitation take place very quickly. As a result, only limited reservoir protection distance can be provided near the wellbore. In a sandstone formation, the squeeze treatment depends on adsorption of the phosphonate inhibitor on the formation. Adsorption squeezes are often performed in reservoirs where a neutralized inhibitor pill solution is injected into the formation. However, compared with precipitation squeeze, little or negligible amount of inhibitor can be retained and released slowly from the formation. A large fraction of the phosphonate tends to flow back within a few days and then decreases to an extremely low value, which is not enough to effectively inhibit scale formation (Shen, et al., 200...

A preliminary research on polyvinyl alcohol hydrogel: A slowly-released anti-corrosion and scale inhibitor

“…Instantaneous scale inhibition efficiency in the dynamic system was not satisfactory. Therefore, more improvements, such as to increase the amount of loaded inhibitors (Brown et al, 2011) and the contact area, should been studied in further research.…”

“…Moreover, as the main concerns of scale and corrosion problems are iron compounds and calcium carbonate (Moghadasi et al, 2004;Martos et al, 2010;Jing et al, 2013), chemical control, such as adding poly-aspartic acid and acetic acid , is generally regarded as the most effective method, both in performance and cost (Lavania et al, 2011;Pillay and Lin, 2014). However, from an operational point of view, chemical dosing by means of a remote control system is the ideal scenario (Khramov et al, 2005;Okafor et al, 2009;Abdullayev and Lvov, 2010;Brown et al, 2011). In recent years, hydrogel has been recognized as an interesting vehicle for delivery (Zhao et al, 2014).…”

Effect of Produced Sand Particles and Fines on Scale Inhibitor: A Review

“…In carbonate formation where the unconventional squeeze treatment method is used, the majority of the acid phosphonate inhibitor is precipitated near the formation face. The formation of Ca-phosphonate resulting from the reaction of acid with carbonate in the formation proceeds very rapidly and this has a shortcoming in a carbonate formation [28]. The unprecipitated inhibitors occurring during these unsuccessful treatments are quickly swept from the formation because they are not retained [23], the result of this being shorter treatment lifetimes and inefficient use of inhibitor, demand for subsequent treatments, lost production time, and significant cost.…”