Prevention of Halite Formation and Deposition in Horizontal Wellbores: A Multi Basin Developmental Study

Because inorganic scales reduce permeability near wellbores, they cause an additional pressure drop in this region (skin damage) and reduce production. NaCl precipitation, particularly in gas-producing wells, is one of the formation damage problems which impair the permeability. The use of backwashing water not only requires a large quantity of water, but is also inefficient. This study examined the effect of the ultrasonic waves in NaCl scale removal. Twenty core samples with different permeabilities were saturated with NaCl. After precipitation of NaCl within the cores, the samples were first subjected to water injection and then to water injection with ultrasonic wave radiation. At each stage, the permeability of cores was measured and recorded. Experimental results reveal that applying ultrasonic waves restores the permeability of cores more than water injection alone. In samples with permeability lower than 20, 30-100, 100-700 md and cores with permeabilities higher than 1000 md, ultrasonic waves recover permeability to 80, 42, 87 and 81%, respectively. In contrast, water injection alone improves permeability to 29, 18.5, 62 and 77%, respectively. The effect of these waves is much more obvious than water injection alone in low-permeability cores. SEM images from cores show that ultrasonic waves destroy the structure of deposits of sodium chloride. This phenomenon is due to propagation of these waves and the resulting temperature increase in the surroundings, which leads to the increased solubility of these scales. After exposure to ultrasonic waves, sodium chloride deposits inside the induced fractures of cores could be removed from the fracture, whereas water injection alone could not wash and remove the deposits from the fracture. According to the results of this paper, ultrasonic waves can be used as a novel and efficient technology in gas wells to remove inorganic scales in the near-wellbore region.

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Impact of Gas Hydrate Inhibitors on Halite Scale Precipitation: An Experimental and Morphological Investigation

Hosseini

Joonaki²,

Buckman³

et al. 2018

Day 2 Thu, June 21, 2018

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Inorganic scale deposition is one of the most serious flow assurance problems. One of these exotic scales is halite (NaCl). Injection of hydrate inhibitors (HIs) [methanol, monoethylene glycol (MEG), triethylene glycol (TEG)] to prevent plugging of flow lines and tubing could induce precipitation of halite scales. Thus, utilizing these chemicals might adversely affect salt solubility, causing scaling problems, particularly halite scales, in high total dissolved solid (TDS) brines. In this study, the influence of HIs on scaling of a supersaturated NaCl solution with and without inhibitor was experimentally investigated. The results of these experiments show that increasing the concentration of HIs results in a higher amount of halite precipitation. Moreover, the effect of methanol on halite precipitation is more severe compared to MEG and TEG. On the other hand, the static efficiency results illustrate that raising the concentration of HI reduces the scale inhibition efficiency in the presence of methanol and TEG to a lower extent, while the inhibitor could have a 100% inhibition efficiency in the MEG solution. Furthermore, in the case of methanol, the optimum inhibition efficiencies at HI concentrations of 10 and 40 wt% were observed at SI concentrations of 500 and 200 ppm, respectively. Alterations in the morphology of halite in the presence of HIs were analyzed using optical microscopy and environmental scanning electron microscopy (ESEM) techniques. In this study, the effect of morphology changes of halite due to the addition of HI is addressed for the first time. These investigations can help provide a better understanding of the mechanism of halite scaling in the presence of HIs.

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Prevention of Halite Formation and Deposition in Horizontal Wellbores: A Multi Basin Developmental Study

Cited by 5 publications

References 8 publications

Metals, Inorganic Salts and Other Inorganics

Metals, Inorganic Salts and Other Inorganics

Using ultrasonic as a new approach for elimination of inorganic scales (NaCl): an experimental study

Impact of Gas Hydrate Inhibitors on Halite Scale Precipitation: An Experimental and Morphological Investigation

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