Calcium Carbonate Scale Inhibition with Ultrasonication and a Commercial Antiscalant

In this study, ultrasonication-assisted calcium carbonate scale inhibition was investigated compared with a commercial antiscalant ATMP (amino tris(methyl phosphonic acid)). The effects of varying ultrasound amplitude, pH, and inhibition duration were evaluated. The inhibition of calcium carbonate scale formation was measured based on the concentration of calcium in the solution after subjecting to different conditions. Scale deposits were also characterized using scanning electron microscopy and X-ray diffraction spectroscopy. Inhibition of scale formation was supported at a pH of 7 for an ultrasound amplitude of 150 W. A 94% calcium carbonate inhibition was recorded when the experiment was carried out with ultrasonication. The use of 5 mg/L ATMP achieved a 90% calcium carbonate inhibition of ATMP. The result of the characterization revealed that the morphology of the crystals was unaffected by ultrasonic irradiation. Sample treatment was performed with two different membranes to evaluate the calcium carbonate deposition, and data reveals that, at identical conditions, ultrasonication provides less deposition when compared to the control experiments.

Co-Deposition Mechanisms of Calcium Sulfate and Calcium Carbonate Scale in Produced Water

Co-precipitation of mineral-based salts during scaling remains poorly understood and thermodynamically undefined within the water industry. This study focuses on investigating calcium carbonate and calcium sulfate mixed precipitation in scaling. Scaling is often observed in the produced water supply as a result of treatment processes. Co-precipitation results were compared with experimental results of a single salt crystallization. Several parameters were carefully monitored, including the electrical conductivity, pH value, crystal morphology and crystal form. The existence of the calcium carbonate scale in the mixed system encourages the loose calcium sulfate scale to become more tightly packed. The mixed scale was firmly adhered to the beaker, and the adhesion of the co-deposition product was located between the pure calcium sulfate scale and the pure calcium carbonate scale. The crystalline form of calcium sulfate was gypsum in both pure material deposition and mixed deposition, while the calcium carbonate scale was stable in calcite form in the pure material deposition. In the co-deposition, apart from calcite form, some calcium carbonate scale crystals had metastable vaterite form. This indicated that the presence of SO42− ions reduced the energy barrier of the calcium carbonate scale and hindered its transformation from a vaterite form to a calcite one, and the increase in HCO3− content inhibited the formation of calcium sulfate scale.

Theories and Work Towards Understanding a Mysterious Case of Severe Bakken Brine Incompatibility

The Bakken formation is well known for producing brine very high in total dissolved solids (TDS). Halite, calcium carbonate, and barium sulfate scales all can pose substantial production challenges. Trademarks of Bakken produced brine include elevated concentrations of sodium (>90,000 mg/L), chloride (>200,000 mg/L), and calcium (>30,000 mg/L), contrasted against low concentration of bicarbonate (50-500 mg/L). In the past 3 years, operators have experienced unexpected instances of severe calcium carbonate scale on surface where produced fluids from the production tubing commingled with the gas produced up the casing. Initially treated as one-off scale deposits despite the application of scale inhibitor, acid remediation jobs or surface line replacement were typical solutions. As time has passed, this issue has become more and more prevalent across the Bakken. Investigation of this surface issue discovered a most unexpected culprit: a low TDS, high alkalinity brine (up to 92,000 mg/L alkalinity measured to date) produced up the casing with the gas. When mixing with the high calcium brine typically produced in the Bakken, the resulting incompatibility posed remarkable scale control challenges. The uniqueness of this challenge required thorough analytical work to confirm the species and concentrations of the dissolved ions in the brine produced with the gas. Scale control products were tested to evaluate their abilities and limitations regarding adequate control of this massive incompatibility. The theory that corrosion contributed to this situation has been supported by a unique modelling approach. Once corrosion was identified as the likely source of the high alkalinity brine, corrosion programs were instituted to help address the surface scaling. This paper highlights the evaluations conducted to fully grasp the severity of the incompatibility, the theories put forth to date, work conducted to try to replicate the phenomena in the lab and in models, and chemical programs used in the field to address corrosion and scale. While not known to exist in other oilfield basins, conventional or unconventional, this discovery may have implications for the broader industry if similar situations occur. The possible explanations for why this may be happening may have implications for scale control, asset integrity, and potentially even the methods by which wells are produced.

Characteritization of Bio-Oil from Tectona Grandis as a Potential Scale Inhibitor

Calcium carbonate scales cause costly flow assurance problems in flowlines during petroleum production. Previous efforts to mitigate this problem using different chemical inhibitors though successful have resulted in environmental pollution during disposal. This study was designed to investigate the potential of bio-oil synthesized from Tectona grandis as an inhibitor to replace the conventional ones. Tectona grandis was obtained from Ibadan sawmill, Oyo state, Nigeria and characterized using Energy Dispersive X-Ray (EDX) analytical technique. Data generated by EDX analysis showed elemental composition of 78% carbon and 22% of other elements including nitrogen and oxygen. Tectona grandis was pyrolyzed at 5500C, a heating rate of 0.50C/sec, and a running time of 4 hours. 45.1% of the mixture of water and oil were collected and separated into phases in a centrifuge while the gasses were vented. The bio-oil was distilled at 120°C and analyzed using FTIR spectrometry. Spectra analyses showed the presence of -COOH and -CONH2 which are essential in the inhibition of calcium carbonate scale. With the help of a newly fabricated testing-rig system, calcium carbonate scales were formed by mixing equal mole of calcium chloride and sodium carbonate at the temperature range of 25-58°C and flow rates range of 8-15 ml/min, with/without inhibitor from 0, 5 g/l of maleic acid and 5 g/l of newly synthesized inhibitor. The mass of the calcium carbonate and the induction time was measured by the weighing balance and the conductivity meter respectively. For all of the experiments, the presence of maleic acid and newly synthesized inhibitor delayed the induction time by at least 10 mins and reduced the weight of calcium carbonates formed by at least 20%. Also, the mass of calcium carbonate scale formed at all the experiments showed less weight when newly synthesized inhibitor was used compared to when maleic acid inhibitor was used showing the effectiveness of the newly synthesized inhibitor over maleic acid. Therefore, this study shows high promise wood-based distilled oil as a potential calcium carbonate scale inhibitor and provides future direction for further studies.

Effect of operational parameters and material properties on hardness removal efficiency by electrochemical technique

Electrochemical water treatment technology can be used for hard water softening, but its removal efficiency and energy consumption problems hinder its application. The effects of electrolysis voltage and cathode materials on efficiency, energy consumption and scale crystal form of electrochemical water treatment technology were studied experimentally. The experimental results show that electrochemical water treatment can effectively remove more than 40% of the TDS (total dissolved solids) in the influent. The electrolysis voltage has a great influence on the removal rate of hardness ions. The optimum electrolytic voltage for the titanium plate cathode is 25 V. At this electrolytic voltage, the treatment capacity of the titanium plate cathode is 16% higher than that of the copper plate cathode, and the energy consumption is 16% lower than that of the copper plate. Titanium plates are more efficient than copper plates and consume less energy. The effects of electrochemical water treatment on the scale crystal form were investigated by SEM (scanning electron microscopy) and XRD (X-ray diffraction). Electrochemical water treatment increases the mass fraction of aragonite in the calcium carbonate scale and changed the microscopic surface structure of calcium carbonate scale.