Prediction and Inhibition of Inorganic Salt Formation under Static and Dynamic Conditions – Effect of Pressure, Temperature, and Mixing Ratio

As a result of waterflooding, inorganic salt precipitation occurs in the different parts of an oil production system, thereby leading to damage of production equipment. Different parameters affect the kinetics of salt precipitation. Scale inhibitors are widely used to prevent inorganic salt formation. In this study, the effect of reservoir pressure, temperature, and mixing ratio of injection to formation water on calcium sulfate and barium sulfate precipitation was investigated. For this purpose, two different formation waters and one injection water were used. In addition, the effect of temperature and mixing ratio on inhibition performance was studied. Four different existing industrial scale inhibitors and one new scale inhibitor were used. The performance of the scale inhibitors was determined under static and dynamic conditions. Results of the study showed that calcium sulfate precipitation increased with an increase in temperature and a decrease in pressure. Barium sulfate precipitation was found to increase with a decrease in the temperature. The effect of pressure on barium sulfate formation was negligible. The developed scale inhibitor showed the highest performance for the prevention of calcium sulfate and barium sulfate formation. A change in temperature from 60°C to 120°C reduced the inhibitor performance by 3%. In the cases of calcium sulfate and barium sulfate, the minimum performance of the scale inhibitor was observed when the mixing ratios of injection to formation waters were 60:40 and 50:50, respectively

Modelling glaciers’ melting in Central Caucasus (the Djankuat and Bashkara Glacier case study)

The A-melt model was applied to assess the contribution snow and ice melting to river flow during the summer period of 2017 for the Bashkara and Djankuat glaciers located in the Caucasus. During the study period, the Djankuat river runoff amounted to 120 thousand m3, while the peak value of snow and ice melting was 300-400 thousand m3 per day, and on average 189 thousand m3. The significant influence of groundwater on the river flow is traced. The melt water contribution to the glacial lake Bashkara outburst manifested in the gradual accumulation of water large volumes over the summer period. The melting of snow and ice the day before the lake outburst reached 31 thousand m3, with an average value of 192 thousand m3 for the Bashkara basin. The total melting volume of the Djankuat basin was 0.016 km3, and of the Bashkara basin – 0.017 km3. As a result, the A-Melt model demonstrates the evaluation ability of glaciers’ impact on mountain rivers runoff

Causes and consequences of the streambed restructuring of the Koiavgan Creek (North Caucasus, Russia)

The restructuring of the lower reach of the Koiavgan Creek channel (the right bank tributary of the Djankuat River) occurred on 1 July 2015 after continuous rainfall with a total precipitation amount of 227 mm. This led to the breakthrough of the Djankuat Glacier lateral moraine. The lower reach of the creek channel was initially formed at the junction of the bedrock slopes and lateral moraine and descended sharply at the end of the moraine to a wide glacial valley of the Djankuat River. The part of the channel from the end of the moraine line to the creek’s outlet in the bottom of the glacial valley had a height difference of 125 m at a distance of about 250 m. The active landslide has been recorded in the place of future breakthrough based on interpretation of 2014 summer satellite image. The linear erosion began to form on the wall of the disruption. Thermokarst processes probably also contributed to this breakthrough. The total volume of sediment eroded during the breakthrough and for four years after is 156 500 m3. The breakthrough has formed the largest sediment cone 300 meters wide and more than 200 m long in the bottom of the Djankuat River valley

Trends, breaks, and biases in the frequency of reported glacier lake outburst floods

Thousands of glacier lakes have been forming behind natural dams in high mountains following glacier retreat since the early 20th century. Some of these lakes abruptly released pulses of water and sediment with disastrous downstream consequences. Yet it remains unclear whether the reported rise of these glacier lake outburst floods (GLOFs) has been fueled by a warming atmosphere and enhanced meltwater production, or simply a growing research effort. Here we estimate trends and biases in GLOF reporting based on the largest global catalog of 1,997 dated glacier-related floods in six major mountain ranges from 1901 to 2017. We find that the positive trend in the number of reported GLOFs has decayed distinctly after a break in the 1970s, coinciding with independently detected trend changes in annual air temperatures and in the annual number of field-based glacier surveys (a proxy of scientific reporting). We observe that GLOF reports and glacier surveys decelerated, while temperature rise accelerated in the past five decades. Enhanced warming alone can thus hardly explain the annual number of reported GLOFs, suggesting that temperature-driven glacier lake formation, growth, and failure are weakly coupled, or that outbursts have been overlooked. Indeed, our analysis emphasizes a distinct geographic and temporal bias in GLOF reporting, and we project that between two to four out of five GLOFs on average might have gone unnoticed in the early to mid-20th century. We recommend that such biases should be considered, or better corrected for, when attributing the frequency of reported GLOFs to atmospheric warming.ISSN:2328-427

Trends, Breaks, and Biases in the Frequency of Reported Glacier Lake Outburst Floods

International audienceThousands of glacier lakes have been forming behind natural dams in high mountains following glacier retreat since the early 20th century. Some of these lakes abruptly released pulses of water and sediment with disastrous downstream consequences. Yet it remains unclear whether the reported rise of these glacier lake outburst floods (GLOFs) has been fueled by a warming atmosphere and enhanced meltwater production, or simply a growing research effort. Here we estimate trends and biases in GLOF reporting based on the largest global catalog of 1,997 dated glacier-related floods in six major mountain ranges from 1901 to 2017. We find that the positive trend in the number of reported GLOFs has decayed distinctly after a break in the 1970s, coinciding with independently detected trend changes in annual air temperatures and in the annual number of field-based glacier surveys (a proxy of scientific reporting). We observe that GLOF reports and glacier surveys decelerated, while temperature rise accelerated in the past five decades. Enhanced warming alone can thus hardly explain the annual number of reported GLOFs, suggesting that temperature-driven glacier lake formation, growth, and failure are weakly coupled, or that outbursts have been overlooked. Indeed, our analysis emphasizes a distinct geographic and temporal bias in GLOF reporting, and we project that between two to four out of five GLOFs on average might have gone unnoticed in the early to mid-20th century. We recommend that such biases should be considered, or better corrected for, when attributing the frequency of reported GLOFs to atmospheric warming

Accelerated glacier shrinkage in the Ak-Shyirak massif, Inner Tien Shan, during 2003–2013

The observed increase in summer temperatures and the related glacier downwasting has led to a noticeable decrease of frozen water resources in Central Asia, with possible future impacts on the economy of all downstream countries in the region. Glaciers in the Ak-Shyirak massif, located in the Inner Tien Shan, are not only affected by climate change, but also impacted by the open pit gold mining of the Kumtor Gold Company. In this study, glacier inventories referring to the years 2003 and 2013 were created for the Ak-Shyirak massif based on satellite imagery. The 193 glaciers had a total area of 351.2 ± 5.6 km2 in 2013. Compared to 2003, the total glacier area decreased by 5.9 ± 3.4%. During 2003–2013, the shrinkage rate of Ak-Shyirak glaciers was twice than that in 1977–2003 and similar to shrinkage rates in Tien Shan frontier ranges. We assessed glacier volume in 2013 using volume–area (VA) scaling and GlabTop modelling approaches. Resulting values for the whole massif differ strongly, the VA scaling derived volume is 30.0–26.4 km3 whereas the GlabTop derived volume accounts for 18.8–13.2 km3. Ice losses obtained from both approaches were compared to geodetically-derived volume change. VA scaling underestimates ice losses between 1943 and 2003 whereas GlabTop reveals a good match for eight glaciers for the period 2003–2012. In comparison to radio-echo soundings from three glaciers, the GlabTop model reveals a systematic underestimation of glacier thickness with a mean deviation of 16%. GlabTop tends to significantly underestimate ice thickness in accumulation areas, but tends to overestimate ice thickness in the lowermost parts of glacier snouts. Direct technogenic impact is responsible for about 7% of area and 5% of mass loss for glaciers in the Ak-Shyirak massif during 2003–2013. Therefore the increase of summer temperature seems to be the main driver of accelerated glacier shrinkage in the area

Debris flows triggered from non-stationary glacier lake outbursts: the case of the Teztor Lake complex (Northern Tian Shan, Kyrgyzstan)

One of the most far-reaching glacier-related hazards inthe Tian Shan Mountains of Kyrgyzstan is glacial lake outburstfloods (GLOFs) and related debris flows. An improved under-standing of the formation and evolution of glacial lakes and debrisflow susceptibility is therefore essential to assess and mitigatepotential hazards and risks. Non-stationary glacier lakes may fillperiodically and quickly; the potential for them to outburst in-creases as water volume may change dramatically over very shortperiods of time. After the outburst or drainage of a lake, the entireprocess may start again, and thus these non-stationary lakes are ofparticular importance in the region. In this work, the Teztor lakecomplex, located in Northern Kyrgyzstan, was selected for theanalysis of outburst mechanisms of non-stationary glacial lakes,their formation, as well as the triggering of flows and developmentof debris flows and floods downstream of the lakes. The differentTeztor lakes are filled with water periodically, and according tofield observations, they tend to outburst every 9–10 years onaverage. The most important event in the area dates back to1953, and another important event occurred on July 31, 2012. Othersmaller outbursts have been recorded as well. Our study showsthat the recent GLOF in 2012 was caused by a combination ofintense precipitation during the days preceding the event and arapid rise in air temperatures. Analyses of features in the entrain-ment and depositional zones point to a total debris flow volume ofabout 200,000 m3, with discharge ranging from 145 to 340 m3s−1and flow velocities between 5 and 7 m s−1. Results of this study arekey for a better design of sound river corridor planning and for theassessment and mitigation of potential GLOF hazards and risks inthe region