Water Compatibility and Scale Risk Evaluation by Integrating Scale Prediction of Fluid Modelling, Reservoir Simulation and Laboratory Coreflood Experiment for a Giant Oil Field in Offshore Abu Dhabi

An offshore field is producing oil from multiple reservoirs with peripheral water injection scheme. Seawater is injected through a subsea network and wellhead towers located along the original reservoir edge. However, because its OWC has moved upward, wells from wellhead towers are too remote to inject seawater effectively, with some portion going to the aquifer rather than oil pool. Therefore, it is planned to migrate injection strategy from peripheral to mid-dip pattern. An expected risk is scaling by mixing incompatible seawater and formation water. Such risk and mitigation measures were evaluated. To achieve the objective, the following methodology was applied: 1. Scale modelling based on water chemical analysis. 2. Define scale risk envelope with three risk categories 3. Tracer dynamic reservoir simulation to track formation water, connate water, dump flood water, injection seawater and treated seawater. 4. Review the past field scale history data 5. Coreflood experiment to observe actual phenomena inside the reservoir with various parameters such as water mixing ratio, sulphate concentration, temperature and chemical inhibitor 6. Consolidate all study results, conclude field scale risk and impact of mitigation measures. Scale prediction modelling, verified by coreflood tests, found that mixing reservoir formation water and injection seawater causes a sulphate scale risk, with risk severity depending on mixing ratio and sulphate concentration. Reservoir temperature was also found to correlate strongly with scale risk. Therefore, each reservoir should have different water management strategy. Scale impact is limited in the shallower wide reservoir with cooler reservoir temperature. Such reservoir should therefore have mid-dip pattern water injection to avoid low water injection efficiency with possible scale inhibitor squeezing as a contingency option. On the other hand, deeper reservoir has higher risk of scaling due to its higher temperature, causing scale plugging easily in reservoir pores and production wells. For such reservoir, peripheral aquifer water injection, treated low-sulphate seawater with sulphate-removal system, or no water injection development concept should be selected. By using modelling and experiment to quantify the scale risk over a range of conditions, the field operator has identified opportunities to optimize the water injection strategy. The temperature dependence of the scale risk means, in principal, that different injection strategy for each reservoir can minimize flow assurance challenges and maximize return on investment in scale mitigation measures.

Anti-trypsin and antihypertensive activity of protein extracts from Nigella sativa seeds

Protease inhibitors (PIs) are a ubiquitous, diverse group of molecules present in multiple forms in all organisms. These inhibitors inactivate proteases from predators/pathogens in addition to regulating intracellular proteolysis. In addition to intracellular localization, storage organs of plants are also a potential site of protease inhibitors. Proteins with trypsin inhibitory activity were isolated from Nigella sativa seed extracts by ammonium sulphate precipitation. Extraction conditions were optimized by choosing an optimum solvent, temperature and incubation period. The highest inhibitory activity of protein extracts was achieved by using 50 mM Tris buffer as solvent and overnight incubation of the suspension at 4°C. The crude seed extract fractionated at 60% ammonium sulphate concentration exhibited highest trypsin inhibitory activity, i.e., 60.15 ± 2.95 %, which was comparable to soybean trypsin inhibitor used as positive control. Ammonium sulphate precipitation of crude extract yielded 39.83-fold purification. Partially purified trypsin inhibitor exhibited 2.39±0.23 TIU mg-1. Additionally, Nigella sativa protein extracts were also investigated for their health-promoting effects against two important proteases, α- Dipeptidyl peptidase-IV (DPP-IV) and angiotensin-converting enzyme (ACE). Highest inhibitory activity against ACE was shown by the crude extract of N. sativa. Among AS fractions, 30% ammonium sulphate concentration exhibited highest inhibition activity against ACE and DPP-IV. Our results suggest that the widely believed role of N. sativa in control of hypertension may at least be partially shared by inhibition of ACE. This is the first study conducted to evaluate the biological activity of N. sativa protein extracts suggesting a potential use of N. sativa proteins in management of hypertension as well as an important source of trypsin inhibitor. Further identification, purification and characterization of different bioactive compounds from N. sativa are being carried out.

An Investigation into Performance of Cement-Stabilized Kaolinite Clay with Recycled Seashells Exposed to Sulphate

Sulphate attack is one of the key issues in geotechnical engineering. This study aims to investigate the efficacy of the seashell to reduce negative impacts of the magnesium sulphate concentration on the cement-stabilized clay mixtures by performing a series of unconfined compressive strength (UCS) tests. Three percent of cement (3, 5 and 7%) was utilized in this study. In addition, the benchmark and exposed specimens were cured for 7, 14, and 28 days before testing and exposure, respectively. A series of the compaction tests were conducted and the optimum moisture content (OMC) and maximum dry density (MDD) values were achieved. In the next stage, the UCS tests were performed on the specimens containing 10, 20, or 30% seashell contents and the specimens were exposed to sulphate concentration. Scanning electron microscope morphology had indicated that seashells are a suitable replacement for cement. Qualitative X-ray diffraction had shown that the presence of magnesium sulphate reduces the formation of calcium silicate hydrate, which causes durability issues in cement-stabilized soils. The results indicated that seashell is effective to improve the sulphate resistance of cement-stabilized soil.

Application of Plackett Burman and Box Behnken Design for the Optimization of a-glucosidase Production by Thermophillic Thermomyces dupontii

A consecutive optimization based on statistical approach was applied for a-glucosidase production by both wild and mutant T. dupontii. Plackett Burman design (PBD) with two levels was employed in order to screen the significant effect of different nutritional and physical parameters through submerged fermentation. Among all nine variables tested in PBD, incubation time, inoculum size and ammonium sulphate concentration were selected. The Box-Behnken approach was further applied for process optimization. The a-glucosidase production for both wild and mutant T.dupontii was obtained at 72 h of incubation, 1.25 mL inoculum size and 0.25% ammonium sulphate concentration with relatively 95% correlation between the experimentally predicted and observed values. The duration of maximum enzyme production in RSM was cost-saving and fast. The quadratic model was in satisfactory adjustment with the experimental data with high R2 value which describes 98.90% of response variability of the model. Moreover, the novel approach of this present work is that, consecutive optimization were applied for maximum a-glucosidase production using response surface methodology by both wild and mutant thermophillic T. dupontii. Results revealed that thermophillic mutant T. dupontii could be potential candidate for industrial applications.

Uptake of Chromium by Portulaca Oleracea from Soil: Effects of Organic Content, pH, and Sulphate Concentration

Phytoextraction is an effective and environment-friendly approach for remediation of soil polluted with toxic metals. Portulaca oleracea is a potential hyperaccumulator of Cr(VI) from polluted soil. In this study, the effect of soil organic content, pH, and sulphate concentration on phytoextraction of Cr(VI) using Portulaca oleracea was investigated. Seedlings of Portulaca oleracea were grown in soils with (i) three organic content compositions, (ii) six levels of pH, and (iii) six concentrations of sulphate salts; all were irrigated with Cr(VI) solutions at 200 ppm concentration. Chromium concentration in different tissues of plants was monitored under the variant conditions. Results indicated that the uptake of Cr(VI) by Portulaca oleracea is favoured at (i) low organic content soil (0.42%), (ii) slightly alkaline pH range (∼8), and (iii) with sulphate concentration in the range of 300–600 ppm.

QTL and candidate genes associated with leaf anion concentrations in response to phosphate supply in Arabidopsis thaliana

Background Phosphorus is often present naturally in the soil as inorganic phosphate, Pi, which bio-availability is limited in many ecosystems due to low soil solubility and mobility. Plants respond to low Pi with a Pi Starvation Response, involving Pi sensing and long-distance signalling. There is extensive cross-talk between Pi homeostasis mechanisms and the homeostasis mechanism for other anions in response to Pi availability. Results Recombinant Inbred Line (RIL) and Genome Wide Association (GWA) mapping populations, derived from or composed of natural accessions of Arabidopsis thaliana, were grown under sufficient and deficient Pi supply. Significant treatment effects were found for all traits and significant genotype x treatment interactions for the leaf Pi and sulphate concentrations. Using the RIL/QTL population, we identified 24 QTLs for leaf concentrations of Pi and other anions, including a major QTL for leaf sulphate concentration (SUL2) mapped to the bottom of chromosome (Chr) 1. GWA mapping found 188 SNPs to be associated with the measured traits, corresponding to 152 genes. One of these SNPs, associated with leaf Pi concentration, mapped to PP2A-1, a gene encoding an isoform of the catalytic subunit of a protein phosphatase 2A. Of two additional SNPs, associated with phosphate use efficiency (PUE), one mapped to AT5G49780, encoding a leucine-rich repeat protein kinase involved in signal transduction, and the other to SIZ1, a gene encoding a SUMO E3 ligase, and a known regulator of P starvation-dependent responses. One SNP associated with leaf sulphate concentration was found in SULTR2;1, encoding a sulphate transporter, known to enhance sulphate translocation from root to shoot under P deficiency. Finally, one SNP was mapped to FMO GS-OX4, a gene encoding glucosinolate S-oxygenase involved in glucosinolate biosynthesis, which located within the confidence interval of the SUL2 locus. Conclusion We identified several candidate genes with known functions related to anion homeostasis in response to Pi availability. Further molecular studies are needed to confirm and validate these candidate genes and understand their roles in examined traits. Such knowledge will contribute to future breeding for improved crop PUE .

Carbon Dots Modification for Escherichia coli Detection: Variation of Colistin Sulphate Concentration

Escherichia coli (E. coli) bacteria widely recognize as a major treatment in water quality as diarrhea disease becoming one of leading causes of mortality worldwide. Carbon dots (CDs) modification study for detection of E. coli with the variation of colistin sulphate concentration has been conducted. The purpose of this research is to evaluate the effect of colistin sulphate concentration variation on fluorescence intensity for detecting E. coli bacteria in water samples. This study started by synthesizing CDs and CDs colistin variation concentrations of 1.0; 1.5; 2.0 and 2.5 mmol through carbonization of ammonium citrate and the addition of colistin. All precursors are characterized by using FT-IR. Morphological forms were evaluated with scanning emission microscopy (SEM) and transmission electron microscopy (TEM). CDs and CDs colistin solutions were measured their spectras with a UV-Vis spectrophotometer. Each of these CDs colistin was determined at the excitation wavelength ranges of 310-450 nm using a spectrofluorophotometer. Subsequently, CDs colistin was used for bacterial detection in samples with variation in E. coli bacteria concentration, thus analyzed by spectrofluorophotometer with an optimum excitation wavelength. The results showed that the highest intensity of fluorescence on CDs colistin occurred at the wavelength excitation of 360 nm. CDs colistin with the variation of colistin concentration 2.5 mmol revealed the highest fluorescence intensity. For the detection of E. coli, all CDs colistin produced the same trends of fluorescence spectra as the higher concentration of E. coli in the samples produced the higher intensity of emission.