Depositional Behaviour of Highly Macro-Crystalline Waxy Crude Oil Blended with Polymer Inhibitors in a Pipe with a 45-Degree Bend

Abstract Production, transportation and storage of highly waxy crude oil is very challenging. This is because they are usually characterised by high content of macro-crystalline waxes, predominantly consisting of n-alkanes (C18 to C36) that which could cause costly deposition within the wellbore and production equipment. The accumulation of deposited wax can decrease oil production rates, cause equipment breakdown, and clog the transport and storage facilities. Currently, different polymeric inhibitors have been utilised in the oil and gas field to mitigate and prevent wax deposition. However, as of today, there is no distinctive wax inhibitor that could work effectively for all oil fields. One of the objectives of this work is to study the efficacy of a blended commercial wax inhibitor - pour point depressant on wax deposition mitigation in a flow rig designed with 0 and 45-degree bends in the pipeline. Standard laboratory techniques using high-temperature gas chromatography (HTGC), rheometer rig, polarized microscope and elution chromatography were employed to obtain n-paraffin distribution, oil viscosity, WAT, pour point and SARA fractions. Series of experimentation were carried out with and without the inhibitor in a straight pipe test section. The severity of wax deposition in the pipeline built-in with a 45-degree bend is compared with a straight pipe. The blended inhibitor was tested at concentrations of 500, 1000, and 1500-ppm, under laminar and turbulent conditions. The crude oil sample was found to be naturally waxy with wax content of 19.75wt%, n-paraffin distributions ranges from C15-C74, WAT and pour point of 30°C and 25°C respectively. The severity of wax deposition in the test section is 43% higher in 45-degree bend compared to straight pipe. However, the severity of the deposition was reduced to 12.3% at extremely low temperature and flow rate. Nonetheless, better inhibition performance was achieved at 25 and 30°C. The wax thickness was reduced from δwax ≈ 0.36mm at 5 l/min to δwax ≈ 0.132mm at 7 l/min at constant coolant temperature (25°C) and 1500-ppm, whereas, no wax deposition was observed at 11 l/min. Mechanisms such as molecular diffusion due to frictional pressure losses, shear dispersion and gravity settling due to momentum change and hydrostatic, alongside with thermal difference are the main drivers for wax deposition in both straight and bend pipe. Whereas, the interaction mechanisms such as the nucleation, alongside with adsorption, co-crystallization, and solubilisation between the new blended inhibitor and the wax crystals provide an improved inhibition performance in the system even at extreme cases

Assessment of Absenteeism and Lateness among Hospitality and Tourism Students in Sunyani Polytechnic

The ultimate aim of every educational institution is to improve the quality of teaching and learning in order to achieve its set objectives. The quality of teaching and the worth of every school is to a large extent assessed on the basis of its academic achievement and how the students performed in the field level. However, it has been observed that, Hospitality and Tourism department in Sunyani Polytechnic face the problem of absenteeism and lateness among students. Nowadays, attitudes of students are constantly changing towards attending lectures. The study is aimed at investigating the causes of the absenteeism and lateness among the students in Hospitality and Tourism department and to seek for solutions to minimize these problems. The study is based on descriptive approach and primary data was mainly used to gather data from the students. The target population includes all students at the department of Hospitality and Tourism of Sunyani Polytechnic with an average age of 18 years.  Questionnaire was used to gather data from the respondents.  Data obtained from the study were analysed by using SPSS and the results were presented in the form of   tables. Results of the study showed that illness, financial constraint and distance to school were the major causes of lateness and absenteeism among students. It is recommended that, Management of Sunyani polytechnic as well as other stake holders such as the Student Representative Council (S.R.C.) should provide shuttle buses with moderate fare to convey students to and from school at various vintage points. Keywords: lateness, absenteeism, hospitality and touris

The effect of temperature on CO2 injectivity in sandstone reservoirs

Carbon Capture, Utilization and Storage (CCUS) is a pragmatic technology that could reduce anthropogenic CO2 and halt climate change. CO2 injectivity is affected by several physicochemical interactions around the injection area of the wellbore which are temperature-dependant. There is a thermal disequilibrium between the injected CO2 and the reservoir rock at the wellbore injection area which has not been thoroughly investigated. A pore-scale model was developed to predict the distance travelled by the injected fluid into the formation before thermal equilibrium is established. In the Snøhvit field where the wellhead injection temperature is 4 °C, it was found that the injected CO2 may attain supercritical state at bottomhole conditions, although a minimum temperature difference of about 40 °C may exist between the bottomhole fluid and the reservoir rock. Thermal equilibrium around the injection area was dependant on the wellhead injection temperature, the injection flow rate and reservoir shaliness.publishedVersio

An outbreak of pneumococcal meningitis among older children (≥5 years) and adults after the implementation of an infant vaccination programme with the 13-valent pneumococcal conjugate vaccine in Ghana.

BACKGROUND: An outbreak of pneumococcal meningitis among non-infant children and adults occurred in the Brong-Ahafo region of Ghana between December 2015 and April 2016 despite the recent nationwide implementation of a vaccination programme for infants with the 13-valent pneumococcal conjugate vaccine (PCV13). METHODS: Cerebrospinal fluid (CSF) specimens were collected from patients with suspected meningitis in the Brong-Ahafo region. CSF specimens were subjected to Gram staining, culture and rapid antigen testing. Quantitative PCR was performed to identify pneumococcus, meningococcus and Haemophilus influenzae. Latex agglutination and molecular serotyping were performed on samples. Antibiogram and whole genome sequencing were performed on pneumococcal isolates. RESULTS: Eight hundred eighty six patients were reported with suspected meningitis in the Brong-Ahafo region during the period of the outbreak. In the epicenter district, the prevalence was as high as 363 suspected cases per 100,000 people. Over 95 % of suspected cases occurred in non-infant children and adults, with a median age of 20 years. Bacterial meningitis was confirmed in just under a quarter of CSF specimens tested. Pneumococcus, meningococcus and Group B Streptococcus accounted for 77 %, 22 % and 1 % of confirmed cases respectively. The vast majority of serotyped pneumococci (80 %) belonged to serotype 1. Most of the pneumococcal isolates tested were susceptible to a broad range of antibiotics, with the exception of two pneumococcal serotype 1 strains that were resistant to both penicillin and trimethoprim-sulfamethoxazole. All sequenced pneumococcal serotype 1 strains belong to Sequence Type (ST) 303 in the hypervirulent ST217 clonal complex. CONCLUSION: The occurrence of a pneumococcal serotype 1 meningitis outbreak three years after the introduction of PCV13 is alarming and calls for strengthening of meningitis surveillance and a re-evaluation of the current vaccination programme in high risk countries

Investigation of the Severity of Wax Deposition in Bend Pipes Under Subcooled Pipelines Conditions

Abstract Curved pipes are essential components of subsea process equipment and some part of production pipeline and riser. So far, most of the studies on of wax deposition and the possible mitigation strategies have been carried out using straight pipelines, with little attention given to curved pipes. Therefore, the objective of this study is to use an experimental flow loop designed and assembled in the lab to study and understand the mechanisms and variable parameters that affect wax depositional behaviour under the single-phase flow. Series of experiments were carried out with pipes curvatures of 0, 45 and 90-degree at different flow rates (2 and 11 L/min). The sequence in which the bends are incorporated creates non-uniformity of boundary shear, flow separation, and caused isolation of fluid around the bends that affect wax deposition, which depends on flow regimes – Reynolds number along with the radius of curvature of the bend. Prior to the flow loop experiment, the waxy crude oil was characterized by measuring the viscosity, WAT (30°C), pour point (25.5°C), n-Paraffin distribution (C10 - C67), and the saturated/aromatic/resin/asphalte (SARA) fractions Results of this study shows that the wax deposit thickness decreases at higher flow rate within the laminar (Re<2300) and turbulent (Re>2300) flow regimes. It was observed that the deposition rate was significantly higher in curved pipes, about 8 and 10% for 45 and 90-degree, respectively in comparison to the straight pipe for all flow conditions. Increase elevation of the curved pipe, however, led to a more wax deposition trend; where a higher percentage of wax deposit was observed in 45-degree compared to 90-degree curved pipe. This trend was due addition of gravity forces to the frictional forces - influenced by the physical mechanisms of wax deposition mainly molecular diffusion, shear dispersion and gravity settling. From the results of this study, a new correlation between wax deposit thickness and pressure drop was developed. A relationship was established between wax deposit thicknesses, bend angle in pipes and wax deposition mechanisms with a reasonable agreement with published data, especially for steady state condition. Therefore, this study will enhance the understanding of the wax deposition management and improve predictions for further development of a robust mitigation strategy

A critical review of carbonate reservoir wettability modification during low salinity waterflooding

The nature of carbonate reservoirs promotes the adsorption of oil onto the rock surface hence making oil recovery a challenge even with the interventions of varied chemical EOR methods. Recently, low salinity water flooding has become of great interest since it is cost-effective and environmentally friendly. Although low salinity waterflooding has been highly investigated in sandstone reservoirs, it is not the same for carbonate reservoirs due to its complexities. Nonetheless, it has been proposed as a favourable technique to mobilise the trapped oil in carbonate reservoirs. Wettability alteration is regarded as the most accepted mechanism for low salinity flooding but has not been well understood making field scale applications doubtful. In this paper, we present a detailed review of the wettability alteration mechanisms in carbonate reservoirs during low salinity waterflooding. Parameters influencing wettability alteration in carbonates and the interactions that occur at the rock/brine/oil interface are also presented. The different methods utilised for wettability measurements during low salinity waterflooding are also reviewed including their drawbacks and advantages and recommendations. This will provide an improved understanding of the low salinity flooding application in carbonate reservoirs

Pyrolysis of municipal food waste: A sustainable potential approach for solid food waste management and organic crop fertilizer production

ABSTRACTFood waste can be converted to a useful product such as biochar as a way of recycling waste to retain nutrients in the soil, which in turn contributes to carbon sequestration and offset some greenhouse gas emissions in the struggle to achieve carbon neutrality. Mixed food waste-derived biochars (FWB1–300°C, FWB2–450°C and FWB3–600°C) were pyrolysed at 300°C, 450°C and 600°C, respectively, using an electric kiln. Tests for physiochemical parameters and germination tests were performed. It was realized that at 300°C biochars produced had high nitrogen, organic matter, bulk density, biochar yield, and longer root lengths. The results indicate that municipal food waste biochars produced at three temperatures were suitable for use as fertilizer. However, biochar produced at a moderately lower temperature is favourable for agriculture purposes, FWB1–300°C and FWB2–450°C obtained moderate pH and ash levels and so are less toxic to the growth of plants

Zeta potential prediction of dominant sandstone minerals via surface complexation modelling

Numerous injection water compositions have been developed by various researchers to optimize the oil recovery via wettability alteration. The ionic composition of the injected brine plays a profound role in the rock/brine and crude-oil/brine interfacial charge thereby its role is pivotal in oil recovery. Numerous experimental techniques have been used to assess the potential of injected brines to optimize wettability via wettability alteration. Notably among them are the spontaneous imbibition, contact angle and core flooding techniques. Zeta potential (ζ-potential) has been used by some researcher to evaluate the wettability alteration during crude oil/brine/rock interactions. However, ζ-potential measurement is relatively expensive and time consuming. Hence, the need for relatively cheap and easy approach of ζ-potential measurements. This was accomplished using Surface Complexation Modelling (SCM) via PHREEQ-C. The focus of this study was to predict ζ-potential using SCM. The qualities and quantities of the materials used during the existing experiment from literature were also used as input in the SCM. Dominant minerals in sandstone reservoir rock notably quartz, calcite, dolomite, kaolinite, illite, montmorillonite, chlorites, ilmenite, muscovite, biotite and anorthoclase were considered in this study. The SCM technique could capture the trend during the ζ-potential measurements. However, out of the 39 mineral-brine ζ-potential measured, the SCM approach could not capture the trend in 5 of these samples namely; dolomite/0.5wt% NaCl (pH = 9.5), microcline/SW (pH = 7.8), muscovite/SW (pH = 7.8), chlorite/SW (pH = 7.8) and ilmenite/20% Dil-SW (pH = 7.6). This was attributed to the effect of atmospheric CO2 on the pH of the brine during the ζ-potential measurement. The ζ-potential of carbonates (calcite and dolomite) were predominantly positive while that of tectosilicates (Quartz, Anorthoclase and Microcline), phyllosilicates (Montmorillonite, Kaolinite, Biotite, Illite, Muscovite and Chlorites) and oxides (Ilmenite) were also predominantly negative. For instance, at the calcite-SW (pH = 7.9) interface, the predicted a ζ-potential value was 20.5 mV while its measured value was observed to be 12.9 mV. The dolomite-SW (pH = 7.9) also predicted 16.7 mV and 19.7 mV for the predicted and the measured ζ-potential value respectively. Considering quartz, anorthoclase and microcline with 0.5wt% NaCl (pH = 7.9), the predicted ζ-potential values were observed to be -11.65 mV, -24.21 mV and -43.00 mV while the measured values were also observed to be -16.9 mV, -33.8 mV and -36.5 mV respectively

Epidemiological profile of SARS-CoV-2 among selected regions in Ghana: A cross-sectional retrospective study.

BackgroundGlobal cases of COVID-19 continue to rise, causing havoc to several economies. So far, Ghana has recorded 48,643 confirmed cases with 320 associated deaths. Although summaries of data are usually provided by the Ministry of Health, detailed epidemiological profile of cases are limited. This study sought to describe the socio-demographic features, pattern of COVID-19 spread and the viral load dynamics among subjects residing in northern, middle and part of the southern belt of Ghana.MethodsThis was a cross-sectional retrospective study that reviewed records of samples collected from February to July, 2020. Respiratory specimens such as sputum, deep-cough saliva and nasopharyngeal swabs were collected from suspected COVID-19 subjects in 12 regions of Ghana for laboratory analysis and confirmation by real-time reverse transcription polymerase chain reaction (RT-PCR).ResultsA total of 72,434 samples were collected during the review period, with majority of the sampled individuals being females (37,464; 51.9%). The prevalence of SARS-CoV-2 identified in the study population was 13.2% [95%CI: 12.9, 13.4). Males were mostly infected (4,897; 51.5%) compared to females. Individuals between the ages 21-30 years recorded the highest number of infections (3,144, 33.4%). Symptomatic subjects had higher viral loads (1479.7 copies/μl; IQR = 40.6-178919) than asymptomatic subjects (49.9; IQR = 5.5-3641.6). There was significant association between gender or age and infection with SARS-CoV-2 (pConclusionThis study has described the epidemiological profile of COVID-19 cases in northern, middle and part of the southern belt of Ghana, with males and younger individuals at greater risk of contracting the disease. Health professionals should be conscious of individuals presenting with anosmia since this was seen as the strongest predictor of virus infection

Using drones to transport suspected COVID-19 samples; experiences from the second largest testing centre in Ghana, West Africa.

BackgroundThe declaration of COVID-19 as a pandemic on March 11 2020, by the World Health Organisation prompted the need for a sustained and a rapid international response. In a swift response, the Government of Ghana, in partnership with Zipline company, launched the use of Unmanned Automated Vehicles (UAV) to transport suspected samples from selected districts to two foremost testing centres in the country. Here, we present the experiences of employing this technology and its impact on the transport time to the second largest testing centre, the Kumasi Centre for Collaborative Research in Tropical Medicine (KCCR) in Kumasi, Ghana.MethodsSwab samples collected from suspected COVID-19 patients were transported to the Zipline office by health workers. Information on the samples were sent to laboratory personnel located at KCCR through a WhatsApp platform to get them ready to receive the suspected COVID-19 samples while Zipline repackaged samples and transported them via drone. Time of take-off was reported as well as time of drop-off.ResultsA total of 2537 COVID-19 suspected samples were received via drone transport from 10 districts between April 2020 to June 2021 in 440 deliveries. Ejura-Sekyedumase District Health Directorate delivered the highest number of samples (765; 30%). The farthest district to use the drone was Pru East, located 270 km away from KCCR in Kumasi and 173 km to the Zipline office in Mampong. Here, significantly, it took on the average 39 minutes for drones to deliver samples compared to 117 minutes spent in transporting samples by road (pConclusionThe use of drones for sample transport during the COVID-19 pandemic significantly reduced the travel time taken for samples to be transported by road to the testing site. This has enhanced innovative measures to fight the pandemic using technology