Petrophysical evaluation of sandstone reservoir of well E-AH1, E-BW1 and E-L1 Central Bredasdorp Basin, offshore South Africa

Magister Scientiae - MScThe Bredasdorp basin is a sub-basin of the greater Outeniqua basin. It is located off the south coast, Southeast of Cape Town, South Africa. This basin is one of the largest hydrocarbon (mainly gas) producing basins within Southern Africa. The petrophysical characteristic of the E-block sandstone units within the Bredasdorp basin has been studied to evaluate their hydrocarbon potential. The data sets used in this research were wireline logs (Las format), core data, and geological well completion reports. The three studied wells are E-AH1, E- BW1 and E-L1. The evaluated interval ranges from 2000.33m to 3303.96m in depth with reference to Kelly bushing within the wells. The sandstone reservoirs of the Bredarsdorp basin are characterized by a range of stacked and amalgamated channels. They originated from materials eroded from pre-existing high stand shelf sandstone and transported into the central Bredarsdorp basin by turbidity current. These sandstones are generally in both synrift and drift section. The basin is thought to have developed from fan deltas and stream overwhelmed to water dominated delta. River dominated deltaic system progresses southward over the Northern edge of the central Bredasdorp basin. The Interactive Petrophysics (IP) software has been used extensively throughout the evaluation and development of interpretation model. The lithofacies of the rock units were grouped according to textural and structural features and grain sizes of well (E-AH1, E-BW1 and E-L1). Four different facies (A, B, C and D) were identified from the cored intervals of each well. Facies A was classified as a reservoir and facies B, C and D as a non-reservoir. Detailed petrophysical analyses were carried out on the selected sandstone interval of the studied wells. The cut-off parameters were applied on the seven studied sandstone interval to distinguish between pay and non-pay sand and all intervals were proved to be producing hydrocarbon. Volume of clay, porosity, water saturation and permeability were calculated within the pay sand interval. The average volume of clay ranged from 23.4% to 25.4%. The estimated average effective porosity ranged from 9.47% to 14.3%. The average water saturation ranged from 44.4% to 55.6%. Permeability ranged from 0.14mD to 79mD. The storage and flow capacity ranged from 183.2scf to 3852scf and 2.758mD-ft to 3081mD-ft respectively. The geological well completion reports classify these wells as a gas producing wells. E-L1 is estimated to have a potential recoverable gas volume of 549.06 cubic feet, E-BW1 is estimated to have 912.49 cubic feet and E-AH1 is estimated to have 279.69 cubic feet

Investigation of the acoustic impedance variations of the upper shallow marine sandstone reservoirs in the Bredasdorp basin, offshore South Africa

Philosophiae Doctor - PhDInvestigation of the acoustic impedance variations in the upper shallow marine sandstone reservoirs was extensively studied from 10 selected wells, namely: F-O1, F-O2, E-M4, E-CN1, E-G1, E-W1, F-A10, F-A11, F-A13, and F-L1 in the Bredasdorp Basin, offshore, South Africa. The studied wells were selected randomly across the upper shallow marine interval with the purpose of conducting a regional study to assess the variations in the acoustic impedance across the reservoirs using wireline log and core data. The datasets used in this study were geophysical wireline logs, conventional core analysis, geological well completion reports, core plugs, and core samples. The physical rock properties such as lithology, fluid type, and hydrocarbon bearing zone were identified while different parameters like the volume of clay, porosity, and water saturation were quantitatively estimated. The reservoirs were penetrated at a different depth ranging from a shallow depth of 2442m at well F-L1 to a deeper depth of 4256.7m at well E-CN1. The average volume of clay, average effective porosity from wireline log, and average water saturation ranged from 8.6%- 43%, 9%- 16% and 12%- 68%, respectively. Porosity distribution was fairly equal across the field from east to west except in well F-A10, F-A13, and F-A11 where a much higher porosity was shown with F-A13 showing the highest average value of 16%. Wells E-CN1, E-W1, F-O1, F-L1 and E-G1 had lower porosity with E-CN1 showing the lowest average value of 9%. The acoustic properties of the reservoirs were determined from geophysical wireline logs in order to calculate acoustic impedance and also investigate factors controlling density and acoustic velocities of these sediments. The acoustic impedance proved to be highest on the central to the western side of the field at E-CN1 with an average value of 11832 g/cm3s whereas, well F-A13 reservoir in the eastern side of the field proved to have the lowest average acoustic impedance of 9821 g/cm3s. There was a good linear negative relationship between acoustic impedance and porosity, compressional velocity vs porosity and porosity vs bulk density. A good linear negative relationship between acoustic impedance and porosity was obtained where the reservoir was homogenous, thick sandstone. However, interbedded shale units within the reservoir appeared to hinder a reliable correlation between acoustic impedance and porosity. The cross-plots results showed that porosity was one of the major factors controlling bulk density, compressional velocity (Vp) and acoustic impedance. The Gassmann equation was used for the determination of the effects of fluid substitution on acoustic properties using rock frame properties. Three fluid substitution models (brine, oil, and gas) were determined for pure sandstones and were used to measure the behaviour of the different sandstone saturations. A significant decrease was observed in Vp when the initial water saturation was substituted with a hydrocarbon (oil or gas) in all the wells. The value of density decreased quite visibly in all the wells when the brine (100% water saturation) was substituted with gas or oil. The fluid substitution affected the rock property significantly. The Vp slightly decreases when brine was substituted with water in wells F-A13, F-A10, F-O2, F-O1 F-A11, F-L1, and E-CN1. Wells E-G1, E-W1, and E-M4 contain oil and gas and therefore showed a notable decrease from brine to oil and from oil to gas respectively. Shear velocity (Vs) remained unaffected in all the wells. The acoustic impedance logs showed a decrease when 100% water saturation was replaced with a hydrocarbon (oil or gas) in all the wells. Clay presence significantly affects the behaviour of the acoustic properties of the reservoir rocks as a function of mineral type, volume, and distribution. The presence of glauconite mineral was observed in all the wells. Thirty-two thin sections, XRD and SEM/EDS from eight out of ten wells were studied to investigate lithology, diagenesis and the effect of mineralogy on porosity and acoustic properties (Compressional velocity and bulk density) within the studied reservoir units. Cementation (calcite and quartz), dissolution, compaction, clay mineral authigenesis, and stylolitization were the most significant diagenetic processes affecting porosity, velocity, and density.Well E-CN1 reservoir quality was very poor due to the destruction of intergranular porosity by extensive quartz and illite cementation, and compaction whereas well F-A13 show a highly porous sandstone reservoir with rounded monocrystalline quartz grain and only clusters of elongate to disc-like, authigenic chlorite crystals partly filling a depression within altered detrital grains. Overall, the results show that the porosity, lithology mineralogy, compaction and pore fluid were the major factors causing the acoustic impedance variations in the upper shallow marine sandstone reservoirs

Influences of river flows on recruitment success of Fynbos riparian vegetation along selected high gradient streams in the Western Cape, South Africa

>Magister Scientiae - MScRiparian vegetation occurs in two distinct zones, the wet bank and the dry bank. Knowledge on how the flow regime influences the zonal structure of riparian vegetation is required to mitigate the adverse effects of water resource utilization on riparian vegetation. The first objective of this study was to determine whether flow exerts a physical influence on zonal structure pre- or post-recruitment. An examination of the survival of seedlings and saplings was conducted along Western Cape rivers to investigate seedling persistence and survival on lateral zones. A comparison of the ratios of seedlings, saplings and adults in different riparian zones for the years, 2004, 2011 and 2013, was carried out. The results suggest that in general seeds are deposited randomly on the banks, where they germinate and become seedlings. Seedlings that become established at locations unsuitable for their persistence into adulthood are removed either by high flows or perish during dry conditions. Thus, lateral zonation eventually develops due to species differences in tolerance to conditions at different positions on the banks. The second objective was to explore the effects of the reduction in dry season low flows on the recruitment success of riparian species at sites upstream and downstream of abstraction points. At most sites plants were arranged into different lateral zones and the numbers of species between upstream and downstream sites were not significantly different. There were significant differences in the abundances between up- and downstream sites, with the loss of herbaceous plants and sedges at downstream sites, both of which favour moist conditions. Also, in the absence of dry season flows, the seedlings of dry bank tree species recruited closer to the channel than those at the sites with summer flows. The shifting of the dry bank into the channel narrows the channel, which may affect the hydraulic pressures exerted during floods. The spatial arrangement in the riparian zone has as much to do with flow conditions post recruitment as it does with conditions during recruitment. This shows that the structure of riparian plants is determined not only by whether or not the minimum flows are met, this points to the need to reinstate the naturally variable flow and adopting a holistic approach for the understanding and management of aquatic systems

Motivated strategies for learning questionnaire - modeling the relationship between motivational beliefs, cognitive learning strategies and academic performance of Mathematics teacher-trainees

Paper presented at the 4th Strathmore International Mathematics Conference (SIMC 2017), 19 - 23 June 2017, Strathmore University, Nairobi, Kenya.Self-regulated learning refers to the conscious planning, monitoring, and evaluation of one’s own learning through use of appropriate behavioral, meta-cognitive and cognitive strategies to enhance academic performance. Self-regulated learners are highly motivated, use a variety of learning strategies in achieving their academic goals and as such are high achievers. Although self-regulated learning has received much attention over the past decades, research on how teacher-trainees regulate their own learning has been scarce and especially in third world countries. Lack of research in this aspect has not only created a knowledge gap but also compromised efforts to tackle to challenge of poor academic performance among teacher trainees. In this study, we examined the relationship between motivational beliefs, cognitive learning strategies and academic performance among Mathematics teacher-trainees in Uganda. The sample comprised of 689 undergraduate students randomly selected from eight universities across Uganda. Data was collected using the Motivated Strategies for Learning Questionnaire (MSLQ) and analysed using structural equation modeling. A structural equation model indicated that cognitive learning strategies mediated the relationship between motivational beliefs and academic performance of these undergraduate teacher-trainees. Motivational beliefs influenced student’s performance through enhancing their critical thinking and organization learning strategies. Therefore, there is need to enhance leaner’s ability to adopt adaptive learning strategies in-order to enhance their academic achievement at the university

Comparative impact of invasive alien trees and vineyards on arthropod diversity in the Cape floristic region, Western Cape

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Invasive alien trees (IATs) and agriculture are rapidly altering the capacity of ecosystems to provide a variety of essential services, with decreasing habitat quality having an adverse effect on arthropod biodiversity. Although both agricultural intensification and IATs have an impact on ecosystems, it is unclear which of these two is currently the most severe. Here I compare the influences of vineyards and IATs on arthropod diversity in the Cape Floristic Region (CFR) from two perspectives. Firstly, insect diversity from four different vegetation types (native fynbos, IATs, cleared invasive alien trees (CIATs) and vineyards), and their ecotones were assessed. Secondly, soil compaction in the different vegetation types was assessed and compared to determine how soil compaction relates to arthropod species richness and abundance. Surface-active arthropods were used for these evaluations, as they were considered to be the most abundant, yet sensitive groups for these comparative assessments. Pitfall trapping, which has been widely used for such comparative studies, was the method of choice. Additionally, as a result of incidental wildfires at some of the study sites (IATs and fynbos vegetation), it was decided opportunistically to assess recovery of arthropod diversity following the impact of fire. The results categorically indicate that IATs had by far the most significant impact, in comparison with vineyards, in reducing arthropod diversity and changing assemblage composition. Both IATs and vineyards, not surprisingly, supported lower arthropod diversity compared to fynbos, while CIATs supported arthropod species richness comparable to that of fynbos. However, different invertebrate species responded differently to IAT invasion, with some species even adapted to conditions in IAT patches. Environmental factors such as leaf litter and soil compaction were strongly correlated with arthropod species richness. However, other factors, such as soil moisture content, were not correlated with species richness, despite varying significantly between different vegetation types. IATs were found to reduce soil compaction, while vineyards increased soil compaction. The ecotone between adjacent land-use types was important for sustaining high arthropod species richness, particularly for the CIATs/fynbos ecotone, followed by the interface between CIATs/vineyard and vineyard/fynbos. Some species even preferred ecotones. Surface-active invertebrate species richness declined substantially immediately after fire in both IATs and fynbos. Nevertheless, recovery was rapid, with some species recolonizing or re-establishing within three months. Indeed, both species richness and abundance were high following fire. Fire had no significant impact on arthropod assemblage within IATs, despite having a serious impact in the fynbos where a different arthropod assemblage was observed after fire. The recovery of the historic assemblages may be dependent on both the pre-fire composition of the habitat and its adjacent vegetation. Effective co-operation among conservation biologists, farmers, and landowners to actively plan the future of CFR landscape biodiversity is required.AFRIKAANSE OPSOMMING: Indringer uitheemse bome (IUB) en landbou bedrywighede is vinnig besig om die kapasiteit van ekosisteme vir die voorsiening van „n verskeidenheid van noodsaaklike dienste, met „n afname in habitatkwaliteit en „n nadelige uitwerking op artropood biodiversiteit, te verander. Alhoewel beide, landbou intensifikasie en IUB‟s, ‟n impak op ekosisteme uitoefen, is dit onduidelik watter van hierdie twee huidig die mees ernstige een is. In hierdie studie vergelyk ek die invloed van wingerde en IUB‟s op artropood diversiteit in die Kaapse Floristiese Streek (KFS) vanuit twee perspektiewe. Eerstens, insekdiversiteit van vier verskillende vegetasietipes (natuurlike fynbos, IUB‟s, verwyderde indringer uitheemse bome (VIUB‟s) en wingerde) en hulle ekotone is bepaal. Tweedens, is grondverdigting in en van die verskillende vegetasietipes ondersoek en vergelyk om te bepaal hoe grondverdigting verband hou met artropood spesies rykheid en volopheid. Oppervlak-aktiewe artropode is vir hierdie bepalings gebruik aangesien hulle beskou word as die mees volopste, maar ook mees sensitiewe groepe vir hierdie vergelykende bepalings. Pitvalvangste, wat alom gebruik word vir sulke vergelykende studies, was die verkose werkswyse. Bykomend, as gevolg van onbeplande veldbrande in sommige studie gebiede (IUB‟s en fynbos plantegroei), is oppertunisties van die geleentheid gebruik gemaak om die herstel van artropood diversiteit na die impak van brand te bepaal. Die resultate toon duidelik aan dat IUB‟s, in vergelyking met wingerde, by verre die mees beduidende impak gehad het deur ‟n verlaging van artropood diversiteit en veranderende groeperingssamestellings. Beide, IUB‟s en wingerde, het, nie onverwags nie, in vergelyking met fynbos, laer artropood diversiteit ondersteun, terwyl VIUB‟s artropood spesies verskeidenheid, vergelykbaar met dié van fynbos, ondersteun het. Verskillende invertebrate spesies het egter verskillend gereageer op IUB indringing, en sommige spesies het selfs by toestande in IUB kolle aangepas. Omgewingsfaktore soos blaarafval en grondverdigting was sterk gekorrelleer met artropood spesies rykheid. Ander faktore, soos grondvoginhoud, was egter nie in ooreenstemming met spesies rykheid nie, ten spyte van ‟n beduidende wisseling tussen verskillende vegetasietipes. IUB‟s het grondverdigting verminder, terwyl by wingerde grondverdigting toegeneem het. Die ekotone tussen aanliggende grondgebruike was belangrik om hoë artropood spesies rykheid, veral by die VIUB‟s/fynbos ekotoon, gevolg deur die kontaksones tussen VIUB‟s/wingerd en wingerd/fynbos, te onderhou. Sommige spesies het selfs ekotone verkies. Oppervlak-aktiewe invertebraat spesies rykheid het onmiddelik na brand in beide, IUB‟s en fynbos, wesenlik afgeneem. Tog was herstel vinnig, met sekere spesies wat binne drie maande teruggekeer of hulle hervestig het. Inderdaad was beide, spesies rykheid en volopheid, hoog na ‟n brand. Brand het geen noemenswaardige invloed op artropood groeperings binne IUB‟s gehad nie, ten spyte van ‟n ernstige impak in fynbos waar ‟n verskillende artropood groepering na ‟n brand waargeneem is. Die herstel van die historiese groeperings van beide, die voor-brand samestelling van die habitat en sy aangrensende plantegroei, mag afhanklik wees. Effektiewe en aktiewe samewerking tussen bewaringsbioloë, boere, en grondeienaars om die toekoms van KFS landskap biodiversiteit te beplan, word benodig

Examining the causal relationships between enjoyment and motivation of high school students towards learning of Mathematics: evidence using autoregressive and cross lagged models

Paper presented at the 4th Strathmore International Mathematics Conference (SIMC 2017), 19 - 23 June 2017, Strathmore University, Nairobi, Kenya.Previous studies have demonstrated a high relationship between student’s motivation and their related enjoyment in learning Mathematics. Apparently, highly motivated students enjoy learning Mathematics just as high Mathematics enjoyment affects subsequent motivation in learning Mathematics. Therefore, in this concept paper, we describe a longitudinal panel survey in which we examine the causal relationship between Mathematics enjoyment and Mathematics motivation among students beginning secondary school education. Three waves of data will be collected with an interval of 3 months starting from March 2017, from four schools in South Western Uganda (N = 1734) using the Math Enjoyment and Math Motivation scales. Data will be analyzed by means of cross-lagged and auto-regressive models (using Mplus 7.4) to answer the following two questions; a) To what extent are students’ motivation and enjoyment in learning Mathematics stable as they progress through year one of lower secondary education? b) What are the causal relationships between Mathematics enjoyment and motivation among senior one student’s? Findings from this baseline study will enable us to develop sustainable interventions to boost learner’s motivation and enjoyment in studying mathematics as early as the first year of secondary school education

Soil compaction and surface-active arthropods in historic, agricultural, alien, and recovering vegetation

Soil compaction is a major threat to natural resources. However, little information is available on the impacts of soil compaction on arthropod diversity especially relative to different types of vegetation, land use and restoration activities. In response to this dearth of information, we studied soil compaction, as well as percentage soil moisture and mean leaf litter depth, associated with four vegetation types: natural vegetation (fynbos, the historic condition), agricultural land (vineyards), invasive alien trees, and vegetation cleared of invasive alien trees (recovering vegetation). Our study took place in the Cape Floristic Region, South Africa, a biodiversity hotspot, yet also an area of intense viticulture and heavy invasion by alien plants. We sampled soil surface-active arthropods using pitfall traps, and compared species richness and abundance in different vegetation types with various levels of soil compaction and other soil variables. Overall, vineyards had the highest soil compaction while natural fynbos and aliens had low and comparable compaction. For both arthropod species richness and abundance, the order of the four vegetation types was, from highest to lowest: natural fynbos, alien cleared sites, vineyards, and alien infested sites. Level of soil compaction negatively correlated with arthropod species richness but not with abundance. Neither soil moisture nor leaf litter depth on their own significantly affected arthropod species richness or abundance. While alien trees overall had a strong negative effect on both arthropod species richness and abundance, and much more so than vineyards, the situation is reversible, with removal of aliens being associated with rapid recovery of soil structure and of arthropod assemblages. This is an encouraging sign for restoration

A Latent profile analysis of the Science teacher-trainees’ self-regulated learning strategies

Paper presented at the 4th Strathmore International Mathematics Conference (SIMC 2017), 19 - 23 June 2017, Strathmore University, Nairobi, Kenya.In the present study, we conducted a latent profile analysis to identify three clusters of Science teacher-trainees based on their self-regulated learning strategies. The sample comprised of 527 undergraduate teacher-trainees (Mean age = 22 years; SD = 2.20) randomly selected from seven universities in Uganda. Data was collected using the modified Motivated Strategies for Learning Questionnaire (MSLQ). These profiles including the (a) competent/expert self-regulated learners (259 students; 49.2%), (b) average self-regulated learners (193 students; 36.6%), and (c) novice self-regulated learners (75 students; 14.2%) differed significantly with respect to their motivational beliefs and academic performance, with the expert and average self-regulated learning profiles having better grade point average (GPA) scores and higher motivation compared to students in the novice self regulated learning profile. All profiles were similar with respect to age, gender and year of study. Additionally, task value and self-efficacy (but not demographic characteristics) significantly predicted latent profile membership. It is therefore important to understand such individual differences among science teacher-trainees in order to improve on their self regulated learning skills. Further implications are discussed in the paper.Mbarara University of Science and Technology, Mbarara, Ugand

The Role of Problem-Based Learning Approach in Teaching and Learning Physics: A Systematic Literature Review [version 2; peer review: 1 approved, 3 approved with reservations]

Problem-based learning (PBL) is a learner-centered method in which complex real-world problems are used to stimulate students thinking and problem-solving abilities during the teaching and learning process. This systematic review aimed to reveal the role of the PBL approach in teaching and learning physics. Relevant articles for the review were sourced from Scopus and Web of Science using keywords such as “problem-based learning” and “PBL in physics” education” as search terms. This search yielded 376 results. Thirty-six articles were included in the analysis after passing a crucial condition of empirically investigating the effect of PBL in teaching and learning physics. Only three of these articles did not show a positive effect; others have shown a positive lead of PBL towards improving academic achievement, attitude to learn physics, problem-solving, critical and creative thinking abilities, cooperative learning enhancement, mental model development, and science process skills attainment. Therefore, the review offers important pointers to various classroom environments and activities that ignite learners’ thinking. Thus, it help policymakers to select and maintain the best methodology that promotes high students’ academic achievement levels

Modeling the relationship between motivational beliefs, cognitive learning strategies and academic performance of Mathematics teacher-trainees

Paper presented at the 4th Strathmore International Mathematics Conference (SIMC 2017), 19 - 23 June 2017, Strathmore University, Nairobi, Kenya.Self-regulated learning refers to the conscious planning, monitoring, and evaluation of one’s own learning through use of appropriate behavioral, meta-cognitive and cognitive strategies to enhance academic performance. Self-regulated learners are highly motivated, use a variety of learning strategies in achieving their academic goals and as such are high achievers. Although self-regulated learning has received much attention over the past decades, research on how teacher-trainees regulate their own learning has been scarce and especially in third world countries. Lack of research in this aspect has not only created a knowledge gap but also compromised efforts to tackle to challenge of poor academic performance among teacher trainees. In this study, we examined the relationship between motivational beliefs, cognitive learning strategies and academic performance among Mathematics teacher-trainees in Uganda. The sample comprised of 689 undergraduate students randomly selected from eight universities across Uganda. Data was collected using the Motivated Strategies for Learning Questionnaire (MSLQ) and analysed using structural equation modeling. A structural equation model indicated that cognitive learning strategies mediated the relationship between motivational beliefs and academic performance of these undergraduate teacher-trainees. Motivational beliefs influenced student’s performance through enhancing their critical thinking and organization learning strategies. Therefore, there is need to enhance leaner’s ability to adopt adaptive learning strategies in-order to enhance their academic achievement at the university.Mbarara University of Science and Technology, Mbarara, Uganda Univesity of Potsdam, Potsdam, Germany Kyambogo University, Kampala, Uganda – [email protected]