Petroleum System Analysis: Middle Magdalena Valley Basin, Colombia, South America

The purpose of this study is to create a petroleum system model and to assess whether or not the La Luna Formation has potential for unconventional exploration and production in the Middle Magdalena Valley Basin (MMVB), Colombia. Today, the Magdalena River valley is an intermontane valley located between the Central and Eastern Cordillera of Colombia. The underlying basin, however, represents a major regional sedimentary basin that received deposits from the Triassic through the Cenozoic. In recent years Colombia has been of great exploration interest because of its potentially vast hydrocarbon resources, existing petroleum infrastructure, and skilled workforce. Since the early 1900s when the MMVB began producing, it has led to discoveries of 1.9 billion barrels of oil (BBO) and 2.5 trillion cubic feet (Tcf) of gas (Willatt et al., 2012). Colombia is already the third largest producer of oil in South America, and there is good potential for additional unconventional exploration and production in the Cretaceous source rocks (Willatt et al., 2012). Garcia Gonzalez et al. (2009) estimate the potential remaining hydrocarbons in the La Luna Formation in the MMVB to be between 1.15 and 10.33 billion barrels of oil equivalent (BBOE; P90 and P10 respectively), with 2.02 BBOE cumulative production to date. Throughout the 1900s and early 2000s, Cenozoic continental and transitional clastic reservoirs were the primary exploration interest in the MMVB (Dickey, 1992). The Cretaceous source rocks, such as the La Luna Formation, are now the target for unconventional exploration and production. In the MMVB, the La Luna formation is characterized by relatively high total organic carbon (TOC) values, moderate maturity, and adequate thickness and depth (Veigal and Dzelalijal, 2014). The La Luna Formation is composed of Cenomanian-Santonian aged shales, marls, and limestones (Veigal and Dzelalijal, 2014). In addition to the in-situ hydrocarbons, the fractured limestones in the La Luna formation act as secondary reservoirs for light oil from other formations (Veigal and Dzelalijal, 2014). Thus the system can be considered more of a hybrid play, rather than a pure unconventional play. The Cretaceous source rocks of the MMVB exhibit excellent potential for unconventional exploration and production. Due to the complex structural nature of the MMVB, an understanding of the distribution of rocks and variations in rock qualities is essential for reducing risk in this play.

Synthesis and characterization of K2Ca5(SO4)6· H2O, the equivalent of görgeyite, a rare evaporite mineral

Görgeyite, K2Ca5(SO4)6··H2O, is a very rare monoclinic double salt found in evaporites related to the slightly more common mineral syngenite. At 1 atmosphere with increasing external temperature from 25 to 150 °C, the following succession of minerals was formed: first gypsum and K2O, followed at 100 °C by görgeyite. Changes in concentration at 150 °C due to evaporation resulted in the formation of syngenite and finally arcanite. Under hydrothermal conditions, the succession is syngenite at 50 °C, followed by görgyeite at 100 and 150 °C. Increasing the synthesis time at 100 °C and 1 atmosphere showed that initially gypsum was formed, later being replaced by görgeyite. Finally görgeyite was replaced by syngenite, indicating that görgeyite is a metastable phase under these conditions. Under hydrothermal conditions, syngenite plus a small amount of gypsum was formed, after two days being replaced by görgeyite. No further changes were observed with increasing time. Pure görgeyite showed elongated crystals approximately 500 to 1000 µ m in length. The infrared and Raman spectra are mainly showing the vibrational modes of the sulfate groups and the crystal water (structural water). Water is characterized by OH-stretching modes at 3526 and 3577 cm–1 , OH-bending modes at 1615 and 1647 cm–1 , and an OH-libration mode at 876 cm–1 . The sulfate 1 mode is weak in the infrared but showed strong bands at 1005 and 1013 cm–1 in the Raman spectrum. The 2 mode also showed strong bands in the Raman spectrum at 433, 440, 457, and 480 cm–1 . The 3 mode is characterized by a complex set of bands in both infrared and Raman spectra around 1150 cm–1 , whereas 4 is found at 650 cm–1.

Exploring first-year academic achievement through structural equation modelling

The purpose of this research was to develop and test a multicausal model of the individual characteristics associated with academic success in first-year Australian university students. This model comprised the constructs of: previous academic performance, achievement motivation, self-regulatory learning strategies, and personality traits, with end-of-semester grades the dependent variable of interest. The study involved the distribution of a questionnaire, which assessed motivation, self-regulatory learning strategies and personality traits, to 1193 students at the start of their first year at university. Students' academic records were accessed at the end of their first year of study to ascertain their first and second semester grades. This study established that previous high academic performance, use of self-regulatory learning strategies, and being introverted and agreeable, were indicators of academic success in the first semester of university study. Achievement motivation and the personality trait of conscientiousness were indirectly related to first semester grades, through the influence they had on the students' use of self-regulatory learning strategies. First semester grades were predictive of second semester grades. This research provides valuable information for both educators and students about the factors intrinsic to the individual that are associated with successful performance in the first year at university.