Lake Maracaibo Research Articles

Forest cover and deforestation patterns in the Northern Andes (Lake Maracaibo Basin): A synoptic assessment using MODIS and Landsat imagery

This work synthesizes results from the application of land cover classification techniques and probability sampling of satellite imagery for estimating forest extent and deforestation in Lake Maracaibo Basin (Venezuela and Colombia). A forest map was produced using a semi-automated supervised classification routine on MODIS 8-day 500-m imagery acquired in January 2010. Results show that forests occupy 29,710 km2 which represents 38% of the basin's total terrestrial landmass. From this extent, 61% belongs to Venezuela and 39% falls within the Colombian region. Findings indicate a drastic decrease in forest cover as a result of anthropogenic agricultural and urban expansion, especially when compared to its potential extent within the ‘Maracaibo dry forests’ and the ‘Venezuelan Andean montane forests’ ecoregions. Using time series of Landsat imagery, deforestation rates for the 1985–2010 time period were calculated. The analysis was performed on 24 samples blocks of 10 × 10 km2 randomly allocated within previously defined change probability strata. The general spatial distribution of deforestation rates was predicted by a simple regression model between sample blocks and prior change probabilities at the basin scale. Our results indicate that deforestation was low (<0.5%/y) in 85% of the basin, with highly focalized deforestation fronts (intermediate-to-high rates, <2.5%/y) in three regions: a) the Motatán river sub-basin in the Eastern Cordillera, b) the lower slopes of the Catatumbo river sub-basin and c) the submontane regions of the Apón and Santa Ana river sub-basins. The results of this paper lead the way for understanding current patterns in socioeconomic drivers of forest clearing in Lake Maracaibo Basin. The study also demonstrates the feasibility of using alternatives methods to the time-consuming and financially unsustainable methods traditionally used at national and sub-national scale in Venezuela and other Latin American countries.

Genetic diagnosis of hyperkinetic movement disorders

People with hyperkinetic movements have always attracted the attention of the public and professionals. Alert colleagues noticed families in which a disease passed from generation to generation around Lake Maracaibo in Venezuela. This study led in 1993 to the localization of the gene for Huntington disease on chromosome 4. The genetic basis of many other familial and sporadic diseases has been identified on human DNA. The clinical presentation of hyperkinesias remains the starting point for diagnosis, but differential diagnosis is a long, difficult process, the first step being to differentiate between inherited and non-inherited forms. The need to know the diagnosis is of major importance for patient and family. Knowledge about the cause limits the number of extra diagnostics. This review of the literature presents the most frequently occurring genetically-determined forms of hyperkinesias, mainly chorea and dystonia and tries to give some practical guidelines. The final part of the review will offer some thoughts and views for future development in a world which probably has more knowledge than we can handle. The drive to find a diagnosis is rewarded by the patient but one also needs to reflect on the use of medical care.

Peces de la subcuenca del río Catatumbo, cuenca del Lago de Maracaibo, Colombia y Venezuela

Registros de literatura, complementados con la revisión de ejemplares de colección de referencia de peces del Instituto Humboldt - IAvH-P (Colombia), Estación Biológica de Rancho Grande - EBRG y Museo de Ciencias Naturales de Guanare - MCNG (Venezuela), muestran que 109 especies nativas de agua dulce y 14 de origen marino y estuarino habitan la subcuenca el río Catatumbo, constituyéndose en el sistema con mayor diversidad de especies de peces de la cuenca del Lago de Maracaibo. Estas especies pertenecen a 10 órdenes, 39 familias y 91 géneros. Los órdenes con mayor número de familias, géneros y especies fueron Siluriformes con 12 familias, 42 géneros y 60 especies, y Characiformes 11 familias, 24 géneros y 32 especies. Las familias con mayor riqueza fueron Loricariidae (16 géneros y 25 especies), Characidae (13 géneros y 18 especies) y Pimelodidae (6 géneros y 8 especies); presentando las restantes 37 familias entre una y cinco especies. De las 123 especies registradas, 69 fueron capturadas y catalogadas como resultados de los muestreos durante el presente estudio y 11 corresponden a nuevos registros para Colombia. Para el río Catatumbo se registraron 61 especies de las 68 consideradas endémicas para la cuenca del Lago de Maracaibo y se establecieron como especies pesqueras 40, de las cuales seis fueron marino-estuarinas y 34 dulceacuícolas. Se discute las variaciones del número de especies registradas en los diferentes listados y sus implicaciones en la riqueza de especies para la subcuenca del Catatumbo.

Caracterización y variabilidad genética de Colletotrichum gloeosporioides sensu lato en plantaciones de palma aceitera (Elaeis guineensis Jacq.) en Venezuela

Characterization was performed on the causal agent of anthracnose affecting leaves, rachis and fruits of oil palms in the southern region of Maracaibo Lake (Venezuela). Morphological tests included colony growth rate, diameter, color and type of mycelium, as well as the shape and size of conidia. Molecular characterization included specific PCR tests, ITS rDNA sequencing and analysis of variability using RFLPs and RAPDs. Finally, pathogenicity tests were conducted on one-year old plants and detached fruit. Morphological evaluations allowed identification of a fungus belonging to the genus Colletotrichum, although the 50 isolates studied showed a wide range of phenotypic variation. Amplifications with the specific CgInt primer and the generic ITS4 primer were positive for all isolates, suggesting that the causal agent of this disease is part of the species complex Colletotrichum gloeosporioides. This result was confirmed by sequencing of ITS regions. Assessments of genetic variability indicated a clonal population structure, although RAPDs allowed for the differentiation of some isolates from the predominant genotype in the population. Finally, pathogenicity tests with C. gloeosporioides sensu lato reproduced the symptoms originally observed in the field, and the fungus was re-isolated from inoculated fruits and plants.

Use of biomarkers, porphyrins, and trace elements to assess the origin, maturity, biodegradation, and migration of Alturitas oils in Venezuela

This work is an analysis of crude oil samples from thirty wells in the Alturitas Field (Lake Maracaibo Basin, western Venezuela). Different biomarkers, ten trace elements, and porphyrins were analysed using GC–MS, ICP–OES and UV–visible techniques, respectively. The characterization of these crude oils leads us to conclude that they all fall into a single non-biodegraded oil family derived from a single pulse of hydrocarbon generation, migration and accumulation from the thermally mature calcareous La Luna source rock deposited in an anoxic marine palaeoenvironment under reducing conditions. The main objective of this work is to present a secondary oil migration model for the Marcelina reservoir of the Alturitas Field. The multivariate statistical study of trace-element concentrations, porphyrin contents, and polar compound proportions shows that these parameters can be split into two groups. The first group (Cd, Cu, Mo, Fe, P, Zn, Ca, and Mg) indicates a chalcophic association (Cd, Cu, Mo, and Zn) or colloidal complexes with naphthenic acids (Ca, Mg, and Fe). The other two trace elements (V and Ni), together with porphyrins and polar compounds, reveal that oil compositions has been affected by geochromatography, indicating a highly probable secondary migration pathway along a preferential axis orientated southeast to northwest.

Characterization of the lightning activity of “Relámpago del Catatumbo”

The “Relámpago del Catatumbo” (Catatumbo Lightning) is a phenomenon known for more than 500 years that occurs in Venezuela. This phenomenon occurs almost all along the year in a very small region of the southwest region of Maracaibo Lake and, according to the Lightning Imaging Sensor (LIS) data, this region presents the highest lightning activity of the world. The region presents a complex topography with particular climatic conditions. The lightning activity of the region was examined using the World Wide Lightning Location Network (WWLLN) data. The results show two very localized high-lightning activity centers: one of them is confined around [9.5°N; 71.5°W] over the southwest region of the Maracaibo Lake, and the other is around [9°N; 73°W] near the Colombia–Venezuela border. The lightning activity has a semiannual behavior with two maxima, one around May and another one around October. The diurnal cycle shows substantial lightning activity during local nights.

The Use of near Infrared Spectroscopy to Determine the Fat, Caffeine, Theobromine and (−)-Epicatechin Contents in Unfermented and Sun-Dried Beans of Criollo Cocoa

Cocoa is an important raw material in international trade, for which the highest quality is demanded. Venezuelan Criollo cocoa beans from the south of Lake Maracaibo or Chuao are of very high quality and are considered to be Venezuela's finest beans. It is therefore important to characterise and define that quality, or its precursors, in the different primary cocoa processing stages. Given the large number of samples to be analysed, new analytical techniques providing fast and reliable quality data are essential. Near infrared (NIR) spectroscopy utilises wavelengths from 780–2500 nm to measure the absorbance by a sample, compute organic functional groups and quantitatively predict a particular factor. It has been extensively used to analyse food quality and to determine the main alkaloids of coffee. Fat, caffeine, theobromine and (−)-epicatechin contents are related to cocoa bean “flavour” quality. These parameters are usually determined using conventional methods, which are time consuming, destructive and expensive. The goals of this study were to use NIR spectroscopy to develop a fast and non-destructive tool to determine compounds in unfermented and sun-dried cocoa beans of high quality. Calibration coefficients of determination ( R2) and standard errors of cross-validation were 0.94 and 0.89%, 0.94 and 0.05%, 0.88 and 0.08% and 0.96 and 0.18% for fat, caffeine, theobromine and (−)-epicatechin contents (% dry matter), respectively. The results confirmed the good predictability of the models and showed that NIR spectroscopy can be used as a rapid method for determining these compounds in cocoa beans.

Six-Year Evaluation of Thermal-Sprayed Coating of Zn/Al in Tropical Marine Environments

The main objective of this research was to evaluate the performance of thermal-sprayed coating of Zn/Al (double layer) after six years of exposure, with and without the use of sealant (wash primer) in tropical marine environments of very high aggressiveness: La Voz Station (located at the Peninsula de Paraguaná/Falcón State) and Lake Maracaibo Crossing Station (located at Zulia State), in Venezuela. To that effect, carbon steel coupons (100 mm × 150 mm × 2 mm) were sprayed by flame process. The coupons were characterized by means of initial weight, thickness, metallographic, adherence, and roughness, being evaluated monthly by visual inspection during six years. After removal, the coupons were evaluated by microscopic analysis to determine the morphology of attack, microstructure, penetration of contaminants, composition, and morphology of corrosion products. The results showed that after six years, the double-layer system represents an excellent choice for corrosion protection of steel by combining the galvanic protection of zinc with the erosion resistance of aluminum. However, due to the erosion-corrosion effect, a sealant such as wash primer can be used in order to extend its service life.

Ecological functions and economic value of the Neotropic Cormorant (Phalacrocorax brasilianus) in Los Olivitos Estuary, Venezuela

ABSTRACTWe present the ecological functions of cormorants and estimate the economic value of these functions to artisanal fishermen, as a valuation exercise for Neotropic Cormorants at Los Olivitos Estuary, Lake Maracaibo, Venezuela. Ecological functions were based on estimating the abundance, distribution and diet of cormorants; economic values were attached to a selection of goods, services and attributes. Based on available information, we selected four ecological–economic functions of cormorants: harvesting for food; contributors to fish diversity; indicators of fish schools; and contributors to fish biomass, due to guano production. Cormorants consumed nine commercial fish species. Mean consumption was 225 g/ind/day. All ecological–economic functions were positive except for the role as contributors to fish biomass. Total value of the cormorant population to fishermen was $5,429,703/year. Unlike many studies, our results show that Neotropic Cormorants have a negligible impact on artisanal fisheries. We emphasize the importance of these results for management policies.

The organic geochemistry of oil seeps from the Sierra de Perijá eastern foothills, Lake Maracaibo Basin, Venezuela

The organic geochemistry of samples from 11 oil seeps was studied. The samples were collected from the Cachirí area, Carboniferous Region of Tulé (Lake Maracaibo Basin, Venezuela), associated with the Tigre Fault. Biomarkers (hopanes, steranes, n-alkanes, acyclic isoprenoids, and aromatic steroids) were analyzed using gas chromatography-mass spectrometry (GC-MS). These hydrocarbon rich fluids have undergone biodegradation (2–6 on the Peters and Moldowan scale), showing both the partial loss of n-alkanes and the microbial degradation of isoprenoids and steranes. These oil seeps were generated from a mature calcareous source rock that was deposited in a marine paleoenvironment under reducing conditions. Moreover, these seeps are likely derived from the Cretaceous La Luna Formation that reached a level of maturity near the peak of oil generation in the study area. The nature of the studied oil seeps, together with the oil generation models reported for this rock unit in the study area, suggests that these oils are a mixture of an initially heavy, altered oil and a second migrated light crude oil resulting from two generation pulses from the La Luna Formation. Evidence for the presence of light oil trapped in the study area should prompt re-exploration in the northwestern coast of Lake Maracaibo in shallow reservoirs, previously discarded because they usually demonstrated a lack of light oils.

An overview of hybrid marine and lacustrine seas and saline lakes of the world

AbstractWater salinity is one of the major environmental factors influencing hydrobionts. Based on the concept of relativity and plurality of barrier salinity zones, barrier salinities are related to the development of the osmoregulatory capacities of hydrobionts and to the chemical composition of the water they inhabit. These zones are not of equal importance. The entire hydrosphere might be divided into freshwater, brackish water, marine and hyperhaline salinity zones and transitional zones between them. Approximate boundaries and corresponding barrier salinities are defined for all these zones. Revealing barrier salinity zones requires studying the osmoregulatory capacities of hydrobionts and the distribution of their salinity boundaries. We distinguish between four barrier salinities or horohalinicums for marine and continental waters: α (5–8‰), β (22–26‰), γ (45–50‰) and ™ (0.5–2‰). In metamorphized continental waters, barrier salinities are shifted to higher concentrations. Salinity barrier values can change the subsequent evolution of salinity adaptations and osmoregulation capacities. Maracaibo Lake is characterized by freshwater and freshwater–brackish water zones. Deepening of the lake shipping lane increased the salt flux, with the appearance of a brackish‐water zone. This study proposes to distinguish hybrid lentic waterbodies that include the Baltic Sea, Black Sea, Sea of Azov and Maracaibo Lake, which have lost their lacustrine characteristics and are now characterized by intermixing marine (saline) and continental (fresh) waters.

839 AMBULATORY BLOOD PRESSURE MONITORING AS PREDICTOR OF SUBCLINICAL ATHEROSCLEROSIS IN ADOLESCENTS

Upper Paleocene to middle Miocene coal samples collected from active mines in the western Venezuelan States of Táchira, Mérida and Zulia have been characterized through an integrated geochemical, mineralogical and petrographic investigation. Proximate, ultimate, calorific and forms of sulfur values, major and trace element, vitrinite reflectance, maceral concentrations and mineral matter content have been determined for 16 channel samples from 14 mines. Ash yield generally is low, ranging from < 1 to 17 wt.% (mean = 5 wt.%) on a dry basis (db). Total sulfur content is low to moderate, ranging from 1 to 6 wt.%, db (average = 1.7 wt.%). Calorific value ranges from 25.21 to 37.21 MJ/kg (10,840–16,000 Btu/lb) on a moist, mineral-matter-free basis (average = 33.25 MJ/kg, 14,300 Btu/lb), placing most of the coal samples in the apparent rank classification of high-volatile bituminous. Most of the coal samples exhibit favorable characteristics on the various indices developed to predict combustion and coking behavior and concentrations of possible environmentally sensitive elements (As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, Th and U) generally are similar to the concentrations of these elements in most coals of the world, with one or two exceptions. Concentrations of the liptinite maceral group range from < 1% to 70 vol.%. Five samples contain > 20 vol.% liptinite, dominated by the macerals bituminite and sporinite. Collotelinite dominates the vitrinite group; telinite was observed in quantities of ≤ 1 vol.% despite efforts to better quantify this maceral by etching the sample pellets in potassium permanganate and also by exposure in an oxygen plasma chamber. Inertinite group macerals typically represent < 10 vol.% of the coal samples and the highest concentrations of inertinite macerals are found in distantly spaced (> 400 km) upper Paleocene coal samples from opposite sides of Lago de Maracaibo, possibly indicating tectonic controls on subsidence related to construction of the Andean orogen. Values of maximum reflectance of vitrinite in oil (Ro max) range between 0.42% and 0.85% and generally are consistent with the high-volatile bituminous rank classification obtained through ASTM methods. X-ray diffraction analyses of low-temperature ash residues indicate that kaolinite, quartz, illite and pyrite dominate the inorganic fraction of most samples; plagioclase, potassium feldspar, calcite, siderite, ankerite, marcasite, rutile, anatase and apatite are present in minor or trace concentrations. Semiquantitative values of volume percent pyrite content show a strong correlation with pyritic sulfur and some sulfide-hosted trace element concentrations (As and Hg). This work provides a modern quality dataset for the western Venezuela coal deposits currently being exploited and will serve as the foundation for an ongoing coal quality research program in Venezuela.

Mercury Speciation in Lake Maracaibo, Venezuela, Using Reversed Phase HPLC and ICP-MS

The objective of this study was to determine and establish for the first time the distribution of mercury species in a tropical lake in order to understand the nature and factors thai influence its biogeochemical cycle. Samples of water, sediments, mussels, and fish muscle tissue collected from Lake Maracaibo were analyzed using a method based on reversed phase high performance liquid chromatography (RP-HPLC) and inductively coupled plasma mass specirometry (ICP-MS) for the separation and determination of mercury species. The effect of physicochemical parameters such as pH, salinity, redox potential, etc., and the nutrients N, P, and S in determining the chemical specialion of these elements were evaluated. The determination of methylmercury and inorganic mercury was perfomed using RP-HPLC and detection by ICP-MS. The species were found in the different environmental samples obtained from Lake Maracaibo.

J. R. McNeill . Mosquito Empires: Ecology and War in the Greater Caribbean, 1620–1914 . (New Approaches to the Americas.) New York : Cambridge University Press . 2010 . Pp. xviii, 371. Cloth $90.00, paper $24.99.

My post‐retirement writing project is a biography of my father, who was a young petroleum geologist in Mexico and South America from 1926 to 1933. He endured two protracted sojourns at Lake Maracaibo, northern Venezuela's dangerous disease environment where many colleagues caught malaria, one acquaintance died from it, and a close friend lost the use of a leg owing to a misplaced quinine injection. My father subsequently spent an entire rainy season in the llanos of central Colombia, a region renowned for its high density of disease‐carrying mosquitoes. Although J. R. McNeill's new book covers an earlier historical period, reading it has been invaluable for reviewing my manuscript in progress, helping me to re‐emphasize and rethink important points, and reinforcing my amazement that my father never contracted malaria. McNeill's book is at once a review of familiar facts and a presentation of a thoroughly researched, clearly articulated thematic approach that is altogether new. The “Greater Caribbean” in the subtitle extends from northeast Brazil to the Chesapeake Bay and includes the Mexican and United States Gulf Coasts, an enormous arc of the New World tropics and subtropics that is far more extensive than what most of us envision as “Caribbean.” McNeill's insight throws an entirely new light on understanding major events in the European colonization and decolonization of much of this vast area.

Two new trans-Andean species of Imparfinis Eigenmann &amp; Norris, 1900 (Siluriformes: Heptapteridae) from Colombia

Two new species of Imparfinis are described from the trans-Andean region of Colombia. Imparfinis timana is diagnosed by having longer anal fin base (12.4-15.5% in SL), in combination with long adipose fin (24.6-31.3% in SL), 5-6 gill rakers on the first ceratobranchial, 42-43 vertebrae and additional measurements. Imparfinis usmai is distinguished by the combination of first ray of dorsal fin longest, but not projected as a long filament, long adipose fin (21.1-27.0% in SL), maxillary barbel exceeding pelvic-fin base, 39-40 vertebrae, upper caudal-fin lobe pointed and longer than lower lobe, lower lobe rounded, 7-8 gill rakers on the first ceratobranchial, as well as additional measurements. Imparfinis timana is only known from río Guarapas, a small tributary of the upper course of the río Magdalena. Imparfinis usmai is broadly distributed in the upper basin of ríos Cauca and Magdalena, and in the lower Patía river basin. The restricted distribution of I. nemacheir to trans-Andean drainages (Atrato, Magdalena, and Lago de Maracaibo) is also discussed.

The Bridge Over the Lake: Spanning Across Lake Maracaibo in Venezuela

The General Rafael Urdaneta Bridge spanning over Lake Maracaibo in Venezuela (1958–1962), designed by Ing. Professor Riccardo Morandi, a masterpiece of Modern engineering, is now a Modern Landmark at Risk. The remarkable and little known story of the construction of this structure “could not be accomplished by a handful of men. From planning to financing, from design to construction, a great number of Venezuelan and European engineers worked jointly in Wiesbaden, Caracas, Rome, Maracaibo, Zürich, Paris, and Lisbon. In this way, one of the most outstanding structures of our time was erected within the stipulated - and brief construction time.”

Taxonomic review of Colombian Parodon (Characiformes: Parodontidae), with descriptions of three new species

We review species of Parodon Valenciennes, 1850 from the Magdalena, Cauca, Orinoco, Amazonas, Atrato and Caribbean-Guajira River basins of Colombia using meristic and morphological characters. We recognize eight valid species, five previously described: P. apolinari Myers, from the Orinoco River basin; P. buckleyi Boulenger and P. pongoensis (Allen) from the upper Amazon; P. caliensis Boulenger, from the upper Cauca River drainage; and P. suborbitalis Valenciennes, from Lake Maracaibo basin. Three new species are described: P. alfonsoi, from the lower Magdalena River drainage; P. magdalenensis, from the middle Magdalena and upper Cauca River drainages; and P. atratoensis, from the Atrato River basin. We redescribe Parodon suborbitalis using type specimens and topotypes, and designate lectotypes. A taxonomic key is included for identification of the species, as well as geographic distribution maps.

Mitochondrial DNA diversity, differentiation and phylogeography of the South American riverine and coastal dolphins Sotalia fluviatilis and Sotalia guianensis.

Here we consider the phylogeography and population structure of the South American coastal and riverine dolphins, Sotalia guianensis and Sotalia fluviatilis, based on samples (n = 76) collected across more than 9000km of the species distribution. Phylogenetic reconstruction of 31 distinct haplotypes based on a combined analysis of two mitochondrial gene fragments (1052bp) revealed clear genetic differences between riverine and coastal individuals consistent with species-level ranking. Within the coastal species, a spatial analysis of molecular variance of the control region sequences showed significant regional population differentiation (FST = 0.4; FST = 0.6; P<0.001). The highest mitochondrial diversity among costal population units was found along the Caribbean Coast of Colombia and Venezuela. The genetic distinctiveness of the Maracaibo Lake (Venezuela) population has conservation implications regarding the threats faced by the animals in this region, including oil exploitation. Brazilian populations of Sotalia showed the lowest mitochondrial diversity and differentiation among the coastal species warranting further investigation. The Amazonian populations showed the highest mitochondrial diversity overall, suggesting a surprisingly large effective population size (Nef) and relatively high female gene flow throughout the sampled regions of the main river and its tributaries. From our results, at least two different conservation strategies need to be developed for each of the proposed sister-species. For the coastal groups, characterized by restricted gene flow and very localized populations along the Caribbean and Atlantic Coast of South America, it is advisable to work at a local level in order to improve the fishing practices and prevent frequent dolphin entanglement in nets. For the Amazonian groups, priority must be given to maintain the connectivity detected between regions. Obstacles to connectivity, including hydroelectric and dam construction, as well as excessive boat traffic, could affect the future of these populations. RESUMEN: En este trabajo consideramos aspectos filogeograficos y estructura poblacional de los delfines Sudamericanos Sotalia guianensis

Compositional Nutrient Diagnosis of a Sample of Plantain from Sur del Lago de Maracaibo (Venezuela)

The aim of the present study was the estimation of reference concentration values for plantain (Musa AAB subgroup plantain cv. Hartón) using the Compositional Nutrient Diagnosis system. Eighty-eight plants were sampled in 2000–2001 in commercial orchards in Sur del Lago de Maracaibo (Venezuela), their yields recorded, and nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), and sodium (Na) concentrations determined in the foliar material. A yield cutoff of 16.98 kg·bunch−1, obtained after modeling the cumulative variance ratio function versus yield relationships with sigmoidal (Boltzmann) equations, was selected as the value above which plants were regarded as high yielders. Estimations from the high-yield group (N = 31) resulted in the following reference concentrations for macronutrients (in g·kg−1): 27.4 (N), 2.0 (P), 41.2 (K), 6.5 (Ca), 2.8 (Mg), 1.9 (S), and 0.5 (Na). For micronutrients the reference concentrations were (in mg·kg−1): 15.6 (Zn), 8.3 (Cu), 64.0 (Fe), and 76.3 (Mn).

Changes Associated with Field-Scale Demonstration in a Steam-Stimulated Crude Oil from the Lagunillas Oilfield (Lake Maracaibo, Venezuela)

Cyclic steam injection with alkali is currently very commonly used to improve heavy-crude oil production in Venezuela. This work is an analysis of oil-associated water and crude samples from LL-2670 well in the Lagunillas oilfield at Lake Maracaibo (northwestern Venezuela). The aim of this research is to analyze the organic acids thus generated and evaluate chemistry changes in the saturated and aromatic fractions of crude oil during the first cycle of steam stimulation by cyclic injection with alkali. It was noted that the percentages of sulfur and saturates, aromatics, resins, and asphaltenes (SARA) and the American Petroleum Institute (API) gravity varied little in the analyzed crude. In contrast, there were significant variations in the biomarker distribution, particularly in the mono- and triaromatic steranes, benzothiophenes, phenanthrenes, and alkyl-naphthalenes of the crude.