Basin Type Research Articles

Sedimentation styles and variability of organic matter types in the Triassic, non-marine half-grabens of west Argentina: implications for petroleum systems in rift basins

ABSTRACT Extensional relaxation due to the collapse of the active margin of Gondwanaland during the Triassic led to rapidly subsiding, fault-bounded half-grabens in west Argentina. The Cuyo rift basin was the largest of these fault-bounded troughs. Two linked asymmetrical half-grabens have been identified in the Cuyo basin: Cacheuta in the south and Las Penas-Tamberias in the north. Their stratigraphy exhibits a classic tripartite internal organization with a basal alluvial and fluvial section followed by a lacustrine interval which in turn is overlain by fluvial deposits. The basin fill in both half-grabens shows significant lateral thickness variations that reflect the contrasting subsidence rates on the fault and flexural margins. The lacustrine shales in the Cacheuta half-graben have an average total organic carbon (TOC) content of 4%, locally reaching 20%, dominated by type I, amorphous, algal organic matter and high hydrogen index (HI) values. The shales are associated with parasequences in river-dominated deltas. Oils derived from these source rocks are waxy and with low sulphur content. The oil shales are associated with sandstones arranged in parasequences deposited in river-dominated Gilbert-type deltas. This interval in the Cacheuta half-graben can be assigned to a slightly overfilled to balanced-fill lake type. In Las Penas-Tamberias, the dominant source rock facies in the lacustrine section is made up of calcareous shales with oil-prone, type I(II) kerogen and TOC values up to 13% and high HI values. The presence of gammacerane and b-carotane, common in saline conditions, is conspicuous. The presence of oolitic and bioclastic grainstones and microstromatolitic limestones on the ramp margin and clastic facies on the border fault suggests a slightly underbalanced to balanced lake type. The Cuyo rift basin branches to the NE into the Ischigualasto-Villa Union half-graben. Lacustrine shales along the fault margin of this half-graben are dominated by type III, gas-prone organic matter with TOC values up to 4% and low HI values. Parasequences with a strong progradational stacking pattern and steep front slopes are interpreted as mouth bars in a Gilbert-type delta. These characteristics are consistent with an overfilled lake basin type where sedimentation rate exceeds subsidence rate. The Triassic rift system of west Argentina shows the gamut of lacustrine source rocks that, combined with the analysis of diagnostic associated facies, allow the discrimination of lake basin types and their influence in the resulting hydrocarbon phase.

Effect of inclination of the external reflector of simple solar still in winter: An experimental investigation for different cover angles

This paper presents an experimental investigation on the productivity of a basin type solar still with internal and external reflector tilted at angles of 0° (vertical), 10°, 20° and 30° for still cover angles of 20°, 30° and 40°. A simple still equipped with internal and external reflectors is investigated in winter at latitude angle of 33.3° N. It was found that the daily productivity is greater for a still with a larger cover angle at any reflector angle. The daily productivity of the still with no reflectors would remain almost the same at any glass cover angle. The benefit of the vertical external reflector in winter is decreased as the cover angle exceeds 40°. The most productive solar still in winter is a still that has a cover angle of 20° and an internal and external reflector inclined at 20°; its productivity will be around 2.45 times that of simple still with no reflectors. The conclusions of this study validated the trend of some of the theoretical results cited in the literature at 30° N latitude.

Species diversity and community structure of pelagic copepods in the marine lakes of Palau

Community structure and diversity patterns of pelagic copepods were investigated for the coastal areas and in the marine lakes of the Palau islands in the West Pacific. We conducted field surveys during 2004–2007 and collected zooplankton samples from eight coastal areas and 16 marine lakes. The marine lakes in the islands of Palau are limnologically classified into two types, meromictic and holomictic lakes. Species diversity indices (Margalef’s species richness d′, Shannon–Wiener index H′, and Simpson’s dominance) were measured at each sampling site. The copepod community structure was analyzed using multivariate analyses, hierarchical cluster analysis, and non-metric multidimensional scaling (MDS) from the PRIMER package. A total of 36 copepod taxa were identified to the genus or species level from Calanoida, Cyclopoida, Harpacticoida, and Poecilostomatoida. Multivariate analysis based on the Bray–Curtis similarity index revealed that copepod assemblages could be classified into three different groups according to their habitat: (I) meromictic lakes, (II) holomictic lakes with an exceptionally shallow and flat basin (type A holomictic lakes), (III) holomictic lakes with a deep basin (type B holomictic lakes), and all coastal areas. The meromictic lakes were characterized by markedly decreased species diversity (d′ = 0.15, H′ = 0.41) in which only two brackish-water species, Bestiolina similis and Oithona dissimilis, were dominant. Type A holomictic lakes were characterized by relatively low levels of species diversity (d′ = 1.25, H′ = 1.35). In contrast, type B holomictic lakes were characterized by relatively high levels of species diversity, which was comparable to that of coastal areas. This result indicated that zooplankton assemblages in the type B holomictic lakes were closely related to a coastal community. The present study showed that the species diversity of pelagic copepods varies according to the level of isolation and the local environmental conditions for each marine lake.

ANALYSIS OF WATER LEVEL OSCILLATIONS BY USING METHODS OF NONLINEAR DYNAMICS

Sea level variations collected in several areas in the world have been analyzed trying to infer their non linear characteristics. Analyzed data were acquired in several sites in West and East coasts of the North American continent, in the Hawaii and Bermuda islands, representing oceanic sites, and in Adriatic sea, representing a well known basin type. Data have been analyzed through Independent Component Analysis, False Nearest Neighbours and the estimation of correlation dimension using Grasberger and Procaccia integral. Results show a clear non linear features in all the sites, characterized by second and third order Landau mode.

Effect of inclination of the external reflector on the performance of a basin type solar still at various seasons

This paper presents an experimental investigation on the effect of internal and external reflectors inclined at angles 0° (vertical), 10°, 20° and 30° on the output of simple-basin solar stills in summer, autumn and winter. A simple still, which has a 20° cover tilt angle and equipped with internal and external reflectors is investigated at latitude angle of 33.3°N. It was found that the average daily yield is increased by the use of internal and/or external reflectors except for summer where the effect of the reflectors is found to be negative. The increase in the productivity of the still with reflector(s) compared to the still with no reflectors (increase ratio) is averaged at 19.9% and 34.5%, 34.4%, 34.8% and 24.7% for still with internal reflector only, still with internal and an inclined external reflector tilted at 0°, 10°, 20°, and 30° respectively. Accordingly, a comparable yearly productivity is expected for external reflector angle ranging from vertical to 20°. The conclusions of this study in winter agree well with the trend of the theoretical results cited in the literature at 30°N latitude angle.

Development of empirical relation to evaluate the heat transfer coefficients and fractional energy in basin type hybrid (PV/T) active solar still

The simple empirical relation is developed to estimate the glass cover temperature for known values of water and ambient temperatures in basin type hybrid (PV/T) active solar still. The empirical relation developed is based on outdoor experimental results of water and ambient temperature in the range of 14°C to 92°C, and 14°C to 36°C respectively. The results obtained for glass cover temperature using proposed relation are validated with the experimental as well as using a numerical results (obtained by numerical solution of heat balance equation) of solar still. The proposed glass cover temperature is obtained with a maximum relative error of 1.12% compared to the value obtained through a numerical solution. The maximum relative error in evaporative mode of energy transfers from water surface is obtained as 1.2%.

Experimental study of a basin type solar still with internal and external reflectors in winter

A basin type solar still with internal and external reflectors was constructed and then examined in outdoor experiments in winter in Kurume, Japan. The external reflector was inclined slightly forward to make the reflected sunrays hit the basin liner of the still effectively. The daily productivity of a basin type still can be increased about 70% to 100% with a very simple modification using internal and external reflectors. The experimental results and the theoretical predictions are in fairly good agreement, especially on clear days.

Performance correlations for basin type solar stills

Many experimental and numerical studies have been done on different configurations of solar stills to reach the optimum design by examining the effect of climatic, operational and design parameters on its performance. Some of the most important parameters investigated were solar radiation, cover tilt angle, brine depth, and using dyes with the brine. The majority of the investigators presented their results in scatter diagrams rather than correlations. Four correlations are derived in this work to illustrate the effect of solar radiation, dyes, cover slope and brine depth on the productivity of the basin type solar still using the available data given by the different investigators. The correlations developed illustrate that the still productivity could be influenced by the brine depth alone by up to 33% and by the tilt angle alone by up to 63%. A cover tilt angle of about 30° gives the highest productivity. The still productivity could be enhanced by adding dark soluble dye to the brine by up to 20%. The still productivity increases with the increase of insulation thickness of the still and the solar radiation received.

Development of a hybrid solar distillator of a basin type distillator and a membrane distillator

A tube-type solar distillator hybridized a conventional basin still with an air-gap membrane distillator using PTFE membrane was numerically and experimentally investigated for drinking water or irrigation. A tube-type basin still is directly combined with a fl at-type membrane distillator through an absorber for solar irradiation within the distillator. Membrane distillation enables water to fl ow under an absorber at the stable state and water vapor to transfer in the downward direction due to support of membrane. Distillate productivity in case of a bilateral water feeding operation at the steady state almost equals to the summation of productivity in case of one-way feeding method independently for basin still and membrane distillator. The numerical simulation revealed that membrane distillation mostly produced distillate water at the range of low solar irradiation and basin distillation contributed to productivity at the high irradiation. Dynamic characteristics of the hybrid distillator were investi...

Performance of solar still with a concave wick evaporation surface

Abstract Surfaces used for evaporation and condensation phenomenon play important roles in the performance of basin type solar still. In the present study, a concave wick surface was used for evaporation, whereas four sides of a pyramid shaped still were used for condensation. Use of jute wick increased the amount of absorbed solar radiation and enhanced the evaporation surface area. A concave shaped wick surface increases the evaporation area due to the capillary effect. Results show that average distillate productivity in day time was 4.1 l/m2 and a maximum instantaneous system efficiency of 45% and average daily efficiency of 30% were recorded. The maximum hourly yield was 0.5 l/h. m2 after solar noon. An estimated cost of 1 l of distillate was 0.065 $ for the presented solar still.

Effect of insulation thickness on the productivity of basin type solar stills: An experimental verification under local climate

To achieve a high efficiency of a solar still, heat losses from the sides and base should be minimized by adequate insulation to insure the storage of the absorbed thermal energy. The effect of insulation on the productivity of a basin type solar still is verified in this study. Solar stills with insulation thickness of 30, 60 and 100 mm are investigated and the results are compared with those obtained for a still without insulation. It was found that the insulation thickness has a significant impact on the productivity of the still up to a thickness of 60 mm. The insulation thickness could influence the productivity of the still by over 80%. A performance correlation for the effect of insulation on productivity is also developed.

On the verification of the effect of water depth on the performance of basin type solar stills

Many experimental and numerical studies have been done on different configurations of solar stills to optimize the design by examining the effect of climatic, operational and design parameters on its performance. The majority of the investigators presented their results in scatter diagrams rather than correlations. One of the most important of the operational parameters that has received a considerable attention in the literature is the brine depth. A good number of the investigations on the effect of brine depth are cited in this study. For each of these studies, a correlation was developed from the data reported by each study. A concluding correlation from all brine depth data was developed. The correlation showed a decreasing trend in the productivity with the increase in the brine depth. An experimental study was subsequently conducted to verify this trend by an experimental investigation on a solar still that was constructed and tested with five different brine depths, namely 1, 4, 6, 8 and 10 cm. The present study validated the decreasing trend in productivity with the increase of brine depth and showed that the still productivity could be influenced by the brine depth by up to 48%.

Effect of inclination of external reflector of basin type still in summer

In this paper, we present a geometrical model to calculate the radiation reflected from an external reflector inclined backwards and then absorbed onto a basin liner of a basin type still. The effect of the inclination of the external reflector on the distillate productivity of the still with both the internal and external flat plate reflector on a summer solstice day at 30°N was theoretically predicted. We found that the distillate productivity of the still can be increased by inclining the external reflector even in summer, but the augmentation is smaller than in winter. Further, the benefit of both the internal and the inclined external reflectors of the basin type still would be considerably less in summer than in winter.

Geological controls on BSR occurrences in the incipient arc-continent collision zone off southwest Taiwan

Bottom simulating reflectors (BSRs) observed on seismic sections are often considered as indicators for the existence of free gas, delineating the base of the gas hydrate stability zone. Abundant BSRs seen on seismic sections acquired off the SW coast of Taiwan indicate the likely and prevalent existence of gas hydrates in the study area. This study aims to characterize the occurrence of BSRs off SW Taiwan and to understand their relationship to topography, tectonic activity, and possible migration paths of gas-bearing fluids in this area. The tectonic setting off SW Taiwan is during the initial stage of arc-continent collision between the Luzon arc and the northeastern continental margin of the South China Sea. A series of west-vergent, imbricated folds and emergent thrusts develop in the accretionary wedge. Each fold-and-thrust sequence corresponds to an elongated submarine ridge if its crest is not buried by flat-lying sediments. By contrast, normal faulting prevails in the northeastern margin of the South China Sea. A correlation between distribution of BSRs, topography, and tectonic features can be observed. Four major occurrences of BSR types of ridge type, basin type, submarine-canyon type, and continental slope type, are recognized on the basis of the relationship of BSRs to topographic and structural features. Main characteristics of BSRs in the study area can be described as: (1) they occur mostly beneath topographic highs; (2) a discordant relationship between surfaces of the seafloor and underlying strata where BSRs are present; (3) BSRs are prevalent especially beneath the crest and flank of the upthrusting, large and inclined slope basins; and (4) in general, a series of high-amplitude dipping reflectors beneath BSRs can be found. These features indicate that gas hydrate may accumulate preferably beneath topographic ridges especially underneath four-way-dip topographic closures. This effect may exist because the buoyancy-driven, gas-bearing fluids tend to migrate upward and laterally toward structural highs and their corresponding topographic ridges. The distribution of BSRs indicates that gas hydrates occur more commonly in the accretionary wedge than in the South China continental margin. We suggest that the more widespread occurrence of gas hydrates in the accretionary wedge is due to the existence of multiple fault zones, which may help to tap more deep-seated gas-bearing fluids, in addition to the shallow biogenic gas, in this region.

Desalination of effluent using fin type solar still

In this work, an attempt is made to produce potable water from industrial effluents. An ordinary basin type solar still integrated with fins at the basin plate is used for experimentation. Since industrial effluent is used as feed, before this still, an effluent settling tank is provided to get clarified effluent. This effluent settling tank is fabricated with three chambers, consists of pebble, coal and sand for settling the impurities and removing the bacteria in the effluents. Sponges, pebbles, black rubber and sand are used in the fin type single basin solar still for enhancing the yield. Results show that the productivity increases considerably due to this modification. A theoretical analysis is also carried out which, closely converges with experimental results. The economic analysis proved that the approximate payback period of such kinds of still is 1 year.

Performance study on solar still with enhanced condensation

Water scarcity and pollution pose critical situation in all walks of life especially in the developing countries. Among the available purification technologies, solar desalination process proves to be a suitable solution for resolving this existing crisis. This renewable energy technology operates on a basic principle of which the solar radiation enters through the glass surface inside a closed chamber touching the black surface generating heat energy, which gets trapped inside. This gradually raises the temperature of the liquid resulting in evaporation process and further condensation, which is drained out for use. In this connection, a basin type solar still (0.5 m 2) with improved condensation technique was designed and built, and a performance study was carried out with different samples such as tap water, seawater and dairy industry effluent. The condensation occurs due to the temperature difference not only on the glass surface but also on the four sidewalls, which can be cooled by water circulation through tubes attached on the wall surface for efficiency enhancement. The maximum daily production of the solar still was about 1.4 L/m 2.d, and its efficiency was about 30%. The condensate water quality was analysed and compared with water quality standards, which was found to be comparable with rainwater and mineral water. Efficiency of the still was calculated for all the samples and compared with each other. The reasons for the findings and their implications for the design of the system are discussed. Some design features that would further enhance the thermal performance of the still were also identified from this present investigation and highlighted.

Single basin solar still with fin for enhancing productivity

Distilled water productivity of the single basin solar still is very low. In this work, to augment evaporation of the still basin water, fins were integrated at the basin of the still. Thus production rate accelerated. Also, for further increase in exposure area sponges were used. Experimental results were compared with ordinary basin type still and still with wicks. The governing energy balance equations were solved analytically and compared with experimental results. It was found that 29.6% productivity increased, when wick type solar still was used, 15.3% productivity increased when sponges were used and 45.5% increased when fins were used. A good agreement had been achieved with theoretical results.

Mesozoic tectonic evolution of the Southeast China Block: New insights from basin analysis

In order to better understand the Mesozoic tectonic evolution of Southeast China Block (SECB in short), this paper describes geological features of Mesozoic basins that are widely distributed in the SECB. The analyzed data are derived from a regional geological investigation on various Mesozoic basins and a recently compiled 1:1,500,000 geological map of Mesozoic–Cenozoic basins. Two types of basin are distinguished according to their tectonic settings, namely, the post-orogenic basin (Type I) and the intracontinental extensional basin (Type II); the latter includes the graben and the half-graben or faulted-depression basins. Our studies suggest that the formation of these basins connects with the evolution of geotectonics of the SECB. The post-orogenic basin (Type I) was formed in areas from the piedmont to the intraland during the interval from Late Triassic to Early Jurassic; and the formation of the intracontinental extensional basin (Type II) connects with an intracontinental crustal thinning setting in the Late Mesozoic. The graben basin was generated during the Middle Jurassic and is associated with a bimodal volcanic eruption; and the half-graben or faulted-depression basin, filled mainly by the rhyolite, tuff and sedimentary rocks during Early Cretaceous, is occupied by the Late Cretaceous–Paleogene red-colored terrestrial clastic rocks. We noticed that the modern outcrops of numerous granites and basins occur in a similar level, and the Mesozoic granitic bodies contact with the adjacent basins by large normal faults, suggesting that the modern landforms between granites and basins were yielded by the late crustal movement. The modern basin and range framework was settled down in the Cretaceous. Abundant sedimentary structures are found in the various basins, from that the deposited environments and paleo-currents are concluded; during the Late Triassic–Early Jurassic time, the source areas were situated to the north and northeast sides of the outcrop region. In this paper, we present the study results on one geological and geographical separating unit and two separating fault zones. The Wuyi orogenic belt is a Late Mesozoic paleo-geographically separating unit, the Ganjiang fault zone behaves as the western boundary of Early Cretaceous volcanic rocks, and the Zhenghe–Dapu fault zone separates the SE-China Coastal Late Mesozoic volcanic-sedimentary basins and the Wuyi orogenic belt. Finally, we discuss the geodynamic mechanisms forming various basins, proposing a three-stage model of the Mesozoic sedimentary evolution.

Productivity enhancement of stepped solar still: Performance analysis

Maintaining minimum depth in conventional basin type solar still is difficult, as the area is large. However this can be achieved in stepped solar still in which the area of the basin is minimized by having small trays. Very few works have been carried so far in stepped solar still and constant depth trays are used in the basin plate. In this work, a stepped still with two different depth of trays are used. The basin plate contains twenty five trays with 10 mm depth and twenty five trays with 5 mm depth. To improve the productivity, experiments were carried out by integrating small fins in basin plate and adding sponges in the trays. Theoretical and experimental analyses are made for fin type, sponge type, and combination of fin and sponge type stepped solar still. When the fin and sponge type stepped solar is used, the average daily water production has been found to be 80% higher than ordinary single basin solar still. The theoretical results agree well with the experimental. Also an economic analysis was made. The payback period of this setup is 400 days.

Increase in Distillate Productivity of Basin Type Solar Still by External Reflector

Increase in Distillate Productivity of Basin Type Solar Still by External Reflector