Oil Belt Research Articles

Lessons Learned in Horizontal Well Workovers and Sand Cleanouts, in Cerro Negro Field, Venezuela

Summary The Orinoco Oil Belt in Venezuela contains the largest known deposits of heavy oil in the world, and Cerro Negro is part of the fields in this area. However, the sand production is a major issue which affects the oil production in this field. There are some major issues that stand in the way of the proper cleanout of these wells. These problems include low reservoir pressure, geometry of the wells, and extremely high oil viscosity. Another major problem is the presence of big pieces of progressing cavity pumps (PCP) elastomers, some metallic parts from pressure and temperature sensors configuration, and other metallic parts from previous workover rig operations, encountered during cleanout operations. As a result of these difficulties, some of the past jobs performed in this field were unsuccessful. After these unssuccessful jobs, a campaign of recent multiple sand cleanout jobs was planned in the Cerro Negro field. Numerous difficulties arose during these jobs. These issues were largely due to the presence of big pieces of PCP elastomers and metallic parts. An additional issue was the low reservoir pressure. Due to the size of the casing/liner and the horizontal section, the annulus fluid velocity obtained was insufficient. Therefore, several techniques were applied to overcome these problems. One of these methods was to use reverse circulation for the sand cleanout in the 9-5/8-in. slanted casing section, while circulation was still possible to obtain a higher fluid velocity. Afterward, once the circulation was lost, a special stroking pump was used alongside a large string of tubing to store large amounts of sand and debris. This tool was also used to recover pieces of PCP elastomers and other metallic parts. This tool uses a piston pump to create a vacuum effect, and fluid circulation is not needed for the cleanout. Without this innovative stroking pump, it would have been almost impossible to recover these large pieces. This was the first time this innovative tool was used in these types of wells. When the open horizontal 7-in. production zone was reached, coiled tubing (CT) was used with the proper proportion of diesel and nitrogen to obtain enough fluid velocity and the proper equivalent density. In the end, when necessary, a smaller reliner was run depending on the information obtained during the analysis of the grain sizes. Some techniques were applied to run the reliner successfully in an old and worn out casing, where the geometry of the well and high doglegs caused difficulties. The challenges to complete the cleanout of the well with lost circulation problems included a large annulus area in the highly slanted and horizontal sections, the extremely high oil viscosity, and the presence of large pieces of PCP and metallic parts. These challenges were overcome by using different methods such as the special stroking pump, reverse circulation in the 9.625-in. section, and CT with the proper diesel and nitrogen proportions. Additionally, to keep sand production under control in the cleaned wells, a smaller reliner was run. Finally, these workover jobs were finalized to bring these wells back into production successfully. The oil production results of these operations are shown in this paper, and demonstrated that it is possible to retrieve the production in the sanded wells of the Orinoco Belt in a profitable way.

Impedance spectroscopy in asphaltene-toluene and maltene-toluene solutions of crude oils from the Orinoco Belt

In this investigation, an impedance and dielectric spectroscopy study was carried out on Asphaltene-Toluene and Maltene-Toluene solutions, prepared from two oil samples from the Orinoco Oil Belt that presented low resistivity at the depths of the oil well where petrophysical logs were taken. The purpose of this work is to investigate whether the asphaltenes and maltenes would be responsible for the low resistivities found in the logs. A Lock-In amplifier, an impedance analyzer, and a coaxial cylindrical cell were used to obtain the impedance measurements. From the plotting of the impedance and phase angle parameters, it was confirmed Asphaltene-Toluene solutions were the least resistive. A fit of the experimental data based on an electrical circuit was realized, finding good correspondence between the experimental data and the fit line. The AC conductivity values were plotted using the fitting data, and it was observed that the Asphaltene-Toluene solution is more conductive. A remarkable difference in the electrical behavior was found between the maltene solutions of both crude oil samples .

Synergistic effects of surfactants on depressurization and augmented injection in high salinity low-permeability reservoirs: Formula development and mechanism study

To solve the application problem of surfactant in depressurization and augmented injection in high salinity low-permeability reservoirs, through various laboratory experiments, we studied the synergistic effects of surfactants, and a new surfactant formula composed of an anionic surfactant and a non-ionic surfactant for depressurization and augmented injection in high salinity, low permeability reservoirs was acquired. The proposed formula remained stable after 3 months at 85 ℃ and produced ultra-low interfacial tension in high salinity conditions (TDS = 794–65,010 mg/L). With total surfactant concentration of 0.40%, the proposed formula effectively decreased the water-injection pressure and unlocked the remaining oil trapped in small pores (0.05–0.5 µm). With average adsorption loss of 8.25%, the novel formula was capable of reducing the water-injection pressure by 24.77% and recover additional 28.86% oil. Moreover, higher salinity is conducive to a lower interfacial tension, therefore, at higher salinity conditions, lower surfactant concentration may be required and the corresponding adsorption loss, would therefore be lower. According to our study, the developed formula lowered injection pressure and improved oil recovery mainly through interfacial tension reduction, emulsification, and wettability alteration. The microscopic functional mechanisms of surfactant mixtures include; (1) adhesion work reduction, boundary fluid activation and free flow area increase; (2) Promote the formation of oil belt and facilitate the displacement process; (3) Increase the oil-water two-phase mobility ratio, reduce the flow resistance and increase sweep efficiency. The test results of the given formula showed that the salinity in water is a key factor affecting the efficiency of depressurization and augmented injection by surfactants, and the concentration as well as the stability of surfactant also showed different rules under different TDS. The synergistic effect between surfactants made the system perform better at high salinity. The findings of this study not only bring more enlightenment on the principle of depressurization and augmented injection when surfactants are used in petroleum development process, but also provide a basis for the establishment of high- performance surfactant depressurization and injection system.

Sedimentary facies of a tide-dominated estuary and deltaic complex in a tropical setting: The middle Miocene Oficina Formation of the Orinoco Oil Belt, Venezuela

Although the middle Miocene Oficina Formation of the Orinoco Oil Belt represents most of Venezuela's hydrocarbon resource, a comprehensive and detailed sedimentary facies model for the whole belt has never been put forward. Based on the analysis of cores and well logs, nine sedimentary facies (FA-I), forming five facies assemblages (FA1-5), have been characterized. Both sedimentologic and ichnologic datasets have been integrated in this study. The Oficina Formation records the typical succession of fluvial incision during relative sea-level fall, fluvial deposition during lowstand, transition from fluvial to estuary valleys during the subsequent transgression and deltaic progradation during highstand. FA1 consists of fluvial-braided channel (FB), floodplain (FG2), and swamp (FH1) deposits, as well as paleosols (FG3). This facies assemblage occurs in the lower member, representing the infill of lowstand fluvial valleys. FA2 consists of meandering estuary-channel deposits (FA, FC, FD, FE, and FI). This facies assemblage occurs in the middle member, representing the infill of tide-dominated estuary valleys during the early stages of the Langhian transgression. FA3 consists of tidal-flat and tidal-creek (FC, FD, FE, FF, and FG2), and swamp (FH1 and FH2) deposits, together with paleosols (FG3). This facies assemblage is present in the middle member, revealing backstepping and retrogradation within the estuary system during a continuing transgression. FA4 consists of outer-estuary sandbar (FC, FD, and FG1); swamp (FH2) deposits and paleosols are present at the margins of the estuary (FG3). This facies assemblage occurs in the uppermost part of the middle members, representing a late stage of the Langhian transgression, culminating in a maximum flooding surface. FA5 consists of deltaic distributary channel (FC and FD), floodplain and interdistributary-bay (FG2), and swamp (FH1) deposits. This facies assemblage occurs in the upper member, recording sedimentation in the delta plain of a tide-dominated delta during a highstand. Freshwater conditions in the fluvial system, as well as in the inner portions of the estuary and the delta plain are further supported by the presence of the Scoyenia Ichnofacies, whereas brackish-water segments of the estuary are characterized by the Skolithos and depauperate Cruziana Ichnofacies. The substrate-controlled Teredolites, and Glossifungites Ichnofacies occur in connection to erosional exhumation during ravinement. The absence of fully marine ichnofaunas is consistent with the embayed nature of the Orinoco Oil Belt. The tropical and humid character of the Oficina depositional systems is manifested in the development of widespread wetlands in marginal-marine settings, with formation of swamps and embayed areas, typically displaying evidence of waterlogged paleosols with pervasive root trace fossils. The abundance of crustacean burrows, such as Ophiomorpha and Thalassinoides, is also typical of low-latitude marginal- and shallow-marine settings. Although tidal forces tend to be weaker in lower latitudes because Coriolis effects are stronger there, both the estuary and delta systems are regarded as tide-dominated, most likely reflecting the embayed nature of the shoreline.

Application of multi-wave and multi-component seismic data in the description on shallow-buried unconsolidated sand bodies: Example of block J of the Orinoco heavy oil belt in Venezuela

The use of multi-wave and multi-component seismic information for reservoir prediction and characterization has been a popular research direction. The study area is located in the Orinoco heavy oil belt in Venezuela. The reservoir is a braided river delta plain deposit and the sandstone is shallowly buried and unconsolidated. Thereby, it is difficult to predict and characterize the type of reservoir effectively with seismic data of conventional P-waves. Based on multi-wave and multi-component seismic acquisition data, the study has conducted petrophysical analysis and seismic horizon calibration with converted wave (PS). Vertically, superimposed sand bodies were identified with PP wave because the PP wave has higher vertical resolution than that of PS wave. Laterally, sectional morphology and plane distribution scale of sand bodies were delineated by using the higher lateral resolution of PS wave. By combining the characteristics of PP wave and PS wave, five models for intersection and sand body superposition were summarized and the architecture units of sand bodies were divided. The seismic attribute (RMS amlpitude) boundary characteristics and continuity of the high amplitude region described by PS wave are more evident to obtain plane distribution of channel bars and braided channels. Three different seismic inversion results of seismic impedance, density and sand thickness from three different methods were compared. The average accuracy of sand body prediction with the method of PP-PS wave combined pre-stack inversion reached approximately 85% which is greater than that of the PP wave post-stack inversion and PP-PS combined post-stack inversion, with accuracy of 64% and 66% respectively. The research results showed that in the study area, the combination of multi-wave and multi-component seismic reflection information can effectively identify and predict multi-stage superimposed sand bodies with clearer vertical superposition and more accurate lateral boundary. Due to the inherent non-uniqueness of seismic information on predicting reservoir distribution, the resolution of seismic data and the difficulty of identification of the highly superimposed shallow-buried unconsolidated sandbodies, reservoir prediction uncertainty still exists. In particular, the interpretation on the sedimentary microfacies distribution and sand-body scale may only be one of the relatively reliable interpretation schemes.

Logging response characteristics and formation process of flushed zone in the Orinoco heavy oil belt, Venezuela

Abstract The origins and logging responses of flushed zones in some blocks of Orinoco heavy oil belt, Venezuela are still unclear. To solve this issue, we examined the conventional logging, nuclear magnetic resonance logging, fluid viscosity, core analysis and oil field production data comprehensively to find out the logging responses and origins of the flushed zones. The results show that the main reason for the formation of flushed zone is surface water invasion, which leads to crude oil densification. The crude oil densification produces asphalt membrane (asphalt crust) which wraps up free water, causing special logging responses of the flushed zones. According to the different logging responses, we classified the flushed zones into two types and analyzed the formation processes of the two types of flushed zones. According to the characteristics of logging curves after water flush, we confirmed that the water flush began earlier than the reservoir accumulation.

A river-dominated to tide-dominated delta transition: A depositional system case study in the Orinoco heavy oil belt, Eastern Venezuelan Basin

The Orinoco heavy oil belt (OHOB), which has the most significant heavy oil reserve in the world, has shown various sedimentary patterns and different evolution processes within its different blocks. We selected two blocks, Junin in the west and Carabobo in the east, to analyze the depositional environment distinctions due to different transgression processes. Based on the interpretation of 3D seismic data and electrical well-logging facies and analysis of depositional phenomena using cores, we clarified diverse depositional associations and constructed a sedimentary evolution model of the depositional system in the study area. We suggest that the depositional system transitioned from a braided river delta to a tide-dominated delta in the Early Miocene and that two factors mainly controlled the transition: paleo-flow and paleo-geomorphology, which are related to tectonic uplift and transgression processes. Transgression increased gradually through tectonic activity, though transgression rates varied area to area, resulting in different depositional environment transitions and sand-body distribution patterns. In the Carabobo block (east), a gentle slope developed, indicating a fast transgression rate. The intense interaction between river and tide flow led to a large inter-distributary channel area with high-sinuosity- or tidal-channels (relative to the Junin block). In the Junin block (west), tectonic activity developed a large accommodation area providing space for the sediment produced, slowing the transgression rate, and contributing to a mainly fluvial delta environment. Due to the gradual intensive transgression, channel stack patterns transitioned from braided-to meandering-channel in the river dominated delta or tidal-channel in the tide-dominated delta.

Gradual Evolution from Fluvial Dominated to Tide Dominated Deltas and Channel Type Transformation: A Case Study of MPE3 Block in the Orinoco Heavy Oil Belt of the Eastern Venezuelan Basin

Based on the data of core description and sporopollen analysis, the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed by seismic phase and well logging facies interpretation. The results show that due to the great sea level rise, the sedimentary system of the Miocene Oficina Formation in the MPE3 block shifted from the distal‐source sandy braided river delta to tide‐affected delta, and eventually to tide‐dominated delta. Vertically, during the early stage of sedimentation of Oficina Formation, the distributary channels of the delta were dominated by braided river channels. While in the later stage, as the tidal effect was gradually intensified, the channel changed from braided channel to meandering channel. On plane, as a result of differential transgression, sedimentary framework and distribution of sand bodies vary across the study area. Compared with the eastern part, the western part has more braided channels, larger channel bars, less developments of distributary bay and higher ratio of sand to mud. Whereas the braided channels in the south are larger than those in the north. It is the first time we pointed out the impact of marine transgression differences on the sedimentary facies distribution and river type transition in the study area. Factors like the structural and paleogeomorphological change, sea level variation, supply of sediments have strong influence on the evolution of sedimentary system and distribution of sandbodies. It is predicted that the major sandbody is more developed in the central south, which can guide the subsequent horizontal well development.

Modelaje de redes en la delimitación de áreas de cobertura para la industria petrolera. Área Carabobo de la Faja Petrolífera del Orinoco

Uno de los elementos generadores de dinámica en cualquier área geográfica corres- ponde a los medios de transporte y las comunicaciones. Para el caso del área Cara- bobo de la Faja Petrolífera del Orinoco se estima que en los venideros años estos elementos cobren un intenso dinamismo producto de los planes de desarrollo pre- vistos por PDVSA y sus Filiales, de allí que utilizando la base cartográfica disponi- ble 1:100,000 junto a la definición de una serie de permisas se ha desarrollado un modelo de red del transporte terrestre para conocer las posibles áreas de cobertura que las vías terrestres en sus diferentes categorías: expresas, colectoras, rurales y operacionales permiten la interconexión de las principales localidades, instalaciones y ciudades.

Temperature Dependence of the Electron Paramagnetic Resonance Spectrum of Asphaltenes from Venezuelan Crude Oils and Their Vacuum Residues

The electron paramagnetic resonance (EPR) technique is used to evaluate the temperature dependence of the aggregation processes in asphaltenes of heavy and extra-heavy crude oils and their vacuum residues from the Venezuelan Oil Belt. All of the EPR spectra of the samples studied show an intense central signal assigned to free radicals (FRs) and a multiplet as a result of the presence of a V+4 porphyrin. From the analyses of the inverse of the normalized area as a function of the temperature for the FR signal and the most intense peak in the vanadium multiplet, we obtain a set of temperatures related to the transition of fast-to-slow motion regions, the temperature of generation–recombination of FRs, and the cracking temperature in all of the samples. On the other hand, applying a Curie–Weiss law, we obtain the order–disorder temperatures and correlated them with the American Petroleum Institute grade of the samples. A computational simulation was performed to propose possible conformers based on the expe...

Deconstructing the Palm Oil Industry Narrative in Indonesia: Evidence from Riau Province

Indonesia is the leading global producer of crude palm oil. Mass production of palm oil requires large-scale land conversion, resulting in Indonesia having the world’s highest rate of annual primary forest loss. Given the contentious nature and scale of palm oil production, this article considers Indonesia as a variant of the developmental patrimonialism model often applied to African countries. Developmental patrimonialism in the Indonesian context suggests that state power—expressed through various discourse and policy coalitions—favours palm oil companies and seeks legitimation through claims about national economic benefits. This development model may lead to absolute poverty reduction, employment and tax revenue, but can also produce inequality, resource dependencies and environmental degradation. From the authors’ observations in Riau province, there is a mismatch between the national narrative of palm oil as a force for good and the conspicuous underinvestment in public services and infrastructure, which undermines the legitimacy of some palm oil industry claims. The complexity of village Riau casts further doubt on generalized claims about rural development. Local variance in Riau’s palm oil belt is attributed to, among other things, the complex nature of political patronage, uneven access to land, volatile pricing trends, problematic financing and loan schemes, and the role played by village cooperatives.

Chemical and stable isotope composition (18O/16O, 2H/1H) of formation waters from the Carabobo Oilfield, Venezuela

In this short note, we present the first data on stable isotope composition of the oilfield waters from Carabobo area of the Faja Petrolifera del Orinoco “Hugo Chavez” (Orinoco Oil Belt). From a chemical point of view, the formation waters show a main Na-Cl level (TDS up to 30g/l) with a dilution trend toward Na-HCO3 composition (down to 1g/l). Until now, such a clear net chemical compositional trend was ascribed to a meteoric dilution (fresh/ brackish bicarbonate) of the seawater endmember (the saltiest chloride). The isotope results of this study reveal that the seawater mother water was modified during a high-temperature thrusting event (120–125°C), forming 18O-enriched diagenetic water (up to +4‰), which was diluted in recent times by glacial meltwater and presentday meteoric water. The hypothetical presence of flood by a meteoric paleo-water also offers new hints to explain the low API gravity (<10°API biodegraded, extra heavy oil) and composition of the local crude.

Sedimentology, ichnology, and sequence stratigraphy of the Miocene Oficina Formation, Junín and Boyacá areas, Orinoco Oil Belt, Eastern Venezuela Basin

Abstract The Miocene Oficina Formation is widely distributed in the subsurface of the Orinoco Oil Belt of eastern Venezuela. Despite its economic importance as one of the most important hydrocarbon reservoirs worldwide, little is known about its sedimentologic, ichnologic and sequence-stratigraphic aspects. Sedimentary facies, trace fossils, depositional environments, stratal stacking patterns and surfaces of sequence-stratigraphic significance have been analyzed in the Junin and Boyaca areas. The Oficina Formation is subdivided here into three informal members: lower, middle, and upper. The lower member consists mainly of lowstand fluvial braided-channel deposits filling an incised valley. No evidence of marine conditions is present and the only biogenic structures detected are root trace fossils present at the top of a few fining- and thinning-upward channelized units. The middle member is much more heterogeneous, both vertically and laterally, comprising high-sinuosity estuarine-channel, tidal-flat, tidal-creek and tidal-sandbar deposits, stacked to form a retrogradational package and representing the transgressive systems tract. The middle member is characterized by widespread evidence of tidal influence (e.g. inclined heterolithic stratification) and by the presence of the impoverished Cruziana Ichnofacies and the Skolithos Ichnofacies, both reflecting brackish-water conditions. This member is thought to represent deposition in an estuarine system. The upper member consists predominantly of highstand delta-plain deposits, stacked forming a progradational pattern. These deposits locally show intense bioturbation with a predominance of continental trace fossils, illustrating the Scoyenia Ichnofacies. Deltaic deposits display a mixed influence of tides and river processes. Previous studies invariably assumed a deltaic model for the whole Oficina Formation. However, integration of sedimentologic, ichnologic, and sequence-stratigraphic datasets suggests a more complex depositional evolution, comprising a fluvio-estuarine valley incised during a relative sea-level fall that became filled during the lowstand and subsequent transgression, culminating with deltaic progradation during the highstand.

Big data paradox and modeling strategies in geological modeling based on horizontal wells data

Abstract Based on analysis of horizontal well data characteristics, the differences of data distribution and variogram between vertical and horizontal wells in MPE3 oil field of Orinoco heavy oil belt were compared, and modeling strategies were proposed to cope with the big data paradox when data of horizontal wells was used directly into geologic modeling. The study shows the horizontal wells in the study area contain a large quantity of information, strong directionality of well trajectories and high drilling ratio of sandstone, causing variogram analysis result unconformable to the geologic understanding, and in turn making errors in the modeling of sedimentary microfacies and reservoir physical properties and prediction of probabilistic reserves. Firstly, the distributary channel distribution variogram was analyzed with data of vertical wells, and then the lithofacies framework was established under the control of the sedimentary facies and seismic data. After that, the horizontal wells data revealing high heterogeneity accuracy of reservoir, was combined with the vertical wells data to analyze argillaceous interlayer variograms and the corresponding reservoir lithofacies models were constructed. Finally, reservoir physical property models were generated and the geological reserves were calculated by wellblocks. This reservoir modeling method does not only reflect the geologic features underground, but also improve the accuracy of inter-well sand body prediction, and enhance the reliability of reservoir geologic model ultimately.

Prevention of infectious complications in predicted severe acute pancreatitis (SAP) – a single center randomized controlled trial

Venezuela has the largest hydrocarbon reserves in the world and most of these are within the Orinoco Oil Belt. The Oficina Formation of the Orinoco Oil Belt and the Oritupano Field comprises a wide range of environments formed under variable salinity conditions. These include freshwater fluvial and fluvio-tidal transition zones, brackish-water estuarine and delta-plain segments, alternating brackish-water and near-normal marine delta-front and prodelta settings, and normal-marine wave-dominated shoreface and offshore-shelf environments. The Oficina Formation thus provides an ideal opportunity to evaluate trace-fossil distribution and ichnofacies gradients along a depositional profile and to calibrate salinity-related trace-fossil models. The Oficina Formation contains four softground ichnofacies (Scoyenia, depauperate Cruziana, Skolithos, and archetypal Cruziana) and two substrate-controlled ichnofacies (Teredolites and Glossifungites). Fluvial deposits in freshwater portions of tide-influenced, estuarine channels and distributary channels of tide-dominated deltas are locally intensely bioturbated, displaying low-diversity occurrences of the Scoyenia Ichnofacies. Brackish-water delta-plain and estuarine deposits display lower degrees of bioturbation and low ichnodiversity, as revealed by depauperate Cruziana Ichnofacies and the Skolithos Ichnofacies. Wave-dominated deltaic deposits display the Skolithos and the depauperate Cruziana Ichnofacies, but the presence of some ichnotaxa (e.g., Chondrites) suggests periods of lower salinity stress, probably during times of reduced freshwater discharge. Open-marine deposits are characterized by intense bioturbation and very high diversity, as shown by the archetypal Cruziana Ichnofacies in low-energy distal settings, whereas high-energy proximal settings are characterized by the Skolithos Ichnofacies. Faunal distribution is strongly controlled by salinity, which makes trace-fossil evidence particularly useful for paleoenvironmental characterization of marginal-marine systems. In addition, the Glossifungites and Teredolites Ichnofacies indicate erosional exhumation of marginal-marine deposits, outlining transgressive surfaces of erosion. The Oficina Formation shows remarkable similarities in sedimentary facies and both trace-fossil and micropaleontological content with the Cretaceous McMurray Formation of western Canada.

The experimental study on H2S generation during thermal recovery process for heavy oil from the Eastern Venezuela Basin

Hydrogen sulfide (H2S) is toxic, corrosive and environmentally damaging. It is not only found in oil and gas development, but is also often found in heavy oil exploitation. In this study, three heavy oils were selected from the Orinoco Heavy Oil Belt in the southern part of the Eastern Venezuela Basin. Thermal cracking experiments in gold sealed tubes were then conducted using the heavy oils. The objective of the experiment is to unravel the H2S generation mechanism and utility in establishing a development program for heavy oil thermal recovery. The results of the oil isothermal cracking experiments show that the H2S yield increases with the increasing cracking temperature and holding time at 150 °C and 250 °C. Carbon dioxide (CO2) is the main component in gaseous products and its concentration is more than 80% in our experiments. The yields of CO2, H2S and total hydrocarbon gas present similar varying trend that increases with increasing isothermal time. The sulfur contents in group compositions of the original oil from the CJS-48 well and that of the residual oils with different cracking time at 250 °C were then measured. The analytical results show that most sulfur (>75%) exists in aromatics both in original oil and in the residual oils cracked at 250 °C, not to mention, no sulfur was measured in saturates. Although the decrease of sulfur in aromatics with the increased cracking time is low, it has great significance to the H2S generation during thermal recovery of heavy oil for more than 75% sulfur existed in aromatics. The decrease of sulfur content in resin and asphaltene of cracking residues with increased cracking time indicates that the sulfur existed in resin and asphaltene has some contribution to H2S generation during the thermal recovery process of heavy oil.

From freshwater to fully marine: Exploring animal-substrate interactions along a salinity gradient (Miocene Oficina Formation of Venezuela)

Venezuela has the largest hydrocarbon reserves in the world and most of these are within the Orinoco Oil Belt. The Oficina Formation of the Orinoco Oil Belt and the Oritupano Field comprises a wide range of environments formed under variable salinity conditions. These include freshwater fluvial and fluvio-tidal transition zones, brackish-water estuarine and delta-plain segments, alternating brackish-water and near-normal marine delta-front and prodelta settings, and normal-marine wave-dominated shoreface and offshore-shelf environments. The Oficina Formation thus provides an ideal opportunity to evaluate trace-fossil distribution and ichnofacies gradients along a depositional profile and to calibrate salinity-related trace-fossil models. The Oficina Formation contains four softground ichnofacies (Scoyenia, depauperate Cruziana, Skolithos, and archetypal Cruziana) and two substrate-controlled ichnofacies (Teredolites and Glossifungites). Fluvial deposits in freshwater portions of tide-influenced, estuarine channels and distributary channels of tide-dominated deltas are locally intensely bioturbated, displaying low-diversity occurrences of the Scoyenia Ichnofacies. Brackish-water delta-plain and estuarine deposits display lower degrees of bioturbation and low ichnodiversity, as revealed by depauperate Cruziana Ichnofacies and the Skolithos Ichnofacies. Wave-dominated deltaic deposits display the Skolithos and the depauperate Cruziana Ichnofacies, but the presence of some ichnotaxa (e.g., Chondrites) suggests periods of lower salinity stress, probably during times of reduced freshwater discharge. Open-marine deposits are characterized by intense bioturbation and very high diversity, as shown by the archetypal Cruziana Ichnofacies in low-energy distal settings, whereas high-energy proximal settings are characterized by the Skolithos Ichnofacies. Faunal distribution is strongly controlled by salinity, which makes trace-fossil evidence particularly useful for paleoenvironmental characterization of marginal-marine systems. In addition, the Glossifungites and Teredolites Ichnofacies indicate erosional exhumation of marginal-marine deposits, outlining transgressive surfaces of erosion. The Oficina Formation shows remarkable similarities in sedimentary facies and both trace-fossil and micropaleontological content with the Cretaceous McMurray Formation of western Canada.

Community-level institutions in the management of palm-forest resources in Southeastern Nigeria

The study examined the role of community-level institutions in the management of palm-forest resources in Southeastern Nigeria. Southeastern Nigeria is undoubtedly the palm-forest and palm oil belt of Nigeria where these resources have been managed for at least the last 100 years on an on individual and a community basis. Using a survey research approach, this study focused on three large communities in three states in the Southeastern region and discovered widespread usage of community-level institutions in the management of palm-forest resources as well as a set of socio-cultural norms and practices regarding access to and exploitation of palm-forest resources. However, while we discovered that these community-level institutions were both effective and conducive to sustainable exploitation of these resources, we also found that these institutions are not particularly bothered with either promoting or encouraging new investments in palm-forest resources. Therefore, there is need to harness these institutions for optimal and sustainable exploitation of palm-forest resources while calling their attention to the need for new investments in palm-forest resources in their communities.

Dividivi tannins: an ecological product for water-based drilling fluids

Modified tannins are used as deflocculant additives in the formulation of water-based drilling fluids (WBDF) for drilling operations in any scenario. Due to their high heavy metals content, these additives are toxic and hazardous for any environmental scenario. Deflocculant efficiency of unmodified tannins (UDT) extracted from fruit pods of “dividivi” (Caesalpinia coriaria) as an additive for WBDF was assessed. Raw materials for UDT elaboration come from the rural and sustainable exploitation of natural occurring dividivi trees, growing in dry tropical forests in Anzoategui state (Orinoco Oil Belt, eastern Venezuela). The tannins extract, in the form of dividivi fruit powder, contains 47.0 % of total tannins (hydrolyzable tannins plus condensed tannins), of which 67.4 % corresponds to hydrolyzable tannins. Dividivi tannins in WBDF showed nine (9) times deflocculant efficiency than heavy metals commercial modified tannins. Moreover, commercial modified tannins do not improve their deflocculant efficiency with increased tannin content. Ecotoxicological studies were carried out for WBDF formulations with UDT, using freshwater microalgae Scenedesmus dimorphus as chronic toxicity bioindicator. Toxicity bioassays performed with these microalgae did not show significant effects on its population growth. The EC50 values resulted in over 100,000 mg L−1, and these formulations were therefore considered non-toxic. Values of LC50 obtained this time with Poecilia reticulata, as acute toxicity bioindicator are around 100,000 mg L−1, with no significant effects on population mortality. Thus, WBDF formulated with UDT can be considered non-toxic formulations for populations of this freshwater fish. From the social perspective, the use of UDT in WBDF fosters organized communities economical activities based on the maintenance of a sustainable supply chain for processing fruits in a quantity enough to obtain three thousand seven hundred fifty kilograms (3750 Kg). The UDT so obtained was used as deflocculant in four (4) oil wells producing excellent performance and relevant savings compared with commercial modified tannin.

Hydrocarbon potential of the Ural\u2013African transcontinental oil and gas belt

Recently, several major hydrocarbon fields have been discovered in the Ural–African transcontinental oil and gas belt. These include the Pobeda field in the Kara Sea (338 billion m3 of gas, >100 million tons of oil), the Velikoe field in the Astrakhan region (90 billion m3 of gas, 300 million tons of oil), and the Galkynysh gas field in Turkmenistan (the world’s second largest, after North Dome). There have also been a number of oil and gas finds in East Africa. All of those corroborate the idea of the Ural–African transcontinental oil and gas belt being a planetary structure hosting unique hydrocarbon concentrations. Analysis of the belt’s metallogeny shows that large and super-large deposits of metallic and nonmetallic minerals are concentrated in an axial zone, highlighting the large-scale redistribution of energy and matter in the Earth’s crust and mantle. These processes are most active in the rift structure where they come together to form the Ural–African transcontinental oil and gas belt. The process that formed the recently identified hydrocarbon deposits within the modern rift structure—the East African Rift system—can be seen as an embryonic stage in formation of oil–gas accumulations. The East African Rift petroleum discoveries are characterized by the continuous flow of hydrocarbons and its short-term residence in local traps. This makes finding major hydrocarbon deposits there unlikely. The potential for large deposits is more likely where large accumulations of hydrocarbons are overlapped by later sedimentary strata, a situation seen offshore of East Africa.