bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconciliation of Production Data and Geology for Robust Development Plan
Authors: Goyal Praffula , Koeck Charles-Henri , Bensadok Abdelaziz , Lavenu Arthur P.C
Published: September 2019

This paper discusses the re-construction of the long-term development plan for an offshore giantfield located in Abu Dhabi with the aim to mitigate the rising challenges in the maturing field. The primary objective is to understand the reservoir behavior in terms of fluid movement incorporating the learning from the vast history while correlating with the geological features.

The field has been divided into segments based on multiple factors considering the static properties such as facies distribution, diagenesis, faults, and fractures while incorporating the dynamic behaviors including pressure trends and fluid movements.

On further analysis, various trends have been identified relating these static and dynamic behaviors. The production mechanism for each of the reservoirs and the subsequent sub reservoirs were analyzed with the help of Chan plots, Hall plots and Lorentz plots which distinctly revealed trends that further helped to classify the wells into different production categories.

Using the above methodology the field has been categorized in segments and color coded to indicate areas of different ranking. The green zone indicates area of best interest which currently has strong pressure support and wells can be planned immediately. The wells in this area are expected to produce with a low risk of water and gas. The yellow zone indicates areas of caution where special wells including smart wells maybe required to sustain production. This area showed relatively lower pressure support owing the location of the water injectors and the degraded facies quality between the injectors and the producers. The red zone highlights areas which are relatively mature compared to the neighboring zones and will require new development philosophy to improve the recovery. The findings from this study were used as the basis for a reservoir simulation study using a history matched model, to plan future activities and improve the field recovery.

This study involved an in-depth analysis incorporating the latest findings with respect to the static and dynamic properties of the reservoir. This has helped to classify the reservoir based on the development needs and will play a critical role in designing the future strategies in less time.
Drainage Strategy Optimization - Making Better Decisions Under Uncertainty
Authors: Sætrom Jon , Wojnar Konrad , Stunell Martha
Published: September 2019

Improved reservoir knowledge is key to extracting additional value from existing oil and gas assets. However, given the uncertainty in the subsurface, it is always a question if our current development strategy is the most robust choice, or if there are alternatives that can further increase the value of our field. This paper presents a novel solution that enables the asset team to answer these questions in a new way. Furthermore, the solution helps teams quickly identify and screen new opportunities that ultimately increase both subsurface understanding and the value of the field. The solution combines a quasi- Newton gradient based numerical optimization scheme with a stochastic simplex approximate gradient (StoSAG) algorithm. Because the algorithm is non-intrusive with respect to the fluid flow simulator, we can directly apply the solution on any flow optimization problem without the need to access the simulator source code. The solution is implemented using a microservice architecture that allows for efficient scaling and deployment either on cloud-based or internal systems. We demonstrate the proposed solution on a field containing 11 oil producers and 7 water injectors by optimizing the water injection and oil production rates. The machine learning algorithm allows us to quickly explore different drainage strategies, given the current understanding and associated uncertainties of the reservoir.

Specifically, the software solution suggests that 6 of the 18 pre-defined well targets are high risk and/or of little value. Running a second development scenario where we do not drill these six wells reduces the investment cost of this field by 163 MUSD and increases the expected net present value per well of the field by 48 percent. Compared with the reactive control drainage strategy approach, we increase the expected net present value of the field by 9.0 %, while simultaneously lowering the associated risk.
Simulation of Enhanced Oil Recovery in Pre-Salt Reservoirs: The Effect of High CO2 Content on Low Salinity Water Alternating Gas Injection
Authors: Carvalhal Arley Souza , Nunes Costa Gloria Meyberg , Vieira de Melo Silvio Alexandre
Published: September 2019

The high CO2 content of Brazil’s pre-salt fields, which may reach values from 20% to 44% molar, presents both a challenge as well as an opportunity. CO2 stripped from the produced gas cannot be released into the atmosphere due to environmental restrictions. Therefore, the whole amount of CO2 produced should be continuously reinjected into the reservoir. This work investigates the effect of CO2 content on the low salinity water alternating CO2 injection technique (CO2LSWAG) using a commercial compositional reservoir simulator. In these field-scale simulations, CO2 is stripped from the produced gas and reinjected into the reservoir. Primary oil recovery methods such as CO2 flooding and LSW flooding are also simulated. Chemical reactions between CO2 and the minerals present in the reservoir are modeled. Wettability change is assumed to be the main mechanism for improved oil recovery due to low salinity water injection. Compositional simulations of CO2 injection usually assume a constant injected gas rate. In this case, CO2 is supposed to come from an external source. In many petroleum reservoirs this assumption is true. Three factors are assessed in the present work. The first one is the natural reservoir pressure, which is the main driving force in primary production. The second factor is the amount of CO2 available for injection. The third one is the wettability change promoted by the reaction involving CO2. It is shown that in primary production, higher CO2 content leads to quicker depletion of the natural energy of the reservoir, leading to lower oil recovery. Nevertheless, higher CO2 content also means that more gas is available for reinjection, potentially leading to increased oil production. Finally, as CO2 reacts with minerals it promotes a change in wettability from an oil-wet to a water-wet state. It is shown that the CO2 content is an important variable to be assessed in a high CO2 content reservoir. Optimal injection practices must take these three aspects into consideration.
Petro-Elastic Modeling Applied to Multi-Porosity/Multi-Permeability Cores through a Simulation to Seismic Method
Authors: Ramsay Travis , Prabhakar Aravind
Published: September 2019

Multi-rock type cores can be characterized by complex higher order connectivity relationships within an agglomerated petrophysical system. A solution that relates multiphase flow simulation in cores to time-lapse seismic properties in order to examine closed-loop 4D integration is performed at a high level on a plug. While a 4D workflow is not explicitly examined in this work, the requisite petro-elastic modeling (PEM) method based on a simulation-driven interpretation of the Gassmann equation is described and a comparison is made with its empirically derived counterpart. This work illustrates that a simulation-driven petro-elastic modeling approach can be used to generate time-dependent saturated rock properties consistent with seismic attribute description at the plug and core scales. The results demonstrate the simulation-driven approach, of a petro-elastic model embedded in a reservoir simulator, as an alternative to relating pressure and saturation from reservoir simulator-to-seismic-derived properties using a priori empirically based correlations. The method discussed in this paper maintains appreciable continuity with the results of empirically based petro-elastic methods but demonstrates differences commensurate with principal fluid differentiation capability inherent to reservoir simulator-derived data and observed time-lapse seismic response. The significance of applied multi-porosity relationships is further realized upon examination of the time-dependent petro-elastic model results.
Numerical Relative Permeability Upscaling Based on Digital Rock Analysis
Authors: Sun Qian , Zhang Na , Alyafei Nayef , Wang Yuhe , Fadlelmula Mohamed
Published: September 2019

Reservoir simulation is commonly performed on upscaled models of complex geological models. The upscaling process introduces a principal challenge in accurately simulating two-phase fluid dynamics in porous media. To tackle this challenge, it is important to upscale relative permeability accurately. In this paper, a numerical method, which is based on the mimetic finite difference method (MFD) and digital rock analysis (DRA), is proposed for relative permeability upscaling. The validation of MFD is tested by two different cases with exact pressure solution. Then, the relative permeability of the digital rock (small element) is calculated based on the pore network modeling. The small elements are combined together to make up a larger model with different sizes (4×4×4, 6×6×6, 8×8×8, 10×10×10 elements). Finally, the accuracy of the proposed method is verified by comparing simulated results of the different sizes with that of the original one. The results show that MFD can solve the multi-phase flow scenarios with high accuracy and the L2 error follows the opposite trend to that of mesh size, which means that more refinement level gives less L2 error. For the upscaling of absolute permeability, the relative error can be decreased to 2.27%, which confirms that the proposed method is capable of calculating the absolute permeability with higher refinement levels. The fitting degree of the simulated water phase relative permeability to the original one is better than that of oil phase. The average relative error of water pahse relative permeability upscaling can decrease to less than 5.0%. It is found that the results will get worse when the model includes less elements. Especially at low water saturation, there exists some fluctuations for relative permeability curves and it may be due to the unstable state of the waterflood front with less elements involved.
Steady-State Multi-Phase Relative Permeability Under Simultaneous Water and Gas Injection: Application on Different Rock Types
Authors: Moghadasi Leili , Renna Dario , Bartosek Martin , Maddinelli Giuseppe
Published: September 2019

Quantification of multi-phase flow processes taking place in natural porous and fractured rocks has a remarkable relevance to economically sustainable management and viable development of oil- and gas-bearing geologic formations. Simultaneous flow of two- and three- fluid phases in porous media is typically based on a continuum scale description which imbues relative permeabilities as key system parameters to be estimated and linked to fluid saturations. Estimates of relative permeabilities are then employed to support better the quantification of productivity, injectivity, and ultimate recovery from reservoirs. In this work, we report the results of laboratory-scale three-phase relative permeabilities on diverse core samples. We also investigate the saturation history dependency (i.e. hysteresis) of three-phase relative permeability during under simultaneous water and gas injection.

Three-phase relative permeability data are obtained at different condition by the way of a Steady-State (SS) technique. We use direct X-Ray technique to assess the spatial and temporal dynamics of in-situ saturations. Dual X-Ray energies are employed to assess the SS three-phase saturations. The use of in-situ X-Ray scanning technology enables us to accurately measure fluid displacement during the core-flooding test. The SS three-phase experiments are condcuted by following various saturation paths including CDI, DDI and IDI. The C, D and I letters represent as Constant, Increasing and Decreasing (i.e., CDI saturation variation abbreviates Constant water, Decreasing oil and Increasing Gas).

We observe in all the of the tests, water relative permeabilities display an approximately linear dependence on the logarithm of its own saturation and show no dependency upon saturation history.

Three-phase oil relative permeability appears to be varied with all saturations and be dependent on all saturations phases. Gas three-phase relative permeability was affected more by saturation history than other phases. However in the test where the gas fractional flow was increased, the dependency of gas relative permeability on gas saturation was observed.

As only a limited quantity of complete three-phase data are available, this study stands as a reliable reference for further model development and testing.
Phased Redevelopment of a Giant Mature Offshore Field Using Maximum Reservoir Contact MRC Wells
Authors: Koeck Charles-Henri , Bensadok AbdelAziz , Goyal Praffula , Alhashmi Ali
Published: September 2019

A giant brownfield re-development project with long horizontal wells was initiated to arrest production decline mainly caused by a lack of pressure support and free gas influx from the large gas cap.

Key value drivers for the project are developing an understanding of the layers with regards to gas breakthrough, and achieving capital efficiency through low-cost well delivery, better planning and technology applications.

Firstly, the field has been segmented based on the analysis of multiple factors influencing the free gas production. It considers geological aspects such as the study of depositional environment and diagenesis, structural elements such as high permeability streaks and fractures, dynamic behaviors such as the water injection efficiency, gas cap expansion or coning.

Secondly, numerical simulations were then run in order to rank the sectors based on the expected model performance, compare them with real data categorization, and test the effect of the new proposed development schemes such as water injection at gas-oil contact and long horizontal wells equipped with downhole control valves.

It was found that each sector has a specific production mechanism and appropriate developments were recommended and then tested in the simulation. For instance, high permeability streaks play a significant role on the development of some sectors instigating a big difference of maturity between sub-layers, early water or gas breakthrough. Also, the inefficiency of water injection is one of the biggest issues of the field. Most of the water injectors are located too far from the oil producers, and have a low injectivity due to the often degraded facies in the aquifer because of diagenesis. This leads to a lack of pressure support that is counterbalanced by the gas injection, ending up with a lot of high GOR wells and a bad sweep from the top of the structure as the gas tends to by-pass the oil.

Simulation work showed that several remaining zones are safe for immediate development and should be prioritized for development in the near future. On the other hand, some of the mature layers prone to gas and water breakthrough need a boost for development, such as water injection at gas-oil-contact, artificial lift, low pressure system, GOR relaxation. Tight and undeveloped reservoirs are improved by implementing long horizontal drains.
Using Flow Diagnostics to Quantify the Impact of Reservoir Rock Typing on Fluid Flow in Complex Carbonate Reservoirs
Authors: Alhashmi Fahed , Geiger Sebastian , Albreiki Mohamed
Published: September 2019

A particular challenge inherent to carbonate reservoirs is reservoir rock typing which impacts model initialisation and saturation distributions and hence STOIIP, phase mobilities, and flow behaviours. We explore how flow diagnostics can be used best to detect subtle differences in reservoir dynamics arising from different model initialisations by comparing flow diagnostics simulations with full-physics simulations.

Flow diagnostics are applied to two reservoirs, a synthetic but realistic model representing an analogue for the Arab-D formation and a giant carbonate reservoir from the Middle East. Saturation modelling and reservoir rock typing is based on uniform and heterogeneous Pc and kr distributions, and further employs a state-of-the-art software that integrates of SCAL data and log-derived saturations. Sweep efficiency and dynamic Lorenz coefficients are then derived from the flow diagnostics results to quantify and compare the dynamic behaviour of the reservoir models. The full-physics simulations, which are used to validate the flow diagnostics results, are carried out with a commercial Black Oil simulator.

The flow diagnostics results can clearly distinguish between different homogenous and heterogeneous rock-type distributions, wettability trends, as well as novel saturation modelling approaches that use dedicated software tools. Flow diagnostics capture the same trends in recovery predictions as the full-physics simulations. Importantly though, the total CPU time for a single flow diagnostics calculation including model loading is on the order of seconds, compared to minutes and hours for a single full-physics simulation. These observation give confidence that flow diagnostics can be used effectively to compare and contrast the impact of reservoir rock typing, saturation modelling, and model initialisation on reservoir performance before running full-physics simulations. Flow diagnostic hence allow us to reduce the number of reservoir models from a model ensemble and select a small number of diverse yet realistic reservoir models that capture the full range of geological uncertainties which are then subjected to more detailed reservoir simulation studies.

Flow diagnostics are particularly well suited for complex carbonate reservoirs which are geologically more complex than clastic reservoirs and often exhibit significant uncertainties. Giant carbonate reservoirs are also challenging to simulate using full-physics simulators due to their size, so the impact of geological uncertainty on the predicted reservoir performance is often underexplored. Flow diagnostics are hence an effective complement to quantify uncertainty in state-of-the-art reservoir modelling, history matching and optimisation workflows, particularly for giant carbonate reservoirs.
Rejuvenating a Depleted Reservoir by Capitalizing Existing Facilities for Secondary Recovery in a Brownfield: A Case Study in Offshore Field
Authors: Usop Mohammad Zulfiqar , Suggust Alister Albert , Mohammad Razali Abdullah , Zamzuri Dzulfahmi , M. Khalil M. Idraki , Hatta M. Zulqarnain , Khalid Aizuddin , Hasan Azhari Muhammad , Jamel Delwistiel , Ting Yeong Ye Diana , Abdulhadi Muhammad , Awang Pon M Zaim
Published: September 2019

Reservoir G-4, a depleted reservoir in field B had been producing from 1992 to 2015 with a recovery factor of 30% before the production was stopped due to low reservoir pressure. Due to the huge inplace volume. A secondary recovery screening was conducted and gas injection was identified as the most suitable solution to revive G-4 reservoir due to its low cost impact of 0.4 Mil. USD whilst managing to deliver the same results as other solutions (i.e. Water injection & Water Dumpflood).

The project had utilized existing facilities in field B including a gas compressor. The project required only minor surface modification to re-route gas into the tubing of injection well BG-03. From simulation results, a continuous injection of 5 MMscf/d will increase the reservoir pressure by 150 psia in 9 months, with incremental potential reserves of atleast 5.0 MMstb from the benefitter wells, BG-02 & as well as incoming infill wells BG-14 & BG-15. It is also envisaged that with future development of additional infill wells, the recovery factor will be increased up to 60%.

In term of gas management, field B is able to deliver additional 15 MMscf/d post petroleum operation reduction (i.e. Fuel Gas, Instrument Gas & Gas lift). With the initiation of gas injection, the project had managed to utilize and optimize 33% of additional gas production for reservoir rejuvenation purposes.

The paper provides valuable insight into the case study and lesson learned of maximizing oil recovery through gas injection with minimal cost incurred. The approach is highly recommended to maximize oil recovery especially in mature fields with similar reservoir conditions and production facilities.
A New Method to Accurately Model Hydrocarbon Saturation in a Reservoir
Authors: Saini Prem Dayal , Van Der Steen Erik H. , De Jong Sander , Van Den Berg Francien
Published: September 2019

Hydrocarbon in place volumes are often inaccurate as a result of poor representation of the reservoir structure (by means of a 3D grid), that in combination with the use of traditional saturation calculation methods, lead to erroneous hydrocarbon volumes and poor investment decisions.

Traditionally a reservoir model is represented with a 3D grid, in a complex setting such as fault intersections and stacked reservoirs. A corner point grid is often used, which has limitations to represent this complexity. Further, the hydrocarbon saturations are then derived on a cell by cell basis on that 3D grid using simple averaging techniques of saturation height functions. The poor structure representation on the pillar grid in addition to the simplistic averaging methods lead to inaccuracies of the in place volumes especially where a prominent transition zone is present.

This paper presents new advanced saturation averaging methods (volume and height weighted) using saturation height functions on 3D grids. The new advanced saturation averaging methods are used on different reservoir models to compare the saturation distribution and volumetric differences against the traditional saturation calculation methods. A 4-way dip closure reservoir model with a tilted free water level (typical example of a carbonate reservoir in the Middle East), and a faulted S-grid model of the F3-FA field (North Sea) are used.

For the 4-way dip closure reservoir model, when comparing the advanced ‘volume weighted’ and traditional ‘by center of the part of the cell’ saturation averaging methods, a significant difference in the water saturations is observed which leads to about 5% difference in the calculation of in place hydrocarbon volumes. Further, it is observed that changing the thickness and orientation of the 3D grid cells can result in even larger differences of 5-10%.

The faulted F3 model shows that the difference between the hydrocarbon saturation values is largest where it matters most, that is, around the fluid contacts and in the transition zone. The new advanced saturation averaging methods give accurate hydrocarbon saturations irrespective of the size or complexity of the 3D grid and without any discretization effects.
Optimization of Oil Production in an Oil Rim Reservoir Using Numerical Simulation with Focus on IOR/EOR Application
Authors: Jaoua Maroua , Rafiee Mohsen
Published: September 2019

Development of oil rim reservoirs is challenging and could lead to low oil recovery, if multiple determining factors are not well understood, that influences successful field development concept. It requires detailed analysis and development of specific procedures to optimize the oil production from a thin oil rim underlaying gas cap. Few IOR/EOR applications for oil rim development have been reported in the literature so far. This study presents a concept for the optimization of oil production from an oil rim reservoir by numerical simulation.

As a starting point, a representative sector of the field was selected for the initial analysis. It was decided to perform IOR/EOR methods including water/gas flooding/injection and surfactant flooding using inverted five-spot horizontal well pattern, for the application in the selected sector. Upon execution of the detailed sensitivity analysis, the pattern was optimized by its characteristic geometric variables including the length of the vertical/horizontal section of the well, the location of the wells, lateral well distances and the orientation of the pattern. The optimization was performed by setting an objective function to improve recovery factor and reduce water/gas cut by using the differential evolution algorithm. The latter was run until converging, and the optimal solution was used to perform further IOR/EOR studies.

Finally, after selection of a base-case scenario and best well pattern, IOR/EOR options were evaluated, and the comparative results were reported. The generated results show that the application of 5-spot horizontal well pattern in the oil rim reservoir could increase the oil recovery by water flooding, but with low sweep efficiency. The losses of injected water into the underlaying aquifer and up laying gas gap are large. Immiscible gas injection into the gas cap can support the pressure but massively increases the gas cut. In addition, displacement efficiency by gas flooding is poor.

Simulation results of the surfactant flooding case shows better displacement efficiency compared to water flooding. Also, the possibility of reducing residual oil saturation could increase the ultimate oil recovery but at very late time.
Fully Implicit Reservoir Simulation Using Mimetic Finite Difference Method in Fractured Carbonate Reservoirs
Authors: Zhang Na , Abushaikha Ahmad Sami
Published: September 2019

A fully-implict mimetic finite difference method (MFD) for fractured carbonatereservoir simulation is presented. MFD, as a novel discritization, has been applied to many fields due to its local conservativeness and applicability of any shape of polygon. Here we extend it to fractured reservoirs. Our scheme is based on MFD method and discrete fracture model (DFM). This scheme supports general polyhedral meshes, which gives an advantage for reservoir simulation application. The principle of the MFD method and the corresponding numerical formula for discrete fracture model are described in details. In order to assure flux conservation, fully implicit method is employed. We test our method through some examples to show the accuracy and robustness.
A Modified Well Index To Account For Shear-Thinning Behaviour In Foam EOR Simulation
Authors: Soulat A. , Douarche F. , Flauraud E.
Published: September 2019

An accurate evaluation of injectivity is essential to the economics of any chemical EOR process. Most commercial simulators enable non-Newtonian behaviour modelling but it is often overlooked due to inadequate grid resolution. Indeed, in cases where shearthinning fluids are injected in a reservoir, shear rates and viscosities in the vicinity of the wellbore can be poorly estimated if the spatial resolution of the well grid-blocks is too coarse. This results in biases in injectivity and economics which we discuss here in the context of foam-based displacements.

We consider continuous foam injection in models of different spatial resolutions ranging from 1 to 100 m gridblock sizes and study the behaviour of injection wells obtained on the coarser grids compared with the results from a high resolution grid. This reference grid is sufficiently refined to account for near-wellbore large velocity gradients and render injectivity accurately. In this work we propose new formulations of the well index that capture shear-thinning behaviour that the conventional Peaceman calculation fails to address.

We first demonstrate that a poor evaluation of near-wellbore velocity leads to erroneously degraded injectivity on the coarser grids when compared to the reference grid. In order to correct these errors our modified well index is applied and validated in various scenarios of foam displacement simulation with radial grids. It captures a more accurate injectivity than the conventional Peaceman calculation once steady-state regime is reached. The modified well index we propose, used under a simplified form as direct input in reservoir simulation, significantly enhances injectivity estimates without resorting to grid refinements or modifying the shear-thinning model of the injected foam. In most cases it yields results that are closer to those obtained using grid refinements than the Peaceman formula at a much more attractive computational cost. Additional work remains to complete our understanding of injectivity in more complex settings, especially in the context of foam injection when effects such as foam dry-out and destruction in the presence of oil are as important on sweep efficiency as its shear-thinning behaviour.

Our workflow successfully corrects biases in the estimation of injectivity and yields more accurate results and avoids resorting to time-consuming methods such as grid refinements and physical input data alteration. Moreover it is simple to implement in most commercial simulators and does not require using empirical criteria. However, it bears some limitations which we also discuss.
Increased Production by Leveraging a Multidiscipline Approach for Fracturing a Complex Carbonate Reservoir
Authors: Bagir Muhammad , Andhika Banu , Zhia Ming Wu Ivan , Wijaya Rio , Lail Nasution Sakti , Chung Yee Lee
Published: September 2019

Numerous carbonate reservoir discoveries were made in Indonesia (Soeparjadi et al. 1975), including the Berai Formation, which consists of high heterogeneity and low porosity characteristics. To optimize production on a field-scale basis, developing an effective stimulation program is necessary to maximize the asset’s output. This integrated study demonstrates the multidiscipline approach of well stimulation and reservoir characterization for designing successful acid-fracturing stages. Understanding reservoir characteristics helps during selection of the effective fracturing design and staging plan for application.

The process involves multiple cycles—from formation evaluation (e.g., geomechanics analysis, design of an effective fracturing method, and production forecasting) through the economic impact to the operator. During the early phase of this integrated study, the uncertainties of all static and dynamic parameters (i.e., geological complexity, rock physics, and stress profile) were considered for fracturing design. Production performances from multiple fracturing stimulation scenarios were then modeled and compared to select the plan that optimizes production for the Berai Formation.

Results demonstrated an effective multidiscipline approach toward a comprehensive strategy to meet the ultimate objective in optimizing production. This project leveraged formation evaluation and fracturing design to deliver integrated solutions from exploration to accurate production forecast. The well stimulations were performed by carefully selecting fluid characteristics based on geological-petrophysical properties, pressure, and stress profiles within the area. Results yielded excellent production gains—for the best case, up to 50% with an average of 40% in comparison with initial production by using an acid that provides optimum fracture geometry and permeability.

This opportunity demonstrated the importance of understanding formation behavior and the parameters that aid the selection of an appropriate fracturing design for a low porosity/permeability carbonate reservoir.
Regional Reservoir Fluid Analysis and Interpretation based on the Integration of Petroleum Systems, Organic Geochemistry and PVT
Authors: Diatto Paolo , Cerioli Regondi Anita , Doering Sascha , Italiano Domenico , Maffeis Ivan , Marchesini Marco , Martin Marco
Published: September 2019

With the aim of improving the understanding of production behaviour in a multi-discovery asset and the evaluation of near-field exploration opportunities, an integrated study has been carried out involving three different disciplines: Fluid Thermodynamics (PVT), Organic Geochemistry and Petroleum Systems Modelling (PSM). The synergistic workflow has been undertaken starting from an accurate quality check of the initial dataset related to fluid samples and lab tests. By merging PVT and geochemical data, it was possible to carry out a robust statistical survey and explore correlations across different parameters and features; in this way, strict connection among many physical parameters and some oil maturity and biodegradation indices were identified. In the following step, after geo-referencing the fluid samples in the framework of the Petroleum Systems Model and tracking the locations of the source rocks, a reliable interpretation of the oil expulsion and migration history became possible over the whole reservoir fluid system. Finally, taking into account the simulated fluid phase envelopes, further insights were drawn in terms of the fluid phase behavior in different areas, contributing to reduce uncertainty and exploration risk for future activity in nearby prospects.
From Concept to Execution: A Successful Integrated Exploitation Philosophy
Authors: Mendoza Maria , Cevallos Gonzalo , Molina Edison , Piñeiros Silvia , Torres Water , Garrido Johnny , Gutierrez Ruben , Fonseca Claudio , Cortez Oscar , Fernandez Edgar , Paladines Agustin
Published: September 2019

An Ecuadorian lease ("Bloque 61") composed of 14 oil fields represents the most productive asset in the country. It contains 5.3 billion barrels of original oil in place (OOIP) distributed in four complex producing reservoirs. After 44 years of production and with a decline rate of 31% per year, maintaining the production from these fields represents an important challenge from the subsurface and execution viewpoints. In December 2015, an integrated service contract was signed with the national oil company (NOC) with a fixed investment for the development of the entire lease.

The challenge of the project was to maximize the value of a depleted asset through the framework of the contract. This mature asset has many opportunities to boost production and reserves by implementing an aggressive fit-for purpose development. The opportunities screened and implemented in only 12 months consisted of reaching new oil in appraisal and exploration areas and redevelopment of mature zones with horizontal and infill drilling with mainly reentry wells. Most valuable of all was the implementation of six waterflooding projects. All of these were executed in the Amazon rainforest where there is a pressing need to reduce environmental and social impact.

This exploitation philosophy has successfully changed the asset’s production decline, ramping production up from 60,000 BOPD to 80,000 BOPD. This integrated field development plan has amalgamated several technologies with a specific objective of optimizing the value of the asset. The long term was assessed through the drilling of exploration and appraisal opportunities where prospective resources were recategorized to reserves. The medium term was tackled by drilling horizontal wells and re-entries to optimize sweep efficiency and implementing water injection in the main structures. The short term was directed by executing workovers in areas where the water injection was in place. The asset value was recovered and increased as shown by a reserve’s replacement ratio of 1.13.

This approach will serve as a framework for the future integrated development of these types of mature assets. The technologies implemented have helped accelerating and optimizing the conceptualization and execution of the project; a few of these include high-resolution reservoir simulation, dumpflooding, closed-loop water source system, and dual-string completions. The integration of strong domain expertise, coupled with advanced technologies and workflows, has led to outstanding results.
Beta-Glucuronidase (GusA) reporter enzyme assay for Escherichia coli
Authors: Huber Madeleine , Soppa Jörg
Published: September 2019

The beta-Glucuronidase (GusA) is a long-known reporter enzyme for many different species [1]. The E. coli gusA gene is often used in plant research because plants lack an endogenous gusA gene. In E. coli, the transcript of the gusA gene is more stable than that of the highly used reporter gene beta-galactosidase (lacZ) [2]. The GusA activity can be determined using the artificial substrate p-nitrophenyl-β-D-glucopyranosid (pNPG). pNPG is converted to glucoronic acid and para-nitrophenol (pNP), which can be quantified spectrometrically at 405 nm. To avoid background, it is best to use an E. coli strain with a deletion of the chromosomal gusA gene, which is available e.g. at the Keio collection [3]. The gusA gene can be used for transcriptional fusions, e.g. to characterize promoters, and also for translational fusions, e.g. to study translational regulation. The assay was adapted to the microtiter plate format to enable the parallel handling of a large number of samples. The “procedure” (see below) describes an application with the gusA gene in a translational fusion with the gene of interest cloned under the control of the inducible arabinose promoter PBAD.
Comparison of dose distributions when using carbon ion radiotherapy versus intensity-modulated radiotherapy for hepatocellular carcinoma with macroscopic vascular invasion: A retrospective analysis
Authors: Shiba Shintaro , Shibuya Kei , Kawashima Motohiro , Okano Naoko , Kaminuma Takuya , Okamoto Masahiko , Kubota Yoshiki , Nakano Takashi , Ohno Tatsuya
Published: September 2019

Background. Studies comparing the dose distributions of carbon ion radiotherapy (C-ion RT) and intensity-modulated radiotherapy (IMRT) in patients with locally advanced hepatocellular carcinoma (LAHCC) are lacking. This study aimed to investigate the dose distributions of these modalities and identify any advantages to using C-ion RT.
Methods. Patients with LAHCC who had undergone C-ion RT between June 2010 and November 2018 were retrospectively analyzed. From among 210 patients with hepatocellular carcinoma who received C-ion RT, 10 consecutive patients with LAHCC were included. The dose-volume histogram parameters of clinical plans using C-ion RT at 60 Gy (relative biological effectiveness [RBE]) and simulated plans using IMRT at 60 Gy and 50 Gy were compared. We evaluated the three plans in terms of the following parameters: the percentage of the minimum dose that covered 95% of the target volume (D95); mean liver dose (MLD); and percentage of the normal liver volume that received at least 5 Gy (V5), 10 Gy (V10), 20 Gy (V20), 30 Gy (V30), 40 Gy, and 50 Gy. Patients at high risk of developing radiation-induced liver disease (RILD) were those with MLD and V30 of >23 Gy and >28%, respectively.
Results. The V5, V10, V20, and MLD were significantly lower in patients who received 60 Gy (RBE) of C-ion RT than in those who received 60 Gy of IMRT, although the D95 values were not significantly different. The V5, V10, and V20 were also significantly lower in patients who received 60 Gy (RBE) of C-ion RT than in those who received 50 Gy of IMRT; moreover the D95 was significantly superior in the former group. The numbers of high-risk patients who developed RILD when administered 60 Gy (RBE) of C-ion RT, 60 Gy of IMRT, and 50 Gy of IMRT were 1, 7, and 6, respectively.
Conclusions. C-ion RT exhibits a better dose distribution to the liver than does IMRT when treating patients with LAHCC. C-ion RT made it possible to treat patients with LAHCC who otherwise could not be treated using IMRT because of the high risk of RILD.
Association Of Diabetes With Sleep Duration and Quality in Urban and Rural Cameroonian Community Dwellers
Authors: LELE Elysée Claude BIKA , DOUMBE Jacques Narcisse , BORNE Philippe VAN DE , MESSOMO Thierry , MBANGO EDISARI , HERMANS Michel , DEGAUTE Jean Paul , LEEMAN Marc , MBATCHOU Hugo Bertrand , NGATCHOU William , LEMOGOUM Daniel
Published: September 2019

Background Sleep disorders are known to be linked with numerous cardiovascular co-morbidities like diabetes. The prevalence and impact of sleep quality and duration on diabetes in the Cameroonian population is not well established. The aim of our study was to evaluate the separate and combined roles of sleep duration and quality on diabetes mellitus in the urban and rural Cameroonian population.Methods This was a cross-sectional prospective survey conducted in 249 rural and 250 urban community dwellers in Cameroon aged 18 years and older. Sleep duration (SD) and quality were self-reported using the Pittsburg Sleep Quality Index (PSQI). Poor sleep quality was considered for PSQI score>5 and short SD was considered ≤6h. Diabetes mellitus was considered for fasting blood glucose≥126mg/dL and/or being on glucose-lowering medication(s). Multivariable logistic regression was used to determine the association of sleep duration and quality with diabetes.Results mean age was 36±12years with 39.1% male participants. Frequency of diabetes was 8.2% and was similar between urban and rural participants (10% vs 6.4% respectively; p=0.188). Frequency of poor sleep quality was 50.3% and was similar in urban and rural groups (48.2% vs 52.4% respectively, p=0.395). Short SD represented 30.5% of the sample and was more frequent in the urban than rural group (36.1% vs 24.8% respectively, p=0.006). Short SD was significantly associated with diabetes (OR 2.62, 95%CI 1.38 – 5.00) while poor sleep quality was not significantly associated with diabetes. Poor sleep quality combined with short SD was strongly associated with diabetes (OR 2.67, 95%CI 1.23- 5.79).Conclusion there is a necessity to take into account sleep duration and quality in the management of diabetes
Burnout level and associated factors in a Sub-Saharan African medical setting: prospective cross-sectional survey.
Authors: MACKANGA Jean-Rodolphe , MOULOUNGUI Emeline Gracia MOUENDOU , IBA-BA Josaphat , POTTIER Pierre , KOMBILA Jean-Baptiste MOUSSAVOU , BOGUIKOUMA Jean Bruno
Published: September 2019

Background Burnout, a real barrier to care, whose knowledge has often been established in the high-income medical context. However, in low and middle-income countries, such as sub-Saharan Africa, which is characterized by a precarious hospital situation and a high stakes linked to the Millennium Development Goals, burnout is poorly studied. The objective of our study was to evaluate, in the medical context of one sub-Saharan African country, the burnout level and associated factors.Methods a prospective cross-sectional study concerning doctors and doctoral student in medicine practicing clinical activity in Gabon. According to the Maslach Burnout Inventory Scale, the burnout symptom was defined by high level in at least one of the 3 dimensions and the severe burnout by high level in all 3 dimensions. Potential factors explored: demographic, socio-professional and psychometric. Multiple logistic regression, by backward method, established the model of factors associated with burnout symptom.Results out of 104 participants, severe burnout prevailed at 1.9% (95% CI: 0.2% -6.8%) and burnout symptom at 34.6% (95% CI: 25, 6% -44.6%). Model of factors associated with burnout symptoms: age (OR = 0.86, p = 0.004), clinical activity in a university hospital center (OR = 5.19, p = 0.006), the feeling of ease of access to the hospital (OR = 0.59, p = 0.012), the number of elderly dependents living with the practitioner (OR = 0.54, p = 0.012), living in a different borough from that of the hospital (OR = 0.24, p = 0.039) and the opinion score favorable to traditional medicine (OR = 1.82, p = 0.087).Conclusion in the Gabonese medical settings, almost one out of two practitioners is symptomatic of burnout. The young age, the university hospital center, the perceived difficulty to access the workplace and paradoxically the proximity to the hospital seems be at risk of burnout. The link between burnout and the perception of traditional medicine questions cultural issues in the doctor-patient relationship in this context.
Inhibition of Type I Interferon Signaling abrogates Early Mycobacterium bovis Infection
Authors: Wang Jie , Hussain Tariq , Zhang Kai , Liao Yi , Yao Jiao , Song Yinjuan , Sbair Naveed , Cheng Guangyu , Dong Haodi , Li Miaoxuan , Ni Jiamin , Mangi Mazhar Hussain , Zhao Deming , Zhou Xiangmei
Published: September 2019

Background: Mycobacterium bovis (M. bovis) is the central causative agent of bovine tuberculosis; however, it also caused serious infection in human beings. Type I IFNs is a key factor in reducing viral multiplication and modulate host immune defense against viral infection. However, the regulatory pathways of type I IFN signaling during Mycobactrium bovis (M. bovis) infection are not yet fully explored. Here, we investigate the role of type I IFN signaling on the pathogenesis of M. bovis infection in mice. Methods: C57BL/6 mice were treated with IFNAR1-blocking antibody or Isotype control 24 hour before M. bovis infection. After 21 and 84 days of infection mice were sacrificed, for analysis of type I IFN signaling on the pathogenesis of M. bovis. qRT-PCR and ELISA was performed to detect the expression of type I IFNs and relative gene. M. bovis induced lung lesions and viable bacterial count was assessed by conducting histopathology and CFU assay. Results: We observed an abundant expression of type I IFNs in the blood serum and lung tissues of M. bovis infected mice. In vivo blockade of type I IFN signaling reduced the recruitment of neutrophils to the lung tissue, mediate the activation of macrophages toward a pro-inflammatory profile and regulate the inflammatory cytokine production; however, no impact on T cell recruitment and activation in the early acute phase of infection was observed. Additionally, blocking of type I IFN signaling reduces bacterial burden in infected mice than untreated infected mice. Conclusions: Altogether, our results reveal that type I IFN mediates a balance between infection-mediated inflammatory reactions and pathogen’s control mechanism of the host during M. bovis infection. Thus, modulating type I IFN signaling could be exploited as therapeutic strategies against a large repertoire of inflammatory disorders, including tuberculosis.
Severe acute malnutrition and its associated factors among under-five children in two districts of Nepal
Authors: Ghimire Umesh , Aryal Binod Kumar , Gupta Ankush Kumar , Sapkota Suman Sapkota
Published: September 2019

Background : The main objective of this study was to identify the risk factors of severe acute malnutrition in under-five children in the two districts of Nepal. Methods: Using a mid-upper arm circumference measure, nutritional status along with the associated factors underlying determinants of undernutrition of 404 children who visited the Outpatient Therapeutic Centres were assessed using a validated structured questionnaire. Multivariate logistic regression was used to determine the factors associated with severe acute malnutrition (SAM) and associated variables. Results: The odds of a child being in the SAM category increased significantly if the family have five or more children and if the household yearly income is below an average. The children in the Madhesi family were 3.6 times more likely to be malnourished. Toilet facility (Adjusted Odds Ratio [AOR]: 4.45; 95% Confidence Interval [CI]: 1.88-10.53) and family with no kitchen garden (AOR: 3.16; 95% CI: 1.28-7.89) were significantly associated with SAM among under five children. Children from moderate food insecure and severe food insecure households were 3.2 and 5.5 times more likely to be malnourished respectively. Compared to the mothers with no job, mother with some sort of paid job had more than six times higher odds of having severely acute malnourished children.Conclusions: These findings suggest that the nutrition interventions as well as awareness on child feeding practices are crucial to improve the nutritional status of children especially among Madhesi community, poorer households and among illiterate mothers.