bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic morbidities of premature newborns
Authors: Balla György , Szabó Miklós
Published: September 2013

The most important chronic morbidities of premature newborns, deeply influencing quality of life, are retinopathy of prematurity, bronchopulmonary dysplasia, intraventricular hemorrhage and periventricular leukomalacia. Since the rate of premature birth has not decreased in recent years in Hungary, and treatments of these end stage disorders are extremely difficult, prevention gains tremendous significance. Effective prevention is based on detailed knowledge of the pathophysiological mechanisms of these special diseases having multifactorial nature sharing several common risk factors, and one is the pathological angiogenesis. This sensitive system is affected by several stress situations which are the consequences of prematurity leading to abnormal vascular growth. After birth, relative hyperoxia, compared to intrauterine life, and decreasing concentrations of vascular growth factors result in vascular injury, moreover, may cause vessel apoptosis. The consequence of this phenomenon is the activation of hypoxia responsible genes resulting in robust pathological neovascularization and organ damage during the later phase. Saving normal angiogenesis and inhibiting reactive neovascularization may lead to better quality of life in these premature infants. Orv. Hetil., 2013, 154, 1498–1511.
Milestones in understanding of the pathogenesis of immunmediated intestinal disorders. Development of their diagnosis and therapy
Authors: Arató András
Published: September 2013

In the last decades our knowledge has been enormously broadened about the structure and function of the gut associated lymphoid system. It was recognized how intricate and finely tuned connection exists between the gut bacterial flora and the intestinal mucosa. This subtle balance ensures mucosal homeostasis, which has a key role in organ defence against pathogens. However, at the same time this system makes possible the development of oral tolerance toward the commensals and the food antigens. In case of any disturbances in this finely tuned process, immunmediated intestinal disorders may easily develop. The first part of this paper reviews the structure and function of the mucosal immune system, while the second part surveys the pathogenesis, diagnosis and therapy of coeliac disease, inflammatory bowel disease and cow’s milk allergy induced enteropathy. Orv. Hetil., 2013, 154, 1512–1523.
Immediate Implant Placement in a Patient With Osteoporosis Undergoing Bisphosphonate Therapy: 1-Year Preliminary Prospective Study
Authors: Siebert Tomas , Jurkovic Richard , Statelova Dagmar , Strecha Juraj
Published: September 2013

The purposes of this preliminary study are to assess the risk of developing bisphosphonate-related osteonecrosis of the jaw (BRONJ) in a patient with osteoporosis using zoledronic acid and to report the results of a 1-year prospective clinical study regarding 5 immediately inserted implants in the anterior mandible. For this comparative prospective study, 24 female patients, aged ≥54 years, were chosen, all with partially edentulous mandibles. Group A consisted of 12 patients with osteoporosis taking zoledronic acid receiving a once-yearly intravenous infusion of zoledronic acid (5 mg). Control group B consisted of 12 other patients without osteoporosis and not taking drugs. In both groups, the remaining teeth were extracted before 120 implants, 3.7-mm wide and 16-mm long, were immediately installed in the interforaminal region of the mandibles. The 1-year implant survival rate was 100%. No apparent necrotic bone was observed among patients receiving zoledronic acid (group A) after implant surgery. Immediate implant osseointegration can be successful in a patient with osteoporosis using bisphosphonates, suggesting the safety of implantology as a treatment modality.
Controle da podridão-parda e características físico-químicas de pêssegos 'Magnum' submetidos a tratamentos pós-colheita com elicitores abióticos
Authors: Sautter Cláudia Kaehler , Brackmann Auri , Anese Rogério de Oliveira , Weber Anderson , Rizzatti Mara Regina , Pavanello Elizandra Pivotto
Published: September 2013

Este trabalho objetivou avaliar as características físico-químicas em pêssegos cultivar Magnum e fazer o controle pós-colheita da podridão-parda dos frutos submetidos a elicitores abióticos durante o armazenamento refrigerado. Os tratamentos foram: testemunha (sem tratamento), irradiação UV-C de 254 nm, ozônio, na concentração de 0,03 μL L-1, fosfito-K (40% de P2O5 e 20% de K2O) e acibenzolar-S-metil (50% de i.a.). Os frutos foram armazenados sob refrigeração a -0,5 °C durante 30 dias, sendo avaliados na saída da câmara e após cinco dias a 20 °C. Somente houve redução do crescimento da lesão causada pelo fungo Monilinia fructicola com o tratamento com ozônio; entretanto, os frutos deste tratamento apresentaram escurecimento na epiderme. Os demais elicitores não apresentaram efeitos na redução do crescimento da lesão.
Reservoir Simulation of Shale Barrier Failure in Heterogeneous SAGD Reservoirs: A Case Study
Authors: Wu Yongbin , Li Xiuluan , Jiang Youwei , Wang Hongzhuang , He Wanjun
Published: September 2013

In Xinjiang, China, a huge volume of heavy oil deposits is not commercially developed yet due to the high in-situ oil viscosity that is higher than 100,000 to 1,000,000+ cp and the strong reservoir heterogeneity. Two SAGD pilot tests with 11 wellpairs in total have been carried out since 2008 while the extensively distribution of shale barriers result in the poor SAGD steam chamber conformance, low production rate and high SOR.

This paper presents the workflow to break shale barriers to improve the steam chamber development along horizontal section, to reduce the SOR and to enhance the economic performance. The first step of the workflow is to select representative core and shale barrier samples and quantify the geomechanic data by high-pressure-high temperature dilation and shale barrier failure experiments. Meanwhile, the geologic model is built taking into account geological uncertainties of the reservoir and the core analysis results. And then, a small set of SAGD wellpair models are selected as the typical wellpair models by classifying different patterns of shale barriers distribution along horizontal section. Finally, the upscaled thermal reservoir models with geomechanics models using the data acquired by geomechanic experiments are investigated to model and optimize operation strategies for dynamic fracturing and shale barrier failure during SAGD phase.

The research reveals that the high-pressure CSS is an effective method to break the shale barrier distributed between the horizontal segments of the producer and the injector, which has been verified by field experience and the numerical simulation. It is forecasted that the case without HP-CSS will have the steam chamber growth at 50% percent of horizontal segment, which is 40% less than the case CSS. The ultimate oil recovery factor is 34.54%, which is 16.31% less than the case with HP-CSS; and the cumulative oil/steam ratio is 0.175, which is 14.5% less than the case with HP-CSS, encouraging SAGD performance after HP-CSS shows a better economic performance, which is worthwhile to carry out and also has a significant guidance for the similar SAGD reservoirs to improve the performance.
A Case Study Underlying the Importance of Sound Reservoir Surveillance Practice to Maximize Recovery from an Onshore Oil Field of UAE
Authors: Pratap M. , Al-Kendi S.
Published: September 2013

The strategy of development with simultaneous downdip water injection adopted in early 90's has enabled efficient pressure maintenance and sustained production from multi stacked reservoirs of an onshore oil field in UAE. Present study addresses bottommost twin reservoirs in the stack sitting one over other. Full field simulation model for these reservoirs built in 2006 encountered great difficulty in matching observed pressure trends in individual wells. The model predicted much higher pressures than observed in the wells. The mismatch was attributed to possible compartmentalization by numerous faults. Accordingly, further improvement in Geological model was affected in 2011 by updating it with more number of faults and modified structural configurations based on new 3D seismic interpretation. The simulation model was updated by incorporating improved geological model and the pressure-production-injection data till 2011. However, the simulation model still suffered from predicting much higher well pressures, as earlier. An MBAL analysis was then performed to investigate the average pressure trend of the twin reservoirs which indicated the possibility of irrational allocation of injected water at perforation level. This finding from MBAL study was later confirmed by the evidences from surveillance data.

The paper discusses how the finding from MBAL study has been confirmed by simulation study by successful history matching of well pressures after rational distribution/allocation of injected water. Evidences for irrational allocation of injected water to individual injectors based on available surveillance data have also been presented. Based on the findings, the management is embarking on the improvement in the surveillance of water injection using continuous and reliable monitoring techniques as accurate accounting of injected water is crucial for the success of ongoing development to ensure uniform sweep and avoid premature water breakthrough in the wells thereby maximizing oil recovery.
A Workflow for Developing Water-Oil Relative Permeability Hysteresis - Super Giant Carbonate Reservoir Case Study
Authors: Ismail Ahmed Mohamed , Hafez Hafez H. , Kalam Mohammed Zubair
Published: September 2013

Numerical modeling of mixed wet systems with a thick transition zone typically requires full hysteresis option to be invoked in the reservoir simulator. In this super giant carbonate reservoir with multi-million active cells and twelve reservoir rock-types, running the full hysteresis option proved prohibitive due to excessive run times, and in many cases the run fails. Traditionally, engineers resorted to generating scanning curves that mimic the hysteresis option manually using algorithms or spreadsheets. These scanning curves are input into the model as saturation functions. This paper aims at presenting the workflow for developing the water-oil relative permeability hysteresis for a mixed wet super-giant carbonate reservoir which optimize the 3D simulation run time.

To develop the appropriate bounding and scanning curves, three models were tested including Corey model, modified Corey, and Killough Hysteresis model. To ensure that the algorithm for each of these models resulted in reliable scanning curves, commercial simulator sector model was built and the resulted scanning curves from this sector model compared with the mathematical approach used to generate scanning curves from each of the three models over a wide range of water saturation.

Results indicate that the three models generate consistent bounding and scanning curves for the oil relative permeability. However, results for the water relative permeability differed for the three models, especially at higher water saturation –transition zone. Killough model shows unusual trend for water relative permeability scanning curves as compared with the bounding curve. Using scanning relative permeability curves show significant reduction in the simulation run times as compared with the full hysteresis option.
3-D Numerical Investigation of Subsurface Flow in Anisotropic Porous Media using Multipoint Flux Approximation Method
Authors: Negara Ardiansyah , Salama Amgad , Sun Shuyu
Published: September 2013

Anisotropy of hydraulic properties of subsurface geologic formations is an essential feature that has been established as a consequence of the different geologic processes that they undergo during the longer geologic time scale. With respect to petroleum reservoirs, in many cases, anisotropy plays significant role in dictating the direction of flow that becomes no longer dependent only on the pressure gradient direction but also on the principal directions of anisotropy. Furthermore, in complex systems involving the flow of multiphase fluids in which the gravity and the capillarity play an important role, anisotropy can also have important influences.

Therefore, there has been great deal of motivation to consider anisotropy when solving the governing conservation laws numerically. Unfortunately, the two-point flux approximation of finite difference approach is not capable of handling full tensor permeability fields. Lately, however, it has been possible to adapt the multipoint flux approximation that can handle anisotropy to the framework of finite difference schemes. In multipoint flux approximation method, the stencil of approximation is more involved, i.e., it requires the involvement of 9-point stencil for the 2-D model and 27-point stencil for the 3-D model. This is apparently challenging and cumbersome when making the global system of equations.

In this work, we apply the equation-type approach, which is the experimenting pressure field approach that enables the solution of the global problem breaks into the solution of multitude of local problems that significantly reduce the complexity without affecting the accuracy of numerical solution. This approach also leads in reducing the computational cost during the simulation.

We have applied this technique to a variety of anisotropy scenarios of 3-D subsurface flow problems and the numerical results demonstrate that the experimenting pressure field technique fits very well with the multipoint flux approximation method. Furthermore, the numerical results explicitly emphasize that anisotropy could not be ignored for the proper model of subsurface flow.
Enhancing Reservoir Understanding by Utilizing Business Intelligence in History Match Quality Check
Authors: Al-Zahrani Tariq , Al-Ghamdi Tariq , Al-Qarni Saad , Al-Tiban Ali , Al-Harbi Bader
Published: September 2013

The technology to process and analyze simulation model outcomes have improved exponentially in the past few years and gave engineers the ability to analyze results of simulation runs efficiently and effectively. Reservoir simulation engineers need to quickly analyze simulation runs based on difference among models calculated data and measured data to determine the quality of the simulation models. With the help of business intelligence tools, engineers are able to do certain quality checks of the model that enhances reservoir fluid flow understanding. History match quality check dashboard provides the required means to perform qualitative and quantitative analysis for simulation runs.

The developed reservoir engineering business intelligence tool helps engineers to extract statistical information of the simulation runs to quality check how close the model mimics historical performance. The tool provides means to quantitatively and qualitatively check critical well performance properties that include water cut, pressure, GOR and oil rate against the measured data. Using this tool, engineers will be able to identify wells (or cluster of wells) with issues in those parameters, allowing the engineer to rank simulation runs according to their history match quality.

This paper will discuss the algorithms behind the history match quality check dashboard that utilizes advanced data mining and visual analytics. A case study will exemplify identifying problematic wells in the history matched pressure, water cut, and oil production rate for one of Saudi Arabia field.
Success and Challenges in Gathering Dynamic Data in Tight Gas Condensate Fields - Lessons Learnt
Authors: Urquhart M. A. , Harrasi M.
Published: September 2013

In 2009 PDO started an ambitious tight and deep gas exploration programme, exploring for previously untapped reservoirs, both conventional tight gas plays as well as deep unconventional gas resources. These resources are typically in previously undrilled formations at great depths, highly overpressurized with high temperatures, and uncertain fluid fill and composition. The unique geological properties of these reservoirs require different strategies to acquire the necessary data to enable the assessment of fluid compositions, permeability and well productivity data that are essential input to development decisions.

The acquisition of formation permeability and productivity data is very challenging in these environments; the paper will demonstrate how well-testing data has been used to gather information on fluid flow characteristics and dynamic properties where hydraulic fraccing is routinely used to achieve commercial production rates.

Hydrocarbon saturation and fluid contacts tend to be highly uncertain in tight gas reservoirs, this paper demonstrates strategies to gather information on likely fluid content of reservoir zones during the exploration and appraisal stage. Acquisition of representative fluid samples for PVT purposes is also extremely challenging in these type of reservoirs and this paper will outline the success and challenges experienced to date in the North Oman Area, and illustrates examples where good quality samples have been recovered.
A New Method of Numerical Simulation for Viscoelastic Polymer Flooding
Authors: Wang Z. B. , Wang Q. , Ma D. S. , Ye Y. Z. , Liu Z. X.
Published: September 2013

Currently, polymer flooding can further improve oil recovery more than 10 percent on the basis of the water flooding in China. Many substantial indoor experiment results have shown that polymer flooding can significantly improve oil recovery because it can improve both sweep efficiency and oil displacement efficiency. Most of the current researches are from the indoor experiment by the ways of description on the rheological characteristics and the flow characterization of polymer solution in porous media. These kinds of research usually involve many parameters. However, it is very difficult to establish the polymer flooding mathematical model by the parameters from indoor experiments. So, the three mainstream percolation model describing the characterization of polymer viscoelastic flooding mechanism are reviewed respectively at first, such as synthetical resistance coefficient category, effective seepage viscosity category and residual oil reduced by normal stress category. Then taken the imperfections of current models as breakthrough, a new mathematical model with full consideration of polymer solution's viscosity and elasticity is established. After that, the corresponding numerical simulation program is completed. All the parameters in the model have clear physical meaning. Among these, characteristics of sweep volume expanded by the polymer solution's viscoelasticity are influenced by its solution properties, injection speed and reservoir pore structure; characteristics of oil displacement efficiency improved by its elasticity are considered by first normal stress difference under different shearing rate conditions. Comparing to relatively conventional mathematical models which only take polymer's viscous flooding mechanism into account, the new model can truly describe the oil displacement mechanism and production increasing effect of polymer flooding in a more comprehensive way. For the future, the establishment of the new simulation method can lay a good foundation for in-depth study on polymer flooding mechanism and its large-scale promotion and application.
Analytical Models for Well Test Analysis in Class 3 Gas Hydrate Reservoirs
Authors: Kome M. , Amro M. , Cinar Y.
Published: September 2013

Well testing in gas hydrate reservoirs is challenging due to the complexity of reservoir behavior. Gas hydrates dissociate when the bottom-hole flowing pressure drops below the hydrate equilibrium pressure, a phenomenon also seen in CBM reservoirs below desorption pressures. Relative permeability of reservoir fluids keeps changing at the dissociation front, depending on the prevailing reservoir pressure, a phenomenon also seen in gas condensate reservoirs. If transient rate and pressure behavior of the hydrate formation are to be interpreted accurately, the analytical model for interpretation should consider both phenomena. This makes well testing in these reservoirs more challenging, not forgetting the multiphase flow and the endothermic dissociation of hydrates during pressure drawdown. This implies a continuously changing bottom-hole flowing temperature for every bottom-hole flowing pressure, unlike what is seen in conventional gas reservoirs.

This paper presents new analytical models for well testing in class 2 gas hydrates. The heat consumption during hydrate dissociation, activated by a pressure depression, requires heat transport models to be incorporated in the diffusivity equation. By combining mass balance and energy balance techniques, a representative diffusivity equation for the reservoir behavior is derived. Constantly changing reservoir temperature, relative permeability and reservoir fluid properties make it imperative to use pseudo-pressure integrals to describe flow. The analytical solutions to the model are represented both for constant rate and constant pressure conditions for pressure transient and rate transient analyses, respectively. By expressing the analytical model in terms of dimensionless pseudo-parameters and considering the presence of free mobile fluid, for the constant terminal rate case, solutions provided van Everdingen et.al, Hantush et al., Jaeger et al. are implemented.

Due to the dependence of hydrate dissociation on the bottom-hole flowing pressure, constant pressure solutions provide a good tool for investigating the reservoir behavior through rate transient analysis. With further simplifications of the numerical approximations of the constant pressure solution provided by Erdwardson et al., semilog and diagnostic plots could be made.

Solutions to the constant rate and pressure are presented in this paper. A more general equation equation for rate decline analysis has been developed, with applicability in conventional gas reservoirs. A dimensionless compressibility-mobility function is incorporated in the model which is then related to the Arps decline curve models. Different methods of rate transient analysis are addressed in this paper to identify different reservoir parameters.
Integrated Three Phase Fluid Analysis Approach of PNC in Miscible Gas and WAG Injections of Complex Carbonate Reservoir
Authors: Gibrata Muhammad A , Kalam M Zubair , Mohsen A , Ashraf S , Basioni M , Mahdi Ahmed E
Published: September 2013

A project study has been performed in reservoir saturation monitoring of carbonate reservoir on-shore Abu Dhabi. An integrated three phase fluid approach of pulsed neutron capture (PNC) in miscible gas and water alternating gas (WAG) injection of complex carbonate reservoir is presented. It has utilized open hole logs, production logs, production test, fluid sampling/PVT and core data in workflow analysis. It has been a challenge to get accurate and reliable reservoir saturation during production phase with gas and WAG wells injection in this carbonate reservoir. It's complex reservoir conditions has added the challenge for reservoir saturation monitoring program, evaluation and management.

Standard logs data quality check and correction need to be performed to ensure of consistency in analysis. PNC-Sigma (Σ), reliable lithology and porosity were used in three phase fluid model approach by optimizing simultaneous equation. It optimizes relationship among tools, parameters and formation component volumes. End point PNC-Sigma gas, oil and water have been determined in analysis to get an accurate gas, oil and water saturation. Openhole sigma, resistivity log and special core analysis (Special Core Analysis-SCAL/Digital Rock Physic-DRP) data have been used to evaluate and validate the changing of reservoir saturation. Furthermore multi spinner/probes production logs, water flow log (WFL) would be recommended in horizontal/high deviation production or injection wells along with surface production test to get an accurate of recent fluid contribution of reservoir. Validated well production profile in logged or nearby area has been used for comparison and calibration for the results.

The integration approach of logs, well production/test and core data in particular carbonate reservoir has been used to provide accurate and reliable reservoir saturation results. It has been observed that the identification of miscible gas and water saturation using three phase fluid approach in reservoir has provided a lot of benefit for reservoir monitoring and management in this field. The integration of formation evaluation in this case study has provided improvement, reliability in reservoir saturation results for carbonate reservoir monitoring and management.
Engineering Workflow for Probabilistic Assisted History Matching and Production Forecasting: Application to a Middle East Carbonate Reservoir
Authors: Maucec M. , Singh A. P. , Carvajal G. A. , Mirzadeh S. , Knabe S. P. , Chambers R. L. , Shi G. , Al-Jasmi A. K. , El Din I. H. , Nasr H.
Published: September 2013

Traditional reconciliation of geomodels with production data is one of the most laborious tasks in reservoir engineering. The uncertainty associated with the great majority of model variables only adds to the overall complexity. This paper introduces an engineering workflow for probabilistic assisted history matching that captures inherent model uncertainty and allows for better quantification of production forecasts.

The workflow is applied to history matching of the pilot area in a major, structurally complex Middle East (ME) carbonate reservoir. The simulation model combines 49 wells in five waterflood patterns to match 50 years of oil production and 12 years of water injection and to predict eight years of production. Initially, the reservoir model was calibrated to match oil production by modifying permeability and/or porosity at well locations and by fine-tuning rock-type properties and water saturation. The second level history match implemented two-stage Markov chain Monte Carlo (McMC) stochastic optimization to minimize the misfit in water cut on a well-by-well basis. While relative to evolutionary algorithms or the ensemble Kalman filter (EnKF), the McMC methods provide a statistically rigorous alternative for sampling posterior distribution; when deployed in direct simulation, they impose a high computational cost. The approach presented here accelerates the process by parameterizing the permeability using discrete cosine transform (DCT), constraining the proxy model using streamline-based sensitivities and utilizing parallel and cluster computing.

While probabilistic assisted history matching (AHM) successfully reduced the misfit for most producing wells, the computational convergence was sensitive to the level of preserved geological detail. The optimal number of representative history-matched models was identified to capture the uncertainty in reservoir spatial connectivity using rigorous optimization and dynamic model ranking based on forecasted oil recovery factors (ORFs). The reduced set of models minimized the computational load for forecast-based analysis, while retaining the knowledge of the uncertainty in the recovery factor.

The comprehensive probabilistic AHM workflow was implemented at the operator's North Kuwait Integrated Digital Oilfield (KwIDF) collaboration center. It delivers an optimized reservoir model for waterflood management and automatically updates the model quarterly with geological, production, and completion information. This allows engineers to improve the reservoir characterization and identify the areas that require more data capture.
Well Inflow Modelling for Wells Not Aligned to a Numerical Grid
Authors: Egberts P. J. , Shatyrbayeva I. , Fokker P. A.
Published: September 2013

In numerical reservoir simulation practise the orientation of the spatial grid is often dictated by geological features of the reservoir model. As a consequence the trajectory of, in particular, a horizontal or slanted well or a well with a complex geometry, possibly with multilaterals, generally is not aligned to the numerical grid. This situation may lead to significant numerical artefacts, as an irregular inflow profile along the well. Although the total flow rate of the well may be reasonably accurate, a non-smooth profile is unwanted if the simulator is coupled to a dedicated wellbore flow model. Another artefact occurs if the ratio of the vertical to horizontal permeability is small (i. e. kv/kh< 0.001): standard models result in an overestimation of the total flow rate.

Well inflow modelling relates the so-called well index, the ratio between well rate times viscosity and the difference between the well pressure and the gridblock pressure, to quantities such as gridblock dimensions and permeability. The origin of the numerical issues is the limitation of the well index estimation as proposed by Peaceman, and generalised by Alvestad for wells not aligned to the grid.

We combined simulation results of a semi-analytic model and simulation results from a dedicated numerical simulation to calculate so-called semi-analytical well indices. We demonstrate that by using these semi-analytical well indices in a numerical reservoir simulator the aforementioned issues are resolved. The semi-analytic model that has been used solves the equation for steady state flow in 3D for line sink(s) with variable influx. The variable influx is then exploited to approximate a uniform pressure condition along the wellbore. This modelling approach allows for a complex geometry of the well such as a multilateral.

To arrive at a practical implementation of our method we propose to use the standard well index along with a corrective skin factor based on our approach. Correlations for such a corrective skin factor then need to be developed based on a great number of well scenarios, anisotropy ratios and grid aspect ratios.
Rock-typing using the complete set of additive morphological descriptors
Authors: Ismail Nurul Izza , Latham Shane , Arns Christoph H.
Published: September 2013

The mechanical and transport properties of reservoir rocks depend on the morphology of microstructure, e.g. connectivity, size and shape of grains and of the pores. Such information can be gained from digital core analysis, which is increasingly used to understand the internal fabric of heterogeneous rocks or for the analysis of samples not amenable to standard laboratory analysis. At the same time, big advances are made on the imaging hardware side including the development of ultra-high resolution CCDs and recording techniques like helical scanning, leading to datasets of enormous dimensions and relatively large field of view. In this context it is highly desirable to develop automatic coarse scale classification methods to e.g. recognize the occurrence and spatial structure of digital rock types within such tomographic images - or existing morphological trends within a rock type, as this may lead to powerful characterization and data reduction techniques as well as upscaling methods.

We use regional Minkowski measures to define fine-sale rock types using a multi-variate Gaussian mixture model for classification. The discriminative power of the method is firstly demonstrated for an artificial sample which consists of a mixture of Poisson processes spatially separated using a Gaussian random field approach. Furthermore, we demonstrate how this method can be used to describe the fractions of two spatially overlapping non-stationary process generating a morphological trend - e.g. a fining up sequence. Finally, the method is applied to discriminate different morphological regimes of a thin- bedded sandstone. Importantly, for morphologies resulting from a Poisson process of grains, the classification result can directly be used to predict physical properties using effective grain shapes. For other processes such a relationship may be developed; in particular, using the classification result subsections of a tomogram can be selected for which such a relationship can be derived explicitly.
Pore-Scale Visualisation of Two-Phase Fluid Displacement Processes in a Carbonate Rock using X-ray micro-Tomography Technique
Authors: Pak Tannaz , Butler Ian B. , Geiger Sebastian , van Dijke Rink , Jiang Zeyun , Elphick Stephen , Sorbie Ken
Published: September 2013

The physics of multi-phase displacement processes in the individual pores of a connected pore-network of a rock ultimately controls how oil, gas and water move in reservoir rocks and how readily they can be produced. These pore scale processes, including piston-like displacement, snap off, film-flow and fluid redistribution have been studied traditionally in pore-network simulations as well as in 2D micro-model experiments. However, recent advances in X-ray computed micro-tomography (CT) techniques now enable us to visualize and monitor these processes in 3D during in-situ core flooding experiments at pore-scale resolution. This provides new information on the spatial and temporal evolution of oil and water phase clusters and films.

In this paper, we present results of a suite of two-phase fluid displacement experiments performed on a dolomite core plug. The experiments consist of a series of fluid injections and in-situ CT scans of the core in certain time steps during the drainage and imbibition displacement processes. The fluid phases are brine and a mineral oil. A simple, low-cost and highly X-ray transparent design for core flooding cells is introduced.

Our experiments and CT images allow us to visualize the 3D fluid structures of each phase during fluid displacements in carbonate rocks with excellent clarity. Piston-like displacement and snap off mechanisms have been captured clearly in 3D. In addition, the formation, collapse and reorganisation of brine films surrounding oil blobs in individual pores were clearly visualised. However, the formation of oil films, which could provide connectivity for the hydrocarbon phase at low saturations, could not be observed in these experiments. The observed displacement processes and the particular oil-water/rock configurations seen in the displacements suggest the rock is preferentially water wet.
Impact of the Spatial Correlation of Microporosity on Fluid Flow in Carbonate Rocks
Authors: Jiang Zeyun , van Dijke Marinus I. , Geiger Sebastian , Kronbauer Denise , Mantovani Iara Frangiotti , Fernandes Celso Peres
Published: September 2013

Pore-network modelling, or digital petrophysics, is an emerging technology which allows computing physically consistent two- and three-phase flow functions such as relative permeability and capillary pressure curves at arbitrary wettability. Considering the difficulty in measuring these functions reliably in the laboratory, pore-network modelling is increasingly used to guide and complement costly and time-consuming SCAL programmes. Although pore-network modelling is now well-established for clastic reservoirs, applying it to carbonate rocks is significantly more challenging due to their complex and multi-scale pore structure, comprising micro- and macro-pores as well as cracks and fractures. We have hence developed a novel method to integrate pore-networks, which have been extracted at multiple scales directly from CT images at different resolutions, into a single pore-network model that can be used in subsequent calculations of two- and three-phase flow functions. This method has been validated by comparing computed two-phase relative permeability and capillary pressure curves for a multiscale network to the corresponding laboratory measurements. However, in this approach it is important to accurately consider the impact of the spatial distribution of fine network elements, which are extracted from high-resolution images. We therefore show the impact of the spatial correlation of high-resolution porosity on single- and two-phase fluid flow and propose a model that allows us to simulate the spatial correlation between coarse-scale pores and fine-scale porosity in the absence of a suitable CT image that segments the rock into three phases (pores, sub-resolution matrix porosity, and solid). We demonstrate the impact of the spatial correlation of microporosity on absolute and relative permeabilities by applying this model to various datasets, including CT images of an off-shore carbonate reservoir. This demonstrates that the spatial correlation of microporosity is one of the key factors controlling recovery from carbonate reservoirs and that our new method allows us to quantify it.
Evaluating Injection Performance With High-precision Temperature Logging And Numerical Temperature Modelling
Authors: Aslanyan Arthur , Wilson Michael , Al-Shammakhy Abdullah , Aristov Sergey
Published: September 2013

The paper shows how high-precision temperature (HPT) logging and numerical temperature modelling for radial flow injection (TERMOSIM) assess the performance of water injection wells, and outlines specific features of modern temperature logging tools and logging procedures. The basic principles and critical elements of temperature modelling for injection wells are discussed. The paper presents five cases illustrating how the fitting of a numerical model to actual temperature logs can be used to describe the injection pattern including complicacies caused by behind-casing channelling. Particular attention is given to how temperature logging and modelling complement information obtained by the conventional PLT technique based on the mechanical spinner. The concept and basic features of the TERMOSIM temperature modelling software are given in the Appendix.
Fracture System in the Carbonate Reservoirs of Abu Dhabi: Implications for Field Development
Authors: Sirat Manhal , Sembiring Edison , Al-Hammadi Mohamed I. , Baguenane Boussad , Elbekshi Amer
Published: September 2013

Characterization of fractured carbonate reservoirs aims at delineate and constraint various data entries to help providing realistic model, which ultimately can be used to predict reservoir dynamic behavior in the near- and far future, hence helps field development planning. In the structurally complicated and highly faulted SE Abu Dhabi region, two hydrocarbon Fields (A and B) are currently under development. We aim at characterizing the fracture system in this region by integrating both direct and indirect data sets to avoid possible early water cut by the existing seismic faults and to help increasing the productivity by the existing relatively short fractures associated with these faults.

In this paper we extensively used seismic attributes analyses including curvature, discontinuity and semblance to characterize the seismic fault system in SE Abu Dhabi. We also incorporated the available well data including FMI, CMI and geomechanical data such as elastic and mechanical properties and stress profiles to characterize these seismic faults with their associated sub-seismic fractures. Further, we used basic structural assumption of the regional paleo- and current stresses together with the in-situ stresses to help estimating the potential openness of these fractures over geologic time.

Results reveal that the SE Abu Dhabi has two regions with different structural settings; an eastern region wherein the two Fields exist, and a central region to the west. The eastern region close to the border with Oman is characterized by relatively high deformation, which has resulted in more intense folding in a highly elevated terrain, and faulted with two prominent conjugate-like fault sets; N75W and N45W. The central region is characterized by low elevated terrain comprising gentle folds and the existence of a prevailing N75W fault and less dominant N45W faults. In both regions these seismic faults are segmented laterally and vertically with the existence of several relay-ramps and small scale flower structures with limited fault throws forming numerous undulations.

The significance of these results is that the development planning has been mainly governed by the existing fault patterns in both regions, where seismic faults with their associated fractures control placement, length and direction of the new planned horizontal wells. It is recommended to place the horizontal wells in the NE direction for well stability and production improvement. The horizontal wells in this direction should be placed relatively away from aquifers both vertically and laterally to avoid early water-cut. The presence of the flower structures, which can be valuable exploration targets, may need different well design for development.
Integration of Permeability Derived From Well Pressure Transient Analysis To Improve Prediction Model Permeability In High Heterogeneous Carbonates Reservoir - Case Study-offshore Abu Dhabi, UAE.
Authors: Khemissa S. RG-Hocine , Lesage P. E-Alexander , Ahmed Akram P. E-Fazeel , Draoui T. L-Elyes , Nakamura T. L-Shinichi , Al-Alyak Abass , Walia Samir , Das Surya
Published: September 2013

The main objective of this study is to enhance a Predicted Permeability (K_Pred) by integrating Permeability resulted from the interpretation of more than 100 P.T.A. Initially the predicted permeability was generated using neural network method (Combining core and log data) over all 254 wells penetrating the reservoir.

To achieve this task a number of workflows have been discussed and tested and finally two methods were implemented which resulted in two permeability models.

The first model, consist of generating enhanced permeability maps for each porous zone using Permeability Predicted (K_pred), core and well test data. These maps were used as multiplier in Upscaled model to generate the total permeability then exported to reservoir engineer for simulation.

The second model, consist of generating the enhanced permeability by integrating Permeability Predicted (K_pred), core and well test (KH) under each well (Log scale) in order to capture the dynamic changes of the property. This enhanced permeability was populated in geological model using stochastic methods conditioned to Rock Type and porosity.
A System of Key Performance Indicators in Intelligent Fields
Authors: Temizel Cenk , Dursun Serkan , Purwar Suryansh , Hancioglu Baris
Published: September 2013

The vast amount of historical and real-time data in intelligent/smart fields can be used to make efficient decisions for improving field production. However, large volumes of data may not necessarily result in high-quality decisions, especially when uncertainty exists in the field development. In this paper, a decision-making approach that can be applied to the problems related to key performance indicators in intelligent/smart fields is presented. The proposed system involves two novel indices, well present performance index (WPPI) and well future potential index (WFPI), which integrate the present and future performance, value, and contribution of each well (production and injection) in the intelligent field. WPPI is an indicator of how the well is performing currently, and WFPI determines the future value of the well to help make workover or shut-in decisions. WPPI and WFPI offer more global solutions, while known key performance indicators focus on field-, pattern-, or well-level analysis. The proposed system can rank the wells in the field using a digital oilfield workflow which automates the decision-making process and helps reservoir management. The main issue in using multiple attributes or performance indicators is the dependency of the attributes on each other and the low-degree representation of the significance of each attribute. As parameters are not ‘mutually-exclusive’, it becomes difficult to avoid using correlated attributes. The exclusiveness and significance of each attribute or indicator together with varying engineering judgment make the automation more difficult. It is challenging to standardize engineering judgment, but automation might be more clear and applicable with a method that tries to simplify a multivariate ranking problem.
Using 4D Seismic to Validate the Geomodel for the South Arne Chalk Field
Authors: Lüthje M. , Stokkendal J. , Lindelow-Marsden C. C. , Johansen K. , Jensen L. J.
Published: September 2013

The South Arne chalk field is located in the Danish sector of the North Sea. It is a double-dipping anticline extending 12½ km by 3½ km. Production started in the summer of 1999 using horizontal wells and water flooding with a cumulative production to date of 141 MMbbl from the two oil bearing intervals: Maastrichtian (Late Cretaceous) Tor Fm and Danian (Paleocene) Ekofisk Fm.

3D seismic was shot in 1995 (pre-production), in 2005 and in 2011. The matrix permeability of the field is low but greatly enhanced due to natural fractures. Based on the 2005 seismic interpretations a geomodel was built with emphasis on capturing the permeability enhancement due to the occurrence of fractures. The modelling was done using discrete fracture network (DFN) modelling. Fracture density was calculated based on various attributes and the outcome calibrated to well test data. Calibration was performed using full field adjustments on fracture properties enhancing predictability in less data dense areas. The model has been history matched to production data with a good overall result. The seismic shot in 2011 was compared to pre-production seismic data giving valuable information about unswept areas and water cutting as well as differences between the two reservoir intervals. The 4D data also shows that the faults have significant influence on fluid flow as modelled in the geomodel. Using fluid substitution modelling, the strongest signal is expected to come from changes in Sw. Comparing the observed changes from 4D seismic to the history-matched modelled changes in Sw, from pre-production to 2011, a very good match is found, thus validating the geomodel.
Quantifying Gas Saturation with Pulsed Neutron Logging—An Innovative Approach
Authors: Al-Nasser Mamdouh N. , Ma S. Mark , Al-Mushrafi Nedhal M. , Al-Muthana Ahmed S. , Riley Steve , Geevarghese Abel I.
Published: September 2013

In reservoir surveillance, gas saturation is routinely monitored both in gas reservoirs for reservoir performance and in saturated oil reservoirs to prevent gas coning or to optimize infill drilling well placement. This paper presents a new pulsed neutron technology and method that enable the quantitative monitoring of the gas saturation variations to address these reservoir management issues. One of the key features of the newly designed pulsed neutron tool is the new type of Lanthanum Bromide (LaBr3) detectors. The extra-long spacing of the far detectors provides a larger volume of investigation that is more representative of the actual reservoir condition. The quantitative aspect of the measurement is achieved by using the ratios of the detector counts, so that the rock matrix effects are diminished, as opposed to the traditional sigma measurement, which can be influenced significantly by the rock matrix properties. This new tool and data interpretation methodology have been tested in both clastic and carbonate reservoirs with encouraging results. This paper presents an overview of the technology and some field application examples.
The use of Geophysical Data in MPS Facies Simulation in a Seismically Tuned Reservoir - a new approach Based on the Direct Sampling Algorithm
Authors: Kombrink H.. , Lallier F.. , Vignau S..
Published: September 2013

A relatively new Multiple Point Statistics algorithm, Direct Sampling (DS), has been tested using a turbidite lobe succession as an example. A seismically derived probability cube was used as auxiliary data. The results show that the combination of low resolution auxiliary data (reservoir is seismically tuned) and a high resolution training image produces geologically realistic reservoir facies geometries. It is shown that it is convenient to use the reservoir grid as a training image, which is an efficient way in order to achieve a reliable correlation between facies in the training image and auxiliary data. Since the training image is highly non-stationary, only the realisations obtained when applying a high weight (>0.4) of the auxiliary variable can be appropriately used. Simulations produced by the IMPALA algorithm are less convincing, which leads to the conclusion that it is recommendable to use DS in similar cases.