bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Behavior in Shale Organic and Inorganic Nanopores From Molecular Simulation
Authors: Jin Bikai , Nasrabadi Hadi
Published: October 2017

Production from shale reservoir is getting more attention from the oil industry. However, the shale is not understood as well as conventional reservoirs. One complexity is the unclear fluid phase behavior in shale nanopores. In previous work, the shale rock is usually built as a simple model without consideration of the material effect on phase behavior. To have a better understanding of phase diagrams in different shale environment, three materials (two inorganic minerals and one kerogen) are used in this work to generate two types of nanopores (slit and cylinder), which are adopted in the phase behavior simulations of pure fluids (methane and propane) and one ternary fluid (C1/C3/nC5). From the pure fluid tests in pores of three diameters (4, 7, 10 nm), confined liquid densities are decreased while vapor densities are increased in slit and cylinder pores. Critical points are shifted to lower densities and higher temperatures. Group tests are conducted for the ternary fluid in slit and cylinder pores at one temperature (160 °F). Under confinement, there is a big shift in the nC5 composition of the vapor phase in the ternary diagrams while only small changes have been observed in the liquid composition. The density difference between two phases is reduced. Additional tests are performed at one typical shale temperature (290 °F) for this ternary fluid in both pore types. Phase separation is computed in slit pore tests while only one phase is formed in tests of cylinder pores. Since the cylinder pore has more adsorption surface area, compared with the slit pore, a stronger adsorption effect is introduced in all tests of cylinder pores. Based on the comparison of all results (pure fluids and ternary case) from three materials, the calcite pores provide stronger confinement effect on fluids and the other two materials have the similar confinement effect on phase diagrams.
Stress-Induced Damage Evolution in Unconventional Shale Monitored by Acoustic Emission
Authors: Jin Guodong , Ali Syed Shujath , Muqtadir Arqam , Hussaini Syed Rizwanullah , Nair Asok , Alshanqaiti Elham , Khodja Mohammed R. , Ali Abdul Wahab
Published: October 2017

This paper experimentally investigates the damage evolution (or the deformation process) induced by externally applied stress on unconventional shale samples. The focus is to understand the physics behind the complex failure process occurring at the micro-scale, and thus provide useful information on the macro-fracture mechanisms of unconventional shales. We perform the compression tests along with the acoustic emission (AE) measurement on cylindrical rock samples selected from Berea sandstone (BS), Eagle Ford (EF) and Marcellus formation. Tests are conducted under the same stress condition: uniaxial unconfined compression test and triaxial compression test with a confining pressure of 10 MPa. AEs are continuously collected to characterize the progressive damage process. The axial stress, axial and radial displacement are also recorded during experiments. Shale samples are drilled perpendicular or parallel to the beddings. The X-ray diffraction (XRD) analysis is used to measure the mineralogy and clay content. Prior to geomechanical testing, the high-resolution micro-CT imaging system is used for quality assessment of rock samples and characterization of microstructure and fracture presence.

All samples studied exhibit distinct characteristics of AE counts. In Berea sandstone, AE counts initially increase slowly with the axial strain, and then surge dramatically after reaching the yield stress point. This is consistent with the observed stress-strain behavior: a linear elastic part followed by the inelastic deformation till the rock fails. Compared to Berea sandstone, shale samples show a different characteristics of AE counts. AEs resulting from EF vertical sample monotonically increase until the sample fails, while three stages of AE activity are observed in the horizontal sample: initial increase followed by a stage of quiet period (no AE events), and increase again. Marcellus samples behave just the opposite: three stages of AE events are observed in the vertical sample, while monotonically increase in the horizontal sample. AEs are also observed to be affected by the test condition: different from the triaxial compression test, Marcellus vertical and horizontal samples have a similar trend in AE counts during the uniaxial compression test. Both initially increase in AE activity with the axial stress, and after a certain stress, a surge in AE activity is observed. The observed discrepancy of AEs can be due to the complexity of shale mineralogical compositions, pore geometry and thin layer structure. More detailed laboratory experiments are necessary to understand the physics behind the complex failure process and AEs occurring at the micro-scale in unconventional shales.
A Novel Mechanism of Alkaline Flooding to Improve Sweep Efficiency for Viscous Oils
Authors: Xiao Rong , Teletzke Gary F. , Lin Michael W. , Glotzbach Rodney C. , Aitkulov Almas , Yeganeh Mohsen , Jaishankar Aditya , Hegner Jessica
Published: October 2017

A mechanism of alkaline flooding to improve recovery for viscous oils was found to be related to the transition of emulsions from low viscosity and low water-oil-ratios (WORs) to high viscosity and high WORs. Distinct behaviors of emulsions formed by alkaline brines and acidic, viscous oils were experimentally observed by mixing alkaline brines and oils at different WOR. Depending on the oil type and the brine formulation, different transition behaviors of the emulsions were observed. In some cases, low viscosity oil-in-water (O/W) emulsions were observed at low WOR while high viscosity water-in-oil (W/O) emulsions were observed at high WOR. This transition of emulsion type and properties was associated with significant uplift in recovery by alkaline flooding over water flooding as observed in sandpack floods. Meanwhile, when the emulsions did not exhibit transitional behaviors and remained the same type with varying WOR, the incremental recovery by alkaline flooding was very small, regardless of whether the viscosities of the emulsions were high or low. A novel mechanism associated with flow re-direction and sweep efficiency improvement was proposed and validated using micromodel experiments. Results of this work lead to new opportunities and screening criteria to apply alkaline flooding for viscous, acidic oils.
Improving Governance of Integrated Reservoir and Information Management Leveraging Business Process Management and Workflow Automation
Authors: Escorcia Alvaro , Mohan Richard , Saputelli Luigi
Published: October 2017

This paper illustrates strategies, methods, and techniques that have been successfully utilized to model and deploy collaborative solutions to help teams and individuals within and across companies execute business processes efficiently and consistently, whilst ensuring adherence to norms, standards and agreed guidelines for the benefits of shareholders and contractual parties. Cases are presented related to Integrated Reservoir Management, E&P Technical Information Management, and Surface Rights Management for O&G operations. Whilst some contextual aspects of information technology are mentioned in this paper, the focus rather lies in the aspects of value delivery through process governance, workflow automation efficiencies, process improvement, and reduction of time to learn how things must be done on a day to day basis by newcomers.

Business process management (BPM) is a technique that brings efficiency and effectiveness to the execution of processes. Rather than replacing big systems, companies are looking at technologies that facilitate implementing operating processes on a workflow orchestration platform that establishes a controlled environment to execute defined activities efficiently. The convergence of business process modeling, business rules engines, process performance monitoring and human workflows has led to adoption of integrated systems leveraging BPM platform solutions.

Wide market availability of BPM platform solutions makes possible chosing from diverse types of architecture, functionality, usability and integration capabilities to meet the information management requirements of an operating company. However, adherence to Business Process Modelling Notation (BPMN) and to data and integration standards, is critical to balance governance of processes with agility and flexibility to adapt workflows, especially in companies that require to scale-up workflows initially created for the needs of one functional or organizational area across and into others. Using standards is critical in cases where collaborative workflows require integration and interaction with data, calculations, and transactions performed in existing back office and/or Petrotechnical systems.

Successful BPM implementations are those that become adopted by business users and create incremental value. This requires a systematic approach to process improvement opportunity identification, creating realistic business cases, defining and tracking process performance metrics, communicating value and strategic alignment lead by management, and effective management of change.
A Meta-Data Framework for Transparency in Rate of Penetration Calculations
Authors: Goncalves Kyle , Ashok Pradeepkumar , Cavanaugh Martin , Macpherson John , Behounek Michael , Nelson Brian
Published: October 2017

Data exchanges between different electronic data recorder (EDR) systems and personnel occur on a regular basis in a well drilling operation. A significant portion of this data is derived; i.e., calculated or manipulated after sensor measurements. Currently, derived data calculations are poorly documented; therefore, the usefulness of this data diminishes through data transfer. The objective of this work is to define a meta-data framework for derived data.

In this paper, we focus our efforts on one derived data channel, the rate of penetration (ROP) and identify the meta-data required to fully understand the values transferred to the end user. We start by identifying the different types of ROP and document the calculation procedure for each type. Part of the meta-data that needs to be captured involves data transformations that occur when this data stream is moved from one EDR to the next. We interviewed various EDR providers in an attempt to understand their current process.

The different types of ROP calculations and their use in different types of drilling performance analysis are described in this paper. The calculation procedures were implemented and tested on an operator's data aggregation system. This effort also documents different EDR systems and how they handle sensed data required for ROP calculations. A meta-data framework is able to capture not just the calculation used, but also data transformations that occur as data hops from one EDR system to the next. Different data transfer protocols such as WITS0, WITSML, and OPC/UA necessitates a broad meta-data framework. While much of the meta-data can be embedded in the data transfer channel itself, a document describing all relevant meta-data is equally effective in communicating the information. Lastly, the meta-data framework developed here can also be applied to other forms of derived data (such as Hole depth, Bit Depth, WOB, etc.).

This meta-data framework improves the transparency by providing guidelines to data aggregation providers on the type of information that should be supplied to end users. It also provides insights into how data gets transformed from its point of origin (sensor) to its point of consumption. Finally, it also documents the various type of ROPs and their appropriateness for the analysis that is performed using them.
Revisiting Thomson Equation for Accurate Modeling of Pore Scale Thermodynamics of Hydrocarbon Solvents
Authors: Al-Kindi Ilyas , Babadagli Tayfun
Published: October 2017

As stated by the classical Thomson equation, the pore scale thermodynamics of solvent is different from bulk conditions being critically controlled by capillary characteristics. This equation shows that the boiling points decrease remarkably as the pore size and interfacial tension become smaller. This paper investigates this phenomenon for hydrocarbon solvents experimentally and compares the results with the values obtained from the Thomson equation to test its applicability in modelling heavy-oil recovery by solvents under non-isothermal conditions. As an initial step, the boiling temperature of different single component solvents (heptane and decane) was measured by saturating Hele-Shaw type cells with variable apertures (ranging from 0.04 mm to 5 mm) and monitoring the boiling process. One experiment was run with a thickness of 12 mm to represent the bulk case. As the aperture (pore size) became smaller, the boiling point temperature decreased. For example, the measured boiling temperatures of heptane and decane were approximately 57.7°C and 107.4°C for the aperture values less than 0.15 mm, which were considerably lower than the "bulk" values (around 40%). In the next step, the same experiments were repeated using micromodels representing porous media. The micromodel (grain diameter of 0.15 mm and a pore throat of 0.075 mm) was designed with uniform properties (constant grain diameter and pore throat). By using the Thomson equation, the boiling points of the selected liquids were mathematically computed and compared with the experimental results from Hele-Shaw experiments.
Case Study: Multirate Multizone Production Logging and Testing Provides Real-Time Reservoir Insight for Stimulation Treatment Optimization in Deepwater GOM
Authors: Khan Waqar , Azari Mehdi , Hamza Farrukh , Hadibeik Hamid , Ramakrishna Sandeep
Published: October 2017

In a deepwater environment, testing of wells can be an expensive process coupled with safety concerns. Properly characterizing a well has a significant impact on asset management. Wells are routinely stimulated to remove formation damage, but subsequent testing to determine the skin after stimulation is rarely performed. This paper discusses a case study where multirate multizone (MRMZ) pressure-transient testing and production logging was performed in a deepwater well in the Gulf of Mexico (GOM) to determine the effectiveness of the stimulation treatment.

MRMZ production logging was performed across the targeted pay intervals. The process was to flow the well at three different flow rates followed by a shut-in period. During these different rates, production logging was performed by three up and three down passes at each choke setting, followed by a stationary measurement at a predetermined depth for 10 to 15 minutes. Following the last production logging run, the tool was parked between the two pay zones, and the well was shut in for a pressure buildup until radial flow was fully established. After that, the tool performed the final routine production logging passes while the well was still shut in.

Although the oil production almost doubled after the initial stimulation treatment with xylene, the high skin observed in real time from the MRMZ pressure-transient analysis prompted the operator to change the formation damage removal program and stimulate with hydrochloric acid (HCl) by coiled tubing rather than only xylene. This resulted in an immediate fourfold improvement of productivity index with a potential of further doubling.

MRMZ testing is a relatively low-risk, low-cost method for acquiring valuable formation data. This paper additionallydiscusses best practices that should be performed while attempting MRMZ and how deviating from these practices can lead to increased uncertainty in the acquired data.
Characterization of Reservoir Heterogeneity for SAGD and ES-SAGD: Under What Type of Heterogeneity is ES-SAGD More Likely to Lower SOR?
Authors: Venkat Venkatramani Arun , Okuno Ryosuke
Published: October 2017

Expanding-solvent steam-assisted gravity drainage (ES-SAGD) is a potential method to reduce steam-oil ratio (SOR) of SAGD, which is a critical concern especially for highly-heterogeneous reservoirs. The main objective of this research is to investigate the flow characteristics of heterogeneous reservoirs in which solvent is more likely to lower SOR of SAGD.

SAGD and ES-SAGD with normal hexane are simulated for fifty geostatistical realizations consisting of clean sand and shale, qualitatively representative of the middle member of the McMurray formation. Thermodynamic models are calibrated with experimental phase behavior data for reliable comparison between SAGD and ES-SAGD, including the water solubility in oil at elevated temperatures.

Results show that the SOR reduction by steam-solvent coinjection is positively correlated with the increase in SAGD's SOR due to heterogeneity. Enhancement of bitumen flow by dilution is more important for lowering SOR for those reservoirs in which the permeability variation makes slow-flow regions during SAGD.

The key observation of simulation results from a statistical standpoint is that a larger amount of bitumen tends to be diluted by solvent in those reservoirs for which SAGD exhibits slow production of bitumen. Then, the observed results are analyzed by use of SAGD analytical equations that clarify several influential factors for bitumen flow beyond the edge of a steam chamber. It is shown that dilution of bitumen by solvent in steam-solvent coinjection becomes more significant where flow barriers limit the local bitumen flow under SAGD even at high temperatures. In such slow-flow regions, the bitumen flow rate can be substantially increased by accumulation of solvent in ES-SAGD, which reduces the oleic-phase viscosity and increases the oleic-phase saturation and, therefore, relative permeability. Solvent accumulation within a steam chamber can also reduce thermal losses because of lower operating-chamber temperatures.
Evaluation of Field and Laboratory Acoustic Sand Monitor Data in Multiphase Flow Production
Authors: McLaury B. S. , Shirazi S. A.
Published: October 2017

Sand particles may be detached from reservoirs and be produced during oil and gas production. Many producers utilize sand prevention methods such as gravel packs and sand screens, but these methods may not be 100% effective in sand exclusion and small particles can still pass through. Small sand particles can also plug a portion of sand screens and promote higher velocity particles passing through other portions causing failure of sand screens. One of the attractive methods for sand detection is utilizing commercially available acoustic sand monitors that clamp to the outside of pipe wall and presumably detect noise from sand impact with the pipe wall. Operators are very interested in these monitors, but the effectiveness of these monitors to detect and distinguish sand impact noise from the background flow noise in multiphase flow is questionable. The objective of this work is to utilize laboratory and field data to determine threshold sand rates that these acoustic detectors can effectively detect. Additionally, the paper presents a novel method for calibration of the monitors that can extend the working range of these acoustic monitors to production rates and flow conditions beyond which the monitor was originally calibrated.
Technical Potential: A Highly Effective Tool for National Oil Companies to Drive and Manage Business Plans – A Real Case Study at PETRONAS Malaysia
Authors: Gupta Vipin Prakash , Dwivedi Satyajit , Roslan Razeif B. , Masoudi Rahim , Razali W. Aziz
Published: October 2017

Sound business decisions require robust production forecasts whose uncertainties are quantified by an assessment of market expectations. While this applies to all E&P ventures, it is much more critical and relevant to National Oil Companies (NOCs) since they depend upon Production Sharing/Operating Contractors (PSCs/PACs) to deliver the business goals. It is critical to continuously improve processes in complex systems to enable a probabilistic range of performance forecasts. Data-driven methodologies support these business value propositions.

Technical Potential (TP) forms the basis for future expectation by defining what is achievable, and thus highlights the gap between possible performance and what is realized regarding hydrocarbon production. This knowledge transforms into initiatives that drive the processes for minimizing the gap. Assessment and forecast of TP workflows provide the appropriate tools for NOCs for driving the operator contractors towards better performance targets. PETRONAS in the past year has seen some clear, tangible benefits from the exercise.

However, the subject is tricky and the path to success, a potential minefield not only due to data frequency and metering issues that are inherent in production well testing but also the fact that TP forecast does not exactly follow the same set of rules as production. Soft-computing models based on data-driven analytics were used to resolve the issues, and a MAPE average of less than 20 was achieved for 80% of the producing assets. Data from a total of 74 producing fields in South East Asia was used to train and optimize data-driven algorithms.

The data-driven forecasts capture the trends, and temporal relationships surfaced through the patterns hidden in the well and reservoir historical data. Traditional type curve fitting and empirical DCA only provide a deterministic forecast, but a probabilistic data-driven methodology offers some key advantages: (1) A range instead of an absolute number and (2) Identification of time-series periods that focus on high and low performance periods optimizing business decision cycles.

We propose a hybrid approach where the traditional type curve fitting and DCA analysis results can act as input data points to a data-enriched probabilistic time-series analysis. The value of DCA cannot be denied as a check. However, the current method will certainly enhance the value tremendously when used in conjunction with DCA.

Blind test workflows or what-if scenarios, a favorite of simulation engineers, to verify the accuracy of the forecast was implemented to verify the performance of the data-driven analytical models.

The paper introduces the relevance of TP methodologies and defines the key components of the production system, their relationships, measurement entities and methods of calculation. It then details the analytical methods for TP forecasts.
Improved Monitoring System for Heavy Oil SAGD Wells
Authors: Baldwin Christopher
Published: October 2017

This paper provides an overview of the development of fiber optic sensing for SAGD applications including a review of more than 10 years of work in development and field applications in Western Canada. Development of a fiber optic monitoring system to withstand the harsh environments experienced in the SAGD application requires consideration of the materials used to protect the downhole optical fiber, the chemistry of the downhole optical fiber, the basic optical fiber sensing technology implemented, and the optical interrogator functionality. Aspects covering corrosion of materials, hydrogen darkening, and system performance for different monitoring applications will be explored. Design and technical information will be provided along with certain case histories providing the applications and use of downhole fiber optics sensing for the SAGD applications including steamflood monitoring, sub-cool monitoring, and well integrity monitoring. Dealing with a harsh environment experienced downhole in the Western Canada SAGD applications including temperatures exceeding 230° C in high hydrogen environments has meant that the fiber optic sensing technologies have had to adapt and improve to be suitable to function reliably. Various technologies have been implemented throughout the previous 10 to 15 years, from Raman scattering based DTS systems to highly multiplexed Bragg grating based thermal monitoring systems. Multiple optical PT gauges have been designed and implemented. These include Fabry-Perot based systems as well as the Bragg grating based PT gauges. This paper will provide much-needed information to practicing engineers in the field of downhole reservoir monitor introducing them to concepts such as multi-point fiber Bragg grating based thermal monitoring and reliability of the monitoring systems. Information provided in this paper is applicable beyond the SAGD applications. The fiber optic monitoring systems may also be used for intelligent wells, subsea wells, and unconventional wells.
The Origin and Mechanism of Severe Stick-Slip
Authors: Shen Yuelin , Zhang Zhengxin , Zhao Jie , Chen Wei , Hamzah Mohammad , Harmer Richard , Downton Geoff
Published: October 2017

A drill bit is subjected to rotational speed variation during drilling, ranging from minor rotational speed oscillations to severe speed variation, including stuck phase. The severe speed variation, referred to as stick-slip, is known to be a major source of problems, such as fatigue failures, bit wear, and poor drilling rates. This paper will provide new insight into the mechanisms that drive severe stick-slip based on continuous high-frequency downhole measurements and 3D transient dynamic drilling simulation.

To understand the mechanism of severe stick-slip, a series of drilling tests were conducted at a full-scale drilling test facility. An advanced downhole measurement tool was placed in the bottom hole assembly (BHA) to record three-axis shock and vibration, RPM, bending moment, downhole weight on bit (DWOB), downhole torque (DTOR) and internal and annular pressure at high frequency. The drilling system was then modeled on a 3D transient drilling simulation platform, including detailed bit-rock interaction based on single-cutter tests, the exact BHA, and the wellbore geometry.

The downhole recorded data showed clear coupling of severe stick-slip, axial load, and bending moment conditions. Interesting patterns observed between RPM, DWOB, DTOR, and bending moment will be presented in detail. The recorded severe stick-slip condition was successfully reproduced by 3D transient dynamic simulation, and the torque, axial load, and bending moment variations along the BHA revealed coupling between torsional, axial, and lateral motions of the drilling system from simulation. Bit-rock interaction and drillstring-wellbore contact are the drivers supporting the coupling. It was found that the coupling of three motions of the drilling system is the most reasonable explanation to the self-sustained severe stick-slip condition. This mechanism can explain the field observed stick-slip trend (i.e., the higher WOB and lower RPM tend to increase the risk of severe stick-slip tendency). Downhole measurements and transient 3D dynamic simulation of the entire drilling system are essential to fully understand this mechanism.

Understanding the stick-slip process opens additional opportunities for controlling severe stick-slip. Because the stick-slip mechanism is driven by the coupling of three motions, it is possible to mitigate this condition by breaking the coupling mechanism. For example, a shock sub possibly will reduce the severity of axial coupling due to added axial compliance. Simulation shows breaking the mechanism could reduce the severity of stick-slip. The study being reported in this paper also proved the validity of applying advanced 3D transient dynamic model to obtain a better understanding of drilling system behavior. Drilling simulation might well be an effective way to plan a drilling system and drilling parameters.
Bridging The Gap Between Subsurface and Surface Disciplines - A Tool for The Modern Facilities Engineer
Authors: Cristea Z. , Cristea T.
Published: October 2017

This paper presents an unbiased Stochastic Workflow (SW), data driven, where surface and subsurface uncertainties are accounted for and their impact on Facilities design and operational decisions quantified. Unlike the traditional approach in Facilities design where typically the ‘most conservative values' are used as design input variables, the proposed workflow accounts for lifecycle variability and correlations of relevant input data. The workflow enables superior risk management and resources allocation. An example is provided, where the traditional Facilities design outcomes are compared with the Stochastic Workflow findings.

Deterministic Models are established to account for the dependencies between design input variables (Static Variables, i.e. bottom hole pressure and temperature) and the desired objective (Static Results, i.e. chemical injection rate). However, in real life situations, the analyzed variables change due to subsurface and surface events with different levels of uncertainty (i.e. condensate banking, lean gas injection, water breakthrough). Stochastic algorithms are used to create Probability Distribution Functions (PDF) for all analyzed design input variables (Stochastic Variables). Stochastic Algorithms are then applied on the Deterministic Model, sampling from the previously defined probability distributions. Stochastic Results are assembled into insightful charts and used to analyze the most relevant variables and their correlations affecting the model objectives.

The workflow provides an objective quantification of risks and uncertainties impacting the design and operation of the analyzed system. The deterministic design approach in the example permits for risk to be still present in 11% of cases and resources to be wasted in 77% of cases. In the revised design, based on the Stochastic Workflow, the risk and wastage are reduced to less than 1%. The associated OPEX component is reduced from USD 12 mln to USD 8 mln (-33%), expressed in Present Value terms.

This paper contributes to the efforts of bridging the gap between subsurface and surface disciplines, and demonstrates the utility of integrated approach in Facilities planning, where both subsurface and surface uncertainties are accounted for. This approach contributes to the elimination of subjective decision biases (Waring, 2017), enabling superior Project and Asset Management. The proposed Stochastic Workflow is scalable and transferable, and suited to collaborative, multidisciplinary project and asset teams.

Additional benefits of the Stochastic Workflow, such as improved Well and Reservoir Management (Virtual PLT) or increased system availability, are also mentioned in the paper.
Impact of Alkali-Silica Reaction ASR on Structural Integrity of Light-Weight Wellbore Cement
Authors: Albers Dylan
Published: October 2017

Wellbores drilled through low-pressure formations encountered offshore or in depleted formations, require use of light-weight cement slurries (less than 13 pounds per gallon (ppg)). These densities in cements can be achieved through foaming, increasing the water content, or using silica-based microspheres. Water-extended cements have a threshold down to weights of approximately 13 ppg and to achieve densities lower than this require the use of foaming and/or silica based microspheres. Each of these methods has limitations that can severely impact hydraulic properties of cement. The foamed cements have the potential to become unstable at high pressures, while silica-based microspheres have chemical instability in the high alkalinity environment of wellbore.

This chemical instability of silica-based microspheres used in cements, creates a hydrophilic gel that is expansive and creates fractures within cement matrix as it expands. This is more formally referred to as alkali-silica reactivity (ASR). Prevention of ASR involves the application of additives to the cement that act as a sink for the alkalinity during hydration for long-term prevention of the ASR. Lithium nitrate is one of these prevention methods that is theorized to allow for other beneficial reactions.

This study investigates the effects of a highly alkaline cement pore-water on the chemical stability of microspheres. Microstructural characterization involves identification of reaction products in alkali- reacted glass beads within 28 days hydrated wellbore cement at wellbore temperatures, as well as the impact of lithium nitrate as a prevention method. The scanning electron microscopy of polished and fractured surfaces reveal two different reaction processes, with the ASR clearly absent in the slurry containing lithium nitrate. The micro-mechanical properties of these changes were also tested using microindentation tool. Lastly, porosity values were tested using helium gas Porosimetry. Lithium nitrate shows an effect on mechanical properties but not on porosity values as compared to cements solely containing microspheres.
Formation Fluid Sampling Technique Allowing to Control Physical Properties of Sampling Medium
Authors: Gutman Roman
Published: October 2017

The present paper addresses the general methods of formation fluids properties determination. Physical properties of formation fluids play a major role in processes of oil and gas deposits calculations and for aspects estimation of hydrocarbon fields development and exploitation. That is required to optimize wells operations, and to perform technological operations on enhance of oil recovery, etc.

Since the volume of samples for physical properties determination is limited, it is necessary that samples completely confirm the formation hydrocarbons. Therefore the most important question here is sampling of clean and representative samples. To solve this problem a technique of formation fluid sampling with use of the bottomhole equipment featuring presence of an additional section with density and viscosity gauge mounted between sampling chamber and inlet valve unit has been proposed.

This way of sampling will ensure receiving density and viscosity parameters of liquids immediately during sampling. That will allow monitoring the type of sampled medium and will increase the probability to receive representative samples by these parameters determination.
A New Approach for Predicting Drillstring Vibration Impact on Wellbore Stability
Authors: Khaled Mohamed Shafik
Published: October 2017

Many studies attributed wellbore instability problems to physical and chemical interactions between rocks and drilling fluids; however the impact of drillstring vibration was neglected. This study aims to investigate the effect of drillstring vibration on wellbore stability; and determine major factors lead to drillstring collision with wellbore.

Drillstring vibration mechanisms are reviewed from literature to identify type of drillstring vibration responsible for wellbore failure. Then, drillstring equations of motion are solved utilizing Runga-Kutta numerical scheme; and sensitivity analysis is done to assess the effect of each variable (inputs) on drillstring radial displacement. Moreover, new model is developed to predict critical ranges of drillstring vibration that collapse wellbore. Model bases on rock mechanics principles, whirl vibration mechanism and Newton second law.

Results show a direct relation between whirl vibration initiation and wellbore instability; however axial and torsional vibrations have negligible effect. Wellbore failures resulted from drillstring vibration are more likely to happen in small hole sizes (6 in) than bigger holes. Drill collar length and drillstring revolutions per minutes are the primary factors aggravate drillstring collision with wellbore, while wellbore inclination and mud weight have minor impact. When drillstring vibrates and hits wellbore wall, hole collapse happens due rock compressive failure, rock fatigue, and reduction in rock strength. The innovated model estimates values of drillstring accelerations that collapse wellbore, and predicts optimum mud weight needed for safe drilling before and after reduction in rock strength due to drillstring vibration.

Research findings reduce risks of wellbore collapse and drillstring failure resulted from drillstring vibration by: presenting recommendations in drillstring design and drilling optimization; and utilizing model outputs to compute critical limits of drillstring vibration and optimum mud weight to prevent drillstring collision with wellbore.
Application of Pressure Transient Concepts for Improved Upscaling of Geologic Models
Authors: Nunna Krishna
Published: October 2017

Upscaling in the context of reservoir modeling is the process of averaging the reservoir properties to obtain coarse dynamic simulation models from high resolution static geologic models. The objective of upscaling is to preserve the maximum amount of heterogeneity with the minimum possible cost of simulation. However, the existing flow based upscaling methods rely on Steady State (SS) concepts of flow which cannot preserve the dynamic connectivity from the fine to coarse scale. This can result in overly homogenized simulation models which systematically yield optimistic results. The objective of this work is to develop an upscaling technique which preserves the dynamic connectivity from the geologic models to simulation models. Application of pressure transient concepts enables us to distinguish between well-connected pay and weakly connected payin the region of upscaling.This allows us to quantify the sub-volume of the resource that is not effectively producible. In terms of monetary value, the approach allows fundamental control on well planning. Over simplified simulation models systematically overestimate sweep, leading to a lower well count in the planning stage. By preserving the dynamic connectivity, the proposed approach helps in preparing a more accurate economic model for field development through proper well planning.Also, capturing the fine scale heterogeneity is important for any forward prediction of complex flow patterns in the reservoir.

The concepts of diffusive time of flight and drainage volume were utilized to accurately capture the local pressure transients. Also, a new volume averaging approach was developed to obtain the effective coarse transmissibility that accounts for non-uniform fluxes and pressure gradients while averaging.The proposed method was validated on SPE10 synthetic model and an onshore tight gas reservoir. The comparison of performance prediction against fine scale numerical simulation and Steady State incompressible upscaling demonstrate the accuracy of the proposed approach.
Bottomhole Assembly Smart Generator
Authors: Shabara Khaled
Published: October 2017

Many studies investigated drillstring vibration as harmful forces cause drillstring failure. However, these huge forces can be converted into useful energy. This paper aims to conserve drillstring vibration forces into electrical energy depending on piezoelectric material.

Drillstring vibration mechanisms are reviewed to study the modes of vibration and recognize mechanical stresses values acting on the drillstring through each level. Then, piezoelectric materials researches on small scale power generation are studied to select proper material with good electrical and mechanical properties to design generator with sufficient capacity. A model was conducted to prove that Lead Zirconate Titanate generator (PZT) has a good mechanical performance against the subjected forces. This model was developed to sense the force acting on well walls depending on the generated voltage at the radial direction. Finally a computer software was designed to connect the generator and sensor outputs with the well logs while drilling. The software design depends on comparing the values of applied forces on the drillstring and well walls with the maximum allowable strength of drillstring.

Results show that vibration levels (mechanical energy) can be converted into electrical energy through piezoelectric generator. This electrical energy is sufficient to provide continuous power to the downhole tools. Obtained readings from the developed model can prevent the drillstring failure. The new software outputs show if the applied forces maintain safe operation on drillstring and well walls which will prevent drillstring failure or well collapse. This will guarantee maximum operating time with less non-productive time.

The most significant part in this paper is that it changes the concept of the drillstring vibration as a harmful energy to useful source of energy can be added to downhole tools; this will reduce tripping out time to replace downhole tools batteries. The values of the generated electrical energy are remarkable as it is one of very limited number of applications using piezoelectric technology in such large scale.
Use of an Iterative Ensemble Smoother Methodology in a History Matching and Uncertainties Assessment Process
Authors: Vasconcellos Soares Ricardo
Published: October 2017

The goal of this work was to apply an ensemble-based technique for data assimilation (Ensemble Smoother with Multiple Data Assimilation, ES-MDA) to link probabilistic history match and uncertainties assessment of a petroleum benchmark field. The first step was the definition of the model uncertainties and its parameterization to stablish the prior ensemble composed by 500 models. After this stage, I applied standard ES-MDA followed by the localization technique which was considered taking into account the area of influence of each well. Then, I conducted production forecast to assess field behavior until the end of the field productive life and compared with the reference response. To evaluate the results, I used two mais indicators: the Normalized Quadratic Deviation with Signal (NQDS) and the Sum of Normalized Variance (SNV). I used NQDS to verify which models were within the specified tolerance while SNV was responsible for evaluating the loss of variability of the ensemble. Through the standard ES-MDA, it was possible to improve knowledge about the reservoir behavior and obtain good data matches with low computation effort. However, I observed certain loss of variability and spurious correlation in the models. Afterwards, I applied ES-MDA with localization to improve results and this approach helped to increase variability of the ensemble and generate smoother images. It was crucial to compare the production forecast with the reference response to validate the methodology. The main advantage of this work is the ability of analyzing the reduction of uncertainties aligned with the benchmark case with a known response, assessing how strong the loss of variability of the ensemble was and comparing the convergence of the forecast with the reference response. Furthermore, this technique required a low computation effort when compared with other similar methods.
Female managers and their characteristics in the Trenčin region, Slovakia
Authors: Delgadová Elena , Gullerová Monika
Published: October 2017

Gender equality has been a major principle of the European Union since the Treaty of Rome introduced the principle of equal pay for men and women in 1957. Gender equality means the same rights and opportunities for women and men across all sectors of society. The primary objective of the paper is to explore the management style of women, as well as their distinctive characteristics. It is believed that these distinctive features have a major influence upon their career-related behavior. The contribution tries to underscore the fact that women of the 21st century can prove themselves successfully in managerial positions within organizations, even though their career development is still hampered by gender inequality, since the world of management is a male-dominated field. Women in management positions have considerable, yet not fully utilized potential, which could help companies to succeed. In the paper, a questionnaire was used to obtain the relevant data on the management style and characteristics of female managers in the Trenčin region, Slovak Republic. At a later stage, the sepre-research findings will be used to conduct a comparative study in cooperation with the colleagues from the Universidad de Valencia and Universidad Catolica de Valencia San Vicente Martir in the Spanish region of Valencia.
Simultaneous excitation and parameter identification for non-linear structural systems
Authors: Wan Zhimin , Wang Ting , Huang Qibai , Zheng Weiguang , Gu Feng
Published: October 2017

In this paper, an algorithm is proposed for simultaneous excitation and parameter identification for non-linear system in state space. The algorithm is based on the sequential application of extended Kalman estimator for non-linear structural parameters and the weighted least squares estimation for unknown excitations. The state and parameter are reformed into the augmented state, and the state space equations are non-linear associated with the augmented state. With the first-order Taylor expansion for nonlinear system and approximately linear minimum-variance unbiased estimation, a recursive algorithm is derived where the identification of the augmented state and the excitation are interconnected. Two numerical examples which identify uncertain parameters of a 3-DOF Duffing-type system and a four-story hysteretic shear-beam building subject to unknown random excitation respectively, are conducted to demonstrate the effectiveness of the proposed approach.
Linear electric generation system to harvest vibration energy from a running vehicle
Authors: Nam K. H. , Chun Y. D. , Ha Yu-Syn , Kim J. H.
Published: October 2017

Methods to harvest energy that is wasted during road vehicle operation have been studied in recent years. Mechanical vibrations from vertical motion induced by road bumps dissipate a large amount of energy. A linear electric generation system is presented to harvest this energy. The system uses mechanical resonance to maximize the efficiency of harvesting. A shock absorber suspension and electric generator mathematical model were created to analyze the vibration characteristics induced by road bumps during vehicle operation. An electromagnetic simulation using the commercial software MAXWELL (Ver. 13, ANSOFT, USA) was performed to predict the electricity generation. Finally, the magnetic circuit design was optimized to improve the amount of electricity generated. The results demonstrate the possibility of using the proposed approach in practical applications.
A case study of rail corrugation phenomenon based on the viewpoint of friction-induced oscillation of a wheelset-track system
Authors: Cui Xiaolu , Chen Guangxiong , Yang Hongjuan , Ouyang Huajiang , Yan Wenyi
Published: October 2017

An interesting rail corrugation phenomenon unreported in open literature is found in Beijing metros, in which the wavelength of rail corrugation in the Cologne egg sleeper section is obviously different from that in the fixed dual short sleeper section, although both sleeper sections are located on an identical sharp curved track. Based on the viewpoint that friction-induced oscillation is the main cause of rail corrugation in some cases, three multiple-wheelset-track models in the transitional section on an identical sharp curved track are built in this paper. The phenomenon is researched by adopting the complex eigenvalue method together with the transient dynamic method. The simulation results are consistent with the corrugation measured in real metros. It can be found that the unstable oscillations mainly occur on the low rail and the relevant frequencies are noticeably different in different sleeper support sections. The dominant unstable oscillation frequencies in the fixed dual short sleeper and Cologne egg sleeper sections are about 201 and 422 Hz, respectively. However, when a sharp curved track is supported only by fixed dual short sleepers or Cologne egg sleepers, the unstable oscillation frequencies are close to each other, which are both about 420 Hz. Therefore, the corresponding wavelengths of rail corrugation are different in different conditions. The local special phenomenon can be satisfactorily explained and the viewpoint of friction-induced oscillation can be further verified.