bluuebunny/crossref_metadata_2025 huggingface dataset:
Ghana’s 2016 elections: An Overview of Selected Relevant Background Themes
Authors: Owusu Nsiah Isaac
Published: October 2020

Seven successive elections have been held in Ghana since 1992, most recently in 2016 when the country made a fourth attempt to embrace constitutional rule. A burgeoning literature provides explanations for the outcome of the 2016 election, which saw the defeat of the erstwhile incumbent National Democratic Congress and a landslide victory for the New Patriotic Party. Yet, little attention has been given to the various undercurrents, events, and significant background dynamics prior to the elections on 7 December. This research therefore provides a partially analytical but largely descriptive presentation of selected relevant issues that contributed to the build-up to the 2016 elections. The study situates the discourse within the broader context of Ghana’s democratisation, revealing how underlying phenomena possibly pose a threat to, and challenge the prospects of democratic consolidation. However, the conclusion indicates that the outcome of elections, which were deemed free and fair, should not be the only area of interest as the processes that lead to the elections are of great concern for a democracy. The work identifies several areas of concern, in particular Ghana’s electoral management, intra-party conflicts, unconventional aggression, vituperative outbursts and personal attacks, internal party elections, campaigns, how some chiefs violated a constitutional provision and outwardly portrayed partisanship, and brief issues concerning vote buying.
Rapid COVID-19 Diagnosis Using Deep Learning of the Computerized Tomography Scans
Authors: Tabrizchi Hamed , Mosavi Amir , Szabo-Gali Akos , Nadai Laszlo
Published: October 2020

Several studies suggest that COVID-19 may be accompanied by symptoms such as a dry cough, muscle aches, sore throat, and mild to moderate respiratory illness. The symptoms of this disease indicate the fact that COVID-19 causes noticeable negative effects on the lungs. Therefore, considering the health status of the lungs using X-rays and CT scans of the chest can significantly help diagnose COVID-19 infection. Due to the fact that most of the methods that have been proposed to COVID-19 diagnose deal with the lengthy testing time and also might give more false positive and false negative results, this paper aims to review and implement artificial intelligence (AI) image-based diagnosis methods in order to detect coronavirus infection with zero or near to zero false positives and false negatives rates. Besides the already existing AI image-based medical diagnosis method for the other well-known disease, this study aims on finding the most accurate COVID-19 detection method among AI methods such as machine learning (ML) and artificial neural network (ANN), ensemble learning (EL) methods.
Vapor-Liquid Equilibria and Diffusion of CO2/n-Decane Mixture in the Nanopores of Shale Reservoirs
Authors: Dong Xiaohu , Chen Zhongliang , Chen Zhangxin , Wang Jing , Wu Keliu , Li Ran , Li Li
Published: October 2020

Numerous laboratory tests on the Northern American shale plays have observed a large number of nanopores. Because of the pore-proximity effect, the vapor-liquid phase equilibrium and transport performance of fluids in nanopores differ significantly from that observed in PVT cell. In recent years, CO2 huff-and-puff has been widely applied to unlock the shale reservoirs. But on account of the high adsorption selectivity of CO2, after the injection of CO2, the original vapor-liquid equilibria of hydrocarbons is changed. The purpose of this study is to predict the phase behavior and diffusion of the CO2/n-decane mixtures in the nanopores. The Peng-Robinson (PR) equation of state is combined with Young-Laplace equation to calculate the phase-composition diagram at the presence of capillary pressure. The equilibrium molecular dynamics simulations (MDS) are also conducted to study the phase behavior, and the number density profiles of different molecules are calculated. Then, based on the discussion of phase behavior, a series of equilibrium MDS runs are carried out to calculate the self-diffusion coefficients of CO2, n-decane, and all fluid molecules. For each MDS with a different CO2 mass fraction, the two types of fluid molecules are thoroughly mixed, the conditions of pore size and temperature are consistent with those in the phase behavior studies.

Results indicate that considering the capillary pressure, when the mass fraction of CO2 is less than 40%, the bubble point suppression is more clearly shown in the phase envelope. The number density profiles of n-decane molecules show the apparent characteristics of adsorption layers. As the mass fraction of CO2 molecules increases, the self-diffusion coefficients of CO2, n-decane, and their mixtures all increase. The self-diffusion coefficients of CO2 molecules are higher than that of the n-decane molecules, and the diffusion coefficients of the entire fluid system are somewhere in between. Appropriate CO2 injection into shale oil reservoirs can not only reduce the confinement-induced bubble point suppression but also improve the flow behavior of oil in nanopores. This study can shed some critical insights for the vapor-liquid phase equilibria of confined fluids in nanopores and provide sound guidelines for the application of CO2 huff and puff in shale reservoirs.
Lessons Learned in Developing Human Capital for The Oil and Gas Industry in Kazakhstan
Authors: Dairov Zhassulan , Syzdykov Murat , Miskimins Jennifer
Published: October 2020

The World Economic Forum's (WEF) Human Capital initiative has been implemented at Satbayev University (SU), Almaty, Kazakhstan for the last two years. Participating in this effort are Chevron, Eni, Shell, and the Colorado School of Mines (Mines). This paper assesses the effectiveness of project components, such as industry guest lectures, summer internships, and program improvement and provides lessons learned for human resources development initiatives.

This paper utilizes the qualitative research method in which data are collected through focus group interviews. Key participants of the study include students enrolled in the WEF program and faculty members. Moreover, the interviewing process involves students that are not part of the WEF program as a control group to measure progress made with additional benefits.

The article explains major challenges of talent development in higher education institutions. It has been determined that the local specifics, especially students' socio-economic and educational background, play an important role on future academic success. For example, students encountered difficulties with understanding course materials and industry guest lectures, which is attributed to English language barriers. Yet, select students have had strong success in the upper-intermediate and above levels. Students' internships revealed that summer experience has greatly strengthened their practical knowledge and skills, opened eyes to industry settings, and more importantly, influenced better planning of career paths. Students reported internships not only provided an industry outlook but also perspectives of continuing graduate studies. It is noted that workforce development requires sufficient faculty development in a case of scarce human resources. The competent and adequate faculty, especially in petroleum engineering (PE), is a prominent problem in most developing oil and gas countries. This issue was articulated among stakeholders, and the project results demonstrate the successful case of company support to raise professional competencies of SU faculty.

This paper covers the human capital development challenges within the WEF project framework, and based on scientific evidence, further elucidates the project-specific tools to propagate similar initiatives around the world. Kazakhstan's experience, as a former Soviet Union state, brings useful suggestions to transform higher education talent development to match the industry-wide standards. It is highlighted that an effective industry-academia collaboration develops from shared visions, values, and goals.
Technology for Rapid Well Ranking and Screening for Pumping Optimization With Regard to Subsurface Risks and Economics. A Case Study of a Giant Oil Brownfield
Authors: Likhoded Ivan , Smirnov Dmitriy , Shkitin Anton , Deriglazov Dmitriy , Gudoshnikov Aleksey , Nyunyaikin Denis , Kochenkov Andrey
Published: October 2020

The authors have developed an algorithm that combines simple, proven, analytical work tools. The algorithm allows one to quickly update the potential, taking into account geological and technical factors, assess risks, estimate current recoverable reserves, incremental oil production, and economics for each well. The purpose of the work is to reduce routine labor costs when searching for and selecting wells, to rank the entire list of relevant candidates, to increase the share of successful operations, as well as to increase incremental oil production by accelerating well optimization with minimal risk. A pilot project helped to improve the success rate of optimization jobs from 75 to 89%, and increase specific incremental oil production by 57% in comparison with the previous year. The tool can also be used for auditing decisions as a retrospective.
Evaluation of A Cyclic Water Injection Program Using A Combination of Artificial Intelligence and Reservoir Physics
Authors: Calad Serrano Carlos Mario , Sarma Pallav , Gutierrez Fernando
Published: October 2020

An innovative technology called Data Physics*, which combines the predictive capacity of traditional numerical simulators with the speed and flexibility of machine learning, was applied to optimize a mature waterflood in the Neuquen basin in Argentina.

A reservoir model was built by combining machine learning techniques with the partial differential equations of fluid flow as applied in conventional reservoirs simulatiors. The approach is probabilistic in nature, thereby supporting the quantification of uncertainty. Given the complex conditions of operation and control in secondary recovery projects, the dearth of data, which was inherently noisy, it is not feasible to define a unique deterministic solution. The proposed approach provides physically possible and statistically viable distributions (ranges and frequencies) of the variables affecting reservoir behavior.

Due to its predictive capabilities, the reservoir model, created at a layer level using raw uninterpreted production and injection data, is capable of reproducing and predicting field production history. This enables continuous closed loop optimization and provides a program of injection water redistribution. The result is optimized production, and reserves development with reduced injection costs.

As part of the assessment of different prescriptions, the operator wanted to evaluate the optimum way to cycle two sets of injectors to reduce water handling and injection costs. A robust connectivity model was built from the reservoir model which was then used to evaluate and compare the different alternatives to cycle injectors during two years versus an optimum injection redistribution. The results include production forecasts for the scenarios evaluated which, when executed, would allow the customer to reduce water cost while maintaining production levels unaltered.
An Efficient Alternative for Joining Internally Clad Pipes Using Innovative Welding Techniques and Equipment
Authors: Riffel Kaue , Gonçalves e Silva Régis Henrique , Carvalho Leonardo , Kejelin Norton
Published: October 2020

High strength steel pipes internally clad with Ni superalloys are components widely used in the oil and gas industry, with distinguished application in the production of rigid steel risers. The joining of clad pipes is carried out through a girth welding process, in which the joint is totally filled with a filler material similar to the internal clad. However, depending on mechanical strength of the pipe substrate, an undermatching condition is created. Thus, a critical weaker region results in the welded joint, where loads and plastic deformations will occur preferentially. In view of this problematic, this work aims to apply an alternative approach as a method of joining clad steel pipes, whereby an overmatching condition is achieved in the joint. This technique is carried out through a double-sided weld, which enables the use of steel filler wire in the joint filling externally, preserving the internal cladding through an inside diameter weld with a CRA filler wire. A C-Mn API X-65 steel pipe, metallurgically cladded with Inconel 625 was used in the study. For joining the pipes, modern welding techniques as GMAW CCC (Controlled Short-Circuit) and GTAW with dynamic wire feeding were applied. The developments showcased weld beads with excellent surface appearance and without welding defects, fact verified by internal videoscopy and cross section macrography. Energy Dispersive X-ray Spectometry (EDS) indicated low iron dilutions, around 2,7% in weight, on the internal weld bead surface. The double-sided welding methodology produces favorable conditions to reach joint properties equalization, enabling the employment of steel filler wire in joint filling, in addition to preserving the internal clad and its corrosion properties.
Advancement of Drilling Hazard Prevention Practices in HPHT Exploration Well – A Case Study in South China Sea
Authors: Guo Shusheng , Gao Yongde , Chen Ming , Shim Yen Han , Wang Chao , Liu Peng , Ding Sai Jung
Published: October 2020

Ledong HPHT gas field in Yinggehai basin of South China Sea. The pore pressure ramp above the over-pressured target sand with narrow safe mud weight window lead to high drilling risk. To improve drilling safety, multiple steps and approaches were taken in real-time monitoring of pore pressure and target zone depth prediction. This paper will describe the different techniques applied in this field to optimize mud weight and accurate prediction of casing shoe position.

Using real-time LWD and mud logging data, pore pressure was calculated and geomechanics model was updated while drilling. The geomechanics model was built and calibrated against drilling and surface data. Intermediate vertical seismic profile (VSP) data was used to correlate with surface seismic profile to predict top of over-pressured reservoir and pore pressure below the bit. Last year, the latest look-ahead technology based on LWD deep electromagnetic measurement was also used to improve the depth prediction accuracy and thin bed detection for high-pressured sands below seismic resolution.

The real-time pore pressure monitoring keeps the mud weight and equivalent circulating density (ECD) within a safe margin to avoid kick and mud loss. The estimated pore pressure coefficient calculated in real-time was within 0.01 SG from actual measurement taken in permeable sandstone intervals. VSP data provides formation top prediction between 50 to 200m ahead of the bit in this area. Predicted depth accuracy varies but generally stay below 10m for the depth range mentioned above. The integration of LWD and intermediate VSP logging has helped to reduce the high depth uncertainty in the predrill model. However, the above technique could not resolve for thin beds or low acoustic impedance contrast formation. This advocate to the use of real-time high-resolution inversion bed boundary detection ranging from 3 to 20m below the bit. Clear prediction of resistivity profile ahead of bit enable proactive decision making while drilling. This additional information helped to improve depth prediction accuracy for casing shoe position and ensure well integrity.
Staged Development of a Marginal Oil Field Under Technical and Market Uncertainty: The Olympus Case
Authors: Fedorov Semyon , Hagspiel Verena , Lerdahl Thomas , Idris Abdulrahman , Ghahfarokhi Ashkan Jahanbani
Published: October 2020

Along with the maturation of main oil exploration and production (E&P) areas in the world, the industry has started to seek for new investment opportunities that have been considered unattractive so far. Among such opportunities might be small oil fields, whose low resource base makes the development marginal in terms of value. Such discoveries remain risky due to lower benefit–cost ratios and geological uncertainty that cannot be reduced so that the downside risk is eliminated. Nevertheless, they still can be attractive investment opportunities if the decision making process captures available operational flexibilities and opportunities to gather additional information allowing to tune the development plan during the course of a project. This can allow to mitigate downside risks associated with the reservoir uncertainty. In order to capture additional flexibilities and account for a possibility to change the course of the project within the investment valuation, the decision maker demands more advanced tools than a static discounted cash flow (DCF) approach, traditionally used in the industry.

In this study, we analyze an opportunity to phase the drilling strategy into two stages as a tool that allows to optimize the field development under technical, cost and market uncertainties. We demonstrate how the decision maker can use additional information generated during the initial stage of the project in order to improve the future development plan by optimizing the decision to drill optional production wells. Using an algorithm based on the least-squares Monte Carlo (LSM) approach, we consider the waiting option to expand the production. We identify additional value created by the staged development strategy for a small offshore oil field, applying the methodology developed in Fedorov et al. (2020) to the synthetic benchmark model Olympus. We also extend the modelling approach of Fedorov et al. (2020) by accounting for cost uncertainty within the LSM algorithm.

The underlying reservoir model allows us to realistically account for the effect of the decision to postpone drilling of the optional wells, on the field production. Our findings in this paper confirm the results of Fedorov et al. (2020), where an analytical modelling approach was used to account for reservoir uncertainty and forecast oil field production. Based on the Olympus case, we show that in case of staged development, the decision maker is able to increase the investment value due to the flexibility to avoid drilling additional wells in case of unfavourable oil price and/or production scenarios. Our conclusion, therefore, is that the staged development has a potential to be applied when the technical uncertainty represents high risk for the project economy.
Operational Efficiency Gains in the Removal of Calcium Sulfate Scale from Electric Submersible Pumps in Offshore Wells
Authors: Reyes-Garcia Enrique , Henkel-Holan Kristina , Campos Katya , Santos Sarai , Villaseñor Omar , Hernandez del Angel Everardo , Barrera David , Avalos David , Manuel Perera Perez Luis , Salazar Munive Angel , Galicia Oscar
Published: October 2020

Removal of wellbore scale from downhole equipment continues to impact well economics due to productivity losses and asset maintenance. The use of first-of-its-class calcium sulfate (CaSO4) scale dissolver in high producing offshore wells equipped with electric submersible pumps (ESP) is presented. The efficiency of the new fluid surpasses the performance of established dissolvers since it does not require long shut-in periods. Anhydrite (CaSO4) scale dissolution and removal can be accomplished with a simple treatment fluid employing a formulation that has been field-proven to restore production and protect downhole equipment in a time-efficient manner.

Mineral anhydrite and wellbore scale samples were tested with the dissolver formulation at 200°F (93.3°C), under static conditions for one hour. Dissolution efficiencies greater than 94% were a requirement. Fluid compatibility with metallic and non-metallic components in the wellbore were assessed at bottom hole static temperature (BHST) conditions for a period of 24 hours. The fluid was deployed from a stimulation vessel at a pumping rate from 1 to 5 bpm. A small volume pill of 5 m3 on average was pumped in at least 20 wells, through the production tubing to the ESP and was allowed to soak for 1 hour. Wells were immediately opened to production after a 1-h soak period.

Minimizing the non-productive time incurred when long soak periods are required has been attained with the use of the new dissolver fluid, leading to greater efficiencies associated with CaSO4-type scale removal. ESP temperature was monitored and reduced by 13°F (7.2°C) after treatment, similar to temperatures before scale build up. After the treatment, the results show a 1.125-fold increase in oil production. The fast-acting formulation exceeds 90% dissolution efficiency within one hour and improves operations by using a fluid that is non-corrosive to downhole materials in a one-stage removal package.

The dissolver formulation provides dissolution of anhydrite at 200°F in ESPs. The fast acting dissolver is delivered as a single fluid package and eliminates the need for separate fluid stages as well as the use of incompatible fluids. Anhydrite scale dissolution and removal can be accomplished with a simple treatment fluid and extend the life of the ESP.
Combined Experimental and Well Log Evaluation of Anisotropic Mechanical Properties of Shales: An Application to Wellbore Stability in Bakken Formation
Authors: Rafieepour Saeed , Zheng Danzhu , Miska Stefan , Ozbayoglu Evren , Takach Nicholas , Yu Mengjiao , Zhang Jianguo
Published: October 2020

Frequently, shales are treated as isotropic formations. However, organic rich shales are anisotropic due to their laminated structure and chemical properties. In this study, shale mechanical properties with respect to different bedding plane orientations was studied. The goal of this study is to evaluate anisotropic mechanical properties of shale by triaxial tests and to predict these properties by well logging data along with a 3-D transversely-isotropic wellbore stability analysis (WBS) in Bakken formation. Shale samples were prepared with bedding plane angles equal to 0, 45, and 90 degrees. Young's modulus, shear modulus, and Poisson's ratio in different directions were measured. Parameters of stiffness tensor were calculated by mechanical properties. The compressive strength of shale samples was measured under different confining pressures: 0, 500, 1000, and 1500 psi. Simple Plane of Weakness was applied to describe shear failure mechanism. Well logging data was used to connect experimental and field data. Next, a three-dimensional numerical wellbore stability model based on finite difference method was used to evaluate stress and deformation alterations due to drilling of vertical to extended reach wellbores in Bakken formation, Williston Basin, North Dakota. Both anisotropic and isotropic conditions were considered and the Mohr- constitutive relations were implemented in the numerical model. Vertical Young's modulus (perpendicular to the bedding plane) found to be smaller than horizontal Young's modulus (parallel to the bedding plane). Shale is a transversely isotropic rock; which isotropy plane is generally the bedding plane. The result of tests for stiffness tensor showed that the shale can be characterized by only five independent stiffness constants. The Simple Plane of Weakness model is suitable to estimate shale anisotropic compressive strength. The P-wave velocity calculated from the stiffness tensor is a used to connect the experimental data and field data. P-wave velocity is increasing as the bedding inclination angle increases. The predicted compressional wave velocity for a 45-degree inclination angle showed a perfect fit with the field logging data. Steps of inverse sonic log data to stiffness parameters were shown by a flow chart. From the WBS model, the effects of anisptropy on stress distribution and wellbore convergence was investigated for two different constitutive models: isotropic model (IM) and transversely isotropic model (TIM). It was found that neglecting shale anisotropy will lead to erroneous prediction of wellbore deformation.
Real-Time Flow Stability Advisor
Authors: Burgos S. R. Andreas , Wollebaek Lars , Elverhaug Vegard , Yang Zongchang , Khaledi Hatef
Published: October 2020

An Aker BP operated oil field in the North Sea has occasionally experienced production flow instabilities in the production lines and risers. The oscillations in multiphase rates are kept within the process capacity limitation at the host installation typically by increasing backpressure (planned flaring is not allowed for on the Norwegian Continental Shelf). The heightened backpressure impacts the production potential of the field. The objective of the project described in this paper has been to develop and implement a new method for real-time production optimization providing an online assessment of slugging severity and suggested actions in order to mitigate slugging and increase production. The developed software tool has been validated using field data.

A statistical approach based on the physical characteristics of the separator has been developed. A combination of transient multiphase flow simulations and data analysis has been employed in order to formulate the risk of exceeding separator constraints as a multidimensional function of the operational conditions. In order to generate a three-dimensional heat map of the risk related to the current state, operational data is continuously gathered from production sensors and transformed into pseudo-steady state values. A heat map is defined by a function where four relevant operational values can be selected. These values are: oil production rate, topside choke setting, gas lift rates and water cut. The software solution is run on a cloud infrastructure with an interactive web user interface.

In a pilot program we have evaluated the ability of the stability advisor to continuously assess the severity of flow instabilities, identify measures to reduce the risk level and minimize associated production losses. The operator has identified valuable operational insights from the tool in a pilot program. The flow instabilities predicted by the model correlate well with observed data from the field. The tool is scalable to other fields with similar flow problems.

Previous papers on slug flow prediction are in general conducted as offline study projects. There has been little success in making real-time scalable solutions available to continuous operations. This paper explains a method on how physical modelling of the flow system combined with statistical methods and access to real-time sensor data can provide a new approach for real-time slug flow prediction. The result demonstrates a scalable solution where output is presented in a format that can be applied by daily operations to act on and provide new and valuable production insights.
Understanding Pitfalls of Non-Reservoir Effects on Pressure Transient-Test Data to Avoid Misleading Interpretation
Authors: Rahman N M , Sarac Sukru , Theuveny Bertrand C
Published: October 2020

The determination of well and reservoir parameters is paramount during exploration, appraisal of new reservoirs, and equally important during the development and production phases of a field. The interpretation of pressure transient-test data is one of the tools to obtain such parameters under dynamic conditions. Often this data is substantially influenced by non-reservoir factors such as gauge drift, adjacent noise due to natural or operational reasons, insufficient gauge resolution and dominant tidal effects. Any of these non-reservoir factors can significantly lead to a misleading interpretation of the formation. Rigorous vigilance against such occurrences is particularly important in designing deep transient well tests. The paper quantifies these effects.

Obtaining strong, unequivocal reservoir responses in the pressure data are imperative in extracting the reservoir and well characteristics. Individual and convoluted effects of noise, drift, resolution, periodic tides have been looked into quantitatively to demonstrate the situations when the reservoir signal is too weak to make any meaningful characterization. Reservoir models have been utilized to develop quantitative criteria to describe the dominance and subsidence of the effects of noise, resolution, drift and periodic tides under different operating conditions. These criteria should guide test design so that the subsequent test can produce meaningful data.

Depending on the amount of disruption caused in the measurements, there are situations when the test objective may not be achieved at all. Failure to create dominant reservoir responses results from insufficient signal-to-noise ratio due to the rate of production and the pressure drawdown. It is a function of formation, fluid properties or mechanical environment. A minimum rate of production for creating the required magnitude of signal-to-noise ratio must be achieved to interpret correctly the reservoir response. The paper provides guidelines to determine the minimum rate and drawdown needed to obtain the presence of deep heterogeneities or boundaries with a reasonable level of certainty. If a test is run with a rate lower than the minimum value, for example, the data will be biased by other hardware or natural factors, unrelated to the reservoir response. Examples are also presented with artifacts of non-reservoir effects to show how misleading characteristics of the reservoir and the well can be deduced with such distorted data.

This study establishes cause-effect relationships due to certain non-reservoir factors so that engineers can select their hardware, choose the methods and timings to mitigate the associated undesirable effects. Such a practical guide to select the most suitable transient test will rightfully fill in its place in the literature. The methodology applies equally to wireline testing operations, deep transient testing, drill-stem testing and production testing.
Sensitivity of Dielectric Properties to Varying Reservoir Properties
Authors: Morte Matthew , Alhafidh Hasan , Hascakir Berna
Published: October 2020

Heterogeneity to some extent is realized in every reservoir. Variable properties, namely fluid saturations and lithology, make it very difficult to accurately estimate the bulk dielectric response of the reservoir. This study isolates and identifies the dependencies of the bulk dielectric response to changing water content, quartz content, limestone content, oil content, and clay content.

A multitude of experiments were run where the identified parameters were systematically isolated and varied to capture both the contribution from the rock matrix and the pore space. Reservoir rock was simulated by mixing the rock matrix components with the fluids to form unconsolidated core samples. The bulk dielectric properties, both the real and imaginary components, were measured for each of the seventy five different samples using a vector network analyzer (VNA) in conjunction with a dielectric probe. Individual experiments were analyzed comparatively and the dielectric responses are presented as a function of each isolated parameter.

Understanding the general dependencies and sensitivity of the dielectric behavior of the reservoir is vital for various aspects of petroleum including electromagnetic heating and well logging. The complex and dynamic downhole environment creates coupled and mutual interactions making estimation of the bulk response very difficult. Isolation of each variable allows for the identification of the governing relationship of each parameter with the dielectric response. In this study, linearity is established for the dielectric response of all investigated parameters. The sensitivity of the complex permittivity is represented as the magnitude of change as a function of variable fluid saturation or lithology. This enables the drivers of dielectric heating to be quantified, namely the increase in complex permittivity with increasing water saturation. The established relationships allow for the estimation of the dielectric response of the reservoir as a result of heterogeneity present. Variable properties that change with position and time are accounted for by understanding the corresponding change in the complex permittivity of the reservoir.

By illuminating the complex permittivity relationship as a function of rock minerology and fluid saturations, a more holistic understanding of absorption mechanics can be achieved. The study offers the unique ability to express the intrinsic relationship experienced under the influence of reservoir properties. The presented relationships also enable the estimation of dielectric properties as a function of reservoir heterogeneity.
Enhancing Resolution of Anisotropic Resistivity Using a Pixel Inversion with Data-Driven Regularization
Authors: Wang Gong Li , Ito Koji , Hong Xiaobo , Salehi Mohammad Taghi , Shi ZhanGuo , Allen David , Rabinovich Michael , Meyer Jeffrey
Published: October 2020

Triaxial induction is a powerful tool to identify thin-bed reservoirs that would be missed with conventional techniques and to improve the accuracy of net pay estimation. On the other hand, it has been noticed that with the standard processing, the resolution of horizontal and vertical resistivities cannot match that of the 2-foot array induction resistivity. Sometimes large apparent anisotropy can be seen in high-resistivity clean sands, which has caused confusion in data interpretation and reserve evaluation.

Researchers have long known that triaxial induction data contains high-frequency information from the formation through the abrupt change and spikes of transverse coupling logs near bed boundaries. In this paper, we present a novel pixel inversion equipped with a revamped cost function and a data-driven regularization scheme to better resolve thin beds by using the high-frequency information that had not been used to its full potential.

The pixel inversion is a variant of the maximum entropy inversion that has proved to be superior for conventional induction data. However, the direct use of the method for triaxial induction data tends to give a slowly varying vertical resistivity log that fails to resolve thin beds as desired. This issue is resolved by means of two adaptive relaxation terms for the smoothness regularization determined by utilizing the data sensitivity to horizontal and vertical resistivities that evolve continuously with the iteration.

In favorable conditions, results on a variety of synthetic models show that a thin bed of less than 1 ft can be detected with deep arrays. In contrast, a bed less than 2 ft can hardly be seen with previous inversions. Results also show that apparent anisotropy ratio is reduced significantly in high-resistivity isotropic cases emulating clean sands. Moreover, the horizontal and vertical resistivities compare favorably with array induction logs in terms of accuracy in the clean sand cases.

Field cases confirm that the pixel inversion is clearly superior to the standard triaxial 1D inversion as far as the vertical (or along-hole) resolution is concerned. The thin beds that can now been seen on horizontal and vertical resistivity logs of the pixel inversion are in good agreement with nuclear logs. In the cases of high-resistivity clean sands, the large apparent anisotropy is largely eliminated with the pixel inversion.
Increasing the Efficiency of Carbonate Acidizing: Kazakhstan Case Studies
Authors: Kalabayev Ruslan , Kruglov Ruslan
Published: October 2020

Hydrocarbon production enhancement by means of acid stimulation in Kazakhstan requires application of a more effective approach to address challenges associated with acid placement and reservoir contact in long pay zones of high-temperature carbonate reservoirs, thereby improving return on investment. Several robust chemical product solutions, coupled with comprehensive modeling in a new advanced simulator, have been successfully implemented to tackle the challenges and successfully increase the efficiency of matrix acidizing.

To improve the productivity of stimulated wells by improving the effectiveness of acid treatments, a detailed study of reservoir rock and its reaction to various acid and fluid systems has been made via laboratory testing and software modeling. Sensitivity analyses involving multiple treatment schedule scenarios incorporating various acid and diverter fluid systems are considered. Enhanced modeling of a novel retarded acid, viscoelastic diverting acid and particulate diverting systems demonstrated more uniform zone coverage, as well as deeper wormhole penetration. The above optimizations were field tested in several oil fields.

Prior to any acid stimulation, the formation injectivity and damage profiles were calibrated based on the well pre-treatment production profile taken from production logs. As the first step, performance of the retarded acid was tested in several treatments. The bottomhole injection pressure decline behavior indicated that a slower reaction takes place during injection of the retarded acid compared to the stages of conventional hydrochloric acid, confirming the retarded nature of the acid as seen from the core tests. Secondly, viscoelastic self-diverting acid was added to the schedule for treatment of long intervals, replacing conventional gelled acid with shorter viscosity peak and lower retained permeability features. Better zone coverage, observed from injection pressure slope changes upon arrival of each diverter stage downhole, and improved post-acidizing formation cleanup were achieved as a result of this implementation. Third, field trials were made using combined application of the viscoelastic diverting acid and degradable particulate diverter pills. Full and uniform coverage of the entire zone of interest has been observed after pressure matching the actual treatments’ schedule and was validated by post-stimulation production logs.

Field application of the approach supports the theoretical findings. Substantial improvement in well productivity was monitored after the application of each optimization step. The above approach demonstrates the value of thorough integration of laboratory testing, comprehensive software modeling and application of enhanced stimulation fluids. The efficiency of the approach is supported by multiple successful field case studies and is the recommended way forward for carbonate acidizing.
Modelling Unconventional Velocities from Acoustic Microscope Measurements
Authors: Simone Alessandra , Hathon Lori , Myers Michael
Published: October 2020

We use integrated micro-CT, thin section, XRF, SEM, and acoustic microscopy to quantify the controls on the acoustic properties of source rock reservoirs. At the smallest length scale a scanning acoustic microscope is used to measure velocities of individual laminae within unconventional samples. For unconventional reservoirs, in which typical particle and pore sizes are substantially smaller than 20 microns (i.e. the resolution of the acoustic microscope using a 20MHz probe), the difference in travel time between the first arrivals from the top and bottom surfaces of the sample provides an accurate measure of the velocity of each layer. The small feature size compared to the acoustic microscope wavelength eliminates the need for ray tracing.

To upscale this data, one inch diameter core plugs are first micro-CT scanned and their acoustic properties are measured as received. After CT scanning, end trim and axial thin section and SEM mounts are prepared. The entire end trim, or 1" axial slice, is ion milled in preparation for SEM and acoustic microscopy. Large area image mosaics are produced using low voltage SE imaging for characterizing porosity, and BSE imaging for characterization of organic content and mineralogy. Scanning CL imaging and image analysis are utilized to differentiate between detrital and authigenic phases. Energy dispersive x-ray mapping is also used for the identification of major mineral phases. The resulting suite of mosaic images are analyzed using University of Houston developed image analysis software. Segmented volumes of porosity, TOC, and mineral phases are determined for each layer type in the sample. After the SEM imaging is complete, the velocity of each layer type is measured on the same sample volume using scanning acoustic microscopy.

A Backus average of the measured velocities of each layer type agrees well with laboratory measurements made at the core plug scale for measurement performed perpendicular to bedding. We illustrate the correlations between segmented porosity, TOC, and mineralogy on the acoustic properties of each layer type. Mineral phases included in the modeling are clay minerals, pyrite, carbonate, and quartz. We include, where possible, the differentiation of authigenic quartz and detrital carbonate phases. Velocities for each layer type are mapped to the microCT data for the core plug. We illustrate the technique applied in several highly heterogeneous formations including the Niobrara, Haynesville, Barnett, Woodford, and Eagle Ford.

As maturity increases, the location of organic material will shift from predominantly bedding plane parallel oriented laminae, to interparticle pores, as kerogen is thermally altered to bitumen. This results in distinct changes in the vertical acoustic velocity signal and in the observed anisotropy. By observing changes in acoustic velocity signals and relating them to bulk mineralogy, TOC and maturity, models can be calibrated to determine the presence and distribution of organic material.
Reducing Crystalline Silica in Oilwell Cementing Operations
Authors: Jones Paul , Keeran Ryan , Osborne Paul , Ruiz Stephanie , Agapiou Kyriacos
Published: October 2020

Reformulating additives to reduce their crystalline silica content and modifying operational techniques are effective means for lowering worker exposure levels while maintaining additive performance. This is an important consideration as materials and methods used in operations are developed to reduce occupational hazards and maintain exposure to crystalline silica below permissible levels. A large opportunity to reduce crystalline silica dust in cement spacer additives exists based on annual consumption and mass fraction of crystalline silica in the additive.

Described herein is an approach to identify candidate additives for a cement spacer system that aligns with crystalline silica reduction efforts. Focus is placed on the evaluation of low crystalline silica spacer designs for efficacy in well cementing and successful application in field operations. The additive components considered for use in reformulated cement spacer systems are analyzed using X-ray diffraction to quantify mineralogy. After identifying low-crystalline silica components, an investigation of the rheology, wettability, and compatibility of the reformulated cement spacer is carried out over the application space by employing a full factorial and space-filling design of experiment techniques.

The reformulated cement spacer exhibits over 90% reduction in crystalline silica dust without sacrifice of rheological properties or material cost increase. The new low crystalline silica cement spacer (LCSS) has been validated in North American land operations. Bond logs confirm equivalent or better mud removal compared to previous cement spacers, with improved fluid interfaces and mud recovery. More than 2000 jobs have been performed with the new LCSS since introduction in January 2019 which corresponds to over 1.2 million pounds of crystalline silica dust eliminated from cementing operations.
Ten Years Forging Business, Management and Leadership
Authors: Capello Maria Angela , Buijs Hernan
Published: October 2020

The role of the Business, Management, and Leadership Committee (BMLC) of the Internatioal Society of Petroleum Engineers International (SPE) has been critical in raising awareness among SPE members regarding the need to develop and enhance interpersonal skills, which such skills are required in addition to "hard" or technical skills to effectively advance careers and sustain growth in the upstream oil and gas sector.

Endorsed at the highest level of SPE, the BMLC have consistently developed a series of activities providing a path of enrichment for SPE's membership of over 156,000 worldwide, in different languages and formats. This paper summarizes the journey of the BMLC, how the committee's work created a change in the perception of the importance of these skills, previously called "soft", to sustain success, and shares some best practices and learned lessons.

The need for enhancing and elevating management, business, and leadership skills is somewhat obvious to those who have experienced the impact these skills can have for advancing in a role, for fostering effective teamwork, for networking with colleagues of the same discipline, for securing a path to a promotion, and for being recognized for a compelling work performance. Historically, for individuals working in the upstream oil and gas sector, having excellent to outstanding technical skills suffices for recognition and reward, to add to this the need for business, management, and leadership skills is not an easy task.

Starting by the meager allocation of training budgets in corporations for non-technical training programs, and considering there is a prevailing bias that some skills like resilience or negotiation are inborn, there is no surprise in noting there is self-shame in admitting that one needs a course in – for example- stress control or similar personal skills. The open conversation about strong skills was needed within SPE, to support members to achieve more, leaving behind misconceptions that hamper success.

The journey of the BMLC has been challenging, and the compilation done for this paper surprised the authors, about the accelerated multiplication of benefits the BML has provided to SPE members. We will summarize some figures pertinent to the activities of the Committee, as well as some historical background on the launching and growth. We will also share what works for launching, maintaining and expanding similar programs for strong skills in corporate environments.