bluuebunny/crossref_metadata_2025_split huggingface dataset:
Can the Unconventional Gas Industry Maintain Their Social Licence?
Authors: Lightfoot Richard 
Published: November 2015

AbstractThe prudent management of resources is a vital part of any company's operation.Unconventional gas plays place demands on companies as they require the development of safe operations without the loss of a Social Licence.The accomplishment of a social licence to operate requires corporations to go beyond conforming to legislation and embrace society's needs.International concern has been voiced about the mature unconventional shale gas exploration and exploitation in North America. This has occurred because of society's lack of understanding of fracking, their perception of the risk and Corporation's lack of engagement.The oil industry worldwide follows the standards laid down by the American Petroleum Institute (API). These standards have served the oil industry well. However, fulfilment of these standards has not always been achieved by all operators.Established technology of fracking introduces a sequencing of high pressure cycles into casing and cementing systems in both vertical and horizontal wells. In shale fracking a well is deviated from the vertical to the horizontal. In doing so, will joints in the casing hold under all circumstances; is cement evenly placed between the steel casings and within geological formation? The risk experience in drilling operations is one concern, others include, financial, health, safety and the environment risk is gauged by stakeholders.The possibility of a methane flow into the aquifer opens the potential of environmental impact on fresh water resources. Methane without adequate capture in populated areas increases the risk to human and animal health. Society has reacted to past failure of mining operations or extractive industries by enacting laws to encourage companies to adopt safer methods of operation.Consequent on the USA experience, more than nineteen States and Countries have legislated to reverse the burden of proof of liability by enacting a series of bills that form the basis of a ‘Rebuttable Presumption of Liability’.Corporations must not fail to control operations. They must identify the potential of damage to the environment and human health. Failure to mitigate risks will result in loss of competitiveness, damage to reputation, legal liability arising from failure to abide by regulations and/or private litigation.The maintenance of a social licence to operate underpins corporate success.
Rock Physics Relationships between Compressional, Shear, and Density Logs in Unconventional Formations, Including Deviated Wells
Authors: Quirein John , Far Mehdi E. , Gu Ming , Gokaraju Deepak , Mekic Natasa 
Published: November 2015

Abstract
This paper compares rock physics trends in the Vp-vs.-Vs crossplot and the Vp/Vs-vs.-compressional slowness crossplot. Trend uncertainties are presented with laboratory data from the Bakken, Bazhenov, Monterey, and Niobrara shales; departures from expected trends attributed to kerogen, hydrocarbon, anisotropy, and well deviation are discussed. Anisotropy models, such as ANNIE (Schoenberg et al.1996), are presented for computing Thomsen parameters and stiffness coefficients.
Castagna mudrock line (Castagna et al. 1993) derived from in-situ sonic and seismic measurements provided an average linear relationship between compressional and shear-wave velocities. Brie (1995) extended previous work to include predicting gas saturation from a Vp/Vs-vs.-compressional slowness crossplot. Projecting the Castagna mudrock line onto a shear-vs.-compressional slowness crossplot proved useful for interpreting sonic data. Classical-rock physics equations were used to model compressional and shear velocities as a function of well deviation. Laboratory anisotropy models allowed for characterizing the effects of dispersion, anisotropy, and well deviation.
Anisotropic-rock physics models for the Bakken, Bazhenov, Monterey, and Niobrara organic shales are presented and compared in terms of the Thomsen parameters, ε, γ, and δ, and stiffness coefficients, Cij. These models are first transposed to trend curves in Vp-vs.-Vs, Vp/Vs-vs.-compressional slowness, and shear-vs.-compressional slowness crossplots and then compared to the Castagna mudrock trend curve. The anisotropy models are then applied to characterize the effect of well deviation on these trend curves. Results are also presented for well log data from the Eagle Ford, Haynesville, and Bakken formations in the context of the discussed crossplots and then compared with the expected trend curves. The Eagle Ford data satisfies the carbonate Vp-vs.-Vs trend predicted in previous literature by Castagna et al. (1993), and the Haynesville data clearly satisfies the gas effect predicted by the Brie Vp/Vs-vs.-compressional slowness crossplot discussed.
In theory, the models describing anisotropy with the Thomsen parameters or stiffness coefficients are equivalent. In practice, not all the parameters for either model can be measured from log data. Preferentially, anisotropic models should be derived by combining log data from multiple vertical, deviated, and horizontal wells for each shale reservoir.
Estimate the Effective Fracture Properties from Tight Formation Production Data
Authors: Tian Wei , Wu Xingru , Zhang Zhenfeng , Ling Kegang 
Published: November 2015

Abstract
Effective fracture properties that contribute to the flow in the tight formations are very important in stimulation job evaluation, productivity estimation, and production forecast. However, there are no direct measurements on the volume of stimulated region or the effective permeability of fracture because hydraulic fractures not only stimulate local matrix, but also connect natural fractures. Therefore, the effective drainage volume contributing to production can be much bigger than the extension of hydraulic fractures.
After a high initial rate, production data for stimulated tight formation has an extended transient flow period in which the matrix functions as a source and behaves in a transient fashion. This behavior can be captured by a dual-porosity model with transient matrix performance under a constant bottom-hole pressure.
This paper studies the problem from an inverse perspective and couples the production data with an interporosity flow model to estimate the effective drainage volume that a well controls as well as the effective permeability that can be used for production rate forecast. The problem is solved in Laplace domain. The proposed model is validated with the numerical simulation and the field production data from Mississippian Lime. Furthermore, the interporosity model is sufficient to forecast the production trend from the given examples.
Slip Velocity and Permeability of Gas Flow in Nanopores for Shale Gas Development
Authors: Okamoto Naoki , Liang Yunfeng , Murata Sumihiko , Matsuoka Toshifumi , Akai Takashi , Takagi Sunao 
Published: November 2015

Abstract
Slip phenomenon is one of major characteristic of gas flow through porous media, of particular in unconventional gas reservoirs with small pore throat, such as tight sands, coal seams, and shale formations. Consequently, a permeability correction needs to be considered for evaluating the flow ability of gas in these reservoirs. There are various analytically derived correction models for engineering applications. However, it is not well understood which one should be implemented in the real problems of shale reservoirs. In this paper, slip velocity and permeability correction for gas flow in nanopores are studied by molecular dynamics simulations. For simplicity, the considered system is methane gas flow in parallel plate channel of quartz. The fluid flow is characterized by the Knudsen number defined as ratio between the mean free path and the representative length of the pores. The studies with various Knudsen number were conducted either by (1) changing the methane density (the mean free path) or (2) plate-spacing (pore size). The simulation results show that the relations between slip velocity (normalized by the maximum velocity) versus Knudsen number and between permeability correction factors versus Knudsen number agree well with Beskok and Karniadakis' analytical solution (BK model) for large nanopores (10-34 nm). This model has considered both rarefaction and compressibility effects to gas microflows and been tested by the experimental results with characteristic dimension of the order of one micrometer. Our simulation results indicate that this model can be further extended to nanoflows as they are in unconventional reservoirs. Some deviations from BK model were noted for small nanopores (2-10 nm), where variance and the apparent gap from BK model became significant. We suggest that the limit for application of BK model may be about 8-10 nm, and it is ascribed to the fact that the overall fluid is no more homogenous (the fluid is structured in the proximity of the walls due to the interaction from the wall molecules).
Simulation of Shale Gas Transport in 3D Complex Nanoscale-Pore Structures Using the Lattice Boltzmann Method
Authors: Ning Yang , He Shuai , Chen Tianluo , Jiang Yang , Qin Guan 
Published: November 2015

Abstract
A shale formation contains numerous organic nano-pores and microscopic fractures, which natural gas flows through during production period. In shale formations, the flow mechanism and the characterization of petrophysical parameters are open and challenging topics for researchers since shale has significantly different characteristics from conventional rocks. Knudsen diffusion is considered as the main flow mechanism in nanoscale pores as the Knudsen number is finite. Many conventional methods have encountered challenges to model natural gas flow in organic nano-pores due to their continuum assumption. The lattice Boltzmann method (LBM) is a good candidate for modelling shale gas flows because it arises from the gas kinetic theory. In this work, three-dimensional (3D) pore structures of a shale core sample are reconstructed based on the Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) technique. The multiple-relaxation-time LBE is used to model gas flows. A slip boundary condition is implemented to capture boundary flows in pores to describe the Klinkenberg effect. In addition, intermolecular forces between pore walls and gas molecules are incorporated to capture the adsorption effects to flow. Methane gas flows driven by gravitational force in square ducts with different sizes have been simulated in order to observe slippage. Permeability of methane gas in 3D complex kerogen pore structures has been investigated. It has been found that the permeability decreases with the pore pressure increases, which follows the Klinkenberg theory.
A New Model to Determine Leakage Factor for a Finite Aquifer Using Pressure Fall off Test in CBM Reservoir
Authors: Wu Xingru , Srivastava Priyank , Escobar Freddy H. 
Published: November 2015

Abstract
Water influx is an important factor which needs to be quantified during early stages of reservoir development to justify project economics. For a CBM reservoir, it is much more important to quantify a degree of connection & boundary between coal reservoir and aquifer (if any) as its production mechanism is based on efficient dewatering process and any communication of coal seams with adjacent aquifer layercan act as a major barrier for development. However, it is difficult to quantify water influx values early in field life as limited data is available from the reservoir; but pressure transient testing, usually done during exploratory stage can play a pivotal part in reservoir characterization. Currently, solutions exist for analyzing pressure falloff test reponses to quantify water influx in the reservoir in communication with an infinite aquifer. However, there can be cases with limited aquifer extent in which case the use of former solution would lead to wrong estimation of water influx communication. So we propose a new model to account for closed outer boundray of aquifer, and use of this model to estimate both aquifer extent and water influx quantification. Leaky aquifer models more accurately describe bottom water drive reservoirs as most of the time aquifer connection with the reservoir is not perfect (ΔPres. ≠ ΔPaquifer). It is extremely important to quantify connectivity between the aquifer and the main reservoir before going for full field development. The method presented in this paper can provide a much needed solution to quantify the aquifer reservoir connectivity and the aquifer extent for a reservoir with bottom water drive earlier in field life using pressure transient data. We demonstrate the robustness of the proposed method using synthetic example for a homogeneous single well radial reservoir.
Flow of Hydrocarbons in Nanocapillary: A Non-Equilibrium Molecular Dynamics Study
Authors: Feng Feng , Akkutlu I. Yucel 
Published: November 2015

Abstract
Unlike flow of fluid in conventional reservoirs, the fluid transport in unconventional reservoirs involves kerogen pore structure with much smaller capillaries. This, in turn, leads to large capillary wall surface area and, consequently, to a significant physical adsorption effect. Measurements are needed to understand the nature of flow inside kerogen structures. However, direct measurements are difficult and have large uncertainties related to kerogen isolation. Non-equilibrium molecular dynamics simulation allow numerical study of fluid transport inside model nano-capillaries representative of kerogen matrices. In this work two different molecular simulation methods are used to study steady-state flow of methane and of methane-butane mixture: External Field Non-Equilibrium Molecular Dynamics (EF- NEMD), the main flow simulation method, and Dual Control Volume Grand Canonical Molecular Dynamics (DCV-GCMD), the simulation method used to verify the results. The flow inside the capillary is simulated under various conditions, e.g., capillary diameter, temperature, average pressure, fluid composition and capillary wall morphology. Based on the simulation results we observe that fluid flow velocity and mass flux are significant near the capillary surfaces where adsorption takes place. Hence, Hagen-Poiseuille equation based on the no-flow condition at the wall significantly under-estimates the fluid flow in nanocapillary. The dependence of surface transport velocity, as well as flow enhancement, are determined quantitatively. The results confirm a previous study by Riewchotisakul and Akkutlu (2015) indicating the presence of a mobile adsorbed-phase in the organic capillaries based on molecular simulation of steady-state methane flow using a moving piston model.
Production Forecasting for Shale Oil: Workflow
Authors: Rincones M. D. , Lee W. J. , Rutledge J. M. 
Published: November 2015

Abstract
Unconventional oil reservoirs have taken a prominent role in the United States as a source of crude oil. Different methodologies to estimate reserves for shale gas and coal bed methane have, thus far, proved to be reliable, but no simple yet accurate workflow has been generally accepted to forecast production and estimate reserves for shale oil. To fill this gap in technology, we proposed and validated a workflow that integrates analytical methods with empirical methods. The final methodology is both easily applied and accurate. In developing the final workflow, we evaluated several alternatives, most of which proved to be unsuitable. We also investigated the use of a filter to eliminate outliers in a systematic way, as proposed by Rastogi (2014).
The workflow was successfully applied to three of four volatile oil wells in the Eagle Ford shale, with similar results. The analytical model that best matched the wells is called the Stimulated Reservoir Volume (SRV) Bounded Model. We tested this and other models using a new field production analysis tool software. While accurate, this modeling approach is too time consuming for routine use. We found that a simple empirical approach that led to the same results as the analytical model was a 3-segment Arps decline model. The early flow regime was transient linear for all the wells; thus an Arps "b" parameter of two was appropriate. When boundary-influenced flow (BIF) appeared later, b-values of 0.2 were found appropriate. The initial decline rate (Di) value during BIF was modified in mid-segment leading to a distinct third segment. Our workflow also led to reliable forecasts of production (to date) of the gas-oil ratio for the three wells.
The Progression of Fracture Stimulations in Horizontal Wells Targeting the Montney Formation in the Heritage Field, British Columbia, Western Canada
Authors: Christie Kyle , Russum Dave , Fitzmaurice Megan , Quinton Aaron 
Published: November 2015

Abstract
Producing unconventional resources through hydraulic fracturing is a continuous learning process where the fracture stimulation design can change throughout the life of the field development. The well completion technique can change because of many reasons such as lessons learned from previous stimulations, new technology, and the heterogeneous nature of the reservoir.
This paper focusses on real world data of hydraulic fracture stimulation properties sourced from public databases which is reported from wells drilled in the Heritage Field near Dawson, British Columbia. These wells are licensed as horizontal wells targeting gas production from the Montney Formation.
By plotting and mapping the fracture stimulation data collected from the area and focusing on a set of operators with major operations in the area, this paper demonstrates how the fracture stimulation has changed over time and illustrates the design changes of the fracture stimulations for each operator over their own development timeline.
This paper also discusses the collaboration initiatives that were implemented as the development progressed to highlight how industry and regulators can work together to responsibly produce the resource most effectively while still maintaining healthy competition.
Investigation of High Resistivities Observed During Azeri-Chirag-Guneshli Oil Field Development
Authors: Aliyarov Rauf , Rzayev Elshan , Ramazanov Rizvan 
Published: November 2015

Abstract
Physical properties of the reservoirs are known to be affected by the dynamic processes dominating during active field depletion. Formation resistivities from the open hole logs are one of the most sensitive measurements influenced by alteration of the reservoir properties due to production. Unusually high resistivity values were noted to occur more frequently with ACG field development. This largely affected water saturation values calculated using Archie model and hence the hydrocarbon volume in place estimates.
Mapping resistivity values across the field revealed the production time dependency of these high readings. A relationship between cumulative oil flux and formation resistivity at irreducible water saturations (away from the water front) was identified based on core experiments from the fields in the similar geological settings and the outputs from the ACG reservoir simulation model. This relationship showed increase of resistivity with the number of pore volumes flushed by oil through the porous medium. Through the systematic analysis of the field data this behavior was determined to be mostly related to the alteration of the wettability as a result of active dynamic processes in the porous medium.
CO2 Emulsified Fracturing Fluid for Unconventional Applications
Authors: AlDuailej Yaser K. , AlOtaibi Fawaz M. , AlKhaldi Mohammed H. 
Published: November 2015

Abstract
The demand for hydraulic fracturing has increased intensely with the transformation from conventional to unconventional reservoirs. High temperatures and extreme depths often amplify the complexity of any fracturing treatment. In addition, the sought synergy between different additives of the fracturing fluid becomes more challenging. As a result, the uncertainty of fracturing performance elevates as these factors become more complicated. Viscosity, propant transport and cleanup are the main criteria for assessing the performance of a fracture fluid. In this study, a fracturing fluid with unconventional composition is evaluated in terms of these parameters for the high temperature applications (300°F).
Most fracturing fluids are mainly composed of water. Since the frequency of fracturing applications is increasing, massive quantities of fresh water are daily consumed in these treatments. Sea-water is an alternative to fresh water; however, it requires accurate and cautious design to prevent incompatibility and instability. Another approach to avoid high water consumption is the use of CO2 emulsified fracturing fluid, where liquid CO2 reaches up to 70 vol%, thus, reducing the need for fresh water. Moreover, CO2 emulsified fracturing fluids offer better cleanup and artificial lift to flow backs.
Series of tests has been conducted to evaluate and optimize a CO2 emulsified fracturing fluid, where liquid CO2 constituted 50-70 vol% of the emulsion. The base gel is non-crosslinked and polysaccharide-based, with environmental friendly properties. The testing was done at different temperatures ranging from 220-300°F. The emulsion of liquid CO2 and base gel generated viscosity values compared to and better than guar-based foamed and gelled fracturing fluids.
Utilization of Single Real Time Data Visualization and Transmission Solution in Oil and Gas Field Development
Authors: Khudiri Musab , Al-Sanie Faisal , Miyajan Ramzi , Wuhaimed Ali , Hawi Maan , Abbas Mazin , Kashif Muhammad , Meraj Hamood , Ahmed Farhan 
Published: November 2015

Abstract
This paper highlights the tremendous impact of real-time data transmission and visualization through the Aramcolink solution for monitoring geosteering operations in Saudi Aramco. It was very challenging to move from multiple real time data providers to a single solution, which can connect with different service providers by utilizing WITSML, which is industry real-time data transmission protocol. Nevertheless, Saudi Aramco has decided to explore this frontier to provide their operational geoscientists/engineers with a single system through which all should be able to simultaneously monitor several actively drilling wells with ease.
Considering the drilling operation in Saudi Arabia, a system with advanced capabilities of data quality control (QC), rescaling, filtering, alerting, and chatting, was essentially required to assist operational geoscientists in optimizing production through geosteering a well by drilling through the sweet zone and achieve good net to gross value. The new solution "Aramcolink" is not only limited to these capabilities but distinguishes itself among other rival solutions by unmatched features such as data cross-plotting, on the fly azimuthal image dip calculation, built in petrophysical analysis and electrofacies computation, 2D and 3D well trajectory visualization, and others.
Moreover, information is now provided on how using such an approach helped in enforcing Saudi Aramco's standard for real-time log naming, measurement unit, and scaling, thereby facilitating more automated operational workflows. The paper concludes by sharing lessons learned and recommendations for future improvements.