bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Practical Workflow for Characterizing Stress-Dependent Behaviour of Coal from Changes in Well Productivity
Authors: Burgoyne M.. , Shrivastava R.. 
Published: November 2015

Abstract
Stress (or pressure) dependence of coal permeability is a commonly observed and generally accepted dynamic behaviour that is often ignored from production performance forecasting. Reasons for this omission typically include (a) the difficulties in reliably characterizing stress dependent effects from a limited number of pressure buildup tests, and (b) large uncertainties in our understanding of both the porosity and compressibility of coals. This paper demonstrates a new analytical workflow, and proposes a new set of equations that overcomes some of those limitations through acknowledging and accounting for stress dependent permeability (SDP) behaviour with radius - during testing and production - by translating expected permeability changes with pressure, to productivity changes with pressure gradient.
This paper utilizes a slightly modified form of Palmer-Mansoori (P&M) model in a workflow that includesEstimation of coal cleat volume compressibility using permeability-depth trendsCharacterization of mechanical skins from interpreted apparent skinsCalculation of "stress dependent pseudo pressure" (SDPP) – converting permeability changes with pressure to productivity changes with pressure gradient – enabling the use of well productivities over time as part of a SDP characterization processThe matching through regression of relative changes in well productivity indices in groups of wells - utilizing the SDPP approach – with a single stress dependent controlling parameter, in a way that is suited to extrapolating away from well control.
The paper provides the theoretical support for this approach via derivations from published models, and then outlines the methodology – sharing the results of a field example – demonstrating the relative ease with which the analytical process can be applied. Further, it highlights pitfalls of using well productivities as a direct proxy for permeability changes, or even utilizing coarse grid numerical simulation in the matching process. Finally, it also discusses further applications and limitations of its application.
This paper addresses existing knowledge gaps in the CSG industry by providing a simple, yet efficient, workflow for characterizing and incorporating stress-dependence of permeability in CSG Reservoir Engineering. This is achieved through the application of new analytical equations to characterize stress dependent pseudo pressure, enabling the direct use of well productivity changes, and can be used standalone, or as a means to accelerate a numerical history matching workflow.
Reservoir Characterisation of the Spring Gully Coal Seam Gas Field
Authors: Lin Xuejun , Weatherstone Petrina , Weichman David 
Published: November 2015

Abstract
The Spring Gully coal seam gas (CSG) field, operated by Origin Energy on behalf of Australia Pacific LNG, is located in the southern region of the Bowen Basin. Commercial production commenced in 2005 from the Late Permian Bandana coal seams. This paper describes the reservoir characterisation methodology employed to history match geologically unique regions of the Spring Gully field and to understand production mechanisms across the field. In addition, the paper presents a detailed discussion on how learnings from the developed region of the field has been applied to characterise the future development regions of the field for forecasting.
The Spring Gully CSG field exhibits a large degree of localized heterogeneity and extensive regional geological variability. Strong gas productivity and rapid water gas ratio decline have been observed in the north-eastern region of the field. While in the western portion of the field there exists moderate gas productivity and minimal water decline. A comprehensive, multi-disciplinary evaluation of the Spring Gully CSG field reservoir and production characteristics was performed in 2014. A reservoir simulation model has been constructed based on a number of geological and reservoir characterisation studies, combined with reservoir inputs and production analysis. The integrated subsurface model forms the basis to understand Spring Gully CSG field production mechanisms and ultimately to perform production forecasts for reserve and resource estimates, for ongoing reservoir management needs and appropriately size gas and water treatment facilities.
A novel approach of constructing the permeability and porosity distribution in the reservoir model was implemented. Historical well peak water and gas rate, rig testing water rate and welltest-derived permeability were used to construct the permeability distribution in the model. The permeability distribution was transformed to porosity distribution. The faulting and compartmentalisation were introduced in the north-eastern region of Spring Gully reservoir model during the history match stage to match the rapid decline of reservoir pressure. The learnings obtained from studying well production mechanisms and model history matching were subsequently applied to the undeveloped regions of the field. Extensive validation and quality control of forecast methodology, forecast parameters assumptions and life-of-field production forecasting were performed.
Effect of Volcanic Intrusions and Mineral Matters on Desorption Characteristics of Coals (Case Study)
Authors: Salmachi Alireza , Wainman Carmine C. , Rajabi Mojtaba , McCabe Peter 
Published: November 2015

Abstract
In this study, coal seams properties in two coal core wells are studied to identify dominant parameters controlling desorption characteristics of coals. Available published data from desorption canister tests including sorption time and gas content (lost gas, desorbed gas, and residual gas) are employed. Proximate analysis data assists in coal characterization and data from high pressure adsorption tests are used to investigate the methane adsorption on coal as a function of pressure. For fracture and cleat analysis, gamma ray, density, and acoustic image logs are used. All data and analysis combined with regional geology assist to study desorption properties of different coal seams in these two wells.
Kalbar-1 and Peebs-1 are the two core wells in this study. Entirely different patterns (gas content versus depth) are observed which can be explained by their different geological setting. A major volcanic intrusion of approximately 60m in thickness and a few minor intrusions in the area explain abnormally high gas content of shallow coal seams. The methane Langmuir adsorption isotherm for shallow coals (composite sample) is steep and has higher gas adsorption capacity compared to other seams. The shallow coal seams have been cooked by volcanic intrusions and have higher than expected gas content.
For Peebs-1, the composite plot of gas content, sorption time, and ash content combined with gamma ray, density, and acoustic image logs provides a useful set to study desorption properties of coal seams. The fracture and cleat analysis reveals that low sorption time generally belongs to coal seams with higher cleat and fracture density. The existence of open cleats and fractures might facilitate gas release from coal matrix. The inverse correlation observed between sorption time and ash content while maceral composition is fairly similar suggests that desorption properties might be controlled by mineral matters in this well.
A Coupled Model for Fractured Shale Reservoirs with Characteristics of Continuum Media and Fractal Geometry
Authors: Wei Yunsheng , He Dongbo , Wang Junlei , Qi Yadong 
Published: November 2015

AbstractThe principle focus of this work is on proposing a new model to evaluate the production performance of complexly-fractured well in shale reservoirs for conducting rate transient analysis (RTA) and pressure transient analysis (PTA). The model is established on the trilinear-flow idealization presented by Brown et al. (2009) for fractured horizontal well and associated with continuum geometry, fractal characterization and anomalous diffusion. The coupled model could take into account the non-uniform distribution of fracture network within stimulated reservoir volume (SRV) and property heterogeneity among hydraulic fractures in the configuration of multiple fractured horizontal well (MFHW).The second focus is put on developing a novel semi-analytical solution to fill the gap between trilinear-flow model for single-fracture hypothesis and actual MFHW configuration. The new solution could account for the effect of fracture-production interaction and property heterogeneity among fractures. Calculative results show that the type, sequence and duration of flow regimes are determined by fractal characteristics, associated anomalous diffusion, fracture number/spacing, fracture conductivity, etc. Hence, it is possible to observe the feature of long-period linear flow trends in the production performance of fractured well and explain the presentation of new flow regimes which are generally not identified by conventional trilinear-flow model. In addition, approximate solutions for corresponding flow regimes have also been proposed to interpret the production performance using straight forward method. Furthermore, a field example from Sichuan Shale in China is presented to demonstrate the practical application of the new model for interpreting production data analysis of MFHW. The model provides us with new knowledge and insight into understanding production characteristics and allows us to correctly predict well performance in fractured shale reservoirs
Proving the Concept of Unconventional Gas Reservoirs in Saudi Arabia Through Multistage Fractured Horizontal Wells
Authors: Al-Momin Ali , Kurdi Mohammed , Baki Sohrat , Mechkak Karim , Al-Saihati Ali 
Published: November 2015

Abstract
Saudi Arabia has embarked on an exploration journey for its unconventional gas resources by recently targeting three different areas across the Kingdom. The targeted formations include tight sandstone, shale and tight carbonate with a permeability range of 200 nano-darcy to 0.1 MD. Extensive exploratory work has been performed in each of the areas through drilling vertical wells to identify and characterize potential targets through coring and open-hole logging along with flow potential testing of those targets after placing vertical fractures, which is beyond the scope of this paper. This paper highlights the progress of the unconventional program through drilling horizontal mono-bore wells and stimulating them with multistage fracturing using Plug-N-Perf technique. Three case studies, one from each targeted formations, are presented in this paper. The subjects addressed are:
Well completion including the selection of tubing and liner sizes, metallurgy and grades along with performing stress and thermal analysis simulating the expected loads during proppant fracturing to determine the maximum safe loads at each stage. Proppant fracturing design including the number of stages and clusters, the spacing of stages, proppant type, size and volume, and fracturing fluid systems. The design is based upon the geomechanical and petrophysical interpretations of the openhole logs together with onsite calibrations and measurements. Plug-N-Perf and fracture stimulation operations and execution Fracture fluid clean up and flow testing
The paper summarizes the workflow adopted, the lessons learned and challenges overcome after drilling, completing, fracturing and flow testing of several unconventional gas wells in Saudi Arabia.
Geochemical Assessment of the Huntly Coalbed Methane (CBM) Field, New Zealand Using a Chloride, Bicarbonate, and Boron Ternary Diagramme
Authors: Abu Bakar H.. , Zarrouk S. J. 
Published: November 2015

Abstract
This study investigates the chemical signature of produced water from the Huntly coalbed methane (CBM) using a newly proposed Cl-HCO3-B ternary diagram. This ternary diagram is used to identify the source of fluid in the different aquifers (ground water, CBM and deep basement) and the potential communication between these aquifers. A comparison study of Huntly with other CBM fields (Maramarua, Powder River Basin, San Juan Basin, Raton, Atlantic Rim, Liulin and Alberta) was also carried out to help characterize and verify the water being abstracted. Results from the ternary diagram show that produced water samples from Huntly CBM wells are plotted in the middle along chloride-bicarbonate axis. This indicates that the water samples are CBM water originated from moderate to good permeability coal seams. The water samples also indicate that they have some communication with shallow aquifer due to significant bicarbonate concentration. Meanwhile water samples from basement well (B1) are plotted near to Boron side along Boron-chloride axis, which signifies basement water. The water originated from low permeable formations and afar from recharge area. Furthermore, results from schoeller diagrams show that Huntly water samples from CBM wells, shallow monitoring well and basement well exhibit distinct water chemistry patterns. The CBM water pattern shows sodium, bicarbonte and chloride as the predominant ions. It is similar to the typical CBM water pattern and comparable with CBM water from selected methane producing CBM fields with minor differences. Water samples from the basement well on the other hand shows sulfate and magnesium as the primary ions and the concentration for all ions are lower than CBM water. Shallow water sample exhibits the lowest concentration for all ions compared to CBM water and basement water with bicarbonate as the main ion. In conclusion, this ternary diagram is a reliable tool to identify the possible links between deep and shallow aquifers, formation permeability and origin of the water in one diagram. It enhances the understanding of the natural CBM reservoir setting for future field development, wastewater management and water quality monitoring.
Evaluating Ion Effect on Residue Content of Fracturing Fluids
Authors: Singh D.. , Inyang U. A. , Chopade P. D. , Boontheung P.. 
Published: November 2015

Abstract
Historically, guar-borate fluids have been the most commonly used crosslinked gel system in fracturing applications. Low cost, shear tolerance, and operational ease of guar-borate fluids often makes them the preferred candidates compared to other fluid systems for viscous fluid applications of fracturing services. However, residue generated in broken guar-borate fluids can have a negative impact on the conductivity of the fractures placed into the reservoir and the permeability of the proppant pack. This paper focuses on evaluating residue generated from guar-based fracturing fluids in the presence of various ions using extensive laboratory methods.
Hydraulic fracturing is a technique used for improving hydrocarbon production from conventional and unconventional reservoirs. The process sometimes involves pumping a high viscosity, proppant laden fluid into the reservoir to create the desired fracture geometry. Crosslinkers are often used to amplify the fluid viscosity of the base polymer to create wider fractures and to support proppant transport into and within the fractures. Breakers then reduce fluid viscosity before and during cleanup to ease flowback of the broken polymer gel. Both cleanup and flowback are crucial steps that can directly impact production of hydrocarbon from the fractured reservoir.
Laboratory results have shown that some ions, when present in the water source, can significantly impact the amount of residue generated from guar-based fracturing fluid. This paper presents a systematic study on the effect of ions, such as potassium, calcium, and magnesium, on guar and guar derivative residue and their hydration properties.
Residue generated after breaking guar-based fluids can have negative impact on the conductivity of the reservoir and the permeability of the proppant pack, which can significantly lower hydrocarbon production. Understanding the impact of various ions on cleanup properties of fracturing fluid can improve fluid design and therefore improve the conductivity of the proppant pack and formation.
Acoustic-based Methodology of Assessing Zonal Production Contribution, Hydraulic Fracture Productive Height, and Reservoir Fluid Type in Tight Gas Condensate and Oil Reservoirs
Authors: Mohsin Labib , Marmin Norhafiz , Mukha Alexander 
Published: November 2015

Abstract
For a tight reservoir, assessment of zonal production contribution is often possible only after the reservoir has been hydraulically fractured. Spinner survey is commonly the tool of choice for diagnosing relative production contribution across perforated interval in a cased-hole and by extension, minimum productive fracture height at the wellbore. However, its limited radial resolution renders such tool unreliable in evaluating flow characteristic within fracture body and across fracture planes. The acquired data is generally insufficient for resolving relative contribution of various productive horizons intersected by the fracture. As the measurements are focused on flow characteristics inside the wellbore, fracture height diagnosis is limited by the extent of perforation interval. Alternatively, radioactive tracing and microseismic survey allow one to see through the casing wall albeit at the expense of heightened cost and operational complexity. Thermal logging, being a cheaper alternative, is time-sensitive and not deployable immediately following proppant placement due to restricted wellbore access. Most importantly, hydraulic and propped fracture heights diagnosed by these methods may not necessarily coincide with effective fracture height that contributes directly to well productivity.
Integrating acoustic logging to conventional production logging measurements may, in addition to increasing resolution for low flow measurement, significantly extend the investigation radius beyond casing wall. Different acoustic characteristics potentially exhibited by flow of different fluid phases may also validate conventional log-derived reservoir fluid types. The paper describes the application of acoustic logging in diagnosing zonal production contribution, fracture height, and reservoir fluid type across hydraulically fractured tight gas condensate and oil reservoirs.
In four naturally flowing wells, zonal production contribution derived from acoustic wave analysis and conventional production log data were both in good agreement. The analysis of depth-specific acoustic wave amplitude provided useful insight in the diagnosis of zonal production contribution and by extension, productive fracture height. In one well, acoustic-derived fracture height could be closely corroborated with that of radioactive tracer data. In addition, one may also observe distinct shape of maximum amplitude of first sound wave arrival in a gas well compared to that in an oil well.
A Semi-Analytical Method for Forecasting Wells Completed in Low Permeability, Undersaturated CBM Reservoirs
Authors: Clarkson C. R. , Qanbari F.. 
Published: November 2015

Abstract
Exploration and development of coalbed methane (CBM) reservoirs is ongoing in the Asia Pacific region, with low permeability, undersaturated coals being the target in some areas. Horizontal wells are typically required to produce low permeability CBM reservoirs at commercial rates, and may experience a period of single-phase (water) transient flow, followed by a transition to two-phase (water+gas) transient flow. Wells exhibiting this behavior are particularly difficult to model analytically, yet simple analytical and semi-analytical tools are desirable for making quick, but reasonably accurate forecasts. The purpose of this work is to therefore provide a new forecasting methodology for low permeability, undersaturated CBM wells.
The new method for forecasting CBM wells introduced in this work is based on the concept of a dynamic drainage area (DDA), recently adapted to forecast tight black oil and gas condensate wells exhibiting two-phase flow. A critical advancement provided in the current work is modeling the transition from single-phase flow of water to two-phase flow of gas and water during the transient linear flow period, which was not attempted for the black oil/gas condensate cases. Above desorption pressure, material balance, performed on the dynamic drainage area to determine average pressure in the distance of investigation, is combined with the linear flow productivity index equation to forecast water production at each time step. For two-phase flow below desorption pressure, the two-phase version of the linear productivity equation and material balance equations for water and gas are solved iteratively for pressure, saturation and fluid production rate within the DDA. The gas material balance equation accounts for desorption effects. In order to calculate the DDA at each time step, the linear flow distance of investigation equation is used. Importantly, using the DDA method, variable operating conditions (flowing pressures) may be accounted for, which is critical for CBM wells during early stages of production.
The new semi-analytical DDA model is used to history-match production data from an actual horizontal well completed in a low permeability, undersaturated, western Canadian CBM reservoir. Further, the match is compared to that obtained from rigorous numerical simulation. The history-match of the field data is reasonable with the new model and comparable to numerical simulation. The new model is however easier to setup and less data-intensive than numerical simulation, providing a practical alternative to CBM reservoir engineers who are responsible for generating a large number of forecasts.
The Effect of Rank and Lithotype on Coal Wettability and its Application to Coal Relative Permeability Models
Authors: Mahoney Shilo A. , Rufford Thomas E. , Dmyterko Anastasia S. , Rudolph Victor , Steel Karen M. 
Published: November 2015

Abstract
We report the effect of rank and lithotype on the wettability of artificial cleat channels in five coals from the Bowen Basin with ranks in the Rmax% range 0.98-1.91%. Wettability was assessed by measuring contact angles of air and water in the artificial cleats using a microfluidic Cleat Flow Cell (CFC) instrument. The artificial cleats were produced by reactive ion etching and had widths in the range 20–40 μm that replicate the width and shape of some natural coal cleats under sub-surface reservoir conditions. These model cleats were developed to allow systematic laboratory investigations of water and gas relative permeability behaviour.
Imbibition and drainage experiments were performed in the artificial channels using air and 0.1 %wt. fluorescein in fresh tap water to observe contact angles, the entry pressure of the air-water and water-air interface to the channel, and the pressure at which the channel was filled by the displacing fluid. Relative contact angles on the coal surface of 110 -140° were determined from images collected in the imbibition experiments. A trend of increasing contact angle with coal rank was observed. The low rank coal exhibited smaller contact angles and lower breakthrough pressures than the higher rank coal samples. In the drainage experiments the injection air displaced the water but left a residual liquid film on cleat walls across dull, inertinite rich bands. This residual film was not observed in the bright, vitrinite rich bands. The results of this study may provide the basis to consider an improved relative permeability model that explicitly accounts for wettability and the effect of coal rank.