As the conventional reservoirs decrease in discovering, producing and reserving, unconventional reservoirs are more remarkable in terms of discovering, development and having more reserve. More fields have been discovered where Barnett Shale and Bakken Shale are the most recently unconventional reservoir examples. Shale reservoirs are typically considered self-sourcing and have very low permeability ranging from 10-100 nanodarcies. Over the past few decades, numerous research projects and developments have been studied, but it seems there is still some contention and misunderstanding surrounding shale reservoirs. One of the largest shale in the United State is the Bakken Shale play. This study will describe the primary geologic characteristics, field development history, reservoir properties,and especially production trends, over the Bakken Shale play. Data are available for over hundred wells from different companies. Most production data come from the Production Data Application (HDPI) database and in the format of monthly production for oil, water and gas. Additional 95 well data including daily production rate, completion, Pressure Volume Temperature (PVT), pressure data are given from companies who sponsor for this research study. This study finds that there are three Types of well production trends in the Bakken formation. Each decline curve characteristic has an important meaning to the production trend of the Bakken Shale play. In the Type I production trend, the reservoir pressure drops below bubble point pressure and gas releasingout of the solution. With the Type II production trend, oil flows linearly from the matrix into the fracture system, either natural fracture or hydraulic fracture. Reservoir pressure is higher than the bubble point pressure during the producing time and oil flows as a single phase throughout the production period of the well. A Type III production trend typically has scattering production data from wells with a different Type of trend. It is difficult to study this Type of behavior because of scattering data, which leads to erroneous interpretation for the analysis. These production Types, especially Types I and II will give a new type curve matches for shale oil wells above or below the bubble point.

The most common way to analyze slope stability is to employ limit equilibrium (LE) theory and obtain a factor of safety (FOS). Methods of LE analysis balance the forces, and/or moments that are driving and resisting slope movement. Generally, in geotechnical engineering practice, a slope that plays host to an important structure is designed with a minimum factor of safety (FOS) of 1.5 and slope movement is monitored throughout the structure’s serviceable life. No further analysis of slope stability is completed until failure occurs when a back analysis is undertaken for the design of remedial measures. This thesis builds on current methods to demonstrate a framework for analysis that can be followed to analyze the state of a slope throughout its serviceable life. The two bridges at North Battleford, Saskatchewan (Battlefords bridges) were used as case studies for this work. In 1967, the older of the two bridges experienced a slope failure at its south abutment immediately prior to its opening to the public. The failure was remediated reactively by means of subsurface drainage, a toe berm, and river training that included diversion/spur dikes to reduce scour at the landslide toe. Since remediation, there has been no other catastrophic failure at either bridge but slow movement continues in the south abutment slope. Laboratory data and field observations from the onsite inclinometers were provided by Clifton Associates Ltd. (CAL) and Saskatchewan Ministry of Highways and Infrastructure (SMHI). The following methodology was followed to develop a framework of analysis for low FOS slopes: 1. Synthesis of data collected during previous investigations at the Battlefords bridges; 2. Detailed site characterization using existing research and terrain analysis; 3. Back analysis of the critical section through original failure using traditional limit equilibrium methods to calibrate the soil strength properties; 4. Application of the calibrated soil strength properties to the original failure after remediation; 5. Estimation of unknown soil properties using instrumentation at the site. 6. Create a model of the new bridge south abutment with the calibrated strength properties from steps 4 & 5 using the finite element method (FEM). 7. Confirmation of the mechanism of failure and assessment of the shear strain and mobilized shear strength; and, 8. Comparison of the results of FEM and LEM models and relationship between factor of safety and mobilized shear strength. The framework presented in this thesis presents a method of modeling the instability of a slope. In the absence of triaxial testing data, it presents a range of mobilized shear strengths along the shear plane.

The present study applies evolutionary and resource-based firm theories to three of the most prominent U.S. shale gas basins – the Barnett, Fayetteville, and Haynesville plays. Rather than broadly considering a host of factors that enabled what has often been labelled a shale gas revolution, an evolutionary approach recognizes the internal agents that have long been in place, but were triggered by technical and economic developments. As geologic understanding, along with innovation and competitive environments, evolves in each play so too does the entire shale gas industry. Building upon the Bureau of Economic Geology shale gas study funded by the Sloan Foundation, this study offers data-driven analyses to test theories of industrial evolution as applied to shale gas plays. Each of the three focus plays has undergone introductory and growth phases as well as a maturation phase in which there is an evident shakeout of operators. Industries are theorized to enter decline phases, yet none of the plays here have definitively declined. Certain economic signals, however, indicate that a decline is imminent, albeit variable in timing and pace. Conceptualizing the entire shale gas industry as an amalgamation of individual and evolving plays correctly describes how the industry is able to rejuvenate its growth trajectory through investment in emerging plays. Although heterogeneous geology, engineering capabilities, and economic environment, particularly natural gas prices, complicate the economics of shale gas extraction, an evolutionary approach proves to be a useful tool in describing the historical development of individual plays as well as the entire shale industry. Importantly, this application sheds light on the future development of valuable shale resources. / text

Air drilling is limited to competent formations that are essentially dry. In these circumstances large shale fragments are often observed and it is believed that these large shale fragments are not from the cutting action of drill bit at the bottom of the hole but from caving in, or sloughing of the wellbore wall. This type of wellbore instability problems may occur when drilling formations have significant amounts of water-sensitive clays. Change in shale water content due to water dehydration induces additional rock stresses near the wellbore, which can destabilize the borehole. The primary cause of this problem may well relate to moisture movement. Because as air is often used as the drilling fluid, the water in exposed pores will start to evaporate into the borehole, so that the water content is reduced. This results in the development of different stress patterns and the shale fractures and falls into the wellbore. The work of this thesis simulates the shrinkage and the consequent cracking pattern. A model of a bonded granular material is created and its properties confirm it to be that of a brittle, isotropic elastic solid. Crack growth is simulated by sequentially removing the most highly stressed bond in turn. A number of different geometries are simulated and the influence of stochastic bond strength on the cracking pattern is investigated. The model results show that cracking pattern produced in the simulations is consistent with the ‘blocky’ debris sometimes seen during air drilling and so the recommendation is made that air used for drilling should be sufficiently humid to avoid the dehydration of the shale.

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Shale gas reservoirs are gaining importance in United States as conventional oil and gas resources are dwindling at a very fast pace. The purpose of this study is twofold. First aim is to help operators with simple screening criteria which can help them in making certain decisions while going after shale gas reservoirs. A guideline chart has been created with the help of available literature published so far on different shale gas basins across the US. For evaluating potential of a productive shale gas play, one has to be able to answer the following questions: 1. What are the parameters affecting the decision to drill a horizontal well or a vertical well in shale gas reservoirs? 2. Will the shale gas well flow naturally or is an artificial lift required post stimulation? 3. What are the considerations for stimulation treatment design in shale gas reservoirs? A comprehensive analysis is presented about different properties of shale gas reservoirs and how these properties can affect the completion decisions. A decision chart presents which decision best answers the above mentioned questions. Secondly, research focuses on production data analysis of Barnett Shale Gas reservoir. The purpose of this study is to better understand production mechanisms in Barnett shale. Barnett Shale core producing region is chosen for the study as it best represents behavior of Barnett Shale. A field wide moving domain analysis is performed over Wise, Denton and Tarrant County wells for understanding decline behavior of the field. It is found that in all of these three counties, Barnett shale field wells could be said to have established pressure communication within the reservoir. We have also studied the effect of thermal maturity (Ro %), thickness, horizontal well completion and vertical well completion on production of Barnett Shale wells. Thermal maturity is found to have more importance than thickness of shale. Areas with more thermal maturity and less shale thickness are performing better than areas with less thermal maturity and more shale thickness. An interactive tool is developed to access the production data according to the leases in the region and some suggestions are made regarding the selection of the sample for future studies on Barnett Shale.

Shale gas formation exhibits some unusual reservoir characteristics: nano-darcy matrix permeability, presence of natural fractures and gas storage on the matrix surface that makes it unique in many ways. It’s difficult to design an optimum fracture treatment for such formation and even more difficult is to describe production behavior using a reservoir model. So far homogeneous, two wing fracture, and natural fracture models have been used for this purpose without much success. Micro seismic mapping technique is used to measure the fracture propagation in real time. This measurement in naturally fractured shale formation suggests a growth of fracture network instead of a traditional two wing fractures. There is an industry wise consensus that fracture network plays an important role in determining the well productivity of such formations. A well with high density of fracture networks supposed to have better productivity. Shale formations have also exhibited production pattern which is very different from conventional or tight gas reservoir. Initial flow period is marked by steep decline in production while the late time production exhibits a slow decline. One of the arguments put for this behavior is linear flow from a bi-wing fractured well at early time and contribution of adsorbed gas in production at late time. However, bi-wing fracture geometry is not supported by the micro-seismic observation. A realistic model should include both the fracture network and adsorbed gas property. In this research we have proposed a new Power Law Permability model to simulate fluid flow from hydraulically fractured Shale formation. This model was first described by Valko & Fnu (2002) and used for analyzing acid treatment jobs. The key idea of this model is to use a power law permeability function that varies with the radial distance from well bore. Scaling exponent of this power law function has been named power law index. The permeability function has also been termed as secondary permeability. This work introduces the method of Laplace solution to solve the problem of transient and pseudo steady-state flow in a fracture network. Development and validation of this method and its extension to predict the pressure (and production) behaviour of fracture network were made using a novel technic. Pressure solution was then combined with material balance through productivity index to make production forecast. Reservoir rock volume affected by the fracture stimulation treatment that contributes in the production is called effective stimulated volume. This represents the extent of fracture network in this case. Barnett shale formation is a naturally fractured shale reservoir in Fort Worth basin. Several production wells from this formation was analysed using Power Law Model and it was found that wells productivity are highly dependent on stimulated volume. Apparently the wells flow under pseudo steady state for most part of their producing life and the effect of boundary on production is evident in as soon as one months of production. Due to short period of transient flow production from Barnett formations is expected to be largely independent of the relative distribution of permeability and highly dependent on the stimulated area and induced secondary permeability. However, an indirect relationship between permeability distribution and production rate is observed. A well with low power law index shows a better (more even) secondary permeability distribution in spatial direction, larger stimulated volume and better production. A comparative analysis between the new model and traditional fracture model was made. It was found that both models can be used successfully for history matching and production forecasting from hydraulically fractured shale gas formation.

The objective of this thesis is to analyze the considerations regarding the environmental impacts of shale gas development by a rational, objective, fact-based assessment. Flowback and produced water from shale gas development can be treated with the related technologies on-site or off-site for recycling, reuse, discharge, and disposal. However, more efficient technologies should be researched even though current levels are high. Besides, the amount of water used in shale gas development is generally lower than that of other energy sources and most shale gas plays are located in areas with moderate to high levels of annual precipitation. However, growing populations, other industrial water demands, and seasonal variation in precipitation should be considered during shale gas development. Groundwater contamination is directly connected to the integrity of the well casing, not hydraulic fracturing, because there are significant spacious gap and several impermeable layers between target formations and ground water zones. Hydraulic fracturing rarely creates unwanted induced seismicity because the seismic energy created from hydraulic fracturing is too low to be detected in the surface, compared to the waste injection well. / text

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