bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unconventional Resource Play Evaluation: A Look at the Bakken Shale Play of North Dakota
Authors: Cox Stuart A. , Cook David M. , Dunek Ken , Daniels Reagan , Jump Connie , Barree Bob 
Published: February 2008

Abstract
Unconventional resource plays can provide a long-term supply of oil and gas to help supplement the North American energy demands. However, obtaining a good economic return from these developments can be challenging. A successful entry into an unconventional play requires careful pre-entry analysis in order to develop meaningful production profiles and set realistic expectations. Wells completed in unconventional plays typically exhibit limited drainage areas and produce a majority of recoverable reserves at low rates. Due to the limited flow capacity of these reservoirs typical development strategies include some form of horizontal completion.
When considering a potential entry into a "new" resource play there are a number of important questions that must be answered such as "What is an appropriate range of initial production rates and reserves for the development?" or "What is the most cost effective completion method?" and "How will post drill completion efficiency be determined?". This paper will present one operator's approach to answer these questions for its entry into the Bakken Shale development of North Dakota. The paper focuses on the effective use of existing public information to frame expectations for the development. It will also present the completion design considerations and initial implementation results from the development.
Stimulating Unconventional Reservoirs: Lessons Learned, Successful Practices, Areas for Improvement
Authors: Cramer David D. 
Published: February 2008

Abstract
The term "unconventional reservoir" has different meanings to different people. Certain reservoirs termed unconventional have a rock matrix consisting of inter-particle pore networks with very small pore connections imparting very poor fluid-flow characteristics. Abundant volumes of oil or gas can be stored in these rocks, and often the rock is high in organic content and the source of the hydrocarbon. Yet because of marginal rock matrix quality, these reservoirs generally require both natural and induced fracture networks to enable economic recovery of the hydrocarbon. Rock types in this class include shale and coalbed methane (CBM.) The term shale is a catchall for any rock consisting of extremely small framework particles with minute pores charged with hydrocarbon and includes carbonate and quartz-rich rocks. Another type of unconventional reservoir is stacked pay units exhibiting somewhat better pore characteristics than in the case outlined above but with the individual units tending to be lenticular in shape and having an extremely small size or volume. These two classes of unconventional reservoirs are amenable to well stimulation and will be the focus of this paper.
The above rock types when commercially exploited are known as resource plays. Once a low-priority, the depletion of conventional reservoirs and improving price for oil and gas has driven unconventional reservoirs to an important place in the oil and gas industry. In some regions (i.e., Rocky Mountain province), unconventional reservoirs represent the primary target of current activity and remaining hydrocarbon development. Given their unique petrophysical properties, each type of unconventional reservoir requires a unique approach to well stimulation, with often differing objectives than exist with conventional reservoir types. This paper reviews the characteristics of the basic unconventional reservoir types, lessons learned and successful stimulation practices developed in completing these reservoirs, and areas for improvement in treatment and reservoir characterization and treatment design.
Stimulating Unconventional Reservoirs: Maximizing Network Growth while Optimizing Fracture Conductivity
Authors: Warpinski N. R. , Mayerhofer M. J. , Vincent M. C. , Cipolla C. L. , Lolon E. P. 
Published: February 2008

Abstract
Unconventional reservoirs such as gas shales and tight gas sands require technology-based solutions for optimum development. The successful exploitation of these reservoirs has relied on some combination of horizontal drilling, multi-stage completions, innovative fracturing, and fracture mapping to engineer economic completions. However, the requirements for economic production all hinge on the matrix permeability of these reservoirs, supplemented by the conductivity that can be generated in hydraulic fractures and network fracture systems. Simulations demonstrate that ultra-low shale permeabilities require an interconnected fracture network of moderate conductivity with a relatively small spacing between fractures to obtain reasonable recovery factors. Microseismic mapping demonstrates that such networks are achievable and the subsequent production from these reservoirs support both the modeling and the mapping. Tight gas sands, having orders of magnitude greater permeability than the gas shales, may be successfully depleted without inducing complex fracture networks, but other issues of damage and zonal coverage complicate recovery in these reservoirs. As with the shales, mapping has proved itself to be valuable in assessing the fracturing results.
Role of Natural Fractures and Slot Porosity on Tight Gas Sands
Authors: Aguilera Roberto 
Published: February 2008

Abstract
Naturally fractured tight gas sands have come of age in the United States. They will also come of age in Canada within the next few years and in the rest of the world within the next few decades.
This work discusses the role of natural fractures and slot porosity on tight gas sands as they relate to geoscience, drilling, completion, stimulations, petrophysics, well testing, and reservoir engineering.
It is concluded that natural fractures and/or slot porosity play, and will continue to play, an important role in the successful and economic production of gas from tight sands. Research leading to innovating technologies that presumably will reduce capital and operating costs will play a key role in the development of this resource. Understanding the rocks and the regional variability of fracture distribution and diagenesis is the cornerstone of this research.
Modeling of Mixed-Gas Adsorption and Diffusion in Coalbed Reservoirs
Authors: Shi J. Q. , Durucan S. 
Published: February 2008

Abstract
Commercial CBM production is almost exclusively through reservoir pressure depletion (primary recovery). Enhanced coalbed methane recovery (ECBM), involving injection of pure N2/CO2 or a mixture of the two, such as power plant flue gas, is a technology that has the potential to recover a larger fraction of methane in place without excessively reducing the reservoir pressure. CO2-ECBM has an added benefit that a potentially large volume of greenhouse gas can be stored in deep coal seams globally. The use of numerical models is essential in the development of the ECBM and CO2 storage technology. The quasi-steady state Fickian diffusion equation, together with the Langmuir equation, has been almost exclusively used in numerical simulation of primary coalbed methane production. Assuming that the individual gas component in a multicomponent system diffuses independently, the quasi-steady state Fickian diffusion equation can be readily extended to model mixed-gas diffusion. In the recent years, attempts have been made to use this approach, in conjunction with the extended Langmuir equation, to model ECBM/CO2 storage field pilots as well as laboratory flooding tests. However, this modelling approach for mixed-gas diffusion lacks theoretical rigour as the interaction between different gas components is not accounted for, though the practical significance of doing so in coalbeds is not well understood at present.
A reservoir simulation sensitivity study on the Yubari CO2 storage pilot project, Japan, is presented. The sensitivity study with CO2 and CH4 sorption times indicates that the sorption time for CO2 has a much pronounced impact on the back-produced gas composition. The study has also highlighted the limitation of the extended Langmuir equation for ternary system predictions. Although inconclusive, the sensitivity results suggest that the N2 component sorption in the coalbed reservoir is over-estimated by at least 20% by the model.
Identifying Bypassed and Ineffectively Stimulated Layers in a Well With Commingled Production From Multiple Layers: Mesaverde Case History
Authors: Craig David P. , Odegard Chad E. 
Published: February 2008

Abstract
In an effort to examine well and reservoir connectivity for wells drilled through multiple low-permeability stacked lenticular reservoirs, we present case histories from the Piceance basin of Western Colorado. We review the completion and subsequent abandonment of an air-drilled high-angle slant hole through the Williams Fork sandstones in Grand Valley field as well as a high-angle slant hole drilled through and completed in two Williams Fork Mesaverde sandstones. We also review a case history describing single-entry-point fracture treatments in vertical wells designed to "frac into" sandstones near the entry point, and we describe a post-frac evaluation of propped fracture communication with sandstones adjacent to the single entry point. Lastly, we present a case history showing the results of a refracture-candidate evaluation and isolated-layer restimulation pilot program in the Piceance Basin where it is known that between 10% and 30% of the Meseverde layers targeted for fracturing are ineffectively stimulated or inadvertently bypassed during primary fracturing operations. The refracture-candidate pilot program provided the following.
An evaluation of production logs as a refracture-candidate diagnostic. An evaluation of short-term pressure buildup tests as a refracture-candidate diagnostic. An evaluation of fracture-injection/falloff tests as a refracture-candidate diagnostic.
Four discrete Mesaverde sandstones were tested as part of the refracture-candidate pilot program. Of the four layers selected for testing, numerous microseismic events were mapped during the initial fracture treatments in two, and no events were recorded in the other two. The refracture-candidate pilot program included recording a new production log and completing short-term pressure buildup and nitrogen fracture-injection/falloff tests in each isolated layer. The nitrogen fracture-injection/falloff tests confirmed the microseismic mapping during the original completion, that is, layers without microseismic events did not have a conductive hydraulic fracture based on the nitrogen-injection/falloff analysis. Consequently, bypassed or ineffectively stimulated layers can be identified with refracture-candidate diagnostics.
Nitrate in Tile Drainage of the Semiarid Palouse Basin
Authors: Keller C. Kent , Butcher Caroline N. , Smith Jeffrey L. , Allen‐King Richelle M. 
Published: February 2008

AbstractTopographically heterogeneous agricultural landscapes can complicate and accelerate agrochemical contamination of streams due to rapid transport of water and chemicals to poorly drained lower‐landscape positions and shallow ground water. In the semiarid Palouse region, large parts of these landscapes have been tile drained to enhance crop yield. From 2000–2004 we monitored the discharge of a tile drain (TD) and a nearby profile of soil water for nitrate concentration ([NO3]), electrical conductivity level (EC), and water content to develop a conceptual framework describing soil nitrate occurrence and loss via subsurface pathways. Tile‐drain baseflow [NO3] was consistently 4 mg N L−1 and baseflow EC was 200 to 300 μS cm−1 Each year sudden synoptic increases in TD discharge and [NO3] occurred in early winter following ∼150 mm of fall precipitation, which saturated the soil and mobilized high‐[NO3] soil water throughout the profile. The greatest TD [NO3] (20–30 mg N L−1) occurred approximately contemporaneous with greatest TD discharges. The EC decrease each year (to ∼100 μS cm−1) during high discharge, a dilution effect, lagged ∼1 mo behind the first appearance of high [NO3] and was consistent with advective transport of low‐EC water from the shallow profile under saturated conditions. Water‐budget considerations and temporal [NO3] patterns suggest that these processes deliver water to the TD from both lower‐ and upper‐slope positions, the latter via lateral flow during the high‐flow season. Management practices that reduce the fall reservoir of soil nitrate might be effective in reducing N loading to streams and shallow ground water in this region.
Impact of Glyphosate‐Tolerant Soybean and Glufosinate‐Tolerant Corn Production on Herbicide Losses in Surface Runoff
Authors: Shipitalo Martin J. , Malone Robert W. , Owens Lloyd B. 
Published: February 2008

AbstractResidual herbicides used in the production of soybean [Glycine max (L.) Merr] and corn (Zea mays L.) are often detected in surface runoff at concentrations exceeding their maximum contaminant levels (MCL) or health advisory levels (HAL). With the advent of transgenic, glyphosate‐tolerant soybean and glufosinate‐tolerant corn this concern might be reduced by replacing some of the residual herbicides with short half‐life, strongly sorbed, contact herbicides. We applied both herbicide types to two chiseled and two no‐till watersheds in a 2‐yr corn–soybean rotation and at half rates to three disked watersheds in a 3‐yr corn/soybean/wheat (Triticum aestivum L.)‐red clover (Trifolium pratense L.) rotation and monitored herbicide losses in runoff water for four crop years. In soybean years, average glyphosate loss (0.07%) was ∼1/7 that of metribuzin (0.48%) and about one‐half that of alachlor (0.12%), residual herbicides it can replace. Maximum, annual, flow‐weighted concentration of glyphosate (9.2 μg L−1) was well below its 700 μg L−1 MCL and metribuzin (9.5 μg L−1) was well below its 200 μg L−1 HAL, whereas alachlor (44.5 μg L−1) was well above its 2 μg L−1 MCL. In corn years, average glufosinate loss (0.10%) was similar to losses of alachlor (0.07%) and linuron (0.15%), but about one‐fourth that of atrazine (0.37%). Maximum, annual, flow‐weighted concentration of glufosinate (no MCL) was 3.5 μg L−1, whereas atrazine (31.5 μg L−1) and alachlor (9.8 μg L−1) substantially exceeded their MCLs of 3 and 2 μg L−1, respectively. Regardless of tillage system, flow‐weighted atrazine and alachlor concentrations exceeded their MCLs in at least one crop year. Replacing these herbicides with glyphosate and glufosinate can reduce the occurrence of dissolved herbicide concentrations in runoff exceeding drinking water standards.
Phosphorus Fertilizer and Grazing Management Effects on Phosphorus in Runoff from Dairy Pastures
Authors: Dougherty Warwick J. , Nicholls Paul J. , Milham Paul J. , Havilah Euie J. , Lawrie Roy A. 
Published: February 2008

AbstractFertilizer phosphorus (P) and grazing‐related factors can influence runoff P concentrations from grazed pastures. To investigate these effects, we monitored the concentrations of P in surface runoff from grazed dairy pasture plots (50 × 25 m) treated with four fertilizer P rates (0, 20, 40, and 80 kg ha−1 yr−1) for 3.5 yr at Camden, New South Wales. Total P concentrations in runoff were high (0.86–11.13 mg L−1) even from the control plot (average 1.94 mg L−1). Phosphorus fertilizer significantly (P < 0.001) increased runoff P concentrations (average runoff P concentrations from the P20, P40, and P80 treatments were 2.78, 3.32, and 5.57 mg L−1, respectively). However, the magnitude of the effect of P fertilizer varied between runoff events (P < 0.01). Further analysis revealed the combined effects on runoff P concentration of P rate, P rate × number of applications (P < 0.001), P rate × time since fertilizer (P < 0.001), dung P (P < 0.001), time since grazing (P < 0.05), and pasture biomass (P < 0.001). A conceptual model of the sources of P in runoff comprising three components is proposed to explain the mobilization of P in runoff and to identify strategies to reduce runoff P concentrations. Our data suggest that the principal strategy for minimizing runoff P concentrations from grazed dairy pastures should be the maintenance of soil P at or near the agronomic optimum by the use of appropriate rates of P fertilizer.
Evaluation of Fumigation and Surface Seal Methods on Fumigant Emissions in an Orchard Replant Field
Authors: Gao Suduan , Trout Thomas J. , Schneider Sally 
Published: February 2008

AbstractSoil fumigation is an important management practice for controlling soil pests and enabling successful replanting of orchards. Reducing emissions is required to minimize the possible worker and bystander risk and the contribution of fumigants to the atmosphere as volatile organic compounds that lead to the formation of ground‐level ozone. A field trial was conducted in a peach orchard replant field to investigate the effects of fumigation method (shank‐injection vs. subsurface drip‐application treatments) and surface treatments (water applications and plastic tarps) on emissions of 1,3‐dichloropropene (1,3‐D) and chloropicrin (CP) from shank‐injection of Telone C‐35 and drip application of InLine. Treatments included control (no water or soil surface treatment); standard high‐density polyethylene (HDPE) tarp, virtually impermeable film (VIF) tarp, and pre‐irrigation, all over shank injection; and HDPE tarp over and irrigation with micro‐sprinklers before and after the drip application. The highest 1,3‐D and CP emission losses over a 2‐wk monitoring period were from the control (36% 1,3‐D and 30% CP) and HDPE tarp (43% 1,3‐D and 17% CP) over shank injection. The pre‐irrigation 4 d before fumigation and VIF tarp over shank injection had similar total emission losses (19% 1,3‐D and 8–9% CP). The HDPE tarp and irrigations over subsurface drip‐application treatments resulted in similar and the lowest emission losses (12–13% 1,3‐D, and 2–3% CP). Lower fumigant concentrations in the soil‐gas phase were observed with drip‐application than in the shank‐injection treatments; however, all treatments provided 100% kill to citrus nematodes in bags buried from 30 to 90 cm depth. Pre‐irrigation and drip application seem to be effective to minimize emissions of 1,3‐D and CP.
When Does Nitrate Become a Risk for Humans?
Authors: Powlson David S. , Addiscott Tom M. , Benjamin Nigel , Cassman Ken G. , de Kok Theo M. , van Grinsven Hans , L'hirondel Jean‐Louis , Avery Alex A. , van Kessel Chris 
Published: February 2008

AbstractIs nitrate harmful to humans? Are the current limits for nitrate concentration in drinking water justified by science? There is substantial disagreement among scientists over the interpretation of evidence on the issue. There are two main health issues: the linkage between nitrate and (i) infant methaemoglobinaemia, also known as blue baby syndrome, and (ii) cancers of the digestive tract. The evidence for nitrate as a cause of these serious diseases remains controversial. On one hand there is evidence that shows there is no clear association between nitrate in drinking water and the two main health issues with which it has been linked, and there is even evidence emerging of a possible benefit of nitrate in cardiovascular health. There is also evidence of nitrate intake giving protection against infections such as gastroenteritis. Some scientists suggest that there is sufficient evidence for increasing the permitted concentration of nitrate in drinking water without increasing risks to human health. However, subgroups within a population may be more susceptible than others to the adverse health effects of nitrate. Moreover, individuals with increased rates of endogenous formation of carcinogenic N‐nitroso compounds are likely to be susceptible to the development of cancers in the digestive system. Given the lack of consensus, there is an urgent need for a comprehensive, independent study to determine whether the current nitrate limit for drinking water is scientifically justified or whether it could safely be raised.
Land Management Impacts on Dairy‐Derived Dissolved Organic Carbon in Ground Water
Authors: Chomycia Jill C. , Hernes Peter J. , Harter Thomas , Bergamaschi Brian A. 
Published: February 2008

AbstractDairy operations have the potential to elevate dissolved organic carbon (DOC) levels in ground water, where it may interact with organic and inorganic contaminants, fuel denitrification, and may present problems for drinking water treatment. Total and percent bioavailable DOC and total and carbon‐specific trihalomethane (THM) formation potential (TTHMFP and STHMFP, respectively) were determined for shallow ground water samples from beneath a dairy farm in the San Joaquin Valley, California. Sixteen wells influenced by specific land management areas were sampled over 3 yr. Measured DOC concentrations were significantly elevated over the background as measured at an upgradient monitoring well, ranging from 13 to 55 mg L−1 in wells downgradient from wastewater ponds, 8 to 30 mg L−1 in corral wells, 5 to 12 mg L−1 in tile drains, and 4 to 15 mg L−1 in wells associated with manured fields. These DOC concentrations were at the upper range or greatly exceeded concentrations in most surface water bodies used as drinking water sources in California. DOC concentrations in individual wells varied by up to a factor of two over the duration of this study, indicating a dynamic system of sources and degradation. DOC bioavailability over 21 d ranged from 3 to 10%, comparable to surface water systems and demonstrating the potential for dairy‐derived DOC to influence dissolved oxygen concentrations (nearly all wells were hypoxic to anoxic) and denitrification. TTHMFP measurements across all management units ranged from 141 to 1731 μg L−1, well in excess of the maximum contaminant level of 80 μg L−1 established by the Environmental Protection Agency. STHMFP measurements demonstrated over twofold variation (∼4 to ∼8 mmol total THM/mol DOC) across the management areas, indicating the dependence of reactivity on DOC composition. The results indicate that land management strongly controls the quantity and quality of DOC to reach shallow ground water and hence should be considered when managing ground water resources and in any efforts to mitigate contamination of ground water with carbon‐based contaminants, such as pesticides and pharmaceuticals.