bluuebunny/crossref_metadata_2025 huggingface dataset:
Anosmin-1 contributes to brain tumor malignancy through integrin signal pathways
Authors: Choy Catherine T , Kim Haseong , Lee Ji-Young , Williams David M , Palethorpe David , Fellows Greg , Wright Alan J , Laing Ken , Bridges Leslie R , Howe Franklyn A , Kim Soo-Hyun
Published: November 2013

Anosmin-1, encoded by theKAL1gene, is an extracellular matrix (ECM)-associated protein which plays essential roles in the establishment of olfactory and GNRH neurons during early brain development. Loss-of-function mutations ofKAL1results in Kallmann syndrome with delayed puberty and anosmia. There is, however, little comprehension of its role in the developed brain. As reactivation of developmental signal pathways often takes part in tumorigenesis, we investigated if anosmin-1-mediated cellular mechanisms associated with brain tumors. Our meta-analysis of gene expression profiles of patients' samples and public microarray datasets indicated thatKAL1mRNA was significantly upregulated in high-grade primary brain tumors compared with the normal brain and low-grade tumors. The tumor-promoting capacity of anosmin-1 was demonstrated in the glioblastoma cell lines, where anosmin-1 enhanced cell motility and proliferation. Notably, anosmin-1 formed a part of active β1 integrin complex, inducing downstream signaling pathways. ShRNA-mediated knockdown of anosmin-1 attenuated motility and growth of tumor cells and induced apoptosis. Anosmin-1 may also enhance the invasion of tumor cells within the ECM by modulating cell adhesion and activating extracellular proteases. In a mouse xenograft model, anosmin-1-expressing tumors grew faster, indicating the role of anosmin-1 in tumor microenvironmentin vivo. Combined, these data suggest that anosmin-1 can facilitate tumor cell proliferation, migration, invasion, and survival. Therefore, although the normal function of anosmin-1 is required in the proper development of GNRH neurons, overexpression of anosmin-1 in the developed brain may be an underlying mechanism for some brain tumors.
Pulmonary Hypertension Associated With Scurvy and Vitamin Deficiencies in an Autistic Child
Authors: Duvall Melody G. , Pikman Yana , Kantor David B. , Ariagno Katelyn , Summers Lisa , Sectish Theodore C. , Mullen Mary P.
Published: November 2013

Restricted dietary intake is common among children with behavioral issues. Here we report a case of a severely autistic child who presented initially with limp but who soon developed cough, tachypnea, hypoxia, and tachycardia. An echocardiogram revealed evidence of pulmonary hypertension (PH) with severely dilated right ventricle and elevated right-sided pressures. The etiology of his PH was unclear but further laboratory evaluation demonstrated severe nutritional deficiencies, in particular an undetectable ascorbic acid (vitamin C) level as well as deficient levels of thiamine (vitamin B1), pyridoxine (vitamin B6), cobalamin (vitamin B12), and vitamin D. Repletion of these vitamins was associated with resolution of his PH and his musculoskeletal complaints. We report this case and a review of the relevant literature as a clinical lesson to expand the differential diagnosis of limp in children who may be difficult to assess as well as to report on an unusual association between severe vitamin deficiencies and PH.
Pediatric Spinal Epidural Abscess: A 9-Year Institutional Review and Review of the Literature
Authors: Hawkins Melody , Bolton Michael
Published: November 2013

Spinal epidural abscess (SEA) is a rare condition that requires prompt diagnosis and initiation of treatment for optimal outcome. Treatment generally consists of surgical intervention and systemic antibiotics. We present 1 of the largest cohorts of nontuberculous pediatric SEA in the English literature, emphasizing the outcomes of conservative (ie, nonoperative) management. We retrospectively identified 9 pediatric patients (≤18 years of age) with SEAs at Our Lady of the Lake Children’s Hospital from 2002 to 2011. Cases were reviewed for demographic, clinical, diagnostic, and treatment characteristics and outcomes. The diagnosis of SEA was made by MRI in all cases, and methicillin-resistant Staphylococcus aureus (MRSA) was the only identified pathogen, isolated via blood culture in 6 of 9 patients. Although every patient received systemic antibiotics, only 2 had neurosurgical intervention. Four of the 7 patients treated conservatively received computed tomography-guided needle drainage. All patients recovered without significant sequelae. SEA is a potentially fatal illness that necessitates a heightened clinical awareness for diagnosis and treatment. Although official recommendations regarding management in pediatrics are lacking, treatment has generally been surgical decompression and drainage in combination with antibiotics; recent reports have suggested that antibiotic therapy alone may be successful in select patient populations. Although the adult literature has suggested that such management can be trialed in specific situations, only a handful of cases in the pediatric literature have reported this nonoperative approach. We present one of the largest reviews in support of successfully treating SEA with nonsurgical therapy.
Changes in Children’s Sleep Duration on Food Intake, Weight, and Leptin
Authors: Hart Chantelle N. , Carskadon Mary A. , Considine Robert V. , Fava Joseph L. , Lawton Jessica , Raynor Hollie A. , Jelalian Elissa , Owens Judith , Wing Rena
Published: November 2013

OBJECTIVE:

To examine the effect of experimental changes in children’s sleep duration on self-reported food intake, food reinforcement, appetite-regulating hormones, and measured weight.

METHODS:

Using a within-subjects, counterbalanced, crossover design, 37 children, 8 to 11 years of age (27% overweight/obese) completed a 3-week study. Children slept their typical amount at home for 1 week and were then randomized to either increase or decrease their time in bed by 1.5 hours per night for 1 week, completing the alternate schedule on the third week. Primary outcomes were dietary intake as assessed by 24-hour dietary recalls, food reinforcement (ie, points earned for a food reward), and fasting leptin and ghrelin. The secondary outcome was child weight.

RESULTS:

Participants achieved a 2 hour, 21 minute difference in the actigraph defined sleep period time between the increase and decrease sleep conditions (P < .001). Compared with the decrease sleep condition, during the increase condition, children reported consuming an average of 134 kcal/day less (P < .05), and exhibited lower fasting morning leptin values (P < .05). Measured weights were 0.22 kg lower during the increase sleep than the decrease sleep condition (P < .001). There were no differences in food reinforcement or in fasting ghrelin.

CONCLUSIONS:

Compared with decreased sleep, increased sleep duration in school-age children resulted in lower reported food intake, lower fasting leptin levels, and lower weight. The potential role of sleep duration in pediatric obesity prevention and treatment warrants further study.
Effects of steel slag admixture with GGBFS on performances of cement paste and mortar
Authors: Guo Xiaolu , Shi Huisheng
Published: November 2013

The feasibility of steel slag powder as a combined admixture with ground granulated blast furnace slag (GGBFS) in cement-based materials was explored. The effects of steel slag powder on normal consistency water requirement, setting times, fluidity, mechanical strength and hydration products of cement paste/mortar were studied. The results showed that the optimum addition content of steel slag powder in combined admixture was less than 20%. Steel slag powder decreased normal consistency water requirement, retarded setting time of cement paste and had positive effects on the fluidity of cement mortar. As the curing ages increased, the flexural and compressive strengths of mortars with combined admixture increased rapidly to even higher than that of the blank sample. Additionally, early-age strength could be improved by increasing the specific surface area of the steel slag powder. Hydration products mainly included calcium-silicate-hydrate (C-S-H) gel, C-S-Al-H gel and Ca(OH)2. Mixing these two powders of GGBFS and steel slag powder had a positive effect regarding the hydration of steel slag powder. Additionally, this research contributes to understanding of how to manage industrial wastes sustainably and has the potential to provide several important environmental and economic benefits.
Carbon storage reservoirs in watersheds support stream food webs via periphyton production
Authors: Ishikawa Naoto F. , Uchida Masao , Shibata Yasuyuki , Tayasu Ichiro
Published: November 2013

We measured the natural abundances of radiocarbon (Δ14C) in macroinvertebrates, fishes, and their potential food sources, collected from the upper and lower reaches of six temperate streams in Lake Biwa basin (central Japan), three of which flow on limestone bedrock. Several carbon storage reservoirs in the watersheds show distinctive Δ14C signatures (e.g., ancient carbonate rocks, −1000‰; modern atmospheric CO2, +50‰). Our analyses showed that the Δ14C values for periphytic algae range from −361‰ to +21‰, reflecting 14C‐depleted signals from watershed storage reservoirs (carbonate rocks and/or soils). In contrast, the Δ14C values for coarse particulate organic matter (CPOM) range from −6‰ to +62‰, reflecting 14C‐enriched signals from modern atmospheric CO2. The periphyton from streams on limestone bedrock was more 14C‐depleted than that from streams in non‐limestone areas, although the Δ14C values for periphyton from the latter were less than modern atmospheric 14CO2 concentration. The Δ14C values for most of the consumers were between those for periphyton and CPOM. Based on a Δ14C two‐source mixing models, the results suggested that the grazers rely on periphyton, while the carbon source for collectors and predators shifts from CPOM in the upper reaches of streams to periphyton in the lower reaches. The Δ14C signature can trace carbon from watershed storage reservoirs to benthic production, which suggests that stream food webs are composed of mixtures of carbon originating from various sources of different ages.
Evolutionary history and the strength of species interactions: testing the phylogenetic limiting similarity hypothesis
Authors: Fritschie Keith J. , Cardinale Bradley J. , Alexandrou Markos A. , Oakley Todd H.
Published: November 2013

A longstanding concept in community ecology is that closely related species compete more strongly than distant relatives. Ecologists have invoked this “limiting similarity hypothesis” to explain patterns in the structure and function of biological communities and to inform conservation, restoration, and invasive‐species management. However, few studies have empirically tested the validity of the limiting similarity hypothesis. Here we report the results of a laboratory microcosm experiment in which we used a model system of 23 common, co‐occurring North American freshwater green algae to quantify the strength of 216 pairwise species' interactions (the difference in population density when grown alone vs. in the presence of another species) along a manipulated gradient of evolutionary relatedness (phylogenetic distance, as the sum of branch lengths separating species on a molecular phylogeny). Interspecific interactions varied widely in these bicultures of phytoplankton, ranging from strong competition (ratio of relative yield in polyculture vs.  monoculture ≪ 1) to moderate facilitation (relative yield >1). Yet, we found no evidence that the strength of species' interactions was influenced by their evolutionary relatedness. There was no relationship between phylogenetic distance and the average, minimum (inferior competitor), nor maximum (superior competitor) interaction strength across all biculture communities (respectively,P= 0.19,P= 0.17,P= 0.14;N= 428). When we examined each individual species, only 17% of individual species' interactions strengths varied as a function of phylogenetic distance, and none of these relationships remained significant after Bonferoni correction for multiple tests (N= 23). Last, when we grouped interactions into five qualitatively different types, the frequency of these types was not related to phylogenetic distance among species pairs (F4, 422= 1.63,P= 0.15). Our empirical study adds to several others that suggest the biological underpinnings of competition may not be evolutionarily conserved, and thus, ecologists may need to re‐evaluate the previously assumed generality of the limiting similarity hypothesis.
Fracture Complexity Impacts on Pressure Transient Responses From Horizontal Wells Completed With Multiple Hydraulic Fracture Stages
Authors: Jones Jack R. , Volz Richard , Djasmari Wahju
Published: November 2013

The well and completion configuration of choice for development wells targeting unconventional gas and oil resources has become a horizontal well stimulated with multiple stages of hydraulic fracturing. The standard pressure transient model for this well and completion configuration assumes that each hydraulic stimulation stage creates one bi-wing, transverse fracture. Microseismic images of stimulation jobs in some wells support the choice of this model but many such images show an overprint of greater complexity in the geometry of the fracture system. Numerical simulator history matching of production does not definitively show that accounting for such fracture complexity is required to explain unconventional well performance data.

This paper is aimed at providing some insight into how pressure transient data might be used to identify the impact of fracture complexity overprint on well response. After reviewing the limited current literature addressing this issue, fine grid numerically simulated well responses for various overprints of fracture complexity on the base multiple transverse fracture model are presented. In particular, responses for cases impacted by the following are presented: 1) opening and propping nearby natural fractures, 2) creating an arbitrarily connected network of orthogonal fractures intersecting the dominant transverse fracture system, 3) creating independent transverse fracture strands at individual perforation sets in each stage and 4) creating initially independent fracture strands at individual perforation sets which then either bifurcate into multiple strands or amalgamate into fewer dominant strands away from the well perforation. Response sensitivity to lengths and conductivities across the spectrum of these complexity types are discussed.

Results are presented in the context of establishing when the pressure transient response including fracture complexity overprint can be definitively differentiated from that for the base model of a multiple transverse hydraulic fractured horizontal well. Analysis focuses on differences in derivative shapes to address this question. This work is especially relevant to analysis and understanding of shale formations but should also apply to other types of low permeability systems.
Economic Ranking of North American Unconventional Oil and Gas Basins: Looking for the Most Cost Efficient Play
Authors: Virine Lev
Published: November 2013

Oil and gas producers focus their exploration and development activities on the most cost efficient oil and gas plays. The challenge is to analyze full cycle cost for each basin on a consistent basis with taking in to an account various cost components such as finding and development cost, operational cost, royalties and taxes, producer’s return, overhead, basis differential and others. This paper describes the methodology of the analysis of oil and gas costs. The focus was made on unconventional resources. A mathematical model was developed to quantitatively assess cost of different producers for various unconventional gas plays. The cost and well production data was obtained from the public sources. The data was statistically processed and geological models for each basin were integrated to the analysis. Oil and gas resources for each basin were estimated and economic models were developed. The proposed methodology has been used to rank most unconventional oil and gas basins based on their costs per unit of production. The study shows the most efficient and the less efficient plays in North America. The proposed methodology and the study can be essential component the corporate planning process. Particularly results of analysis in form of cost curves can be used for oil and gas price forecast.
Stress Shadow Evaluations for Completion Design in Unconventional Plays
Authors: Nagel N. , Zhang F. , Sanchez-Nagel M. , Lee B. , Agharazi A.
Published: November 2013

In horizontal well shale completions, multiple stages, each often with multiple clusters, are used to provide sufficient stimulated area to make an economic well. However, each created hydraulic fracture alters the stress field around it, and when hydraulic fractures are placed close enough together, the well-known stress shadow effect occurs in which subsequent fractures are affected by the stress field from the previous fractures. Further, new completion techniques, like simultaneous fracturing and zipper fracs, have been proposed to take advantage of stress shadows to enhance production and are therefore dependent upon a proper understanding of stress shadow effects.

In recent years, several papers, by the authors and others, have been published attempting to describe the stress field associated with hydraulic fracturing. Often, the authors focus on the change in the stress field as indicative of increasing ‘complexity’ where the evaluations are based upon the common modeling of multiple hydraulic fractures assuming a parallel, planar hydraulic fracture geometry. However, for hydraulic fracturing in unconventional plays, parallel, planar hydraulic fractures are unlikely to occur. If there are few natural fractures – or if these are tight with narrow initial apertures - whether pumped simultaneously (as in multiple clusters per frac stage) or sequentially (one stage pumped after the other), the stress shadow effect will force subsequent fractures to grow away from the first fracture. Alternatively, if there are many, hydraulically open natural fractures, the stress shadow effect may be muted by the many open natural fractures and reduced length and aperture of the main hydraulic fracture.

In this paper, we present the results of a numerical evaluation of the effect of multiple hydraulic fractures on stress shadowing as a function of the natural fractures, hydraulic fracture spacing, rock mechanical properties, and in-situ conditions. The results of the study provide a quantitative means to optimize shale completions by understanding the effect of hydraulic fracture spacing on the stress shadow effect and the potential for changing fracture complexity. In addition, the results show the relationship between stress shadowing and microseismic events along multi-stage horizontal wells, which allows for better interpretation of the microseismic data.
Tip-Effect Microseismicity - Numerically Evaluating the Geomechanical Causes for Focal Mechanisms and Microseismicity Magnitude at the Tip of a Propagating Hydraulic Fracture
Authors: Agharazi Alireza , Lee Byungtark , Nagel Neal B. , Zhang Fengshou , Sánchez-Nagel Marisela
Published: November 2013

There have been extensive industry efforts to understand the geophysical implications – and limitations – of microseismic analyses; however, a critical issue that is often overlooked is the geomechanics of the rock failure that is represented by microseismicity. Recall that microseismicity is the acoustic representation of rock failure, whether tensile failure or shear failure, which is driven by the coupled hydro-thermo-mechanical effects of injecting cool fluids at high rates into naturally fractured formations. Often overlooked in the analysis of microseismic data is the stress and deformational effects at the tip of a propagating fracture that cause a significant percentage of the total microseismic record. Previous publications, for example, have noted that at the horizontal leading edge of a propagating fracture, the dominant shear is in a horizontal plane. Conversely, at the upper and lower vertical leading edge of the propagating fracture, vertical shear has been reported to dominate. These would be expected to not only cause a different microseismic response, but also, likely, a different stimulation response.

In this paper, we present a detailed numerical evaluation of the stresses generated at the tip of a propagating hydraulic fracture under varying field conditions. The simulations were performed with a finite difference continuum code. The results of the simulations show that field conditions and position along the perimeter of the propagating hydraulic fracture can significantly impact local stresses, which will have then have an impact on the generated microseismicity. The results of the work will allow for a better interpretation of field microseismicity for completion optimization.
New Technologies Eliminate Drill Bit Wear in Oil Sands Applications
Authors: Beaton Tim , Cyre Jeff , Isnor Sid , Herman J. J.
Published: November 2013

Oil sands applications are well known to be one of the most demanding drilling environments in the industry with regard to durability. The bodies of the cutters and the body of the bit experience severe wear in these applications, leading to inconsistent drilling performance. Extensive efforts in the past decade to solve this issue have been met with limited success. In oil sands applications, the sands are highly abrasive and unconsolidated. The result is that the sand particles quickly become suspended in the drilling fluid and mimic the effect of sandblasting the bit for the duration of the run. In many cases, the bit body wear around the cutters is extensive enough to cause premature bit failure due to cutter loss. The bodies of the PDC cutters themselves also suffer extreme material loss, which leads to cutter breakage and an associated reduction in drilling performance. Finally, in the lateral interval, the sands in cutting beds lying on the low side of the hole cause serious wear to both the gage and backreaming portions of the bit.

This paper will discuss new technologies that have proven to eliminate bit wear in the horizontal reservoir interval. Comparisons will be made detailing the severe wear experienced with conventional bits and the absence of wear experienced with identical bit designs using a new body construction technology. A novel PDC cutter will also be presented that has been developed to eliminate cutter body wear.

The requirements for improving drilling performance in oil sands applications are as unconventional as the wear experienced in these applications. Unlike traditional applications where improving performance includes an effort to drill faster or further, oil sands applications are typically control drilled and the entire interval is almost always completed in one run. The focus in these applications to augment performance is to improve directional control, enhance backreaming efficiency and hole quality, and increase bit durability. The new technologies detailed in this paper have proven to dramatically enhance each of these key performance indicators, resulting in the ability to drill further and faster, while improving the possibility of success of the well completion.
Uncertainty Quantification Improves Well Construction Cost Estimation in Unconventional Reservoirs
Authors: Valdes Alejandro , McVay Duane A. , Noynaert Samuel F.
Published: November 2013

The success of petroleum development projects depends to a large degree on well construction costs. Well construction cost estimates often contain high levels of uncertainty. In many cases, these costs are estimated using deterministic methods that do not reliably account for uncertainty, leading to biased estimates. The objectives of this work were to improve the reliability of deterministic well construction cost estimates by incorporating external probabilistic methods into the estimation process.

The method uses historical well cost estimates and actual costs to develop probabilistic correction factors that can be applied to future well cost estimates. These factors can be applied to the entire well cost or to individual cost components. Application of the methodology to estimation of well construction costs for horizontal Barnett shale wells in the Fort Worth basin resulted in estimated well cost estimates that were well-calibrated probabilistically. Overall, average estimated well cost using this methodology was significantly more accurate than average estimated well cost using deterministic methods.

The methodology is intended for use by individual engineers to improve their well construction cost estimation and by management to externally revise and improve well cost estimates for budgeting purposes. Systematic use of this methodology will provide for more accurate and efficient allocation of capital for drilling campaigns, which could have significant impacts on reservoir development and profitability.
Practical Directional Drilling Techniques in Pinedale Field Wyoming to Improve Drilling Performance
Authors: Han Guangzhi , Lemesany Lane , Azizov Azar A. , DeLeon Frank
Published: November 2013

The giant Pinedale anticline gas field, which is approximately 35 miles long and 6 miles wide, contains 159 Tcf of conservatively estimated in-place natural gas. The field ranks as the third-largest gas field in United States by proved reserves. Gas production is primarily from a 5,500-ft thick "Lance Pool" that overlies the top of the Ericson Sandstone Formation. The Lance Pool consists of the Lance Formation, the Upper Mesaverde Group, and a Paleocene "unnamed" unit. The reservoir is classified as tight gas, with low porosity and micro-darcy permeability. Horizontal drilling is not practical and therefore deviated well (S-well) drilling is prevalent, due to the lenticular sands and stratigraphic nature of this area.

A typical deviated well has a 5° to 25° inclination in the upper section, then a tangent section varying from 1,000 to 5,000 ft, with a total depth (TD) of around 15,000 ft MD. The extensive reach, long tangent and various formation strata encountered place an extremely challenging drilling environment for directional drilling using a conventional adjustable kick-off sub (AKO), positive displacement motor (PDM), and a polycrystalline diamond compact (PDC) drill bit. However, if proper directional drilling techniques are applied, this approach can accomplish the task in a timely manner and provide outstanding cost effectiveness over automated vertical-seeking tools (Han et al., 2013).

This paper discusses difficulties encountered in the Pinedale directional drilling process with a conventional AKO PDM, such as successfully landing in the driller target, predicting the reactive torque under various scenarios, holding the tool face (TF) with a PDC bit, and extensive hole drag. Several practical directional drilling techniques are presented as solutions, such as point-turn-tag, turn-tag-point, tag-turn-point, jerking-while-sliding, counting-number and 6-in.-wiper. These techniques are practical, field-proven and invaluable for Pinedale operations and numerous oil and gas fields with similar directional drilling obstacles. Thorough understanding and mastering of these techniques can substantially increase directional drilling efficiency, reduce drilling time, enhance borehole quality, and improve overall drilling performance.
Optimal Salinity Study to Support Surfactant Imbibition into the Bakken Shale
Authors: Zhang Jin , Wang Dongmei , Butler Ray
Published: November 2013

abstract

In our previous study of Bakken shale imbibition, a group of surfactant formulations were examined. These surfactants consistently altered the wetting state of Bakken cores toward water-wet, and appeared to have a substantial potential to improve oil recovery from the Bakken Formation compared to brine water alone. To advance this development, this paper investigates the optimal salinities of surfactant solutions by phase behavior and IFT studies using Bakken formation water and oil. The ultimate objective of this research is to determine the potential for surfactant formulations to imbibe into and displace oil from shale, and also examine the viability of a field application.

Using glass tube and encased-pipette methods, as well as a spinning drop tensiometer, dilute surfactant formulations were studied with various surfactants molecular structures (anionic, nonionic, cationic, and amphoteric). In most cases, optimal salinities obtained by phase behavior and IFT study aid surfactant imbibition into the Bakken Shale. In other cases, surfactant formulations were effective in imbibing into and displacing Bakken oil from Bakken cores, even though there were no obvious optimal salinities observed—suggesting that wettability alteration was a more dominant mechanism than IFT reduction in the imbibition process. Where optimal salinity behavior was obtained, the IFT between surfactant water and crude oil were reduced by one to two orders of magnitude with alkaline formulations. Under the same conditions, the inverse Bond number NB-1 which dominates the displacement mechanism, could be decreased below a value of 1 in cores from the Middle member of the Bakken.

Based on phase behavior and IFT measurement at optimal salinity, we found: for Bakken reservoir conditions, (1) at lower concentrations (0.1%), of an anionic surfactant, internal olefin sulfonate shows a fast imbibition rate but lower oil recovery compared with a higher concentration surfactant (2%) with same molecular structure. (2) With 0.1% concentration, nonionic surfactants with an ethoxylated alcohol molecular structure exhibit a fast imbibition rate and strong effect on oil recovery at reservoir temperature (~120°C). (3) A cationic surfactant with a large carbon number and ethoxylated tallow amine structure at 0.1 % concentration has a favorable effect on oil production at high temperature. (4) An amphoteric surfactant with dimethyl amine oxide structure shows a stronger effect on oil recovery at 0.1% concentration. (5) At optimal salinity, the incremental oil recovery (during imbibition into Bakken cores at 120°C) can be up to 18% OOIP higher than seen during comparable experiments using formulations with 15~30% TDS, and the average instantaneous imbibition rate increased up to 45%.
Evaluating Long Term Flow Regimes in Unconventional Oil Reservoirs with Diverse Completion Technology
Authors: Kurtoglu B. , Rasdi F. , Salman A. , Kazemi H.
Published: November 2013

Innovative completion techniques for unconventional oil and gas reservoirs have been developed at a rapid pace. Deciphering the flow regime characteristics of the pressure-time signature of flowing wells associated with these new completion techniques is critical for evaluating well performance and ultimate hydrocarbon recovery. In this paper we present the flow regimes observed in the plots of field production data for several of these new completion techniques. We also present the simulated model results for these completions.

Several rate-transient analyses (RTA) for different well completion techniques from 1990 to 2010 were analyzed to determine how different completion techniques would affect flow regime characteristics—specifically, the linear flow period. Reservoir simulation results for homogenous and heterogeneous reservoirs showed that hydraulic fracture and natural fracture properties are the most crucial variables affecting the linear flow period. A statistical analysis of the Arp’s decline b-factor was also used to show the impact of increased reservoir connectivity with advanced completion techniques and stimulation.

This paper demonstrates that (a) completion techniques can influence the linear flow period and the length of the transition period before boundary-dominated flow prevails, and (b) different completion techniques lead to different flow regime diagnostics and different Arp’s flow rate exponent b.
Wellbore Efficiency Model for CO2 Geological Storage Part II: Wellbore System
Authors: Nabih Ahmad , Chalaturnyk Richard
Published: November 2013

Storing carbon dioxide (CO2) in deep geological formations is one part of the carbon capture and storage (CCS) process that is defined as geological CO2 sequestration or CO2 geo-sequestration. Injecting CO2 into a reservoir does not guarantee safe storage because CO2 could leak back to the surface and/or may contaminate specific strata where other energy, mineral and/or groundwater resources are present. Two mechanisms control assurance of storage integrity, which are geological leakage mechanism and wellbore leakage mechanism (Espie, 2005).

Wellbore element was presented as a basic unit for developing a model of an entire wellbore system. This paper is the second to assess the performance of a wellbore system for geological storage purposes. The analytical model adopts concept of sequence scenarios of possible leakage paths, concept of wellbore efficiency for storage purposes and concept of the reference state.

A new analytical model for modeling leakage through a wellbore system has been proposed. The analytical model represents the wellbore system as serially connected wellbore elements. This provides an advantage that each element can differ from the subsequent one and will have its own characteristics. Effective wellbore permeability also can change from element to another. The effect of site formation arrangement between general system and repeated aquitard-aquifers is investigated and compared. The analytical model is validated with the results of Nordbotten et al. (2004).
Interventionless, Pre-Perforated Liner Using Smart Engineered Materials to Provide Flow Assurance
Authors: Carrejo Nick , Norris Jason , Gaudette Sean L
Published: November 2013

Cased-hole completions utilize solid pipe to protect the wellbore from fluid losses. The casing provides a flow path for cementing or for completion brines and other completion tools without risk of damaging the formation. After the operations have finished running the tools downhole and have completed the well below the target zone, the casing is perforated to provide an optimized flow path. It is common for operators to use gun perforating systems or wireline perforating platforms to complete the casing perforation. These systems call for costly rig downtime while this intervention is completed. Perforating the casing results in a large amount of debris, known as skin damage. The debris from the perforation job can become a production risk, lead to damage of tools above the zone, and reduce the flow area. The debris can also lead to costly interventions needed to stimulate the well. A new smart-engineered, metallic composite has been developed to optimize this process and provide flow assurance. This new technology eliminates the need to later perforate the liner, further reducing costly interventions. High-strength corrodible material (HSCM) is a metallic composite designed to degrade in the presence of brine or acid in a predictable and uniform manner. This paper will explore the development and reliability of this new technology, and discuss how HSCM can reduce production risks while providing flow assurance for the completion.
Pump-Friendly Wellbore Design and Case Study from Mississippian Play of Oklahoma/Kansas
Authors: Reid Leslie C. , Mcdonald Clarence , Baker Ty , Jones Timothy P. , Hess Jeremy , Sharp Kevin
Published: November 2013

Wellbore designs and completions can positively impact long-term production in directional wells, but many directionally drilled wells are designed today without regard for future pump applications. Communication between drilling, completion, and production teams is often poor, and this negatively impacts the ability to produce in liquid-rich multiphase environments. This situation is especially true as the well matures. Early collaboration between these groups is imperative to maximize production options. Without such cooperation, many directional wells are designed without future pump success in mind. Consequently, electrical submersible pumping systems (ESPs) are excluded as a viable artificial lift solution in a majority of directionally drilled wells.

ESP technology advances have made ESPs viable in many multiphase liquid-rich wells. Ignoring current ESP capabilities ultimately diminishes production over the life of some wells. Many of these directional wells flow naturally, but liquid loading reduces production without artificial lift. ESPs can be the most productive method for reducing reservoir pressure and optimizing production, and they should be considered when designing a wellbore. The Mississippian Lime in Oklahoma and Kansas (though not a shale play) has many similar attributes of a liquid-rich shale.

This paper includes a case study from the Mississippian play for a horizontal drilling plan and completion technique aimed at optimizing pump performance. "Pump-friendly" fundamentals for wellbore design and geometry are presented.

This paper concludes that increased awareness and implementation of a few basic principles will pay huge early dividends as the well matures.
Measuring Liquid Uptake of Organic Shales: A Workflow to Estimate Water Loss During Shut-in Periods
Authors: Makhanov K. , Dehghanpour H. , Kuru E.
Published: November 2013

The imbibition of fracturing fluid into the shale matrix is identified as one of the possible mechanisms leading to high volumes of water loss to the formation in hydraulically fractured shale reservoirs. In an earlier study (Makhanov et al., 2012), several spontaneous imbibition experiments were conducted using actual shale core samples collected from Fort Simpson, Muskwa and Otter Park formations, all belong to the Horn River shale basin. This study provides additional experimental data on how imbibition rate depends on type and concentration of salts, surfactants, and viscosifiers. The study also proposes and applies a simple methodology to scale up the lab data for field-scale predictions.

The data shows that an anionic surfactant reduces the imbibition rate due to the surface tension reduction. The imbibition rate is even further reduced when KCl salt is added to the surfactant solution. Surprisingly, viscous XG solutions show a considerable spontaneous imbibition rate when exposed to organic shales, although their viscosity is much higher than water viscosity. This observation indicates that water uptake of clay-rich organich shales is mainly controlled through preferential adsorption of water molecules by the clay particles, and high bulk viscosity of the polymer solution can only partly reduce the rate of water uptake.

The field scale calculations show that water loss due to the spontaneous imbibition during the shut-in period is a strong function of fluid/shale properties, fracture-matrix interface, and soaking time. The presented data and analyses can be used to explain why some fractured horizontal wells completed in gas shales show an immediate gas production after extended shut-in periods.
A Novel Model for Fracture Acidizing with Important Thermal Effects
Authors: Lyons John , Nasrabadi Hadi , Nasr-El-Din Hisham
Published: November 2013

Fracture acidizing is a well stimulation technique used to improve the productivity of low-permeability reservoirs. The reaction of injected acid with the rock matrix forms dissolution channels (that depend on injection rate, mass transport properties, formation mineralogy, reaction chemistry of the acid, and temperature) through which oil and gas can then flow upon production.

The use of a model that can effectively describe fracture acidizing is an essential step in designing an efficient and economical treatment. Several studies have been conducted on modeling fracture acidizing, however, most of these studies have not accounted for the effect of variation in acid temperature (by heat exchange with the formation and the heat generated by acid reaction with the rock) on reaction rate and mass transfer of acid inside the fracture.

In this study, a new fracture acidizing model is presented that uses the lattice Boltzmann method for fluid transport and takes into account these temperature effects. The lattice Boltzmann method incorporates both accurate hydrodynamics and reaction kinetics at the solid-liquid interface. This method is also well known for its capability to handle reactive transport in complex geometries. This enables the method to model realistic fracture shapes, on a pore-scale level, and predict the shape of the fracture after acidizing. Results of carbonate fracture dissolution with and without the thermal effects are presented. It is found that including thermal effects alters the predicted shape of the fracture after acidizing.
Multi_Well Gas Reservoirs Production Data Analysis
Authors: Sureshjani M. Heidari , Behmanesh H. , Clarkson C. R.
Published: November 2013

Production analysis models are normally developed with the assumption of fixed drainage boundaries. However, this assumption is not always applicable. Examples where drainage areas may vary include: drilling of infill wells; shut-in of non-economic wells, and severe rate changes in some wells in the field. In such conditions, drainage volume of each well may not remain constant as time elapses.

A solution to this problem is simultaneous production analysis of all active wells in the reservoir to estimate total field gas-in- place instead of gas-in-place affected by individual wells. Such analysis requires a new boundary-dominated flow equation (BDFE) that forms a basis for analysis of field production data. In this study, a total normalized pseudopressure is defined. We show that a plot of total normalized pseudopressure versus real time forms a straight line with the slope equal to the reciprocal of total gas-in-place multiplied by initial gas compressibility. We further propose use of a new material balance time, referred to as total material balance pseudotime. We illustrate that a plot of single-well normalized pseudopressure versus this material balance time would result in a straight line with same slope. These plotting techniques account for conditions such as drilling new wells, closing damaged wells, and variations in well rate/pressure data. The introduced BDFEs are validated using several synthetic examples.

Two simulation cases are used to test the suggested techniques. In the first example, 4 wells are simultaneously producing with variable and different rates and in the second example, a new well is put on production in the reservoir every few months to simulate an infill program. In this example, 9 wells are drilled over a 6 year period. In another example, real field production data but with arbitrary reservoir systems also were used. These examples reveal the ability of the introduced techniques for estimating field gas-in-place and average pressure in multi-well gas systems. The method is very simple and can be extended to other unconventional reservoirs such as coalbed methane reservoirs and also reservoirs under two phase flow.
Production Data Analysis of Liquid Rich Shale Gas Condensate Reservoirs
Authors: Behmanesh H. , Hamdi H. , Clarkson C. R
Published: November 2013

With the current focus on liquids-rich shale plays (LRS) in North America and the importance of gas condensate reservoirs globally, there is an increased need to develop reservoir engineering methods to analyze such reservoirs. Commercialization of LRS plays is now possible due to new technology, such as multi-fractured horizontal wells (MFHW). Efficient production from such reservoirs necessitates understanding of flow mechanisms, reservoir properties and the controlling rock and fluid parameters. Production-decline analysis is a robust technique for analysis of production data and obtaining estimates of recoverable reserves. Nevertheless, these techniques, developed for conventional reservoirs, are not appropriate for ultra-low permeability reservoirs. There are substantial differences in reservoir performance characteristics between conventional and ultra-low permeability reservoirs. LRS reservoirs produce much leaner wellstreams compared to conventional reservoirs due to very low permeabilities that result in very large drawdowns. Methods for analysis of two-phase flow in conventional reservoirs, with underlying simplifying assumptions, are no longer applicable.

This paper discusses production data analysis of constant flowing bottomhole pressure (FBHP) wells producing from LRS (gas condensate) reservoirs. A theoretical basis is developed for a gas condensate reservoir during the transient linear flow (drawdown) period. The governing flow equation is linearized using appropriately defined two-phase pseudopressure and pseudotime functions so that solutions valid for liquids can be applied. The derived backward model is employed to compute the linear flow parameter, xf√k.

Simulation results show that the liquid yield will be approximately constant for LRS wells during the transient linear flow, from the early days of initial testing, if flowing BHP is almost constant. An analytical formulation is used to prove this finding for 1D transient linear flow of LRS wells.

The proposed production data analysis (PDA) method is illustrated using simulated production data for different fluid models and relative permeability curves. Fine-grid compositional and black oil numerical models are used to this purpose.
Hydraulic Fractures Interference in Horizontal Wells: Compact and Diffuse Patterns of Fracture Growth
Authors: Geilikman Mikhail , Wong Sau-Wai
Published: November 2013

Multiple hydraulic fractures interference due to induced stress is considered in the framework of approximate analytical model. The induced stress structure is generalized for the case of fractures of arbitrary length and height which allows to describe stress evolution in the process of fracture growth. Two main regimes of hydraulic fracture growth are considered: isotropic (circular) growth and limited-height (Perkins-Kern-Nordgren) regime. Major control parameters for each of them have been found, capturing dependence on pumping rate, spacing and cumulative injected volume as well as mechanical properties of the reservoir. For isotropic growth the fracture interference can be avoided by sufficiently low pumping rate and /or sufficiently large spacing whereas for limited-height growth certain limitation of total volume of pumped fluid is needed. The concept of "compact" and "diffuse" pattern of hydraulic fracturing is introduced which corresponds to weak and strong fracture interference respectively. The identified control parameters provide recommendation for optimal hydraulic fracturing design.