bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of Elastic Properties of Organic Matter and Woodford Shale Through Nano-indentation Measurements
Authors: Kumar Vikas , Curtis Mark E. , Gupta Nabanita , Sondergeld Carl H. , Rai Chandra S.
Published: October 2012

Shales are one of the most heterogeneous and complex natural materials found. Recent spike in the activities in shale gas and oil plays has been possible through horizontal drilling and hydraulic fracturing, which requires better understanding of mechanical properties. Complexities associated with elastic properties of shale are amplified with presence of wide range of organic fraction present in them. There is a need to understand the mechanical properties of organics and their associated impact on bulk mechanical properties.

Scanning Electron Microscopy with focused ion beam milling and nano-indentation have been employed to calculate mechanical properties of kerogen at the submicron level in Woodford shale samples of different maturities. A displacement of 500 nm was applied to investigate mechanical properties of kerogen and force in the range of 400–500 mN was applied to measure average mechanical properties of shale.

Young’s modulus of kerogen was found to be linked to localized porosity as well as maturity. Kerogen in different samples with vitrinite reflectance range of 0.5–6.36 % and almost no porosity showed Young’s moduli in the range of 6–15 GPa, whereas, kerogen with significant porosity showed values as low as 1.9–2.2 GPa. Young’s modulus measured by nanoindentation on small shale samples (~ 5–10 mm) was found to be in good agreement with dynamic modulus measured on core plugs (~cm). Young’s modulus is most sensitive to the Total Organic Carbon present. Increase in organics is found to qualitatively reduce both Young’s modulus and hardness.

Measurement of elastic properties of shale is significant for optimizing hydraulic fracture design, for well stability study and better seismic velocity prediction in shale. This technique requires small sample dimension, on the order of millimeters, for experiment and thus eliminates the requirement of larger, centimenter, size samples. This is particularly significant for shale as they are mechanically and chemically unstable which makes retrieval of larger core samples challenging.
Executing Minifrac Tests and Interpreting After-Closure Data for Determining Reservoir Characteristics in Unconventional Reservoirs
Authors: Ewens S. , Idorenyin E. , O’Donnell P. , Brunner F. , Santo M.
Published: October 2012

Pore pressure (pi) and flow capacity (kh) are difficult to ascertain in ultra-low permeability formations due to poor inflow prior to stimulation. Furthermore, radial flow does not develop in horizontal wells completed with massive multi-stage hydraulic fractures. As a result, industry is turning to alternate testing methods, conducted prior to the main hydraulic fracture treatments. Of these, minifrac tests are rapidly gaining acceptance as the most practical way to obtain good estimates of pore pressure and flow capacity in unconventional reservoirs. Unfortunately, these test objectives are often unrealized when design and execution of the minifrac test are conducted with other objectives in mind. Even after a mechanically successful test has been concluded, there can be confusion over how to interpret the after-closure data.

This paper outlines recommended operational guidelines for conducting minifrac tests with the purpose of estimating pore pressure and flow capacity. In addition, various aspects of after-closure analysis are investigated and examples are used to show that all after-closure analysis techniques, when applied correctly, are applicable and give consistent estimates of pore pressure and flow capacity. The power of using analytical models to enhance after-closure analysis is demonstrated.
Comparative Microseismic Interpretation of Hydraulic Fractures
Authors: Maxwell Shawn
Published: October 2012

Microseismic monitoring is often used to evaluate differences in hydraulic fracturing that result from either changes in the stimulation or geologic setting. Often the various microseismic images of individual fractures are each separately interpreted for fracture geometry, and then these absolute interpretations of the various fractures are compared. However, comparisons can be made of variations in specific fracture dimensions between each image, including using statistical tests to quantify significance of relative differences. Such a relative comparative interpretation is more robust and relies on a simpler assessment of the location precision, in contrast to the need to consider all aspects of location accuracy for absolute interpretations. Furthermore, statistical analysis methods can be applied to the relative interpretation to map microseismic location uncertainties to the relative fracture dimension along with defining statistical probabilities to better define the confidence level for further interpretation. The resulting comparative microseismic interpretation can be used as part of a comparative hydraulic fracture evaluation to test the response to different designs and ultimately optimize the stimulation. This paper describes different workflows for a comparative interpretation of microseismic images.
A Semi-analytical Model For Multi-stage Fractured Horizontal Wells
Authors: Yao Shanshan , Zeng Fanhua , Liu Hong , Zhao Gang
Published: October 2012

Multi-stage fractured horizontal wells are widely applied to develop tight reservoirs and shale gas reservoirs. Testing and evaluating well productivity are necessary in horizontal well multi-stage fracturing. Through analyzing the post-fracturing transient pressure data, key parameters affecting the productivity, such as effective fracture lengths, fracture conductivities, fracture skin factors and average formation permeability, can be estimated.

This paper presents a semi-analytical model based on Green’s function and source/sink method to facilitate the transient pressure analysis for a multi-stage fractured horizontal well in a closed box-shaped reservoir. The fluid flow for a multi-stage fractured horizontal well includes the fluid flowing from the reservoir to fractures, the fluid directly from the reservoir to the horizontal wellbore, fluid flow inside the fractures and fluid flow inside the horizontal wellbore. Compared with previous models, fluid flow directly from the reservoir to the horizontal wellbore and pressure drop caused by pipe flow inside the wellbore are considered. In this model, fractures and horizontal wellbore are discretized into vertical plane segments and horizontal line segments, respectively. The fluid flow from the reservoir to fracture and that directly from the reservoir to the horizontal wellbore at each segment are modeled based on analytical solutions of vertical plane source and horizontal line source, respectively. The fluid flow inside the fracture is modeled based on 1-D linear flow. The fluid flow inside the horizontal wellbore is described with Penmatcha and Aziz’s model (1999). Then, the flow equations are coupled together by using the flux- and pressure-continuity conditions on the interfaces.

The effects of the fracture lengths, fracture conductivities and fracture skin factors on the transient pressure behavior are studied and type curves are generated. The results suggested that in a tight or shale-gas reservoir, the transient pressure behavior during a testing period is mainly dominated by fracture stages, fracture lengths, conductivities and skin factors. The fluid flow directly from the reservoir into the horizontal wellbore reduces the pressure drop slightly. A field case is analyzed and reliable results are obtained. This model can be applied to optimize the fracture spacing and fracture length for a multistage fractured horizontal well.
The Effect of Previous Counter-flow Production on the Interpretation of Velocity String Gas Wells Using DTS Temperature Surveys
Authors: Huebsch H , Bruns J , Tripp G , Brown G , Sanchez A , Gonzalez Y
Published: October 2012

Over the past 3 years fiber optic slickline distributed temperature measurements (DTS) have become a commonplace method of monitoring Canada’s Deep Basin commingled gas wells produced through velocity string completions. The use of velocity string completions prohibits conventional production logging, so the wells are flowed up their annulus for a short period of time and a DTS slickline is used to monitor the flowing temperature profile. This temperature profile is then interpreted to give the flow from each reservoir zone. DTS is a much more cost effective solution than having to pull the tubing in order to run a conventional production log and allows testing of lower rate wells that would otherwise liquid load.

The analysis technique conventionally assumes that during the annular flow period, where the DTS is used to acquire the flowing temperature, all the thermal effects of the previous counter-flow production period have dissipated and the problem can be solved by an upward flow thermal model only. This paper evaluates the magnitude of the residual thermal effect of a period of counter-flow on the annular flow response over the timescales typical for DTS monitoring.

A counter-flow thermal model has been developed for typical well scenarios and the shut-in decay of the thermal response of this model is superposed on the conventional annular flow model to highlight the magnitude of influence of previous counter-flow production. The model is used to interpret the counter-flow response of annular flowing gas wells using real well DTS data and demonstrates the magnitude of the effect and how to use this method to improve the accuracy of the resulting flow analysis.
Temporal Evolution of Stress States from Hydraulic Fracturing Source Mechanisms in the Marcellus Shale
Authors: Williams-Stroud Sherilyn , Neuhaus Carl W. , Telker Cherie , Remington Christine , Barker William , Neshyba Garrett , Blair Keith
Published: October 2012

Hydraulic fracture stimulation treatments of 17 wells have been monitored with a shallow buried array for induced microseismicity in the Marcellus Shale in West Virginia, USA. The wide azimuth and large coverage area (18 square miles) of the shallow buried array allowed identification of the source mechanisms of all of the detected events, enabling a statistical analysis of failure mode and associated stress state at failure for all the events in space and time. Detailed analysis of source mechanisms of the largest events revealed heterogeneous failure plane orientations and slip directions, with a combination of dip-slip and strike-slip failure and varying amounts of volumetric failure. Stress inversion analysis of these source mechanisms allowed characterization of the local stress tensor, and how the stress tensor changed from the beginning to the end of the stimulation treatment. The failure mechanisms observed to occur more frequently at the beginnings of the fracture stages were dip-slip and strike-slip failure mechanisms were more common at the ends of the fracture stages. Utilizing the timing of the types of source mechanisms to define temporal groups, the stress inversion analysis showed that the stress state in the stimulated rock changed from being consistent with the regional NE-oriented maximum horizontal stress orientation with sigma1 vertical to a stress state where the maximum horizontal stress becomes sigma1 and is horizontal. The temporal stress state is quantitatively identified and it is demonstrated that the fracture growth directions responds to the temporal stress state. This information can be used by operators to respond to or exploit the expected fracture failure mode and direction, and also to design stimulation treatments that develop complex fracture networks.
Factors That Impact the Performance of Resin Coated Proppant in Low Temperature Reservoirs
Authors: Burke Lyle H. , Roney Dana , Elgar Tyler , Hersey Andrea
Published: October 2012

Pumping a tail stage of resin coat proppant (RCP) is well documented method to control proppant flowback in a wide variety of oil and gas wells. The performance of RCP can be impacted by reservoir temperature and closure stress, as well as fluid and fracture placement parameters. RCP systems were originally designed for higher temperature applications although the use of lower temperature curable resins in shallow lower stress reservoirs has been discussed since at least mid-2005. 1,2,3 Strong oil prices and relatively weak gas prices have recently (2012) been driving the development of relatively shallow tight oil reservoirs within the Western Canadian Sedimentary Basin (WCSB) including the Slave Point, Cardium, Bakken, Viking and others. These reservoirs typically have relatively low reservoir temperatures and closure stresses which highlight the importance of looking beyond the reservoir temperature with a holistic evaluation of the fracture fluid interactions and fracture placement efficiency that can significantly impact RCP placement and performance; existing SPE publications also provide good background to the impact of these contributing factors.4,5

Most RCP literature focuses on clastic applications. In conjunction with our proppant supplier and pumping service partner, Lone Pine Resources Canada Ltd (LPR) has recently conducted laboratory testing designed to optimize the use of RCP within the Slave Point carbonate reservoir that LPR is successfully developing with multi-fractured horizontal wells (MFHZ). The Slave Point reservoir presents a challenge to RCP performance with a combination of a cool reservoir temperature of 40°C (100°F) and low closure pressures of roughly 20 MPa (2,900 psi).

During Q1/Q2 2012 LPR identified a proppant flowback that was inhibiting production and increasing workover expenditures. Study of the problem identified proppant mixing and a lack of RCP bonding as root cause issues. A holistic review of the LPR Slave Point fracture program resulted in significant changes to the fracture treatment design and execution including the RCP type, resin activation parameters and base fluid changes.

LPR has been able to minimize proppant flowback to the point that bottomhole pump failures as a result of proppant production have been significantly reduced, if not eliminated, and no incremental proppant clean-out operations have been required since the implementation of an optimized fracturing program that includes higher viscosity fracturing fluid and an optimized RCP-LT and activator program. In addition, no measurable proppant flowback volumes have been recovered during initial CT clean-out from the last four July 2012 fractured wells.

These are very positive indicators that the RCP-LT and activator changes, improved fracture fluid viscosity and proppant placement has solved the proppant inflow problem.
Productivity Modeling of Multifractured Horizontal Wells Coupled With Geomechanics - Comparison of Various Methods
Authors: Islam A. , Settari A. , Sen V.
Published: October 2012

The advances in hydraulic fracturing technology and horizontal well completions have led in recent years to rapid rise in exploitation and development of tight gas and shale plays all over the world, and particularly in North America. The popularity of new field technology has in fact raised many new questions. In particular, for forecasting the productivity and EUR of multifractured horizontal wells, it is not clear if conventional reservoir simulation concepts can be adapted for modeling or if extra physics must be included to obtain realistic solutions.

This paper presents various methods to model multifractured horizontal wells in tight gas sands using a conventional reservoir simulator coupled with geomechanics. Two actual wells in the same formation but with different fracturing techniques (i.e., Xlink gelled water fracs and un-gelled water (slick water) fracs) are studied. Detailed investigation of the role of fracture conductivity, effects of initial permeability level, net pay thickness, assumed size of the stimulated reservoir volume (SRV), and pressure or stress dependent permeability of the SRV and virgin reservoir were carried out by history matching the rate and cumulative production. It was established that i) history match is not possible without use of stress or pressure dependent permeability and ii) permeability dependence of pressure inside stimulated reservoir volume must be larger than in the rest of the reservoir. It was also observed that the standard method for using the same geomechanical data both in uncoupled reservoir and coupled geomechanical model will give incorrect results in terms of cumulative production.

A new method based on uniaxial deformation theory is proposed to more accurately approximate the geomechanical effects in conventional reservoir simulators without running a fully coupled geomechanical simulator. The results from uncoupled reservoir modeling using the new method for correcting the permeability data for poroelastic effects were remarkably similar to rigorously coupled geomechanical modeling.

This work will be of importance to engineers in analyzing and forecasting production performance of multifractured horizontal completions using numerical models. It will allow engineers to use uncoupled (conventional) reservoir modeling as a practical approximation of more complex coupled geomechanical models.
New Coiled-Tubing-Deployed Multizone Stimulation Method Increases Reservoir Access
Authors: Dunlop Tyson , McNeil Fraser
Published: October 2012

Multiple-zone stimulation poses unique challenges for completion engineers. Achieving accurate fracture and proppant placement while performing an efficient and low-risk operation can be unattainable when using conventional stimulation methods. The uncertainty with respect to fracture and proppant placement is amplified when fracturing in ductile rock, where, to maximize access to the reservoir, more fractures must be placed along a given lateral. This increase in fracture intensity can result in an increased risk of unplanned well intervention and downtime, with more trips to run guns, as well as more plugs to drill out.

Stimulation techniques involving coiled tubing (CT) deliver improved efficiencies in horizontal completions because of the ability to instantly address contingencies by having CT in the hole throughout the operation. This method enables accurate fracture and proppant placement, as these operations typically focus on placing one fracture at a time. Isolation is commonly achieved using sand plugs, which have demonstrated to be especially effective; however, when fracture intensity is applied, sand plugs might not achieve the spacing required. This is because of the length of sand plugs often necessary to achieve isolation. Also, the time to set sand plugs can be considerable if they do not properly set the first time.

This paper introduces a new CT annular fracturing (CTAF) system, referred to as CTAF-Anchor, that offers a low-risk, operationally efficient, and effective multizone stimulation method designed to reduce the non-productive time (NPT) between stages and allow for closer fracture spacing to maximize stimulated reservoir access. Also included is a detailed study of the process and case histories that translated into a maximized return on investment (ROI) for the operator.
Case Study - Evaluation of Horizontal Well Multi-stage Fracturing in the Viking Oil Formation
Authors: Mogensen Arvil C. , Bachman Robert C. , Singbeil Peter
Published: October 2012

The Viking formation in Western Saskatchewan and East to Central Alberta is comprised of many different oil pools. These plays have seen resurgence in activity over the last 6 years as a result of the horizontal multi-stage fracturing revolution. A wide variety of fracturing technologies have been applied, encompassing open versus cased hole, variable proppant tonnage per stage and fracture spacing along the wellbore. How does the average company make meaningful decisions as to how to stimulate their wells? There is a need to make sense of the production response of the wells given reservoir quality differences, primarily permeability variation, and the variety of fracturing technologies being applied. The paper will develop a workflow which integrates publically available production data to first identify a production rate metric. This metric can be used for production forecasting and as a basis to compare area and pool production performance. Combining this information with well ownership leads to a preliminary assessment of whether production success is due solely to the reservoir, or the drilling and completion strategy applied.
Understanding Induced Fracture Complexity in Different Geological Settings Using DFIT Net Fracture Pressure
Authors: Potocki Dan
Published: October 2012

A review of several hundred Diagnostic Fracture Injection Tests (DFITs) from vertical and horizontal wellbores in a variety of lithologies (tight sandstone, siltstone and shale) within a spectrum of geological settings (passive margin, foreland, and active strike-slip/thrust basins) was conducted to determine potential controls on stimulation complexity determined from the DFIT Net Fracture Pressure (NFP). Not surprisingly large differences in NFP complexity exist within this diverse data set and the variability is best explained by grouping the data according to the tectonic setting of the basin. Tectonic setting is interpreted as the first order control on NFP complexity since increasingly complex tectonic and burial histories elevate stresses and create tectonic fractures that promote increasingly complicated interactions between induced hydraulic fractures and intrinsic rock fractures. As a result, rocks in the Gulf Coast passive margin basin (Haynesville, Bossier) which have relatively simple burial and tectonic histories exhibit the lowest NFP complexities whereas rocks in strike-slip/thrust basins with high present day tectonic stress and abundant tectonic fabric have the largest complexity. Rocks in foreland basins (Montney, Horn River, Cretaceous Deep Basin sandstones) have NFP complexity that is generally variable between passive margin and strike-slip/thrust basins. Within any particular tectonic setting, NFP complexity is controlled by a complicated interplay between the natural fracture intensity, net horizontal stress (NHS) and wellbore geometry. Increasingly stiff and brittle rocks are commonly increasingly naturally fractured and this favours greater NFP complexity, and DFITs from vertical wellbores generally exhibit lower NFP complexity as fracture initiation and growth is simpler from vertical wells than from horizontal wells. Relations between NFP complexity and NHS (closure – pore pressure) are complicated by the degree to which tectonics has diminished and overprinted the pore pressure control on closure stress. In the Gulf Coast passive margin setting (eg.Haynesville shale) pore pressure is the dominant control on closure stress and NFP complexity is increased where pore pressures are lower, possibly due to frac geometry changes associated changing stress profiles. In more tectonically complex settings (foreland and strike-slip/thrust basins) pore pressure exerts less influence on closure while tectonic stresses increasingly influence regional NFP complexity.
Understanding Permeability Measurements in Tight Shales Promotes Enhanced Determination of Reservoir Quality
Authors: Suarez-Rivera Roberto , Chertov Maxim , Willberg Dean , Green Sidney , John Keller
Published: October 2012

Proper characterization of reservoir quality of tight shales is critical for evaluating reservoir potential. These reservoir quality properties typically include hydrocarbon filled porosity, permeability, organic content and maturation, and pore pressure. Of these, permeability measurements are among the most complex to obtain, and have been subject to much discussion. Key concerns are the lack of analytic modeling, poor reliability, poor consistency, and ignoring stress sensitivity in the measurements. This paper reviews the pressure decay permeability method using crushed rock, and includes laboratory test results to validate the findings. Part of the review is a numerical model for the pressure decay method. This model includes significant processes of pipe flow in the equipment, thermal effects, diffusion into rock fragments, Klinkenberg effects, and size, shape and anisotropic permeability of the fragments.

The paper shows that the measured permeability stress dependence, in tight shales, arises from coring induced microcracks. These result from failure of weak contact planes that are naturally occurring within tight shales and fail during coring and core retrieval. Permeability stress dependence in-situ is slight, as is show by compression test measurements to greater than thirty thousand psi. Crushing the rock to create small fragments for permeability measurements effectively removes these microcracks, and allows evaluation of real in-situ properties. Alternatively, closing microcracks by applying confining stress on plug samples, as routinely done for steady state and pulse decay measurements, is possible, but problematic because the critical stress required for microcrack closure changes from rock to rock facies.

The pressure decay permeability method on crushed rock is shown to provide very consistent results that agree with other measurement techniques. The numerical model relates specific ranges of fragment sizes and testing conditions, to measured ranges of permeability. This allows permeability measurements and numerical model analysis for a broad range of variability in permeability that can be measured in heterogeneous tight shales. With some exceptions (e.g., Cui et.al. 2009), the fundamental understanding of the petrophysical properties of tight shales have not previously included rigorous confirmation of experimental measurements by analytical methods.
New Multistage Fracturing Process Offers Real-Time Control of Rate and Proppant Concentration at the Perforations
Authors: Mcneil Fraser , Harbolt William
Published: October 2012

The demand for more efficient, effective, and environmentally acceptable hydraulic fracturing solutions will continue into the future as shale reservoirs play more of a critical role in meeting the rising energy demand. The measurement of success for tomorrow’s wells will not just be improved operational efficiency and initial production, but will include long-term well performance and reduced environmental impact. Operators and service companies must remove the uncertainty associated with conventional hydraulic fracturing techniques and aim simply to generate the desired number of fractures while ensuring that proppant is placed accurately to achieve good conductivity for the life of the well. Some of the disadvantages of conventional well stimulation methods include the following: Uncertainty of the number of fractures initiated within cluster perforations.Uncertainty of proppant distribution along multiple fractures.Proppant schedules designed to avoid screenout and not provide optimum conductivity.Overflushing of the near-wellbore (NWB) region.NWB damage as a result of conventional perforating.

This paper presents a coiled tubing (CT) fracturing solution designed to eliminate these issues, while also delivering a new level of treatment flexibility by using real-time control of rate and proppant concentration at the perforations. This new approach to hydraulic fracturing reduces hydraulic horsepower requirements and reduces overall water usage significantly, while maximizing the return on investment (ROI) for the operator.
The Effect of Hole Angle and Cementing Complications on HPHT Well Integrity
Authors: Yuan Zhaoguang , Schubert Jerome , Teodoriu Catalin
Published: October 2012

The failure probability of wellbore is high in HPHT gas wells because of the effect of the hole angle, the cementing complications and the high pressure high temperature environment. However, most of the researches about the cement problems are studied by two dimensional modeling. The effect of hole angle and cement complications on HPHT well integrity in three dimension is hardly studied.

In the analysis, the finite element method was used to build a three dimension simulation model where the hole angle, casing eccentricity, and cement channels are considered. One cement system (118-lbm/ft3) commonly applied in oil field is used to study the effect of cement complications on the wellbore integrity. The hole angle, cement channel angle, and casing eccentricity are the variables taken into account and an attempt is made to which parameter is the most important and its effects on wellbore failure.

In the cement channeling, the casing has highest von Mises stress at the hole angle of 90°, and the cement tends to fail in tension. The casing eccentricity tends to reduce cement shear stress, and tensile stress but increase cement compressive stress. The cement has the highest compressive failure probability in casing eccentricity condition. At the casing eccentricity lower than 40%, for different hole angle, the casing eccentricity has minor effect on the casing.

This paper presents the sensitivities of the variables and gives a better understanding of the effect of hole angle and cement complications on the HPHT well integrity.
Play-Wide Well Performance Analysis in Montney Siltstone
Authors: Okouma V. , Vitthal S. , Nair Narayan , Miller Mark A.
Published: October 2012

Multi-stage fractured horizontal wells (MFHW) in unconventional resource plays often present formidable reservoir management challenges, particularly with regard to capital utilization and allocation. In this study, well performance histories of some 74 wells in the Montney siltstone play were investigated with a common and consistent analytical framework. Parameters determined from the analyses are key indicators of the combined result of reservoir quality and hydraulic fracture performance (subsurface and completions). The analytical approach utilized in this study was then used to provide robust physics-based forecasts that directly recognize and incorporate interpretation non-uniqueness. Through a forecasting regimen that explicitly provides expected ranges of results, insights and conclusions in field optimization, well spacing and completions design have been drawn.

A real distribution of well productivity and predicted recovery enabled identification of "sweet spots". Openhole completions technique did not show poorer performance compared to limited entry style completions, though further evaluation and surveillance would seem warranted. Wells that were flowing under a "high-drawdown" showed a lower productivity, higher completion resistance (skin) to flow, and lowest predicted final recovery.

Wells completed at 50 m fracture spacing and 30 tonnes of proppant per cluster performed similarly to 100 m spacing and 60 tonnes per cluster, suggesting no apparent difference in capital efficiency between these two completion styles. Results indicate that the frac half lengths in the 50 m cluster spacing wells are shorter compared to wells with 100 m cluster spacing (based on the reduction in the amount of proppant pumped per cluster). Trends of estimated original gas-in-place inside the SRV and predicted 30-year recovery for wells drilled at close well spacings, (closer than 400 m between wellbores) indicate effects of inter-well interference. Performance of wells at 200 m well spacing seem to be affected the most by inter-well interference.

A consistent workflow for analyzing well performance and predicting future performance of MFHW in unconventional gas wells is presented that provides a means to assess the impact of business and development decisions and determining practices worth replicating across the Montney play.
Unique Solution to Repair Casing Failure in a HTHP Wellbore Allows for Successful Multi-Stage Stimulation Treatment in an Unconventional Reservoir
Authors: Wellhoefer Ben , Stegent Neil , Tunstall Michael , Veillette Christian , Frazier Garrett
Published: October 2012

Horizontal shale completions require multi-stage high-pressure hydraulic fracturing stimulation treatments in order to deliver commercially viable production in low permeability reservoirs. Unconventional shale plays, such as the Eagle Ford and Haynesville Shale, often can require stimulation treatments that must be implemented in high pressure and high temperature (HPHT) conditions. Typically, these wells are completed with long casing strings, and it is critical that these monobore casing strings withstand high injection pressures as well as maintain mechanical integrity during thermal contraction/expansion. So what happens when the pre-frac casing pressure integrity pressure test fails? What is the "fix" that will allow treatments to be pumped at high pressure and rate? How will frac stages be isolated during the completion? Typically, remediation techniques have included everything from casing patches and expandable casing to coiled tubing completions. Unfortunately, these solutions can have pressure limitations, and in addition, can be cost prohibitive.

The authors of this paper will discuss how design of a 4-in. tie-back string with flush joint connections equal to the properties of the casing was capable of repairing a 5-1/2-in. monobore production casing that experienced extensive casing failure. The extremely small annular tolerance did not allow a conventional packer assembly or cementing for pressure isolation; thus, swellable packer technology was used to anchor the casing in place. A special flow-thru frac plug was designed so that it could be pumped through the 4-in. tie-back casing and set in the 4-1/2-in. lateral, allowing a plug-and-perf fracture completion to be performed. The stimulation treatments were pumped to completion and demonstrated 1), that the pressure isolation integrity of the casing system was satisfactory; and 2), that the flow-thru frac plugs could maintain isolation between stimulation treatments. This wellbore was in the Eagle Ford Shale. True vertical depth (TVD) was ~ 13,000 ft, bottomhole temperature (BHT) was ~325°F with a 0.95 psi/ft frac gradient, and surface pressures exceeded 10,000 psi during the stimulation treatments.
Re-injecting Produced Water into Tight Oil Reservoirs
Authors: Yong Chen , Wu Oliver , Xiao Jon H , Klotz Eric
Published: October 2012

The technical challenges regarding re-injection of produced water into tight oil reservoirs are discussed based on commercial experience. This paper demonstrates a successful case study based on a project that launched in 2005. The objective was to treat 320 m3/day of produced wastewater for tight oil reservoir re-injection. The effluent requirements were less than 1ppm oil, less than 1ppm TSS, and less than 0.8 micron particle size. The performance during the past 5 years of operation will be reviewed. Due to the unique composition of the influent water and very strict treatment requirements, this process was designed to overcome significant technical challenges. The process includes dissolved air flotation, micro-media filtration and UF membrane technology.

This paper discusses the process configuration with an emphasis on actual operating results. The improvement in oil production and other significant findings will also be presented and reviewed.
How the Compagnie Générale des Eaux survived the end of concession contracts in France 100 years ago
Authors: Pezon Christelle
Published: October 2012

The end of the nineteenth century coincided with the end of concession contracts as a desirable option for French municipalities to organise their water services. An increasing number of disagreements between municipalities and their water concessionaires were brought to administrative courts, while the most difficult cases went to the French Supreme Court, the Conseil d'Etat. All cases dealt with the same issue: the conditions to renegotiate and/or terminate concession contracts. The Compagnie Générale des Eaux, the biggest French water company, lost its biggest concession contracts and had to negotiate new contractual arrangements to survive.
Market efficiency and welfare effects of inter-sectoral water allocation in South Africa
Authors: Juana James S. , Strzepek Kenneth M. , Kirsten Johann F.
Published: October 2012

The need for increased agricultural production to meet the growing demand for food, coupled with concerns for environmental sustainability, economic growth and poverty reduction has increased demand on the already scarce water in South Africa. At the same time, because of agriculture's minimal contribution, compared to the industrial and mining sectors, to South Africa's GDP and employment, the call to reallocate water from agriculture to non-agricultural use has been intensified.

This study updates the 1998 Social Accounting Matrix (SAM) for South Africa and uses the computable general equilibrium model to analyze the impact of water reallocation from agriculture to the non-agricultural sectors on output growth, value added at factor cost, which captures the payments from the production sectors to the factors of production, and households' welfare.

Using different water reallocation scenarios, the simulation results indicate that water reallocation from agriculture to non-agricultural sectors beyond the level of a market allocation scenario will lead to a decline in sectoral output and a significant deterioration in the welfare of poor households. It thus undermines development efforts aimed at reducing the existing level of poverty in the country.
Allocation discourses: South African water rights reform
Authors: Movik Synne
Published: October 2012

Perceptions of increasing water scarcity have caused many countries to reform their water legislation. South Africa, in the vanguard of reform efforts, passed the National Water Act in 1998. The Act was lauded as a progressive piece of policy as it posited the redress of past injustices as one of its overarching aims. But there has been little progress in terms of redistribution of water use rights. This paper argues that bringing water under the ambit of the state, in combination with the particular political conjunctures in post-apartheid South Africa, opened up space for the emergence of narratives around water use rights that framed the continued use of existing users as pivotal for sustainability and that redistribution is associated with a high degree of risk. Although water allocation reform is essentially a deeply political issue, the increasing technocratisation and bureaucratisation of the reform process served to mask contested understandings through, for example, the use of innocuous-sounding terms such as “existing lawful use”. This, in combination with a highly under-resourced water management sector tasked with the responsibility of shouldering a heavy and complex system of licensing, resulted in reform efforts ending in a temporary impasse.
The Danish Atopy Database (DAD): Rationale and Methods
Authors: Francis Thomsen Simon , Mutanu Jungersted Jakob , Clausen Maja-Lisa , Agner Tove
Published: October 2012

Atopic dermatitis is a multifactorial chronic disease that poses a great burden for patients and society. In recent
decades the prevalence has increased substantially in many countries, notably in Western societies, and the causes for this
increase are not completely understood. There are still many unanswered questions regarding atopic dermatitis with respect
to aetiology, pathophysiology, co-morbidity as well as subgrouping and treatment of the disease. Establishment of
the Danish Atopy Database (DAD), a cohort with ongoing inclusion of outpatients with atopic dermatitis from a tertiary
referral centre, allows the study of these aspects of the disease. Herein we present our methodological considerations in
regards to establishment of this cohort.
Bijective proofs of Jensen’s and Mohanty-Handa’s identities
Authors: Loehr Nicholas , Mauldin Daniel
Published: October 2012

This article provides bijective proofs of Jensen?s identity and a
multivariate generalization called Mohanty-Handa?s identity. Our proofs
employ suitable combinatorial operations on lattice paths.
Auditors' Consideration of Material Income-Increasing versus Material Income-Decreasing Items during the Audit Process
Authors: Desai Naman K. , Gerard Gregory J.
Published: October 2012

We examine how auditors' consideration of material items is affected by each item's directional impact on income. Prior research indicates that auditors face greater litigation risk for non-detection of fraudulent income-increasing items compared to income-decreasing items. Therefore, we expect that auditors will spend greater cognitive effort evaluating material income-increasing (as opposed to income-decreasing) items, resulting in superior memories for such items. However, in an effort to direct auditors' attention to both increasing and decreasing material items, we manipulate whether or not auditors were asked to form expectations about the future effects of material items. Our results indicate that auditors' memories for income-increasing items are significantly greater than that for income-decreasing items when auditors are not asked to form expectations about the future effects of the items. However, this difference is not observed when auditors are asked to form expectations about future effects of each item. Furthermore, our results indicate that auditors are less likely to refer back to the work papers to verify the accuracy of income-decreasing items compared to income-increasing items. This suggests that auditors are not inclined to compensate for their poor memory of income-decreasing items by referring to working papers. However, it also suggests that auditors compensate for the greater risk associated with income-increasing items by requiring greater verification of such items.

Data Availability: Contact the authors.
Lessons From the Mixed-Meal Tolerance Test
Authors: Besser Rachel E.J. , Shields Beverley M. , Casas Rosaura , Hattersley Andrew T. , Ludvigsson Johnny
Published: October 2012

OBJECTIVE

Mixed-meal tolerance test (MMTT) area under the curve C-peptide (AUC CP) is the gold-standard measure of endogenous insulin secretion in type 1 diabetes but is intensive and invasive to perform. The 90-min MMTT-stimulated CP ≥0.2 nmol/L (90CP) is related to improved clinical outcomes, and CP ≥0.1 nmol/L is the equivalent fasting measure (FCP). We assessed whether 90CP or FCP are alternatives to a full MMTT.

RESEARCH DESIGN AND METHODS

CP was measured during 1,334 MMTTs in 421 type 1 diabetes patients aged <18 years at 3, 9, 18, 48, and 72 months duration. We assessed: 1) correlation between mean AUC CP and 90CP or FCP; 2) sensitivity and specificity of 90CP ≥0.2 nmol/L and FCP ≥ 0.1 nmol/L to detect peak CP ≥0.2 nmol/L and the equivalent AUC CP; and 3) how the time taken to reach the CP peak varied with age of diagnosis and diabetes duration.

RESULTS

AUC CP was highly correlated to 90CP (rs = 0.96; P < 0.0001) and strongly correlated to FCP (rs = 0.84; P < 0.0001). AUC CP ≥23 nmol/L/150 min was the equivalent cutoff for peak CP ≥0.2 nmol/L (98% sensitivity/97% specificity). A 90CP ≥0.2 nmol/L correctly classified 96% patients using AUC or peak CP, whereas FCP ≥0.1 nmol/L classified 83 and 85% patients, respectively. There was only a small difference seen between peak and 90CP (median 0.02 nmol/L). The CP peak occurred earlier in patients with longer diabetes duration (6.1 min each 1-year increase in duration) and younger age (2.5 min each 1-year increase).

CONCLUSIONS

90CP is a highly sensitive and specific measure of AUC and peak CP in children and adolescents with type 1 diabetes and offers a practical alternative to a full MMTT.
Diabetes Impairs Stem Cell and Proangiogenic Cell Mobilization in Humans
Authors: Fadini Gian Paolo , Albiero Mattia , Vigili de Kreutzenberg Saula , Boscaro Elisa , Cappellari Roberta , Marescotti Mariacristina , Poncina Nicol , Agostini Carlo , Avogaro Angelo
Published: October 2012

OBJECTIVE

Diabetes mellitus (DM) increases cardiovascular risk, at least in part, through shortage of vascular regenerative cells derived from the bone marrow (BM). In experimental models, DM causes morphological and functional BM alterations, but information on BM function in human DM is missing. Herein, we sought to assay mobilization of stem and proangiogenic cells in subjects with and without DM.

RESEARCH DESIGN AND METHODS

In a prospective trial (NCT01102699), we tested BM responsiveness to 5 μg/kg human recombinant granulocyte colony–stimulating factor (hrG-CSF) in 24 individuals with DM (10 type 1 and 14 type 2) and 14 individuals without DM. Before and 24 h after hrG-CSF, we quantified circulating stem/progenitor cells and total and differential white blood cell counts. We also evaluated in vivo the proangiogenic capacity of peripheral blood mononuclear cells using the Matrigel plug assay.

RESULTS

In response to hrG-CSF, levels of CD34+ cells and other progenitor cell phenotypes increased in subjects without DM. Patients with DM had significantly impaired mobilization of CD34+, CD133+, and CD34+CD133+ hematopoietic stem cells and CD133+KDR+ endothelial progenitors, independently of potential confounders. The in vivo angiogenic capacity of peripheral blood mononuclear cells significantly increased after hrG-CSF in control subjects without DM, but not in patients with DM. DM was also associated with the inability to upregulate CD26/DPP-4 on CD34+ cells, which is required for the mobilizing effect of granulocyte colony–stimulating factor.

CONCLUSIONS

Stem and proangiogenic cell mobilization in response to hrG-CSF is impaired in DM, possibly because of maladaptive CD26/DPP-4 regulation. These alterations may hamper tissue repair and favor the development of cardiovascular complications.
Cystic Malformation of Lower Female Genital Tract Resulting in Hydrops Fetalis: A Case Report
Authors: Taweevisit Mana , Manotaya Saknan , Thorner Paul Scott
Published: October 2012

Genitourinary tract malformations causing hydrops fetalis are rare. The authors report a case of a female delivered at 32 weeks gestational age following a prenatal diagnosis of an abdominopelvic cystic mass with hydrops fetalis. The neonate was persistently hypoxic with unstable cardiovascular status and survived only 7 days. At autopsy, a cystic malformation replaced the vagina and uterus, associated with lower vaginal atresia and anorectal agenesis. The cyst had interfered with the normal process of Müllerian duct fusion, leading to a longitudinal vaginal septum and bifurcation of endocervix, with absent uterus and fallopian tubes. The urinary bladder was compressed by the cyst, resulting in bilateral hydronephrosis. The cyst impeded the inferior vena caval and umbilical venous circulations and impinged upon the thoracic cavity with resultant pulmonary hypoplasia. This malformation, which might be termed “cystic dysplasia” of the vagina, represents an extreme form of hydrometrocolpos that resulted in hydrops fetalis.