bluuebunny/crossref_metadata_2025 huggingface dataset:
A Net Map Method on Vehicle Structural Fatigue Damage Analysis
Authors: Yongchen Liu , Li Sun , Lichao Xu
Published: March 2015

In order to effectively use the vehicle road test load spectrum data and adjust road test specifications, a net map
method on vehicle structural fatigue damage analysis is proposed, by taking the vehicle subframe as a study objective.
This article consists of three parts. First part discusses that, the finite element analysis model of the vehicle subframe was
built in ANSYS software, and its construction stress was calculated and analyzed under the action of lateral and
longitudinal forces, respectively. The hot points on the control arm were determined, which could bring about fatigue
damage. The location was identified as load testing point P, where strain rosette was pasted. Second part discusses that,
the strain load of the subframe was measured under the condition of proving ground, eight kinds of roads that fall under
combination roads were chosen in the proving ground and the vehicle speed was found to be different on each road. After
finishing the data processing, and the pure signal of vehicle subframe was acquired. Using rain flow counting method, the
load spectrum of the subframe was worked out, and load distribution histogram on the testing point was obtained. On this
basis, according to local stress-life method and Miner standard and stress concentration correction factor, the fatigue
damage analysis was completed for the subframe under the combination road and each of the enforced roads. Third part
discusses that, the fatigue damage density and weight of each road conditions were calculated under the condition of each
enforced road about subframe structure, and a net map that represented its closed area fatigue damage was drawn. In the
net map, the central angle represents the damage weights on different road conditions and the radius length represents the
damage density on each road. The results show that the network diagram can easily express the vehicle structural damage
under the conditions of all the different combination of roads when the size of the central angle and length of radius were
changed, vehicle structure damage relative to the change would be obtained by drawing a new net map. This method
provided a convenient and effective way to analyze vehicle fatigue damage.
Load Calculation and Design of Roller Crowning of Truck Hub Bearing
Authors: Xia Xintao , Dong Shujing , Sun Liming , Chen Tianju
Published: March 2015

Double-row tapered roller bearing 353112 is used in trucks, and the external load and pressure distribution of
the bearing are calculated combining with the specific operating conditions. Tapered roller bearings typically employ
roller profile modification to equalize the load distribution, minimizing the stress concentration at the roller ends. Doing
FEA (finite element analysis) on the contact stress with the changing roller crowning between roller and races, the
appropriate roller profile and the crown drop of roller can be achieved. Finally the best control equation of roller crowning
is obtained. It has important guiding significance for the improvement of roller crowning design of truck hub bearings.
Research and Application of Work Roll Contour Technology on Thin Gauge Stainless Steel in Hot Rolling
Authors: Jian Shao , Anrui He , Fanfu Kong , Yang Xiang , Zhou Zhou
Published: March 2015

Shape control is the key technology for thin gauge stainless steel in hot rolling. Because of high rolling force,
work roll can suffer from serious uneven wears, edge drop of strip temperature and so on. And in turn these imperfections
lead to defects in thin gauge stainless steel production, such as big crown value, quarter wave, edge profile anomalies,
poor rolling stability. In order to improve shape the control ability, one will have to eliminate the quarter wave, make roll
wear uniform, increase rolling stability in the thin gauge stainless steel production, use high performance variable crown
technology in upstream stands, use mixed variable crown technology in last stand, and use conventional work roll with
variable shifting stroke strategy in other downstream stands. The above technologies have been successfully applied in
several stainless steel productions, which have completely independent intellectual property rights, and the crown control
precision of thin gauge stainless is 98.1%, flatness control precision is 97.5%, also a 1260 mm × 1.6 mm ultra-thin gauge
stainless steel was successfully developed.
Does Real-Time Reporting Deter Strategic Disclosures by Management? The Impact of Real-Time Reporting and Event Controllability on Disclosure Bunching
Authors: Tian Xiaoli (Shaolee)
Published: March 2015

The SEC is moving toward requiring real-time reporting. Proponents have predicted that disclosing a news event immediately after it arises could reduce information aggregation and disclosure bunching. But evidence from the theoretical literature suggests that the effect depends on whether managers can time the underlying required reporting event. Managers, for example, can time regular poison pill adoptions, but have limited ability to time in-play pill adoptions. Thus, I test whether real-time reporting deters disclosure bunching around the disclosures of regular and in-play poison pill adoptions to examine whether managers' ability to time events affects whether real-time reporting deters strategic disclosure. I find that real-time reporting does not deter disclosure bunching for regular poison pills, but does deter it for in-play pills. These results suggest that real-time reporting will reduce disclosure bunching only if managers cannot time the underlying event.

JEL Classifications: M40; M41; M48
Influence of unilateral maxillary first molar extraction treatment on second and third molar inclination in Class II subdivision patients
Authors: Livas Christos , Pandis Nikolaos , Booij Johan Willem , Halazonetis Demetrios J. , Katsaros Christos , Ren Yijin
Published: March 2015

Objective: 

To assess the maxillary second molar (M2) and third molar (M3) inclination following orthodontic treatment of Class II subdivision malocclusion with unilateral maxillary first molar (M1) extraction.

Materials and Methods: 

Panoramic radiographs of 21 Class II subdivision adolescents (eight boys, 13 girls; mean age, 12.8 years; standard deviation, 1.7 years) before treatment, after treatment with extraction of one maxillary first molar and Begg appliances and after at least 1.8 years in retention were retrospectively collected from a private practice. M2 and M3 inclination angles (M2/ITP, M2/IOP, M3/ITP, M3/IOP), constructed by intertuberosity (ITP) and interorbital planes (IOP), were calculated for the extracted and nonextracted segments. Random effects regression analysis was performed to evaluate the effect on the molar angulation of extraction, time, and gender after adjusting for baseline measurements.

Results: 

Time and extraction status were significant predictors for M2 angulation. M2/ITP and M2/IOP decreased by 4.04 (95% confidence interval [CI]: −6.93, 1.16; P  =  .001) and 3.67 (95% CI: −6.76, −0.58; P  =  .020) in the extraction group compared to the nonextraction group after adjusting for time and gender. The adjusted analysis showed that extraction was the only predictor for M3 angulation that reached statistical significance. M3 mesial inclination increased by 7.38° (95% CI: −11.2, −3.54; P < .001) and 7.33° (95% CI: −11.48, −3.19; P  =  .001).

Conclusions: 

M2 and M3 uprighting significantly improved in the extraction side after orthodontic treatment with unilateral maxillary M1 extraction. There was a significant increase in mesial tipping of maxillary second molar crowns over time.
Orobanche Laxissima Uhlich & Rätzel (Orobanchaceae) – A New Species for Dagestan (Russia) and Azerbaijan
Authors: Piwowarczyk Renata , Tatanov Ivan
Published: March 2015

Orobanche laxissima Uhlich & Rätzel (Orobanchaceae) is a probably endemic Caucasian parasite of trees. New localities of this species are reported from the Greater Caucasus: Russia (Dagestan) and Azerbaijan. These are the easternmost sites known for the species, so they extend its distribution range. Its hosts, abundance, and habitat preferences at the new localities are described, and a supplemented map of distribution of this species in Caucasus Mts. is provided
The influence of neighbouring species on ecological variation of the selected subpopulations of Iris sibirica L.
Authors: Kostrakiewicz-Gierałt Kinga
Published: March 2015

Ecological variation of the selected subpopulations of Iris sibirica L. were studied in the years 2011-2012, in the abandoned patches of Molinietum caeruleae dominated by small meadow species (Patch I), macroforbs (Patch II), largetussock grasses (Patch III), shrubs (Patch IV), as well as shrubs and trees (Patch V). The abundance of subpopulations and dimensions of aggregations of ramet clusters increased gradually from Patch I to Patch IV and subsequently declined in Patch V. During the whole study period, all subpopulations showed signs of senility due to the absence of individuals in prereproductive stages. The share of generative ramet clusters diminished, while contribution of senile and fragmentised ramet clusters increased substantially in consecutive patches. The dimensions of ramet clusters increased significantly in successive plots and years. The number and height of generative stems and production of flowers and fruits did not show the temporal variability. The abundance of generative stems was considerably lower in the plots dominated by small meadow species, than in the sites dominated by large-tussock grasses, shrubs or overgrown shrubs and trees. Both the height of flowering stems and production of flowers and fruits increased gradually from Patch I, via Patches II, III and IV, to Patch V. The augmentation of flower production might contribute to better visibility of inflorescences for pollinators, whereas an increase in the production of fruits may increase the chances for successful seed dispersal to new sites.

This study results show that the I. sibirica subpopulations occurring in the site dominated by small meadow species and macroforbs were in unsatisfactory condition, those inhabiting the sites dominated by large-tussock grasses and shrubs were in a quite good condition, while the subpopulation inhabiting the plot overgrown by shrubs and trees showed the worst condition
Carex flava agg. (section Ceratocystis, Cyperaceae) in Poland: taxonomy, morphological variation, and soil conditions
Authors: Więcław Helena
Published: March 2015

Sedges of Carex flava agg., typical of moist or wet habitats, are difficult to classify because of a lack of clear-cut morphological differences between them and the existence of numerous hybrids. This monograph presents results of research conducted in 2007-2012 in various parts of Poland. The plant material consisted of 1852 living specimens of Carex flava agg., collected from 80 localities, and dried specimens from 26 herbaria and from 7 private collections. The analysis involved 45 morphological characters (34 quantitative and 11 qualitative) and 9 soil parameters. Univariate, bivariate, and multivariate statistical methods were used to process the data. The results confirm the taxonomic classification dividing the C. flava group into 4 species: C. flava s.s., C. lepidocarpa, C. demissa, and C. viridula. This classification is based on (i) a high observed level of morphological separation of these taxa, resulting mostly from differences in generative characters, i.e. length of the utricle and its beak, and percentage ratio of beak length to total utricle length; (ii) integrity of the taxa at the sites where they coexist, although some intermediate forms resulting from hybridization are also present; (iii) habitat preferences of the taxa, especially the preference of C. lepidocarpa for calcareous sites and of C. demissa for slightly acidic soils. Thus in Poland the analysed taxa are morphologically well-defined and show clear ecological preferences. Continuous variation of morphological characters was observed among specimens of C. viridula, so it is not justifiable to distinguish its subspecies (sometimes classified even as separate species), described previously in literature. Consequently, the 2 subgroups of C. viridula were treated as local variants (i.e. varieties: var. viridula and var. pulchella), considering their different habitat requirements. Additionally, 5 hybrids were distinguished within C. flava agg.: C. ×alsatica [= C. demissa × C. flava], C. ×ruedtii [= C. flava × C. lepidocarpa], C. ×schatzii [= C. lepidocarpa × C. viridula], C. ×subviridula [= C. flava × C. viridula], and C. demissa × C. viridula; as well as 2 hybrids with C. hostiana as one of the parents: C. ×fulva [= C. demissa × C. hostiana] and C. ×leutzii [= C. hostiana × C. lepidocarpa].
Carex flava agg. (section Ceratocystis, Cyperaceae) in Poland: distribution maps and locality lists
Authors: Więcław Helena
Published: March 2015

This paper presents lists of localities and distribution maps of Carex taxa of the section Ceratocystis in Poland. Distribution maps of individual taxa are based on the ATPOL grid, using material deposited in Polish herbaria and private collectionsas well as material collected during field research in 2007-2012. The collected data indicate that (i) in Poland C. flava s.s. is the most common species of the section Ceratocystis, whereas C. hostiana is the rarest one; (ii) most of the localities of C. demissa are situated in southern Poland, especially in Małopolska, Podkarpacie, and Silesia Provinces (iii) C. lepidocarpa is most frequent in Polesie, Lublin Upland, Małopolska, and Pomerania; no records of this species in southernmost parts of Poland have been confirmed; (iv) C. viridula var. viridula is frequent in Poland, whereas C. viridula var. pulchella is only known from 2 localities in the north; (v) the most frequent hybrid in Poland is C. ×alsatica [C. demissa × C. flava], while C. ×ruedtii [C. flava × C. lepidocarpa], C. ×subviridula [C. flava × C. viridula], and C. ×schatzii [C. lepidocarpa × C. viridula] are reported less often; the rarest hybrids are C. demissa × C. viridula, C. ×fulva [C. demissa × C. hostiana], and C. ×leutzii [C. hostiana × C. lepidocarpa].
Rediscovery of Jasminum parkeri Dunn, an endemic and endangered taxon from the western Himalaya, India
Authors: Lal Brij , Datta Arunava , Parkash Om , Deosharan Rakesh
Published: March 2015

The present article deals with the rediscovery of Jasminum parkeri Dunn (Oleaceae) collected from its type locality after a lapse of about 100 years. J. parkeri is a highly endangered and narrowly endemic taxon restricted to a small pocket in the remote mountain area of Chamba district, Himachal Pradesh in the western Himalaya, India. In order to facilitate identification of this species, the plant description along with a brief history of its discovery, affinity with the other taxa of Jasminum, ecological notes, and pictures are provided. Subsequently, possibility of cultivation of this species in ex-situ conditions is also discussed.
Lepidium s. str. (Brassicaceae) in the flora of Ukraine
Authors: Ilyinska Antonina P.
Published: March 2015

The key to the 14 species of Lepidium occurring in the Ukraine, including basionyms and the most important synonyms, and distribution of these species within the floristic regions, especially in Ukraine, are presented
Alien plants in Poland: research directions and putting the results into practice
Authors: Tokarska-Guzik Barbara , Bzdęga Katarzyna , Nowak Teresa , Lewandowska Agata , Gancarek Małgorzata , Frelich Małgorzata
Published: March 2015

The aim of this study was: (i) to complete and verify the prior review of research on alien plants conducted in Poland and the practical use of their results, and (ii) to attempt to assess the contribution of the research from the area of Poland to the research conducted on an international level. The analysis was performed based on the information gathered during a literature search which covered the last 200 years, using over 1400 publications out of the 3000 which were available in the pool. As a result, the main areas of biological sciences in the context of the research undertaken on alien plants in Poland (distribution, ecology and biology of the species), the most common thematic studies (new species, new localities, and lists of alien species), and the most often investigated species, as well as tendencies over time were indicated. Although studies on the migration and distribution of alien plants in Poland have over 100 years of tradition, and the part of the studies conducted by Polish researchers contributes to the international scale research, it is still necessary to further analyse many issues and answer numerous questions.
A Method for Security Estimation of the Spn-Based Block Cipher Against Related-Key Attacks
Authors: Kaidalov Dmytro , Oliynykov Roman , Kazymyrov Oleksandr
Published: March 2015

Symmetric block ciphers are the most widely used cryptographic primitives. In addition to providing privacy, block ciphers are used as basic components in the construction of hash functions, message authentication codes, pseudorandom number generators, as a part of various cryptographic protocols, etc. Nowadays the most popular block cipher is AES (Advanced Encryption Standard). It is used as a standard of symmetric encryption in many countries. Several years ago it was found a theoretical attack exploiting the AES key expansion algorithm that allows reducing significantly the complexity comparing to the brute force attack. This article presents an advanced method of finding the number of active substitutions that helps to estimate the security of encryption algorithms against related-key attacks. The method was applied to a prospective block cipher, which is a candidate for the Ukrainian standard
Non-Interactive Secure Multiparty Key Establishment
Authors: Eskeland Sigurd
Published: March 2015

Cryptographic schemes that provide establishment of secret keys among a number of participants are generally known as conference key establishment schemes and key broadcasting schemes. In any case, such protocols provide secure establishment of group-oriented cryptographic keys, but with the costs of multiple transmissions of key establishment messages and in some cases multiple secret user keys. In this paper, we present a simple and straightforward efficient non-interactive group-oriented key establishment scheme that provides off-line computation of secret group keys, without computations and transmissions of key establishment messages
A Micro-Controller Implementation of a Fialka M-125 Based Stream Cipher
Authors: Antal Eugen , Hromada Viliam
Published: March 2015

In 2013, a new stream cipher was proposed in Antal, E.-Hromada, V.: A new stream cipher based on Fialka M-125, Tatra Mt. Math. Publ. 57 (2013), 101-118. Its design was inspired and motivated by a Soviet encryption machine Fialka M-125. The authors proposed three versions of the cipher with different inner state bit-lengths. They provided the design, software implementation on a personal computer and a preliminary statistical and performance analysis of the cipher.

In this article we extend their work by implementing all three versions of the cipher on two different micro-controllers: EBV SoCrates evaluation board [Official SoCrates webpage (EBV SoCrates evaluation board), www.rockerboards.org] and STM32F407VG [Official STM webpage (STM32F407VG), www.st.com]. We evaluate the performance of all implementations on both platforms. We also investigate the possibilities of performing a simple power analysis of the implementation of the 8-bit version of the cipher implemented on STM32F407VG micro-controller. It stems from our experiments that we are able to determine a part of the secret key of the cipher by observing the power trace (power consumption) of the encryption/decryption process
Using Poly-Dragon Cryptosystem in a Pseudorandom Number Generator Mstg
Authors: Hromada Viliam , Vojvoda Milan
Published: March 2015

This paper deals with a new pseudorandom number generator MSTg proposed in 2010. Its construction is based on random covers for finite groups. We have used a public-key cryptosystem Poly-Dragon to generate these random covers and have studied the statistical properties of the resulting pseudorandom number generator by testing its output using the NIST Statistical Test Suite
Moments of Markov-Switching Models
Authors: Petričková Anna
Published: March 2015

In this paper we have focused on the class of regime-switching time series models with regimes determined by unobservable variables, concretely Markov-switching models. We have derived 2nd central moment of the MSW models for two cases-state-independent and state-dependent model
Three-Polar Space Over the Semi-Field of Double Numbers
Authors: Gregor Tomáš
Published: March 2015

Multi-polar space is a generalization of the notion of vector space. In this paper, we deal with a three-polar vector space over a semi-field of double (hyperbolic complex) numbers. We introduce and study operations of addition and multiplication such that they form a commutative ring with unit on the three-polar space
A Risk Analysis Approach: From Subsurface to Surface
Authors: Contento F. Michela , Godi Antonella , Nicotra Giovanna , Pizzo Anna
Published: March 2015

The quantitative assessment of the risk associated with the economic exploitation of a hydrocarbon field is mandatory to support, in an efficient and comprehensive way, the decision process guiding the development management system of an oil company.

The Full Range Risk Analysis (FRRA) approach developed in Eni E&P Division allows the identification of uncertainties arising from each step of an integrated reservoir study, and the evaluation of their impact on recoverable reserves and on the economic value of a project. This methodology has already been successfully applied in the concept selection and concept definition phases of field development projects. Recently it has been further improved to be employed both in the evaluation stage, of a new discovery, and in the revamping of mature fields with production history.

Introduction

The Full Range Risk Analysis is aimed at investigating the whole range of possible reservoir development combinations. Its main objectives are:the support of the sanction of an economic discovery, considering an acceptable and accepted risk; the estimation of the value of information (VOI) of new data acquirement and the comparison between different appraisal strategies; the choice of the best development plan taking into account the main impacting reservoir uncertainties (mainly during concept selection phase);the quantification of downside/upside potential of the reservoir and of residual risk associated to field with production history.

The presented workflow is a valuable tool in assessing the risk associated to a particular development scenario taking into account the entire surface and sub-surface uncertainties and therefore a methodology to support decisions in development projects.

The FRRA methodology is fully based on Montecarlo approach and massive simulations of 3D reservoir models.

Full Range Risk Analysis Workflow

The current paper describes in detail the standard FRRA workflow along with the latest developments of the methodology, starting from the uncertainty definition phase up to the frequency distribution of the target variable, i.e. ultimate recovery, plateau length, NPV.
Chayvo Field, Sakhalin Island, Russia: Identification of a Significant Oil Leg From 3D Seismic and Execution of a World-Class Extended-Reach-Drilling Program
Authors: Apotria Ted , Poffenberger Mike , Powell Rick , Venner Bridget
Published: March 2015

In 1997, the ExxonMobil operated Sakhalin I Consortium acquired a 3-D seismic survey over Chayvo Field, located off the northeast coast of Sakhalin Island, Russia. At the time of the acquisition, Chayvo was thought to contain primarily gas given the results of five pre-existing crestal wells. Interpretation of 3-D seismic revealed seismic amplitude anomalies that conformed to structural spill, were down dip of gas accumulations seen in crestal wells, and indicated the potential for very large, previously unrecognized oil rims. Based on the 3-D seismic interpretation, an appraisal well was drilled in 2000 and penetrated several large oil legs. This appraisal well and associated sequence stratigraphic studies resulted in a significant oil project in a field previously thought to be mostly gas.

When the oil rims were confirmed, the challenge was how to develop the Chayvo field lying 8 to 10 kilometers offshore. Development drilling at the field began in 2003, with the first phase comprising a series of extended reach wells drilled from an onshore location reaching offshore to the western limb of the Chayvo anticline. These wells are technically complex and very expensive, but attractive considering offshore platform costs in a remote, environmentally sensitive location characterized by seismic activity and icebergs.

In 2002, a multi-disciplinary team was assembled to address the challenges associated with designing and executing extended reach wells in stacked deltaic reservoirs comprised of prograding clinoforms. The primary geological concern was the accuracy with which the horizontal well bores could be placed within the oil column, as reservoir simulation indicated the need to be within 10 m of a specified vertical depth to delay water/gas breakthrough. Ongoing drilling has proven to be successful with actual reservoir depths within a few meters of prognosed depths at well reaches of 9–11 kilometers, underscoring the value in the integrating seismic interpretation and extended-reach well planning in a 3-D visualization environment.
Shot-Domain Data Reconstruction and Its Application to Suppression of 3D Surface-Related Multiples
Authors: Baumstein Anatoly , Hadidi Mohamed T. , Hinkley David L.
Published: March 2015

We present a DMO-based technique for reconstruction of densely and regularly sampled shot records from conventional marine data. The reconstruction process allows us to overcome aliasing that typically affects marine data in the cross-line direction and enables us to apply high-end processing techniques, such as 3D SRME, to conventional marine data without imposing additional acquisition requirements. A low-cost version of our reconstruction method, which is particularly suitable for use as a part of a multiple-suppression processing flow, is introduced and its advantages and limitations discussed.

An example of performing data reconstruction for a conventional marine field dataset, followed by application of 3D SRME, is presented. This field data example is used to illustrate how the choice of data reconstruction method impacts the quality of multiple suppression.

Introduction

Many advanced seismic processing techniques, such as 3D surface-related multiple suppression (SRME) and 3D shot-record wave-equation migration (SRWEM), require regularly and densely sampled input data. In particular, 3D SRME requires dense sampling of both shots and receivers, while SRWEM efficiency is a function of the number of shot records in the data set. Current marine acquisition geometries do not provide the data suitable for either one of the above processing algorithms. In the case of 3D SRME, shot (and to a lesser degree, streamer) crossline spacing is too coarse for the algorithm to predict 3D multiples correctly. In the case of SRWEM, run times could be greatly reduced if multiple shot records could be combined in one "super-shot", thus reducing the total number of shot records.

We discuss a DMO-based method for transforming conventional marine data into an equivalent set of data on a finely sampled regular and dense grid including all source-to-receiver azimuths. The new data are equivalent in the sense that a migration code would accurately map a reflection event associated with a single subsurface interface in the new data to the same subsurface locations as the corresponding data in the input data set.
Cement Designs for High-Rate Acid Gas Injection Wells
Authors: Benge Glen
Published: March 2015

High rate acid gas injection wells pose a significant challenge for the design of cementing systems. CO2 conversion of Portland cement to calcium carbonate is a significant problem. This paper describes the design and use of two cement systems for high rate acid gas injection wells. The paper compares risks and benefits of a high alumina cement slurry to those of a specialty Portland based system. Case history reviews of the application of both systems on liner cement jobs are detailed. The systems were used on wells designed for a 65% H2S, 35% CO2 injection stream at a rate of 65 million scf/day.

High alumina cement is used in many applications to address the problem of CO2 conversion of Portland cement. The cement is resistant to CO2, but high temperature fluid loss control was not available, preventing its application on long liners. Lack of an effective high temperature fluid loss additive required the development of an alternate Portland based system. Later development of an effective high temperature fluid loss additive ultimately allowed use of the high alumina cement system.

A CO2 resistant Portland system was developed by limiting the cement concentration and reducing total system permeability by use of specialty sized particles. This paper discusses the development and testing of a Portland based cement system and the associated risks with the use of this specialty system. Quality control steps to address the complex blending process and steps taken to improve system reliability are presented.

Background

Two acid gas injection wells (AGI 3–14 and 2–18) were drilled in the western United States as part of an overall gas plant de-bottlenecking. Plant throughput capacity was being increased by converting the plant to acid gas disposal by injection. The anticipated waste gas stream was 65% H2S and 35% CO2, with the design volume for the wells being based on the capacity of the plant plus adequate backup.
Front-End Engineering Studies for Carbonate Stimulation Optimization
Authors: Lizak Kenneth F. , Fulton Dwight David , Van Domelen Mary Susan
Published: March 2015

This paper describes an integrated approach to stimulation treatment design for carbonate reservoirs. Using this process helps ensure that appropriate candidates are stimulated with the optimum treatment. Historically, many of the steps described have been applied in sandstone reservoir stimulation, but industry has lagged in the application of these technologies to carbonate reservoirs.

The discussion begins with preliminary candidate selection based on estimated productivity gains from various stimulation options. Well history and formation data is reviewed to evaluate near-wellbore damage and identify possible fluid-formation compatibility issues that will affect treatment choices. Productivity analyses indicate formation flow capacity, which can then be used to rank potential treatment options such as comparing the expected results from a matrix treatment to an acid fracturing treatment.

Core testing demonstrates that specific carbonate "rocks" will have uniquely different reaction characteristics when treated with various acid systems. This is a valid design consideration, whether the proposed treatment is matrix or fracture acidizing. This paper reviews the specialty core testing programs which are used to optimize acid treatments and present illustrative data.

All the previously-gleaned data provide inputs to selection of the most appropriate approach to stimulation and set the stage for the final design. In matrix treatments, the biggest challenge is often fluid placement and diversion. Fluid placement modeling, which also predicts skin reduction and stimulation results, is critical to evaluate the potential effectiveness of a possible treatment. When fracture acidizing is required, the same data can be used to refine the treatment design and provide more realistic simulation of the expected well response.

Part 1– Candidate/Treatment Selection

For any field with more than one well, candidate selection for stimulation is a part of the field development decision processWise use of available budget funds for well treatment requires selecting wells with the greatest potential to improve both short-term productivity and long-term reservoir management and recovery.
Development and Application of Combining a Real-Time Hydraulics Model and Automated Choke To Maintain a Relatively Constant Bottomhole Pressure While Drilling
Authors: Reitsma Don
Published: March 2015

The increasing demand to drill wells having narrow pore pressure and fracture gradient margins and the increasing concern that irreparable damage from extreme overbalanced drilling negatively impacts productivity and recoverable reserves, requires a new method of controlling bottomhole pressure while drilling, beyond the current capability of conventional drilling techniques. Where the dynamic pressure or equivalent circulating density can be supported, a solution has been developed to drill with a relatively constant bottomhole pressure equal to the dynamic conditions rather than static conditions, thereby reducing the maximum bottomhole pressure. The method also establishes a continuous method of well control that should reduce the risk of taking a kick.

Shell International Exploration & Production Research & Development has developed a robust solution using a flow model running in real time coupled to an automated choke control system to continuously maintain the bottomhole pressure at a relatively constant value. Several applications of this method have been implemented or proposed, including fractured reservoirs where it is difficult to control losses, HPHT wells subject to ballooning and wells with narrow pore pressure and fracture gradients margins subject to kicks and losses. Underbalanced drilling is another application where increased control of bottomhole pressure to limit inflow and decrease the potential for borehole instability can be realized. The development, testing, application and results of this automated system will be presented.

Introduction

With the advent of circulating drilling mud, bottomhole pressure has been subjected to two different pressure conditions; a static pressure state when the pumps are off and a higher dynamic pressure state caused by the addition of frictional pressure when the drilling pumps are on and drilling fluid is being circulated in the well.

The recently developed Dynamic Annular Pressure Control (DAPC) system now changes that by making it possible to drill with a relatively constant bottomhole pressure equivalent to the dynamic pressure at a given depth in the well by holding the necessary backpressure on the annulus as shown in figure 1. In essence, the pressure curve is reversed by having the increase in pressure at surface using backpressure control rather than at the bottom of the hole.
Application of an Efficient Multiscale Finite Volume Simulator to Practical Reservoir Models
Authors: Wolfsteiner Christian , Gadelle Frederic , Lee Seong Hee , Tchelepi Hamdi A.
Published: March 2015

A reservoir simulator was developed for accurate modeling of multiphase flow and transport in large scale heterogeneous reservoirs. The simulator is based on a multiscale finite volume (MSFV) method. In MSFV, the pressure equation is solved on a coarse grid, where coarse scale transmissibilities are computed via dual basis functions (i.e., localized interpolators). The fine scale pressure and velocity field is computed as a superposition of basis functions using the coarse pressure information. These reconstructed properties are very accurate when compared to results from a conventional fine grid simulation. In the second step, a localized and adaptive transport scheme is employed to update the saturation distribution. Both IMPES and sequentially implicit formulations are described. To resolve the fine scale flow field around wells, a special well basis function is devised. The multiscale algorithm is also extended to include gravity, capillary pressure and compressibility.

The multiscale simulator achieves the robustness and computational efficiency through scalable (efficient for large problems) adaptive computation of flow and transport. We establish the accuracy of MSFV relative to conventional methods with several test examples. The multiscale simulator is subsequently applied to large field scale reservoir models to demonstrate its practical use and efficiency, compared with the conventional finite difference simulator.

Introduction

The trend in modern reservoir characterization is to build geocellular models with an ever increasing level of detail and number of cells. In addition, specific applications (e.g., history matching, Monte Carlo Simulation) may require running large numbers of these detailed simulations. The multiscale framework is a particularly promising method for solving these highly detailed problems directly without resorting to traditional upscaling techniques. In the multiscale approach, the problem is decomposed into a coarse scale operator and local fine scale reconstruction operators. The local problems are small, independent from each other (via appropriate closure assumptions) and typically weak functions of time (for large parts of the reservoir). The resulting method is efficient and scalable.
Fracture Characterization Using Multicomponent Surface Seismic Data
Authors: Kristiansen Pal , Gaiser James E. , Probert Tony
Published: March 2015

In reservoirs producing primarily from secondary porosity like fractures, the flow is largely controlled by the fracture system and characterizing these fractures is key to effectively managing these reservoirs. Aligned fractures will affect the average stiffness of the rocks even when fractures are smaller than seismic wavelengths. Small scale aligned fractures lead to variations in the seismic velocities that are directionally dependent, an effect known as anisotropy. Measuring this seismic anisotropy provides information on the fracture systems properties, such as fracture density and orientation. Such information can be used to identify sweet spots and in general be used for better reservoir management, like guiding directional and infill drilling.

Since fractures are often nearly vertical to bedding the dominant seismic effect is azimuthal anisotropy, which is observed both on P- and S-waves. AVOA (azimuthal AVO-effect) and variations in the NMO velocities have been used to estimate P-wave anisotropy. S-waves will split into one fast and one slow mode and this splitting is very sensitive to small changes in the subsurface. The fast shear-wave direction aligns with the fracture strike and the amount of time splitting between the fast and slow mode depends on fracture density.

Apart from the difference in sensitivity between the P- and S-wave measurements there are attributes of the fracture system that can only be observed on the S-wave data. The asymmetry in the converted waves (PS-data) can say something about the tilt of the fractures. Multicomponent seismic provides access to both the P- and S-wave azimuthal information. Combining these two can enable the extraction of information about the fluid in the fractures. In this paper we will give an overview of the theory and several cases where multi-component data has been used to characterize fractures and fracture attributes.

Introduction

Whilst many fractured reservoirs have been profitably produced, few of them have been depleted in an efficient manner. Nelson points out the importance of classifying fractured reservoirs based on the amount of heterogeneity and anisotropy observed in the porosity and permeability. Quantifying this anisotropy with surface seismic data should provide an optimal strategy for fractured reservoir management by integrating the geophysical data from all scales with the engineering data.
Experiences Using EQR Modelling for Saturation Predictions in a Middle East Carbonate Reservoir
Authors: Engstrom Finn , Toft Jorgen
Published: March 2015

The EQR (Equivalent Radius) method was developed as a "saturation-height" model for the North Sea Chalk in the early 1990s, but experience with the application of the EQR model has demonstrated that it is a general model applicable to any type of reservoir. The objective for the development of the EQR model was to allow an accurate modelling of the long capillary transition zones in chalk and to extract the areal variations in the FWL caused by hydrodynamic and geodynamic effects.

The EQR method includes a preliminary calibration of the "saturation-height" model by core data and an iterative procedure involving forward and reverse modelling of the logged saturation and porosity data from individual wells. The iterative procedure allows an improved calibration of the "saturation-height" model, an improved calibration of the log analysis models, extraction of the depth of FWL(s) at the vertical well locations and along horizontal wells, inferral of the presence/absence of capillary pressure barriers and inferral of the state of the hydrocarbon system (e.g. active drainage or active imbibition).

Data from the EQR modeling of the individual wells in a field can be applied to map the areal variations in the controlling FWL's and provide data on the controlling mechanisms for the hydrocarbon distribution outside well control. This allows a much more accurate prediction of the hydrocarbon distribution outside well control and therefore a more accurate prediction of HCIIP. These two features have proven very helpful in the analysis of the large low permeability carbonate reservoirs in the North Sea and Middle East areas.

This paper describes the background and basic principles behind the EQR-modelling concept and how it has been used to unravel the complex fluid distribution in the Kharaib limestones (Al Shaheen Field, Block 5, Qatar).

Introduction

Calculation of hydrocarbon saturation profile(s) between/outside well control is typically done by use of a "saturation-height model" and with a single pressure defined horizontal FWL.

Experience from the large carbonate reservoirs in the North Sea and Middle East areas, however, has demonstrated that this approach often is far too simplistic and may result in poor understanding of the areal distribution of hydrocarbons and thus also an uncertain hydrocarbon in-place estimates. The uncertainty is partly a consequence of the long transition zones and partly a consequence of the prevailing hydrodynamic and geodynamic effects in these reservoirs.
Motivation and Retention of Young Workforce in the E&P Industry: A Key Issue of Today for Tomorrow's Successes
Authors: Tealdi Loris , Bruni Thomas
Published: March 2015

The paper presents an interpretation of the Young Exploration and Production Professionals status in the oil industry today. It encompasses several themes from job satisfaction, to employees' motivation and education/training/development issues.

In the oil business, many 'intangibles' like the employee potentials and competence are a critical factor for success and an important source of competitive advantage for the companies. The aging workforce in the oil industry demographics indicates that the attraction and retention of the Young Exploration and Production Professionals population represents a key strategy today for successes of tomorrow. Recent surveys have confirmed that as much as 25% of the sampled population sees it unlikely to stay with the same company ten years from now. It follows that a lack of attention to the young population satisfaction and motivation may finally results in the loss of talented young resources that, with an eye to the long term, represent an important, if not the most important strategic asset for the today's companies.

The paper presents an in depth review and analysis of the survey results with focus on talents retention, motivation and development. Results and trends are drawn which are then used to develop a new approach to the development of young professionals with attention to their satisfaction proposing hints for today's companies in their difficult, but crucial task of developing and maintaining the pool of skilled resources fuelling the worldwide oil and gas industry. The philosophy used throughout this work was to start from the end-users (the new hires) – without neglecting the company side of the equation.

Introduction

Demographic analysis of age distribution in oil and gas industry reveals under-representation in the people younger than 35 years old. With the average age of the SPE membership rising to 48 years and assuming such statistics representative of the Oil and Gas business, a large portion of the current workforce will retire within the next 10 years (Figure 1).
Use of Advanced Reservoir Data Collection and Interpretation Techniques
Authors: Pedersen Morten H. , Noman Rashed , Frank Soren , Ohrt Henrik Bjerre
Published: March 2015

This paper presents three examples of reservoir data collection under challenging operational conditions in carbonate and sandstone reservoirs in the Al Shaheen Field offshore Qatar. The examples demonstrate how Formation Pressure Testing and Fluid Sampling can provide early and often decisive information for field development.

Logging operations in the Al Shaheen Field are often performed in wells with horizontal sections in excess of 20,000 ft in thin, unconsolidated sandstone reservoirs. To accommodate these conditions, which are far outside the normal operating envelope of the logging tools, new procedures and techniques have been developed to address 'extended reach logging' and to mitigate potential problems with unconsolidated sand. These procedures and techniques are discussed along with the three field cases.

The first field case describes how in-situ hydrocarbon mobility was determined, and how it justified immediate continuation of an appraisal program. The second field case explains how a fluid contact in a very thin sand was confirmed by fluid sampling, and how it eliminated the need for a horizontal sidetrack. The third field case describes how determination of in-situ fluid properties improved saturation modeling and allowed real-time optimization of the data collection program.

Introduction

The Al Shaheen Field, Block 5, offshore Qatar consists of multiple carbonate and sandstone reservoirs. The reservoirs are laterally extensive, but relatively thin and consequently the field is optimally developed with long horizontal wells. Wells drilled in the sandstone reservoirs are up to 22,000 ft while wells drilled in the carbonate reservoirs exceed some 30,000 ft. Production is currently ongoing from five reservoirs, while water injection is taking place in the three main reservoirs.

In thin laterally extensive reservoirs like those present in the Al Shaheen Field, flow continuity can be affected by lateral facies variations and faulting. Detailed pore pressure information from long horizontal wells therefore provides essential data for understanding and managing reservoir dynamics.