bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation on Combined CO2 Sequestration and Electrical Heating Assisted Gravity Draingage to Enhance Heavy Oil Production
Authors: Zhong Liguo , Yu Di , Zhang Chengjun , Dong Zhaoxia , Ma Shuai , Wang Cheng , Du Xiaoming , Guo Liang
Published: May 2015

In consideration of the challenges of SAGD process such as the high watercut, the elevated temperature of produced fluid, and the heat loss to the overburden layer, combined CO2 sequestration and electrical heating assisted gravity drainage (CSEAGD in short) is taken into consideration to enhance heavy oil production, especially for water sensitive reservoirs as well, the condition of water short such as offshore and desert. In a typical CSEAGD process, two parallel horizontal wells are drilled as injection well and production well respectively, both wells serve as electrodes or two electrical heaters located in the wells separately, CO2 is injected in the upper injection well, and heated oil and gas are drained to the lower production well by gravity enforced by CO2. At the same time, part of the injected CO2 is sequestrated or stored underground.

Both experiment and numerical simulation were carried out using conventional heavy oil and extra-heavy oil (the viscosities at 50°C are 1640 mPa•s and 12500 mPa•s, respectively) sampled from Bohai offshore oilfield to evaluate the feasibility of CSEAGD process. The study include the effect of electrical heating capacity, CO2 injectivity, distance between injection well and production well. The results show that a similar and even higher oil production rate could be achieved by CSEAGD compared to SAGD or SAGP processes for the heavy oils used (the average oil production rate is 2 to 6 times higher than cold production). The temperature distribution of CSEAGD is an asymmetric dumbbell, different from the inverse triangle in SAGD and the ellipse in SAGP, which is derived from the difference of heating chamber development between injection well and production well. A larger heating chamber could be developed based on the synergetic effect of electrical heating and CO2 injection of the new process. It is found that CSEAGD is more feasible for conventional heavy oil (viscosity lower than 10000 mPa·s under reservoir condition) production, accordingly 3 – 5 PV CO2 could be sequestrated in place depending on the reservoir condition, and input electrical power is larger than 1.0 MW, rational CO2 injection intensity is 50 – 100 m3/d·m, and a larger well distance is recommended.

In the CSEAGD process, CO2 sequestration and electrical heating are combined to enhance heavy oil production due to its environment-friendly feature, water free injection, and competent oil recovery compared to conventional SAGD process. Moreover, flue gas, nitrogen, or natural gas could be injected to replace CO2 or with CO2 together according to the actual condition. It has already been selected as the potentional and prospective offshore heavy oil recovery method in Bohai oilfield.
Physical and Numerical Simulations of Subsurface Upgrading using Solvent Deasphalting in a Heavy Crude Oil Reservoir
Authors: Ovalles C. , Rogel E. , Alboudwarej H. , Inouye A. , Benson I.P. , Vaca P.
Published: May 2015

Physical and numerical simulations of subsurface upgrading using solvent deasphalting (SSU-SDA) at laboratory conditions will be presented using a heavy crude oil and propane as solvent. In this work, propane flood experiments were carried out in a live crude oil (8.8°API) saturated sand at 120°F and 1000 psi. The results showed oil recovery of 85 wt.% with increases of API up to 14°API for the produced crude oil. Using lab characterization data, a new asphaltene precipitation model was developed that involves four pseudo components to numerically simulate the lab experiments. The pseudo components used are Deasphalted Oil, Heavy Fraction, and Soluble and Solid Asphaltenes. History match showed very good agreement between the experimental and calculated oil and gas rates and cumulative oil. Also, reasonably good match between lab and theoretical API of the produced oils was found throughout the propane flood experiments. Using this model, a field-scale one-well pair in SAGD configuration was simulated for steam only and two steam+ propane cases (10:1 and 1:1 vol. ratio) in a typical heavy crude oil reservoir. Results showed accelerated oil production and higher API crude in the presence of propane in comparison with the steam only case. For the 1:1 steam/propane case, the model predicted that the oil quality improved enough to make the oil transportable through a pipeline. Subsurface upgrading via solvent deasphalting is an innovative concept that has the potential of being a game-changer technology in terms of acceleration of oil production, lower CAPEX and OPEX and environmental benefits. The results presented show the potentiality of SSU-SDA for the exploitation of the vast reserves of heavy and extra heavy oils available in the world.
Coupled Reservoir and Geomechanical Modeling of Sand Production in Waterflooding of Heavy Oil Reservoirs
Authors: Nassir M. , Walters D. , Yale D. P. , Chivvis R. , Turak J.
Published: May 2015

Optimizing the efficiency of the waterflood displacement process in heavy oils is critical to reaching the oil recovery goals. However, in the process of finding an economic and stable throughput for the process, in some cases significant sand production and generation of wormholes have resulted in premature water breakthrough and channelling destroying volumetric efficiency. In order to understand such events, a simulation study using a coupled reservoir and geomechanical simulator was used to determine the physics controlling the initiation and propagation of dilated zones resulting from sand production giving the premature breakthrough. An attempt was made to identify the importance of well configuration and what operating constraints can be altered to reduce the risk of these breakthrough events.

The complex physics of sand production during oil recovery requires it to be modeled as a coupled process: multiphase fluid flow causing transient pressure gradients and geomechanics to calculate the resultant stress variation, permeability enhancement and shear/tensile failure around the induced dilated zone and finally coupling failure criterion for the dilated zone propagation combining pressure gradient and effective stress. A force balance criterion calculates the threshold fluid pressure gradient for sand mobilization based on the effective confining stresses in each numerical element. The stress variation across the loosely supported sand body (damage zone) at the edge of a dilated zone is captured by an elasto-plastic constitutive model using a Mohr-Coulomb shear failure surface combined with softening of the Young's modulus.

The application of the coupled simulator in modeling waterflooding reveals critical insights regarding the significance of different factors contributing to the sand production problem. Multiphase flow, over vs. under-injection, and inter-well pressure gradient effects are critical to controlling the sand production initiation and evolution. Gas liberation below bubble point pressure conditions causes excessive pressure gradient and increases the possibility of sand production. The oil/water relative permeability impact emerges if the mixture mobility at a certain fraction is lower than the end points. As dilated zone geometry appears to follow the weakest zones often associated with high permeable layers; it highlights the significance of the reservoir heterogeneity in contributing to the sand production problem. The results of the current study add understanding to the significance of different mechanisms contributing to sand production and may be used to help mitigate the premature breakthrough problem observed in many waterflooding operations.
Optimized Solvent for Solvent Assisted-Steam Assisted Gravity Drainage (SA-SAGD) Recovery Process
Authors: Khaledi Rahman , Boone Thomas J. , Motahhari Hamed Reza , Subramanian Ganesan
Published: May 2015

Solvent Assisted-Steam Assisted Gravity Drainage (SA-SAGD) process is an enhancement to SAGD recovery technology. In this process a hydrocarbon solvent is injected simultaneously with steam to accelerate the oil production rate and reduce steam-to-oil ratio (SOR) compared to classical SAGD. SA-SAGD is a complex process; its physics and mechanisms are not fully understood. ExxonMobil and its affiliate Imperial Oil have been investigating SA-SAGD through an integrated research program that includes fundamental laboratory work, advanced numerical simulation studies, laboratory scaled physical modeling, and field piloting. This research program aims at in-depth understanding of process physics and mechanisms, evaluating process performance and behavior, and improving SA-SAGD recovery technology.

This paper focuses on SA-SAGD optimization and assessing the effects of operating conditions and solvent choice on the process performance. The complex solvent-steam phase behavior and their interaction under reservoir operating conditions are investigated in the current work. Phase behavior analysis shows that the solvent boiling range affects solvent-steam condensation temperature at the condensation and mixing front and consequently it affects the solvent effectiveness in terms of performance enhancement. The effect of phase behavior on SA-SAGD performance has been evaluated by analyzing experimental and simulation performance data. It is shown that the composition of injected fluid significantly affects the process performance. It is also shown that the solvent composition can be customized to improve SA-SAGD process performance under different operating conditions.
Monitoring and Optimization of an In-Situ Combustion Pilot Applying STAR™ Technology
Authors: Gil E. , Quintero N. M. , Rojas L. A. , Fuenmayor M. , Farouq Ali S.
Published: May 2015

An in-situ combustion (ISC) pilot project was operated in the Quifa heavy oil reservoir in Colombia from Nov 2011 to July 2014. A modified inverted-nine spot pattern was used. As part of the project all wells were instrumented with pressure and temperature devices.

Parameters such as bottom hole temperature and pressure, gas composition (N2, CO2, CO, O2, SO4, H2S and hydrocarbons), water composition (minerals, pH), oil gravity and gas, oil and water production rates were measured and analyzed daily in order to control the combustion process resulting in improving the volumetric sweep efficiency and oil recovery factor. The continuing monitoring of these variables helped redirecting the combustion front, optimizing air injection and increasing production.

This paper introduces the STAR™ (Synchronized Thermal Additional Recovery) technology, based on ISC concepts, which aim increase the recovery factor and creating value in ISC in a heavy oil reservoir. STAR™ is based on the Synchronization Integrated Model (SIM), a suite of software applications which help to generate the main combustion-related parameters such as H/C ratio, oxygen utilization, air-oil ratio (AOR), air requirement, etc.; evaluate the process performance and identify the position of the combustion and fluids fronts in real time.
Case study of Solvent-Assisted Start-up in Fengcheng SAGD Project
Authors: Wu Yongbin , Li Xiuluan , Zhao Rui , Li Jun , Liu Xueqi , Zhou You , Du Xuan
Published: May 2015

Effective communication between the injector and producer with a reasonable conformance during SAGD start-up phase is crucial for the success of SAGD conversion and the following ramp-up phase. The start-up operation normally relies on heat conduction mechanism to establish heat and fluid communication between the wells. For super heavy oil reservoirs in Fengcheng project in China, since the pay zone has low thermal conductivity and extremely high oil viscosity, establishing the temperature profile required for SAGD conversion using conduction as the only heating mechanism is not efficient and can take 150 to 180 days to achieve. In order to shorten the circulation time and accelerate the ramp-up phase after SAGD conversion, an approach using solvent injection with steam simultaneously to enhance injectivity was successfully designed and implemented.

This paper reviews the design criteria, tests the thermal properties of cored samples, selects the typical wellpair based on geological modeling results, carries out the reservoir engineering design of solvent injection using CMG-STARS, and discusses the implementation performance of warm solvent injection in the start-up phase of a pilot wellpair in Fengcheng project. It also compares production responses of solvent-treated wellpair with other wellpairs with comparable reservoir properties in the same pad by conventional start-up to evaluate the performance of the designed pilot.
Impact of Formation Dilation-Recompaction on Development of Cyclic Steam Stimulation (CSS) in an Unconventional Heavy-Oil Reservoir: Seal's Cadotte Case
Authors: Jamaloei B. Yadali , Singh A. R.
Published: May 2015

Murphy has commenced horizontal CSS at Cadotte (Seal Lake, Peace River Oilsands). Cadotte is an unconventional reservoir due to compositional gradient, faulting, water pockets, and variations in oil viscosity, rock dilation/fracturing and pay-zone thickness. Gravity and viscosity are marked by declining quality with depth, biodegradation and compartmentalization.

High oil viscosity and low water mobility at Cadotte cause low initial injectivity. High injectivity during CSS is achieved by high pressure injection to fail the formation mechanically and trigger fracturing and deformation (dilation-recompaction triggers relative permeability hysteresis). Evidence of dilation at Cadotte includes greater steam injectivity than is expected and surface uplifts (larger than can be attributed to thermal expansion/tensile fracturing).

History-matching high injectivities is challenging when reasonable fracture lengths/rock compressibilities are used. To match injectivities, most simulations (Cold Lake/California CSS) have either used larger compressibility (‘spongy-rock’ approach) or long fractures. Spongy-rock approach predicts a steady increase in injection pressure, whereas in early cycles pressures increase and then level off for most of the cycle.

We describe enhancements made to a commercially-available simulator to incorporate modeling of deformation and relative permeability hysteresis to match injection/production pressures at Cadotte that are otherwise difficult to reproduce. The geomechanical model explains surface heave and high injectivity caused by dilation due to shear failure, increase in pore pressure/formation compressibility, and decrease in effective stress: A dilation pressure is specified, below which behavior is elastic (low compressibility) and above which, higher compressibility is used. Above a maximum porosity, further dilation is not permitted (low compressibility). The hysteresis model calculates grid-block relative permeabilities that lie on/between imbibition-drainage curves, making it possible to use laboratory-derived relative permeabilities and still match field WOR.

Impacts of dilation-recompaction factors (fracturing pressure, maximum pressure, dilation pressure, recompaction pressure, and formation compressibility) are quantified through field results, history-match/sensitivity analysis, performance optimization, and uncertainty assessment, utilizing reservoir simulation, Latin hypercube designs and Monte Carlo simulation.

Addressing geological/reservoir/operational variances, this modeling project helps determine optimum CSS development at Cadotte. It provides insight on how to screen the reservoir/operational parameters for successful CSS application in geologically-complex unconventional reservoirs with varying PVT behavior.
Mini-Frac Analysis in Oilsands and their Associated Cap Rocks Using PTA Based Techniques
Authors: Bachman Robert , Afsahi Behnaz , Walters Dale
Published: May 2015

The Alberta Energy Regulator (AER) requires mini-frac tests to be performed on thermal or polymer injection projects as part of the licensing process. Mini-fracture closure stress in the cap rocks is the key item used in determining the maximum operating pressure (MOP) for injection wells. The MOP has a significant impact on the economics of the project. This paper will establish a physics based interpretation method that covers all injection/fall-off mini-frac tests.

In the field, mini-frac tests are typically performed with multiple injection/fall-off cycles (usually 5 to 7 cycles) on each zone. Multi cycle testing is unique to the oilsands and their associated cap rocks. Multiple zones are also tested in a well, in both pay intervals (typically McMurray sands) and cap rocks (Clearwater shales etc.). Each cycle is analyzed for closure events and hopefully a consistent stress is found for each zone. Industry currently faces a conundrum as there is no agreement among analysts as to how to interpret these tests. As a result, reports submitted to the AER follow different methodologies. This may partially explain the wide range of reported closure stresses within individual basins.

This paper will show using field mini-frac data that traditional interpretation techniques can lead to ambiguities/incorrect interpretations. These issues can be overcome by using a pressure transient analysis (PTA) based interpretation approach. PTA has a long history of analyzing injection/fall-off and production/build-up tests where the rock fabric does not change during the test. The PTA interpretation methodology has remained remarkably consistent over the past 25 years. It can be summarized as follows: first identify flow regimes with a special kind of derivative plot, and second use flow regime specific specialized plots to calculate formation properties. This paper will show that PTA can now also handle dynamic fracturing (i.e. mini-fracturing) and all of its associated special cases; which include pressure dependent leak-off, height recession/transverse storage and tip extension.

Mini-frac analysis is now just a sub-set of the larger PTA methodology. It has the added advantage in that a rules based procedure can be established for the entire interpretation workflow.
Practical Data Mining and Artificial Neural Network Modeling for SAGD Production Analysis
Authors: Ma Zhiwei , Liu Yaqi , Leung Juliana Y. , Zanon Stefan
Published: May 2015

Quantitative evaluation of steam-assisted gravity drainage (SAGD) performance of heterogeneous reservoir is important for reservoir management and optimization of development strategies for oil sand operations. Although conventional commercial simulators are capable for detailed appraisal SAGD recovery performance, they are usually deterministic and computationally-demanding. Artificial intelligence approaches can be employed as a complementary tool for production forecast and pattern recognition of highly non-linear relationships between system variables.

In this paper, a comprehensive dataset, consisting of petrophysical log measurements, production and injection profiles is assembled from various publicly available sources, encompassing ten different SAGD operating fields with approximately two hundred well pairs. Only fields with complete data records are selected. Artificial neural network (ANN) is employed to facilitate the production performance analysis. Predicting (input) variables that are descriptive of reservoir heterogeneities and operating constraints, including log-derived petrophysical parameters, dimensionless shale index, effective numbers of producers and injectors for a given well pair, total production time and cumulative steam injection, are formulated, while parameters pertaining to cumulative production and steam-to-oil ratio are considered as prediction (output) variables. Principal components analysis (PCA) is performed to reduce the dimensionality of the input variables, improve prediction quality and limit over-fitting. Clustering analysis is integrated to identify internal groupings among data. Finally, statistical analysis is conducted to study the influences of data uncertainty because of limited size of field dataset and imprecise log-interpretation criteria, together with model parameter uncertainty due to learning algorithm and initialization on the final ANN predictions. Workflows involving Monte Carlo and bootstrapping methods are applied successfully. A comprehensive uncertainty analysis using an actual SAGD dataset is a novel contribution.

The modeling results are demonstrated to be both reliable and acceptable. This paper demonstrates the combination of artificial-intelligence approaches and data-mining analysis can be implemented in a practical manner to analyze large amount of field data, which is often prone to uncertainties and errors, with high reliability and feasibility. Considering that many important variables such as bottom-hole pressures, PVT properties, permeability measurements, multi-phase flow functions and thermal conductivities are typically unavailable in the public domain and, hence, are missing in the dataset, this work demonstrates how practical data-driven analysis approaches can be tailored to construct models capable of predicting SAGD recovery performance from only log-derived and operational variables. Another advantage of the proposed approach is that it can be updated when new information is obtained.
Heavy Crude Oil Dewatering Processes for Fluid Property Measurements: Comparison, Impact, and Suitability of Methods
Authors: Zhao Hongying , Memon Afzal , Gao Jinglin , Taylor Shawn David , Sieben Donald , Ratulowski John , Alboudwarej Hussein , Pappas James , Creek Jefferson
Published: May 2015

A representative clean heavy oil sample (<1% BS&W) is crucial to obtain accurate fluid property data, which are required for heavy oil production, processing, and transportation designs. However, it is always a challenge to remove water from a heavy oil sample (<20° API) due to its near-water density (10° API) and high viscosity (slow separation). The objectives of this study include qualifying three heavy oil dewatering methodologies, determining their impact on heavy oil properties, and recommending suitable method(s) for preparing heavy oil samples for laboratory fluid phase behavior and property measurements.

The three demulsification methods – centrifugation, the addition of demulsifiers, and distillation – were systematically evaluated and compared. Three dead heavy oil samples ranging from 20 to 11 API gravity degrees and with viscosities ranging from 100 to 5,000 mPa·s at 310.9 K (38°C) were selected. A stable emulsion with a 30 vol% synthetic brine were prepared using each heavy oil sample, which was used to evaluate each of the demulsification methods. Viscosity, density, and composition of the dewatered samples were measured and compared with the corresponding original oil data.

This study demonstrated that centrifugation had the minimum impact on sample properties, although it was difficult to reduce the residual water content below the dewatering target of less than 1 wt%, especially for sample densities nearest the water density. The addition of chemical demulsifiers followed by mild centrifugation resulted in samples that met the dewatering target. The change in fluid properties caused by the demulsifier method was similar to the minor changes observed by the centrifugation method. Distillation could remove water from all three emulsions to below the dewatering target, if appropriate experimental procedures were followed. However, distillation had the strongest impact on dewatered oil properties due to the loss of light/intermediate components, despite precautions to minimize the mass loss.

In current open literature, the effect of the heavy oil sample preparation procedure on the measured heavy oil properties and PVT data is rarely reported in detail, which makes it a challenge to properly perform the data interpretation and use them in relative modelling and design work. This simple, systematic study provides insight into the effect of three common dewatering procedures and guidance for developing reliable laboratory sample preparation protocols for heavy oils.
Non-Linearity and Stress-Dependency In Unconsolidated Formations and the Associated Impacts on Thermal Recovery: An Analytical Assessment
Authors: Hosseini Amir H
Published: May 2015

In thermal recovery from unconsolidated oilsands reservoirs and in association with fluid mobility, formation compressibility and modulus of elasticity are closely related to pressure transient and stress redistribution behavior, which can collectively affect the steam chamber development. The non-linearity and stress-dependency in bulk compressibility and modulus of elasticity of rocks has been captured through the development of elegant constitutive models (e.g. nonlinear elastic hyperbolic model) and has been readily integrated into coupled reservoir-geomechanical simulation packages. To assess the significance of these nonlinearities for reservoirs with different initial stress states, this paper presents an analytical study where the associated impacts on the redistribution of stress (stress-paths) and the onset of geomechanical mobilization (shear dilation) under the assumption of uniaxial deformation are quantified. Within the scope of this paper, (semi-) analytical modeling is conducted while special attention has been devoted to (1) the vast range of depths of the existing oilsands reservoirs and the associated implications on the initial stress distribution as well as stress redistribution due to steam/water injection, (2) the impacts on the onset of geomechanical mobilization within the practical ranges of injection pressures, and (3) the evaluation of geomechanical mobilization potential for thermal (steam injection) versus non-thermal (cold water injection) pressurization. The results show that (1) the potential impact of stress dependency on the variability of the geomechanical properties (modulus of elasticity, Poisson's ratio and formation compressibility) is more significant for shallow reservoirs as compared to mid-depth and deep reservoirs, (2) the injection pressure required to onset the geomechanical mobilization may be under/overestimated if the non-linearity in the mechanical properties is overlooked, and (3) the thermal geomechanical mobilization (steam injection) may have a higher potential within practical ranges of operating pressures as compared to non-thermal techniques (cold water injection), especially for shallower reservoirs. The inherent limitations of the analytical workflows as well as the requirements of supporting efforts through coupled reservoir-geomechanical simulations are also discussed.
Surveillance Techniques for Recovery Factor Optimization in a High Viscosity Unconsolidated Sand Reservoir
Authors: Aguero S. D. , Best R. Ortiz , García M. Perea , Cremonini A. S.
Published: May 2015

The current article describes waterflooding surveillance techniques applied in El Corcobo Norte and nearby fields, operated by Pluspetrol S.A., in the northeast margin of Neuquén Basin. The main productive target is the Centenario formation, a relatively shallow unconsolidated sandstone reservoir. The API gravity is 19° and the oil viscosity under reservoir conditions is between 150 and 250 cP.

Producer and injector well completion is performed applying the so called CHOPS technique (Cold Heavy Oil Production with Sand), which consists of promoting sand production during completion by producing at high rates. Sand production causes the generation of caverns and “wormholes” that increase productivity/injectivity indexes that are necessary to achieve economical productions. Due to the low original reservoir pressure (30 kg/cm2) and fast decline of primary production, it was necessary to support reservoir pressure from the very beginning of the field's operation. The heterogeneity caused by the CHOPS technique and the high oil viscosity represent a challenge for waterflooding performance. However, important waterflooding response was observed in producer wells. Strong water wettability of the reservoir rock and reservoir continuity favor displacement and volumetric efficiencies.

Waterflooding surveillance relies on strong data acquisition of injection and production, which allows, among others, daily injection/production parameter revision, weekly revision for producer well extraction, monthly revision for rates and VRR (voidage replacement ratio), and processing factors (produced or injected pore volumes a year). With the objective of promoting a homogeneous sweep and lower water cuts in producer wells a strategy was designed to determine specific injection and production rates.

The constant application of this surveillance strategy and constant modification of injection and production regime have allowed to obtain recovery factor as high as 20% in the more mature zones in only 6 years of production and to sustain a production plateau during this time. On the other hand, this continuous modification generates uncertainties for forecasting the behavior of the field production and therefore the ultimate recovery factor.

Additionally, actions taken to increase oil production in the field have led to severe producer-injector channeling issues, which affect negatively in oil recovery and need to be prevented in order to optimize ultimate recovery.

Regarding this topic, empirical limits were defined to avoid channeling between producer and injector, and also remediation techniques were developed to recover channeled wells.
Rigorous coupling of geomechanics and thermal-compositional flow for SAGD and ES-SAGD operations
Authors: Garipov T. T. , Voskov D. V. , Tchelepi H. A.
Published: May 2015

Steam Assistant Gravity Drainage (SAGD) is widely used to recover heavy oil and bitumen reservoirs. Typical SAGD operations involve a pair of horizontal wells separated vertically. Steam, or a steam-solvent mixture (e.g., Expanding- Solvent SAGD), is injected into the upper well to form a steam chamber and mobilize oil, which drains to the lower production well. Significant mechanical stresses associated with this process can increase the risk of fracturing the reservoir, or cap-rock. We perform a fully-coupled thermal-compositional-mechanical numerical simulation of SAGD and ES-SAGD processes for a typical bitumen reservoir in the Fort McMurray region of Alberta, Canada. A mixed finite-volume approximation for the flow and a Galerkin finite-element approximation for the mechanics are used, and the resulting set of nonlinear equations are solved using a fully implicit formulation. The two discretizations share the same unstructured grid. We demonstrate that thermo-mechanical effects can be quite significant in SAGD operations. The sharper gradients associated with the standard SAGD process increase the risk of damaging of the cap-rock. On the other hand, ES-SAGD operations lead to more dispersed temperature and pressure distributions, which decreases the possibility of damaging the cap-rock.
Bridging the Gap: An Integrated Approach to Solving Sustained Casing Pressure in the Cana Woodford Shale
Authors: Landry G.. , Welty R. D , Thomas M.. , Vaughan M. L. , Tatum D..
Published: May 2015

Many wells in the Cana-Woodford shale suffer from chronic sustained casing pressure (SCP). With more stringent SCP regulations on the horizon, operators need a way to prevent SCP effectively during primary cementing because remediation can prove costly or detrimental to business. At the start of a recent project virtually all cement bond logs showed poor coverage and a lack of zonal isolation. Due to the poor cement sheath bonding, SCP was occasionally observed before fracturing and almost always occurred after fracturing. This paper discusses a method that has resulted in a high success rate in preventing SCP - where previously, failure was common.

An integrated approach between multiple service company operations and operator was used to address the cement bonding issues and the long-term integrity of the cement sheath. The ultimate objective was to not have any SCP on any annulus of the well for the lifetime of the well. Initially, high-resolution ultrasonic bond logs were run to evaluate slurry placement and methodologies. Placement of the slurry around the casing was then optimized using laboratory testing and modeling software based on lessons learned from log evaluation. The success of the engineered approach was evaluated with ultrasonic logs utilizing flexural attenuation, thereby validating simulations. Finally, the long-term set cement properties were evaluated through the use of stress analysis software, which simulated stimulation treatments and their effect upon the mechanical properties testing.

Cement placement was optimized with an oil-based mud (OBM) recovery in mind. Using simulation software, centralization of the production casing was evaluated, and an optimized frictional pressure hierarchy then designed. A cement bond log was run to evaluate the proposed solution. The results proved that zonal isolation was achieved throughout the curve and into the casing-to-casing section. The logs showed excellent coverage in this well relative to its peers and the best results to date. Continued monitoring showed no casing pressure after stimulation and 1.5 years of production. The operator's other seven wells in this section, which did not have the engineered approach applied, showed SCP immediately after stimulation.

The engineered placement method ensured complete cement coverage around casing through an optimized frictional pressure hierarchy. This multilayered approach using mechanically optimized slurries with different mechanisms of action, including self-healing, provided a comprehensive cementing portfolio that contained layers of contingency. To date, the method has a high success rate in the prevention of SCP in the Cana-Woodford shale. Unconventional gas/liquid plays have changed our industry. The methodology outlined in this paper has been successful, and the lessons learned can be applied to many other unconventional gas/liquid plays that include fracturing stimulation for development.
Cutting patterns of membrane structures
Authors: Rancic Svetozar , Zlatanovic Milan , Velimirovic Nikola
Published: May 2015

Membrane structures are very lightweight and highly optimized structures. Due
to the constant stress state, strength of materials is used optimally. In
order to prevent the occurrence of large deformations even for small external
loads, membrane structures are designed as a double curved surfaces and are
stabilized by applying prestress. Minimal surfaces has zero mean curvature
and the basic advantage is that the stress at all points and directions is
equal and there are no extreme stresses anywhere on the surface. Also have
minimal area for the given contour, so the weight and amount of material is
reduced to minimum, which make them suitable for application in architecture.
Practical realization involve process of cutting pattern generation, which
divide surfaces in parts that are developable surfaces. When patterns are
assembled and prestressed they provide three-dimensional surface. Ideally,
the cutting lines should follow the geodesics lines. We use geodesics as the
shortest path between two points on a surface. In the article we give method
for finding shortest paths on polygonal representations of surfaces follows
continual Dijkstra paradigm which, on some conditions, can give improved
accuracy on a computer despite the restriction of available memory and
execution time.
Renoprotective effect of ramipril in children with chronic renal failure: The experience of one centre
Authors: Peco-Antic Amira , Virijevic Verica , Paripovic Dusan , Babic Dragan
Published: May 2015

The objective of our study was to evaluate the changes of blood pressure
(BP), urinary protein excretion (PRT/Cr) and renal function (GFR) after
long-term administration of ACE inhibitor, ramipril. This prospective trial,
a part of the European Multicentric Escape Study, included 14 patients (5
girls and 9 boys), meanage 11 years, with congenital renal malformations. The
basic inclusion criteria were stable chronic renal failure (CRF) and mean
arterial pressure (MAP) above 50 percentile defined by 24-hour ABPM or
earlier antihypertensive medication. The patients were studied 6 months
before and up to 36 months after the introduction of ramipril therapy. The
dosage of ramipril ranged from 4.7 to 7.7 mg/m2 SBA, mean 37.8 (?4.03) mg/m2
SBA. The patients were controlled every two months for BP, proteinuria and
GFR, while 24-hour ABPM was performed in 6 months. The significant decrease
of regular and 24-hour ambulatory blood pressure (ABP), systolic, diastolic
and MAP, was found within the first months of treatment, while
ramipril-induced reduction of proteinuria and slowing down of GFR were
delayed. BP did not differ significantly among patients, but antiproteinuric
effect and influence on GFR showed large individual variations.
Antiproteinuric and antihypertensive effects of ramipril correlated with
underlying proteinuria, GFR and blood pressure. However, there was no
constant relationship be?tween changes of proteinuria and BP. Ramipril has
been shown to: lower BP significantly, decrease proteinuria slowly, and
significantly decelerate GFR after 18 months of treatment. Considering
favorable preliminary results of lower BP, decrease of proteinuria and
decelerated GFR, an optimal renal protection by long-term therapy with ACE
inhibitors may be expected in children with CRF caused by congenital renal
malformations.
Human β-Cell Proliferation and Intracellular Signaling: Part 3
Authors: Stewart Andrew F. , Hussain Mehboob A. , García-Ocaña Adolfo , Vasavada Rupangi C. , Bhushan Anil , Bernal-Mizrachi Ernesto , Kulkarni Rohit N.
Published: May 2015

This is the third in a series of Perspectives on intracellular signaling pathways coupled to proliferation in pancreatic β-cells. We contrast the large knowledge base in rodent β-cells with the more limited human database. With the increasing incidence of type 1 diabetes and the recognition that type 2 diabetes is also due in part to a deficiency of functioning β-cells, there is great urgency to identify therapeutic approaches to expand human β-cell numbers. Therapeutic approaches might include stem cell differentiation, transdifferentiation, or expansion of cadaver islets or residual endogenous β-cells. In these Perspectives, we focus on β-cell proliferation. Past Perspectives reviewed fundamental cell cycle regulation and its upstream regulation by insulin/IGF signaling via phosphatidylinositol-3 kinase/mammalian target of rapamycin signaling, glucose, glycogen synthase kinase-3 and liver kinase B1, protein kinase Cζ, calcium-calcineurin–nuclear factor of activated T cells, epidermal growth factor/platelet-derived growth factor family members, Wnt/β-catenin, leptin, and estrogen and progesterone. Here, we emphasize Janus kinase/signal transducers and activators of transcription, Ras/Raf/extracellular signal–related kinase, cadherins and integrins, G-protein–coupled receptors, and transforming growth factor β signaling. We hope these three Perspectives will serve to introduce these pathways to new researchers and will encourage additional investigators to focus on understanding how to harness key intracellular signaling pathways for therapeutic human β-cell regeneration for diabetes.
Weight Management in Type 2 Diabetes: Current and Emerging Approaches to Treatment
Authors: Van Gaal Luc , Scheen André
Published: May 2015

Diabetes is a growing global health concern, as is obesity. Diabetes and obesity are intrinsically linked: obesity increases the risk of diabetes and also contributes to disease progression and cardiovascular disease. Although the benefits of weight loss in the prevention of diabetes and as a critical component of managing the condition are well established, weight reduction remains challenging for individuals with type 2 diabetes due to a host of metabolic and psychological factors. For many patients, lifestyle intervention is not enough to achieve weight loss, and alternative options, such as pharmacotherapy, need to be considered. However, many traditional glucose-lowering medications may lead to weight gain. This article focuses on the potential of currently available pharmacological strategies and on emerging approaches in development to support the glycemic and weight-loss goals of individuals with type 2 diabetes. Two pharmacotherapy types are considered: those developed primarily for blood glucose control that have a favorable effect on body weight and those developed primarily to induce weight loss that have a favorable effect on blood glucose control. Finally, the potential of combination therapies for the management of obese patients with type 2 diabetes is discussed.
Smoke or Fire? Acute Pancreatitis and the Liraglutide Trials
Authors: Gale Edwin A.M.
Published: May 2015

Over the past few years, substantial clinical data have been presented showing that incretin-based therapies are effective glucose-lowering agents. Specifically, glucagon-like peptide 1 receptor agonists demonstrate an efficacy comparable to insulin treatment with minimal hypoglycemia and have favorable effects on body weight. Thus, many of the unmet clinical needs noted from prior therapies are addressed by these agents. However, even after many years of use, many continue to raise concerns about the long-term safety of these agents and, in particular, the concern with pancreatitis. This clearly remains a complicated topic. Thus, in this issue of Diabetes Care, we continue to update our readers on this very important issue by presenting two studies evaluating incretin-based medications and risk of pancreatitis. Both have undergone significant revisions based on peer review that provided significant clarification of the data. We applaud both author groups for being extremely responsive in providing the additional data and revisions requested by the editorial team. As such, because of the critical peer review, we feel both articles achieve the high level we require for Diabetes Care and are pleased to now present them to our readers. In keeping with our aim to comprehensively evaluate this topic, we asked for additional commentaries to be prepared. In the narrative outlined below, Prof. Edwin A.M. Gale provides a commentary on the report that focuses on clinical trials of liraglutide in the treatment of diabetes. In the narrative that follows Prof. Gale’s contribution, Dr. Laurent Azoulay provides a commentary about the remaining uncertainty in this area and also discusses the results from a nationwide population-based case-control study. From the journal’s perspective, both of the articles on pancreatitis and incretin-based therapies reported in this issue have been well vetted, and we feel both of the commentaries are insightful.

—William T. Cefalu

Editor in Chief, Diabetes Care
Key words analysis as identifier of implementation of the European Landscape Convention into the strategic documents of regions, towns and rural settlements
Authors: Šebo Dušan , Huba Mikuláš
Published: May 2015

The implementation process of the European Landscape Convention (ELC) still does not receive sufficient academic attention. Its reflection in Slovak Republic municipal strategic documents has especially been neglected. This article presents a simple but appropriate method of rectifying this inadequacy. An analysis of ELC key words occurrence resulting from screening three urban and three rural municipal strategic documents from a region with important cultural-landscape features is presented. A comparison of the results with actual landscape changes is also introduced.
Landscape diversity and biodiversity of Fann Mountains (Tajikistan)
Authors: Rahmonov Oimahmad , Majgier Leszek , Andrejczuk Wiaczesław , Banaszek Jarosław , Karkosz Dominik , Parusel Tomasz , Szymczyk Artur
Published: May 2015

Rahmonov O., Majgier L., Andrejczuk W., Banaszek J., Karkosz D., Parusel T., Szymczyk A.: Landscape diversity and biodiversity of Fann Mountains (Tajikistan). Ekologia (Bratislava), Vol. 32, No. 4, p. 388-395, 2013.

The aim of study is a presentation of main vegetation landscape diversity and biodiversity in case of endemic species in the Fann Mountains area, in horizontal and vertical approach. In terms of biodiversity, the high-mountain ecosystems of Central Asia include the most valuable areas in the world called as hotspot, and also are exposed to intense human pressure causing the destruction of habitats. Vegetation landscapes of Fann Mountains are very diverse because of high-mountain character of this area, local climatic conditions, topography and habitats. That differentiation leads up to biodiversity and formation of unique plant landscapes and endemic species. The vegetation landscapes in altitude order are represented by forbs meadow steppe, thymes, swamp, broad-leaf forest, juniper forests, flood-plain small-leaved forest, tugai, light deciduous forest, pistachio, forbs wormwood, almond, rare vegetation with cushion-shaped species, wormwood eurotia, steppe, thorny grasses with shrub-steppe, rocks and taluses with rare vegetation alpine zones. High level of endemism in Fann Mountains is connected to natural conditions such as geological structure, relief, high-mountain ranges and climate conditions. This fact has an influence on forming mosaic biotops, often isolated by orographic barriers.
Assessment of landslide risk using gis and statistical methods in kysuce region
Authors: Barančoková Mária , Kenderessy Pavol
Published: May 2015

The landslide susceptibility was assessed based on multivariation analysis. The input parameters were represented by lithology, land use, slope inclination and average annual precipitation. These parameters were evaluated as independent variables, and the existing landslides as dependent variables. The individual input parameters were reclassified and spatially adjusted. Spatial analysis resulted in 15 988 combinations of input parameters representing the homogeneous condition unit (HCU ). Based on the landslide density within individual units, the HCU polygons have been classified according to landslide risk into stable, conditionally stable, conditionally stable and unstable (subdivided into low, medium and high landslide risk). A total of 2002 HCU s were affected by landslides, and the remaining 13 986 were not affected. The total HCU area affected by landslides is about 156.92 km
Non-surgical management of endodontic failure - An observational study
Authors: Prajapati K , Joshi N
Published: May 2015

In the present study, possibility of non-surgical endodontic re-treatment for correction of symptomatic endodontic failure with and without periradicular pathosis was evaluated both clinically and radiologically. The main objective of this study was also to assess, verify and establish the non-surgical re-treatment method as primary approach to resolve endodontic failures irrespective of sex. A total 69 cases of endodontic failure with or without periapical pathosis were studied of which 24 (34.78%) were male and 45 (65.21%) were female .The mostly affected teeth were Mandibular 1st molars 19 in number (27.53%) followed by Maxillary central incisors 17 in number (24.63%). After one year follow up, the final outcome was success- 47 (75.80%), doubtful- 2 (3.22%) and failure-13 (20.96%).DOI: http://dx.doi.org/10.3126/jcmc.v5i1.12561