bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Step Change in Shallow Extended Reach Wells in Venezuela Enables Drilling Optimization and Increased Heavy Oil Production
Authors: Chamat Elias , Cuadros Guillermo , Trejo Ely , Scrofina Jose , Cermeno Elio , Rodriguez Oscar
Published: May 2015

In an operation in the Venezuelan Faja, well placement and rotary steerable systems (RSS) enabled drilling faster, longer, and shallower ERD wells than those that have been drilled with mud motors in the field over last 20 years. The results demonstrate a performance step change in this area.

Standard drilling in the Faja includes dogleg severity (DLS) requirements as high as 8°/100 ft and rates of penetration (ROPs) as fast as 2,000 ft/hr; these were perfect conditions for using mud motors to drill build sections and horizontal wells. As drilling in the Faja moved south, reservoirs at true vertical depth (TVD) from 1,200 to 1,600 ft started to be developed. Shallow reservoirs and even higher DLS made it inefficient to drill the long 4,000-ft extended reach sections planned as this requires multiple pipe swaps to redistribute heavy bottomhole assembly (BHA) components and wiper trips to clean the hole to allow weight-on-bit (WOB) transmission to reach the bit.

To reduce tortuosity, torque and drag, and stuck-pipe events; to improve hole cleaning, WOB transmission, and ROP; and to drill longer horizontal sections, a point-the-bit RSS was tried for the first time in Junin division. The first RSS well drilled in a shallow horizontal well exceeded all objectives and expectations set. Seven more horizontal sections drilled with the same RSS proved the system was robust enough to break a different drilling record on each well.

The current shallow extended reach well (SERW) record in the Faja was drilled with a mud motor to 1,231 ft TVD with 4,404 ft of horizontal section and a TVD versus horizontal stepout ratio of 1:4.4. Advanced drilling engineering, bed boundary mapping LWD technologies, RSS, and improved drilling practices in six horizontal sections enabled drilling to similar ERD ratios, while breaking records for ROP, horizontal section length, and drilling and completion speed at similar TVDs.

The performance step change in the Faja accomplished through the use of RSS and novel drilling practices has enabled increasing heavy oil production through drilling longer horizontal sections and through the reduction of mud filtrate and formation damage. The performance increase along with lesser tortuosity and friction factors have allowed drilling longer horizontal sections, saving valuable rig time, producing wells earlier, and running liners to total depth (TD) trouble-free unless stopped by oil production.
Type Curves for Cyclic Steam Operations in the Grosmont Saleski Pilot and Their Implications for Recovery Mechanisms
Authors: Yang D. , Hosseininejad M. , Stewart D. , Brand S.
Published: May 2015

Type curves that are developed for bitumen recovery from the Grosmont carbonate reservoir by cyclic operation of steam injection and production through a single horizontal well, consistently match field data, thereby confirming the validity of two key simplifying assumptions: heat flow is conductive; the heat capacity of the rock dominates: This is consistent with the low porosity and high heat capacity of dolomite. As a result, heat retention in the reservoir is efficient.gravity drainage dominates the recovery mechanisms: Thermal Assisted Gas-Oil Gravity Drainage (TA-GOGD) is the dominant recovery mechanism.

The type curve method is used to evaluate unrestricted reservoir performance by quantifying operational constraints and to forecast new cycles in the pilot operations.
Thermal Formation Damage and Relative Permeability of Oil Sands of the Lower Cretaceous Formations in Western Canada
Authors: Romanova U. G. , Ma T. , Piwowar M. , Strom R. , Stepic J.
Published: May 2015

Canada ranks third in the world in terms of oil reserves which are primarily heavy oil and oil sands. In situ production of heavy oil and bitumen by thermal methods based on steam injection is a commercial technology. However, as the availability of better quality deposits is declining, the industry is moving towards development of lower quality oil sands. Lower quality oil sands are typically finer, have lower initial oil saturation and a more complex mineralogy.

Thermal formation damage associated with steam injection is discussed in the paper in regards to oil sands located in the Lower Cretaceous formations in Western Canada. The focus of the paper is the McMurray, Clearwater and Grand Rapids oil deposits. Petrographic data (thin section analysis, X-ray diffraction and scanning electron miscroscopy) and physical rock properties are used to compare three oil sand formations. Results of laboratory experiments to obtain relative permeability data and evaluate thermal formation damage are discussed. Examples of the high temperature-high pressure water-oil relative permeability and steamflood data for three formations are presented. The paper shows that thermal formation damage is reservoir specific.

A multidisciplinary approach is needed to obtain a good understanding of oil sand deposits, in particular lowerquality reservoirs. Laboratory testing to evaluate formation damage effects and obtain relative permeability data is essential for reservoir simulation and feasibility studies for a specific project.
Experimental Study on Geomechanical Dilation during Injection
Authors: Wang Xinkui , Chalaturnyk Rick , Huang Haibo , Leung Juliana
Published: May 2015

The SAGD process can be achieved only after the thermal and hydraulic communication between the injection well and the production well has been established during the start-up operation. The start-up operation involves interactions of geomechanical responses and multiple phase flow behaviors in the inter-well formation. Such interaction would have an impact on SAGD in terms of recovery performance. This paper presents an experimental study on investigating the mechanisms and mechanics of geomechanical dilation and fundamentals during cold-water injection.

A triaxial experimental program has been designed and conducted to verify geomechanical dilation through experimental measurements. A series of reconstituted water-wet/bitumen sand specimens were prepared with different fluid saturation and almost identical void ratio. Reclaimed/cleaned tailings sand from oil sands mining operations was used to prepare artificial specimens, which are representative of McMurray Formation oil sands. A water-wet or bitumen sand core plug was then tested in an environmental chamber to simulate reservoir boundary conditions in terms of stress state, temperature, and pore pressure. A series of experiments were carried out in a triaxial cell under either initial isotropic or initial anisotropic stress state. Experimental results highlight the promising potential to dramatically enhance effective permeability to water and porosity in the dilated zone with pore pressure injection at modest levels of stress anisotropy.

The lab-scale experimental data provides supports on development of numerical models for predicting SAGD start-up performance and on proactive utilization of the dilation as start-up process for in-situ oil sands development.
Geo-Mechanics of a Sugar-Cube Box: Cyclic Injection and Production in a Fractured Carbonate at the Saleski Pilot
Authors: Yang Daniel , Xu Jinze
Published: May 2015

Since 2012, horizontal wells at the Saleski pilot are operated with cyclic steam injection and production, recovering bitumen from the naturally fractured Grosmont carbonate reservoir. Steam has been injected in a continuous matter similar to SAGD, as well as in cyclic alteration with production from individual wells. Injection pressure is 50-60% of the overburden stress.

The Grosmont reservoir is a highly fractured carbonate rock with excellent reservoir properties (i.e. high fracture permeability and porosity). The targeted producing horizons in this reservoir are Grosmont C (20 m pay) and D (30 m pay) unit, which are separated by a laterally extensive, 1-2 m thick Marl.

The initial injectivity, which is superior to bitumen saturated sand reservoirs, can be explained by either high initial water mobility in the fractures or large system compressibility, or a combination of both.

Since the Grosmont C unit is highly fractured, it can be characterized as a box filled with sugar cubes. The ‘stiff’ cubes can locally be displaced if the fractures are allowed to drain. Geo-mechanical simulations with deterministic fractures allow the calculation of the system compressibility and Young's Modulus, based on variations of fracture and matrix properties. Results indicate that the fracture properties dominate the system characterization.

Using these insights, initial injectivity of a pilot well is matched with a reservoir model and a coupled geo-mechanical reservoir model to quantify the roles initial water mobility, matrix displacement and temperature play during cyclic operation of a naturally fractured reservoir.
Effects of Lithofacies and Reservoir Heterogeneity on Improved Oil Recovery Processes
Authors: Nguyen T. B. , Dang T. Q. , Chen Z. , Nghiem L. X.
Published: May 2015

A comprehensive understanding of reservoir geology plays an important role in the success of oil/gas recovery processes. Several emerging IOR (improved oil recovery) techniques have been proposed in the past decades with promising results. However, a systematic study of reservoir heterogeneity on these advanced processes has yet been presented in the literature. This paper provides one of the first comparative evaluations of the effects of reservoir heterogeneity on various IOR processes such as water flooding, CO2 flooding, Low Salinity Waterflooding (LSW) and CO2 LSWAG for a wider and more successful implementation of these projects. Since several weaknesses exist in the current simple and unrealistic models, detailed geostatistic models are employed in this study to provide a more realistic and unbiased evaluation of reservoir heterogeneity.

We first present an innovative approach that allows us to capture the critical effects of geological heterogeneity. This new approach involves the integration of geological software, a reservoir simulator and a robust optimizer in a closed-loop for generating multiple geologically driven realizations and uncertainty assessment of different recovery processes. Then a series of numerical simulations have been conducted to investigate the influences of fining- and coarsening-upward sequences on oil recovery. Finally, we evaluate the uncertainty range of reservoir heterogeneity using a large number of geological realizations with significant differences on porosity and permeability distributions. The effect of the Kv/Kh (aspect) ratio is also addressed in this study.

The simulation results indicate that the lithofacies has a dominant effect on oil recovery in all recovery processes. The coarsening-upward distribution demonstrates superior performances over the fining-upward distribution. However, it is observed that the differences on oil recovery from two stratified reservoir models are not similar in all injection methods. Although the lithofacies distribution has a slight effect on the conventional waterflooding, this effect becomes significant in CO2 flooding and more drastical in LSW and CO2 LSWAG. This observation is very important for maximizing oil recovery by taking into account the crucial effects of reservoir geology in these emerging technologies that have never been considered in the past. Additionally, the heterogeneity of lithofacies also affects the flow direction and injectivity of displacing fluids, and, consequently, influences the ultimate oil recovery factor.

Reservoir heterogeneity plays a critical role in the successes of IOR processes but it has never been comprehensively quantified, especially for some emerging techniques. Thus the results from this paper are very important to overcome the current challenges in capturing the importance of geological uncertainties in the current and future IOR/EOR projects.
On the Accuracy of Surface Movement Measurement over a SAGD Operation in Northern Alberta through Effective Survey Design
Authors: Henschel Michael D. , Sato Shinya , Lehrbass Brad , Deschamps Benjamin
Published: May 2015

Surface movement over a Steam Assisted Gravity Drainage (SAGD) operation can be related to production and injection. The amount and location of surface change can indicate the location of thermal dilation within the reservoir and may provide an indication of conformance. While the deformation expected in a SAGD operation is related to the depth of the reservoir and the stratigraphy, the typical ground movement is approximately 2-5 cm/year. This represents a relatively slow inflationary process over the ground. The movement may be confused with changes that are related to seasonal ground changes including water level changes in muskeg, for instance.

This work provides a description of the accuracy of Interferometric Synthetic Aperture Radar (InSAR) measurement techniques including corner reflectors and advanced point and neighbourhood algorithms designed for the measurement of ground movement in Northern Alberta. The paper will describe the application of these methods to measuring surface movement above a SAGD operation. Specifically, this article describes methods for the determination of the accuracy of ground movement estimates as derived from InSAR. An effective survey design is critical to the monitoring of ground movement. The location and availability of measurement points is crucial to the use of high resolution Synthetic Aperture Radar (SAR) satellites for monitoring. The design and implementation of a survey includes an understanding of the relationship between available infrastructure and the ground signal to be expected. However, a critical aspect of monitoring is a verification of the accuracy of the measurement provided. By using repeated observations and even a combination of satellites, we show how the measurement of accuracy can be provided on an operational basis.

This work provides a novel description of the calculation of accuracy of ground movement using emerging techniques in multiple-track / multiple-satellite observation of enhanced oil recovery operations.
Improvement of the Recovery Factor Using Nano-Metal Particles at the Late Stages of Cyclic Steam Stimulation
Authors: Farooqui Jamal , Babadagli Tayfun , Li Huazhou Andy
Published: May 2015

Cyclic steam stimulation (CSS) has recently re-gaining attention as an alternative to the current applications, such as SAGD or CHOPS. However, low recovery factor and excessive water production are critical problems to tackle. These late-stage experiences require a revisit to the options of recovery improvement and reduction of water production at the mid- and late-stages of the cycles. This research proposes a new approach for this purpose and investigates the effects of nano-metal particles introduced into the reservoir on the recovery factor after several cycles of steam injection. We begin with CSS experiments on heavy-oil saturated sandpacks studying and clarifying the influence of the nanoparticle presence on the efficiency of the process. It is confirmed that the use of nanoparticle in the first place increases the oil recovery factor along with a higher water production. Then, one run of experiment is performed by introducing the nanoparticle in the sixth cycle of CSS treatment. It is found that a substantial increase in the recovery factor is achieved in such a simulated CSS experiment, which cannot be achieved by injecting steam alone. This experimental study on the addition of nickel particles to improve the recovery factor and extend the life of CSS process will not only add value to nano-technology use in the oil industry from a physics point of view, but will also provide insight into the operating parameters for better late- stage CSS project development.
Thinking Beyond the Conventional - A Case Story of Using a Surface Read out Wireline Device while Ranging to Reduce Risk of Failure During Drilling of a Sagd Well in Hot Zone
Authors: Ray Jeremy
Published: May 2015

Objectives/Scope

In the SAGD industry, it has become more common for operators to drill into active or pre-heated oil- sands zones. These hot zones provide for a challenging environment to drill a single well, let alone use electronics for active ranging technology for accurate wellbore placement.

This paper will discuss the intent of a new head tension-compression device and the process leading from extending conventional thinking into using it as a solution for a challenging wellbore environment. Through a case story, the challenges proposed by a client in Western Canada will be examined, as will the lessons learned from the unconventional solution.

Methods, Procedures, Process

When drilling SAGD well pairs, it is common practice to have an active ranging device placed in the “target” wellbore to aid in accurate well placement. The active ranging devices are electronic in nature and are limited to temperature exposure for reliable performance. Collaborating with the operator, a secondary measurement provided by an e-line device was used in conjunction with field proven magnetic ranging equipment in order to provide real-time feedback to surface with the purpose of mitigating risks due to the high temperatures. The diagnostic device was used to monitor the effects of pumping fluid into the wellbore in order to cool sufficiently and thus protect the sensitive electronics in the active ranging device.

The case story presented in this paper will discuss the adaptation of an existing head tension- compression sub to work in conjunction with active ranging technology, providing real-time readings to surface. These real-time readings not only measure the tension and compression of the downhole toolstring but also temperature.

Results, Observations, Conclusions

To date, this system has been used in a number of operations for operators in Western Canada in active thermal zones. Operations have successfully monitored the temperature real-time for the protection of the downhole devices in addition to evaluating the cooling methods of pumping fluids from surface.

This system now enables operators to consider further e-line interventions in wellbores with high risk of exposure by providing real time diagnostic data to allow for better decision making at surface, which will reduce risk of failure. For many operators drilling in pre-heated oil-sands formations this has proven a cost effective and desired system.

Additive information

The use of this diagnostic sub is now a proven solution to place in the target well in conjunction with active ranging technology.
Optimization of CO2 Flooding Strategy to Enhance Heavy Oil Recovery
Authors: Huang Tuo , Yang Huaijun , Liao Guangzhi , Zeng Fanhua
Published: May 2015

CO2 flooding is one of the most promising techniques to enhance both light and heavy oil recovery. In light oil recovery, the production pressure in CO2 flooding in general keeps constant in order to maintain the miscibility of injected CO2 and crude oil; while in heavy oil recovery, a depleting pressure scheme may be able to induce foamy oil flow, thus the oil recovery could be further enhanced. In this work, different pressure control schemes were tested by 1-D core-flooding experiments to obtain an optimized one. Numerical simulations were then conducted to history match all experimental data to understand the mechanisms and characteristics of different CO2 flooding strategies.

For the core-flooding experiments, 1500mD sandstone cores, formation brine and a heavy oil sample with a viscosity of about 869.3 cp at reservoir condition (55 °C and 11 MPa) were used. Before each CO2 flooding test, early stage water-flooding was conducted until the water cut reached 90%. Different CO2 injection rates and production pressure control strategies were tested through core-flooding experiments. Experimental results indicated that a slower CO2 injection rate (2ml/min) led to a higher recovery factor from 31.1% to 36.7%, compared with a high CO2 injection rate of 7ml/min; for the effects of different production strategies, a constant production pressure at the production port yielded a recovery factor of 31.1%; while a pressure depletion with 47.2KPa/min at the production port yielded 7% more oil recovery; and the best pressure control scheme in which the production pressure keeping constant during CO2 injection period, then depleting the model pressure with the injector shut-in yielded a recovery factor of 42.5% of the initial OOIP.

Numerical simulations were conducted to history match the experimental results. The same oil relative permeability curve was used to match the experimental results to all tests. Different gas relative permeability curves were obtained when the production pressure schemes are different. A much lower gas relative permeability curve and a higher critical gas saturation was achieved in the best pressure control scheme case compared to other cases. The lower gas relative permeability curve indicates that foamy oil was formed in the pressure depletion processes. Through this study, it is suggested that the pressure control scheme can be optimized in order to maximize the CO2 injection performance for enhanced heavy oil recovery.
Enhanced Thermal Well Integrity Through The Use Of A New Cement Tensile Strength-enhancing Fiber
Authors: Iremonger Simon S. , Bolt Mitchell , Lawrence Sally C.
Published: May 2015

Cement plays a vital role in maintaining the long term integrity of oil and gas wells by forming a robust and impermeable barrier and ensuring zonal isolation by restricting the flow of fluids between different geological zones. In-situ thermal stimulation methods such as SAGD place the casing cement under extreme stresses due to the rapid temperature increases that occur during initial steam stimulation. The prevailing mentality in the industry for many years was that compressive strength alone was a satisfactory predicator of a cement's ability to withstand downhole stresses. However, the stresses induced in a SAGD well are often not compressive, but rather radial in nature due to the large thermal expansion of the casing during heat up, making tensile failure of the cement more prevalent. This problem is compounded by the fact that the tensile strength of conventional oil well cements is typically only 8 – 12% of the maximum compressive strength. To best mitigate the risk of cement failure, cement with a higher tensile strength is a better choice.

In this paper a new fiber based tensile strength-enhancing cement additive for thermal oil well applications, such as those used in SAGD, is described. At an optimized loading of 0.5% by weight of blend (BWOB) the fibers gave a 20% improvement in tensile strength under mild temperatures (25–50 °C) and over 35% improvement in tensile strength at 250 °C. This significant enhancement in tensile strength occurs without significant detrimental effects on other mechanical or slurry properties. The stability of the additive is demonstrated by a full mechanical property evaluation (tensile strength, compressive strength, Young's modulus) after long-term high temperature exposure (one month at 250 °C). Extensive field testing with fiber-containing blends demonstrated that the fibers could be readily dry bulk blended on a multi-tonne scale, and successfully pumped with existing conventional dustless mixing systems. The significant enhancement in tensile strength, without sacrificing any other performance parameters, is expected to substantially improve well integrity in the demanding environments encountered in SAGD.
A Parametric Study of the Hydrodynamic Roughness Produced by a Wall-Coating Layer of Oil during the Pipeline Transportation of Heavy Oil-Water Mixtures
Authors: Rushd S. , Sanders S.
Published: May 2015

In the water lubricated pipeline transportation of heavy oil and bitumen, a thin oil film typically coats the pipe wall, which is often referred to as ‘wall fouling'. A detailed study of the hydrodynamic effects of wall fouling is critical to the design and operation of oil/water pipelines, as the viscous layer can increase the pipeline pressure loss (and pumping power requirements) by 15 times or more.

In this study a parametric investigation of the hydrodynamic effects caused by the wall coating of viscous oil was conducted. A custom-built rectangular flow cell was used as the principal apparatus. The controlled parameters include the thickness of the wall coating layer, oil viscosity and water flow rate. For each test condition, the pressure loss across the test section was measured and the hydrodynamic effect of the wall coating on the pressure loss was determined. A novel procedure using CFD simulations was developed to determine the hydrodynamic roughness. The procedure was also applied for a set of pipeloop test results published elsewhere. The effects of wall coating thickness and water flowrate on the hydrodynamic roughness were evaluated. The most significant outcome of this analysis is a new correlation for the hydrodynamic roughness produced by a wall-coating layer of viscous oil.

The knowledge gained from the current research will be beneficial for designing, operating and troubleshooting pipeline systems in which a viscous wall coating is produced, including water lubricated bitumen transport in the oil sands industry, CHOPS and SAGD surface production/transport lines. The methodology can also be extended to the analysis of any unknown hydrodynamic roughness.
Experimental Evaluation of H2S Yields during Thermal Recovery Processes
Authors: Lin Riyi , Song Duopei , Wang Xinwei , Yang Daoyong
Published: May 2015

Experimental techniques have been developed to quantitatively evaluate in-situ H2S generation as a function of solution alkalinity, SO42− concentration, and carrier gas during thermal recovery processes. Experimentally, well-designed laboratory tests have been conducted to quantify the in-situ generation of H2S in a surface passivation reactor. The reaction gases were analyzed by using a gas analyzer, while the pH values were measured by using a glass electrode after adding anions or cations into the solution. Solution alkalinity is found to restrain the formation of H2S after subtracting the amount of H2S that neutralizes alkali in the solution. H2S production increases with increasing SO42− concentrations, more evidently at a high temperature. As temperature increases, using either carbon dioxide or nitrogen as carrier gas increases the H2S production; carbon dioxide as a carrier gas, however, yields more H2S up to 57.6% than nitrogen at temperature of 200-280°C. It is suggested that effect of pH of the formation water be taken into account while predicting the produced acid gas rates.
Impact of Flow Control Devices on SAGD Performance from Less Heterogeneous to Strongly Heterogeneous Reservoirs
Authors: Su Yi , Gates Ian
Published: May 2015

Steam Assisted Gravity Drainage (SAGD) has proven itself to be a commercial success in McMurray oil sands reservoirs. In this process, steam delivered into the reservoir mobilizes bitumen which then flows under gravity to the production well. A countercurrent flow situation results where steam rises and bitumen and condensate drains within the reservoir. Given the vertical and horizontal flow within the reservoir, SAGD performance is strongly affected by reservoir heterogeneity. In the field, poor SAGD performance commonly arises from two challenges: first, steam breakthrough from the injector to the producer and second, non-uniform chambers along the length of the well pairs. Flow control devices (FCDs) offer the potential to improve SAGD performance but it remains unclear how to place and design these devices to maximize steam conformance and minimize steam-to-oil ratio. Here, to understand the behavior of FCDs in SAGD operations, detailed reservoir simulations, including wellbore hydraulic modeling, are conducted in a simple clean sand model and a detailed point bar model dominated by inclined heterolithic strata. The study includes the use of FCDs on the injector only, the producer only, as comparisons to conventional well completions cases. The results indicate that SAGD performance improved by using FCDs with better control of steam breakthrough between the wells.
A New Polymer Flooding Technology for Improving Heavy Oil Reservoir Recovery-from Lab Study to Field Application- Case Study of High Temperature Heavy Oil Field Z70
Authors: Wu Xingcai , Song Shemin , Xiong Chunming , Guo Zhiqiang , Xu Hanbing , Jiang Peijun , Zhang Jian , Zhang Yong , Chen JingJing , Tian Xiaoyan , Shao Liming
Published: May 2015

The heavy oil block field Z70 has oil viscosity of 165mPa.s and high temperature of 93°C, and is highly heterogeneous. After water injection, the water cut rose quickly and achieved 83% when oil recovery was only 7.6%. In order to control the quick rising of water to oil rate ratio, from 2001 to 2003, crosslinked polymer gel was injected as field test, but the effect was limited. Besides, the highly viscose polymer damaged the low permeability layers or zones, leading to hard water injection on some injectors. Since 2010, A new type of polymer flooding (NPF) technology has been applied and greatly improved oil recovery.

The new polymer is particle-type polymer with various particle sizes. When working, it is dispersed in injected water, and has low apparent viscosity, 1–4 mPa.s, so it is easy to be injected into formation. While the polymer particle moves into formation, the size may increase by water absorbing, and it may temporarily plug the prevailing filtration throats, making the carrying water be diverted into the relatively small pores/throats and displace the remaining oil there. The polymer particle has high deformation capacity, so it can deform and pass through the throat under the follow-up pressure, and then it will go to plug another throat. The process will be repeated again and again, so the technology can inhibit water production and enhance oil production.

The particle size and slug sequence were designed for Z70 field by physical simulation on physical models. Sub-millimeter grade of particle was suitable for some wells, and micrometer grade of particle was suitable for some other wells, while some wells need both of them. Totally 0.086PV of the dispersion fluid was injected in the whole field with the concentration of 3000mg/L. After one month injection, the water cut started decreasing quickly and the oil rate started increasing quickly. During the new polymer injection, the water cut decreased to 74.8% from 81.1%, and the oil rate doubled. During the follow-up water injection period, the water cut continued decreasing to 75%. Until now, the water cut has returned to more than 77%, but the NPF keeps taking effect, and the oil recovery is increased by 5.8%.

Summing up the lab studies and field application, NPF works through decreasing water effective permeability and overcoming the unfavorable mobility ratio. It is different from the conventional polymer flooding, which works through increasing the viscosity of the displacing phase. The new technology is more efficient, and the mechanism deserves further studying.
Integration of PC-SAFT Equation of State into Heat Assisted Solvent Recovery Simulation
Authors: Ma Mingxu , Chen Shengnan , Abedi Jalal
Published: May 2015

The accuracy of Equation of State (EoS) in phase behaviour modeling plays an important role in compositional and thermal reservoir simulations. PC-SAFT (Perturbed-Chain Statistical Associating Fluid Theory) EoS can predict solubility and density of bitumen/solvent systems more accurately than Peng-Robinson and Soave-Redlich-Kwong EoS. In this work, a simplified version of PC-SAFT EoS was integrated into a thermal reservoir simulation to model heat assisted solvent recovery process.

Bitumen was characterized into two scenarios for the simplified PC-SAFT modeling: eight pseudo-components (8-PCs) and three pseudo-components (3-PCs) using a well-developed bitumen characterization method. The solubility and density modeling ability of 3-PCs was evaluated and verified with that of the 8-PCs system. The simplified PC-SAFT with 3-PCs bitumen characterization method was then applied to generate data of K-Value, density, compressibility, and thermal expansion coefficient of each pseudo-component. The generated fluid properties were integrated with reservoir simulation to model a warm C3H8 VAPEX experiments at 40, 50 and 60 °C.

In the 8-PCs characterization, the overall Average Absolute Relative Deviations (AARDs) for the solubility and density of CH4, C2H6, C3H8 and CO2-saturated bitumen were within 6.6 % and 2.3 % respectively, and the predicted AARDs for the density of n-C5H12, n-C10H22, n-C14H30, toluene and xylene-diluted bitumen were as low as 0.9 %. Results of the 3-PCs characterization were found to be as accurate as those of 8-PCs in modeling bitumen/gas solvent systems. In addition, the results of the fluid properties were successfully integrated into commercial reservoir simulator. Relative permeability was history matched with the measured data at 40 °C, and then tested against the measured data at 50 and 60 °C. The reservoir simulation results indicated good agreement with the measured data. The numerical results showed that although bitumen viscosity decreased due to high temperature solvent, solubility was reduced at the same time, compensating the viscosity reduction effects by solvent diluting.
Mathermatical Modeling of Dynamic Mass Transfer in Cyclic Solvent Injection
Authors: Jia Xinfeng , Li Jianli , Chen Zhangxin
Published: May 2015

In a cyclic solvent injection (CSI) process, a solvent gas is cyclically injected, soaked, and released to produce heavy oil. Through this process the operating pressure is decreased and increased cyclically. This causes a dynamically changing pressure gradient across the solvent–oil mixing zone, leading to a convective mixing of solvent and oil in addition to molecular diffusion. This study aims at modeling the effect of pressure gradient-induced convection on the solvent–oil mixing process in the transition zone. A diffusion–convection model is developed to simulate the dynamic solvent–oil mass transfer in the transition zone during the CSI process. This model consists of two sub-models: a pressure model and a solvent concentration model. The pressure model considers the effect of a practical viscosity profile and the concentration model considers the effect of a dynamic convective mass transfer velocity. These two models are coupled through the convection velocity and oil viscosity across the transition zone. The entire model is semi-analytically solved, in which a piecewise linear approximation scheme is applied for the variable convection velocity and viscosity in the transition zone. Results show that during the solvent injection period, convection can significantly enhance the mixing of solvent and heavy oil. Larger solvent injection rates can be more efficient for heavy oil–solvent mass transfer. In addition, it is found that considerable solvent remains in the oil zone at the end of the production period, and this part of solvent is difficult to retrieve within a short time period.
Restoring Casing Integrity Using an Expandable Steel Patch Prior to Drilling Ahead With Minimal Reduction of Next Hole Size
Authors: Saltel Benjamin , Gonzalez Luis , McIntosh Trevor , Weems Matt
Published: May 2015

The purpose of this paper is to provide field experience feedback on achieving surface casing integrity with the use of an expandable steel patch. Casing integrity may be jeopardized during cement remediation or due to mechanical failure. If cement remediation requires casing perforations, then an expandable steel patch can be used to provide pressure integrity across the perforations. If casing pressure test cannot be achieved due to mechanical failures such as leaking DV tool or casing collar leak, a similar approach can be used to achieve pressure integrity. This paper will describe how to restore casing integrity allowing maximum pass-through diameter to continue drilling operations and maintain planned casing sizes when presented with these challenges.
Well Testing by Sinusoidal Stimulation
Authors: Zenith Federico , Foss Bjarne , Tjønnås Johannes , Hasan Agus
Published: May 2015

A new approach to testing of oil and gas wells by means of sinusoidal oscillations in flow and pressure instead of the traditional buildup test is proposed in this article. This approach allows faster testing and simultaneous testing of several wells, with no need for a dedicated test header; it can also be adjusted to strike an appropriate compromise between measurement precision and production loss. This study details various operating issues such as generation of input signals, choice of test frequencies, applicability, and interpretation of results. To demonstrate the method, both a synthetic test and several field tests are presented.
Current status, problems and control strategies of water resources pollution in China
Authors: Wu Lei , Qi Tong , Li Dan , Yang Huijuan , Liu Guoqing , Ma Xiao-yi , Gao Jian-en
Published: May 2015

The surface water of 10 major river systems across China has been under intermediate pollution with striking eutrophication problems in major lakes (reservoirs). More data from the Ministry of Environmental Protection of China showed that underground water in 57% of monitoring sites across Chinese cities was polluted or extremely polluted. Rural water pollution, the rising number of incidents of industrial pollution, outdated sewerage systems, and the overuse of pesticides and chemical fertilizers also endanger the health of rural inhabitants in China. Nearly 0.2 billion rural residents could not use drinking water in accordance with the national standard, and there were reports of ‘cancer villages' and food-borne diseases (cancer village refers to a village where a certain proportion of its inhabitants suffer from the same kind of cancer or where there is a hike in cancer incidence in that area). This study aims to raise awareness of the prevention and control of water pollution and to propose a set of national research and policy initiatives for the future safety of the water environment in China.
An assessment of farmers' willingness to participate in water trading in southern Spain
Authors: Giannoccaro Giacomo , Castillo Manuela , Berbel Julio
Published: May 2015

This study applies contingent valuation to assess farmers' willingness to trade irrigation water. We analyse farmers' willingness to pay for water and their willingness to accept the selling of water through a seasonal market, under both normal rainfall and drought conditions. A survey of 241 farmers (irrigators and non-irrigators) in the Guadalquivir River Basin and in the Mediterranean (Almanzora) Basin in southern Spain is used as a basis to construct the irrigation water supply and demand curves for both basins. Assuming that each basin operates as a single country, an international commerce framework is applied to study inter-basin trading. Results show that there is scope for both intra-basin and inter-basin markets. The equilibrium market price increases from 0.17 EUR/m3 in the baseline scenario to 0.21 EUR/m3 under drought conditions. These results are in line with observed market prices during 2006–2007. We also find a threshold volume under which start-up costs for irrigation infrastructure make it unprofitable for non-irrigators to enter the market. Finally, we conclude that farmers' ethical perspective of considering irrigation water as a non-tradable commodity constrains them from participating in such markets.
Social capital in large-scale environmental collaboration: the case of the Platte River Recovery Implementation Program
Authors: Reed Christine , Campbell Anthony , George Mike , Leuenberger Deniz , McCarty John
Published: May 2015

Environmental collaborative governance arrangements have the potential to build social capital, leading to long-term cooperation among parties with a history of conflict over water use, in particular in irrigation, hydropower production and riverine wildlife habitat. Previous research on social capital in the context of collaborative governance has emphasized small-scale grassroots initiatives where actors hold common membership in civic associations. This study explores a large-scale policy level collaborative arrangement as a case of collective action facilitated by elements of social capital, with a special emphasis on the concept of the institution as social capital. The Platte River Recovery Implementation Program is the basis for initial findings that social capital formation and cooperative implementation of innovative approaches to water policy can occur at both the local action and large-scale policy levels of collaboration.
Closing the (widening) gap between natural water resources and water needs in the Jordan River Basin: a long-term perspective
Authors: Tsur Yacov
Published: May 2015

The supply of renewable natural water available in a sustainable fashion in the Jordan River Basin, comprising Israel, Jordan and the Palestinian Authority, will soon drop below 100 m3/person/year. Drawing on recent technological progress and policy innovations, a comprehensive policy to address the region's water problems in the long run is offered. The policy has a dual goal: to satisfy the needs of a growing population (domestic, irrigation and industry) and to preserve important environmental amenities, including restoration of the Lower Jordan River and stabilization of the Dead Sea level. The gap between natural water supplies and the basic needs of the growing population will be closed by conservation and desalination; at the same time, all domestic water will be recycled and will be available for reuse in irrigation and environmental restoration. Over time the supply of recycled water that should be allocated for environmental restoration (accounting for the compensation of irrigators) will suffice to partially restore the Lower Jordan River and contribute to the stabilization of the Dead Sea. The analysis is relevant in a wide range of real-world situations, where satisfying the basic needs of a growing population and preserving environmental amenities become critical.
A Study of Probabilistic FEMs for a Slope Reliability Analysis Using the Stress Fields
Authors: Farah Khaled , Ltifi Mounir , Hassis Hedi
Published: May 2015

In this paper, the applicability and the effectiveness of the probabilistic finite element methods (FEMs) such as the perturbation method, and the Spectral Stochastic Finite Element Method (SSFEM) applied to the reliability analysis of the slope stability have been studied. The results were checked by the Monte Carlo simulation and a direct coupling ap-proach combining the deterministic finite elements code and First Order Reliability Method (FORM) algorithm. These methods are presented considering the spatial variation of soil strength parameters and Young modulus. The random field is used to describe the spatial variation. Also, the reliability analysis is conducted using a performance function formulat-ed in terms of the stochastic stress mobilized along the sliding surface. The present study shows that the perturbation method and SSFEM can be considered as practical methods to conduct a second moment analysis of the slope stability taking into account the spatial variability of soil properties since good results are obtained with acceptable estimated rela-tive errors. Finally, the perturbation method is performed to delimit the location of the critical probabilistic sliding surfac-es and to evaluate the effect of the correlation length of soil strength parameters on the safety factor. In addition, the two methods are used to estimate the probability density and the cumulative distribution function of the factor of safety.
Timelike rotational surfaces of elliptic, hyperbolic and parabolic types in Minkowski space E41 with pointwise 1-type Gauss map
Authors: Bektaş Burcu , Dursun Uğur
Published: May 2015

In this work, we focus on a class of timelike rotational surfaces in
Minkowski space E41 with 2-dimensional axis. There are three types of
rotational surfaces with 2-dimensional axis, called rotational surfaces of
elliptic, hyperbolic or parabolic type. We obtain all flat timelike
rotational surface of elliptic and hyperbolic types with pointwise 1-type
Gauss map of the first and second kind. We also prove that there exists no
flat timelike rotational surface of parabolic type in E41 with pointwise
1-type Gauss map.
A note about the torsion of null curves in the 3-dimensional Minkowski spacetime and the Schwarzian derivative
Authors: Olszak Zbigniew
Published: May 2015

The main topic of this paper is to show that in the 3-dimensional Minkowski
spacetime, the torsion of a null curve is equal to the Schwarzian derivative
of a certain function appearing in a description of the curve. As
applications, we obtain descriptions of the slant helices, and null curves
for which the torsion is of the form ? = -2?s, s being the pseudo-arc
parameter and ? = const ? 0.
Some properties of ET-projective tensors obtained from Weyl projective tensor
Authors: Stankovic Mica , Zlatanovic Milan , Vesic Nenad
Published: May 2015

Vanishing of linearly independent curvature tensors of a non-symmetric affine
connection space as functions of vanished curvature tensor of the associated
space of this one are analyzed in the first part of this paper. Projective
curvature tensors of a non-symmetric affine connection space are expressed as
functions of the affine connection coefficients and Weyl projective tensor of
the corresponding associated affine connection space in the second part of
this paper.
Some cosmological solutions of a nonlocal modified gravity
Authors: Dimitrijevic Ivan , Dragovich Branko , Grujic Jelena , Rakic Zoran
Published: May 2015

We consider nonlocal modification of the Einstein theory of gravity in
framework of the pseudo- Riemannian geometry. The nonlocal term has the form
H(R)F(?)G(R), where H and G are differentiable functions of the scalar
curvature R, and F(?) = ??n=0 fn?n is an analytic function of the d?Alambert
operator ?. Using calculus of variations of the action functional, we derived
the corresponding equations of motion. The variation of action is induced by
variation of the gravitational field, which is the metric tensor g?v.
Cosmological solutions are found for the case when the Ricci scalar R is
constant.
Isoperimetric inequality, F. Gehring’s problem on linked curves and capacity
Authors: Mateljevic Miodrag
Published: May 2015

In this mainly review paper, we discuss connections between F. Gehring?s
problem and some results of isoperimetric type. We also prove a few new
results and give novelity at some places.