bluuebunny/crossref_metadata_2025 huggingface dataset:
A protocol for carbon emissions accounting in infrastructure decisions
Authors: Jowitt Paul , Johnson Adrian , Moir Stuart , Grenfell Robin
Published: April 2012

Concerns about climate change have resulted in a need to address the whole-life atmospheric impact of infrastructure projects. But if emissions of carbon dioxide and other ‘greenhouse gases’ are to be included in overall project appraisals, what spatial and temporal boundaries should be used in assessing emissions, and how should the results be included in project decision making? This paper addresses both these issues within the context of UK legislation, proposing a global protocol for ‘carbon accounting’ based on best practice, but questioning the simplistic concept of ‘carbon pricing’ as an effective instrument of reducing emissions.
Scaled-up commercial production of reactive magnesium cement pressed masonry units. Part I: Production
Authors: Liska Martin , Al-Tabbaa Abir , Carter Kneale , Fifield John
Published: April 2012

Reactive magnesia cements have recently emerged as a potentially more sustainable and technically superior alternative to Portland cement as they set by absorbing carbon dioxide and as a result gain significant strength. This two-part publication investigates the application of reactive magnesia alone as the cement component in pressed masonry units and compares it to those containing Portland cement. Laboratory-scale production was performed followed by a scaled-up commercial production at the Forticrete plant in Dewsbury, West Yorkshire, UK. A range of aggregates were used in the blocks including natural aggregates, Lytag, an ash mix and a limestone mix. This paper, the first of a two-part publication, details both the laboratory-scale and commercial production processes including scaling-up issues faced and an assessment of the physical integrity of the produced blocks. This paper highlights the feasibility of producing reactive magnesia-aggregates masonry blocks on a commercial scale. It also highlights the correlation between laboratory work and the commercial production process and how commercial production activities strongly influence the production outcome.
Non-linear finite-element analysis of punching capacities of steel–concrete bridge deck slabs
Authors: Zheng Yu , Robinson Des , Taylor Su , Cleland David
Published: April 2012

Punching failure is the common failure mode in concrete bridge deck slabs when these structural components are subjected to local patch loads, such as tyre loads. Past research has shown that reinforced concrete slabs in girder–slab type bridges have a load-carrying capacity far greater than the ultimate static loads predicted by traditional design methods, because of the presence of compressive membrane action. However, due to the instability problems from punching failure, it is difficult to predict ultimate capacities accurately in numerical analyses. In order to overcome the instability problems, this paper establishes an efficient non-linear finite-element analysis using the commercial finite-element package Abaqus. In the non-linear finite-element analysis, stabilisation methods were adopted and failure criteria were established to predict the ultimate punching behaviour of deck slabs in composite steel–concrete bridges. The proposed non-linear finite-element analysis predictions showed a good correlation on punching capacities with experimental tests.
GW vulnerability assessment based on entropy and fuzzy method
Authors: Baoxiang Zhang , Cheng Yu , Fanhai Meng , Li Wan
Published: April 2012

Groundwater vulnerability assessment and mapping are basic tools for groundwater environmental protection. The Drastic index system is the most popular in the world but many details still need to be improved. This paper introduces an entropy weight fuzzy optimisation method to a groundwater vulnerability assessment coupled with a geographic information system. Weights are not needed for anthropogenic influences, and the result could be continuous in this approach, which avoids the subjectivity of assigning weights of indicators and the discontinuity in assessing groundwater vulnerability. Taking the Huangshuihe River catchment as an example, the entropy weight of Drastic parameters and the optimal membership degree of overlay area were calculated. Thus, the groundwater vulnerability of Huangshuihe River catchment was divided into three grades: high (0·0091–0·1499), medium (0·1500–0·7400) and low (0·7401–0·9917), respectively corresponding to about 19·3%, 29·7% and 51% of the whole area. Compared with the traditional Drastic method, good results were obtained and the approach seems to be a good improvement on the classic method. A sensitivity analysis showed that topography is the most sensitive to vulnerability.
New equation for estimation of radial gate discharge
Authors: Zahedani Mohsen R. , Keshavarzi Alireza , Javan Mahmood , Shahrokhnia Mohammad Ali
Published: April 2012

The flow discharge under a radial gate is a function of the geometric and hydraulic parameters upstream water depth, downstream water depth, gate opening, gate radius and trunnion pin height. A new equation for estimating radial gate discharge for movable trunnion pin height radial gates was developed based on comprehensive experimental testing with three such gates in a large laboratory flume (60×1×1 m). Data from previous field studies of 29 radial gates in the Doroodzan dam irrigation network were also used to derive new equations as functions of the above-mentioned parameters under free and submerged flow conditions. Dimensional analysis and non-linear regression were used to derive the water flow discharge relationships. These equations were validated using data of radial gates in the Doroodzan network and were also compared with several previously suggested equations for radial gates. Statistical results show good agreement between the proposed equations and field and laboratory data and they are hence recommended for use in practical applications.
The Global Dimensions of Public Health Preparedness and Implications for US Action
Authors: Moore Melinda
Published: April 2012

The globalization of public health is both real and relevant throughout the United States and to Americans traveling or residing abroad. US public policy responses are evolving, but a crisper and more comprehensive global perspective is needed.

I suggest four timely US actions to address today’s competing realities of globalization and economic austerity: raise awareness among clinicians and local health departments; capture and share exemplary disaster management practices across countries; ensure that US global health investments are effective, efficient, and sustainable; and think globally while acting locally to enhance US health security.

The reauthorization of the Pandemic and All-Hazards Preparedness Act of 2006 provides an opportunity to more clearly address the global dimensions of domestic preparedness.
A Dynamic Model of US Adolescents’ Smoking and Friendship Networks
Authors: Schaefer David R. , Haas Steven A. , Bishop Nicholas J.
Published: April 2012

Objectives. We investigated the associations between smoking and friend selection in the social networks of US adolescents.

Methods. We used a stochastic actor-based model to simultaneously test the effects of friendship networks on smoking and several ways that smoking can affect the friend selection process. Data are from 509 US high school students in the National Longitudinal Study of Adolescent Health, 1994–1996 (46.6% female, mean age at outset = 15.4 years).

Results. Over time, adolescents’ smoking became more similar to their friends. Smoking also affected who adolescents selected as friends; adolescents were more likely to select friends whose smoking level was similar to their own, and smoking enhanced popularity such that smokers were more likely to be named as friends than were nonsmokers, after controlling for other friend selection processes.

Conclusions. Both friend selection and peer influence are associated with smoking frequency. Interventions to reduce adolescent smoking would benefit by focusing on selection and influence mechanisms.
Recent Progress and Effects Analysis of ASP Flooding Field Tests
Authors: Zhu Youyi , Hou Qingfeng , Liu Weidong , Ma Desheng , Liao Guangzhi
Published: April 2012

Alkali-surfactant-polymer combination flooding (ASP flooding) is one of the main chemical EOR techniques for the significant increase of crude oil recovery in PetroChina. In this paper, the progress in field tests of ASP flooding, effects analysis and related problems in application are introduced and discussed. The development trend of ASP flooding is suggested.

Field tests of ASP flooding in PetroChina have been performed since 1994, including six pilot tests in both sandstone and conglomerate reservoirs and three industrial tests, and the incremental oil recoveries of such tests were more than 19–20%.

It is found that three factors are responsible for successful ASP flooding field tests : (1) Good performance of oil displacement agents. (2) Good profile control and oil displacement ability. (3) Reasonable well pattern and well spacing.

Side effects encountered in field tests are as follows: (1) scaling and corrosion damaged the lifting system and shorten the average pump-checking cycle accordingly. (2) Strong emulsification resulted in many liquid treatment problems such as the excess of solid particle content over the standard of water circulation and high cost of water treatment. (3)The liquid production decreased greatly.

The development trends in chemical combination flooding technique are proposed based on results of ASP flooding field tests. The strong alkali ASP flooding should be replaced by weak alkali ASP flooding or even alkali-free SP combination flooding. The application reservoir will cover from sandstone to conglomerate and carbonate, from low salinity and low temperature reservoirs to high salinity and high temperature ones, etc. The corresponding key techniques such as development of new chemical agents and advanced produced liquid treatment system should be considered in future tests and application of chemical combination flooding.
Three-Phase Relative Permeability and Hystresis Model for Simulation of Water Alternating Gas (WAG) Injection
Authors: Shahverdi H. , Sohrabi M.
Published: April 2012

Water- Alternating- Gas (WAG) injection in waterflooded reservoirs can increase oil recovery and extend the life of these reservoirs. Reliable reservoir simulations are needed to predict the performance of WAG injection before field implementation. This requires accurate sets of relative permeability (kr) and capillary pressure (Pc) functions for each fluid phase, in a three-phase flow regime. The WAG process also involves another major complication, hysteresis, which is caused by flow reversal happening during WAG injection. Hysteresis is one of the most phenomena manipulating the performance of WAG injection and hence, it has to be carefully accounted for.

In this study we have benefited from the results of a series of coreflood experiments that we have been running since 1997 as a part of the Characterization of Three-Phase Flow and WAG Injection JIP (joint industry project) at Heriot-Watt University. In particular we focus on a WAG experiment carried out on a water wet core to obtain three-phase relative permeability values for oil, water and gas. The relative permeabilities exhibit significant and irreversible hysteresis for, oil, water and gas. The observed hysteresis, which is due to the cyclic injection of water and gas during the experiment, is not predicted by the existing hysteresis models.

We present a new three-phase relative permeability model coupled with hysteresis effect for modelling of the observed cycle- dependent relative permeabilities taking place during WAG injection. The approach was successfully tested and verified using the measured three-phase relative permeability values obtained from WAG experiment. In line with our laboratory observations, the new model predicts the reduction of the gas mobility during consecutive water and gas injection cycles as well as the increase in oil relative permeability happening in consecutive water injection cycles.
Implementation of Relative Permeability Modifiers in Krasnoleninskoe Oil Field: Case Histories
Authors: Parkhonyuk Sergey , Levanyuk Olesya , Oparin Maxim , Sadykov Almaz , Mullen Kevin , Lungwitz Bernhard , Enkababian Philippe , Mauth Kevin , Alexander Karpukhin
Published: April 2012

Excess water production is a major concern for Russian oil companies. Maturing fields are producing at ever-increasing water cut resulting in problems such as the cost of disposal and environmental issues. In recent years, operators have shown a rising interest in Relative Permeability Modifiers (RPMs) as a potential solution to reduce water production.

RPMs are designed to disproportionately reduce the relative permeability to one phase (water) over the oil phase. RPMs are a preventive approach to reduce water production. Ideally, they should completely block water flow without affecting oil flow. While RPMs are used worldwide, they must be adjusted to the reservoir conditions. This becomes even more important in the case of hydraulic fracturing of formations with nearby water-saturated layers.

Commonly, service companies recommend one type of RPM which fits all reservoirs. This paper demonstrates how RPM selection on reservoir cores is critical for successful application in the field. We describe laboratory testing and review field trial results of RPMs in a low permeability (2 to 14 mD), highly laminated formation. Because RPMs are typically used only in high-permeability reservoirs, this application is unique. We evaluated chemically different RPMs on actual core material and found strong performance variations of the tested RPMs. We selected a suitable RPM following both core flow testing and compatibility testing.

For the field test, wells in the Krasnoleninskoe oilfield were selected for RPM treatments. Oil production was increased in most cases while the water cut was reduced or only slightly increased by up to 5% during 6 months following the treatment. These results show that with proper evaluation, RPMs can also be successfully used in low-permeability reservoirs. We demonstrated also that otherwise proven successful RPMs may not fit every reservoir and proper evaluation and monitoring is critical for success.
Beaver Creek Madison CO2 Enhanced Oil Recovery Project Case History; Riverton, Wyoming
Authors: Peterson Charles A. , Pearson Edward J. , Chodur Veronica T. , Periera Carlos
Published: April 2012

The Beaver Creek Madison project is the most recent CO2 EOR project in the state of Wyoming. Having pre-project oil production of 43 MMBO, this flood is projected to increase recovery by 11.1 MMBO or 10% of the estimated 109 MMBO OOIP. Early CO2 flood response has yielded production increasing from a pre-flood rate of 280 BOPD to its current rate of 5100 BOPD since July, 2008. Since project initiation, the reservoir has realized 2.6 MMBO of incremental oil.

The Madison reservoir, located in the Beaver Creek Field, 14 miles SSE of Riverton, Wyoming, is found at an average depth of 11,235’ placing it among the deepest CO2 EOR projects in the United States. Reservoir temperature is approximately 234° F. in this limestone/dolomite reservoir. The Madison is a highly structured, fault bounded reservoir encompassing just under 1000 acres with an average net pay of 212’, and an oil column thickness of 740’. The CO2 flood is a mixed design peripheral and gravity stable flood incorporating localized continuous gas injection and water alternating gas (WAG) processes which takes advantage of the reservoir's geometry and structural relief. The flood incorporates 32 wells.

This report provides a case study for a deep carbonate CO2 flood. It includes the Beaver Creek Madison's geologic and reservoir characterization, flood design, early production performance, and reservoir management. Also included in this presentation is a discussion of the pre-flood evaluation and design which incorporated a 3 phase evaluation process progressing from preliminary scoping and screening to more costly laboratory testing, detailed reservoir modeling and flood design. Early life reservoir management includes some minor, yet functionally significant, changes to the injection pattern and WAG cycles intended to optimize the reservoirs performance compensating for early deviations from the field's anticipated responses.
Anomalous Foam Fractional Flow Solutions at High Injection Foam Quality
Authors: Roostapour A. , Kam S. I.
Published: April 2012

A thorough understanding of foam fundamentals is crucial to the optimum design of foams for improved/enhanced oil recovery. This study, for the first time, presents anomalous foam fractional flow solutions which deviate significantly from the conventional solutions at high injection foam qualities, by comparig Method of Characteristics and mechanistic bubble-population-balance simulations.

The results from modeling and simulations based on coreflood experiments revealed that (1) there exist three regions: region "A" with relatively wet (or high fw) injection conditions where the solutions are consistent with the conventional fractional flow theory; region "C" with very dry (or low fw) injection conditions where the solutions deviate significantly; and region "B" in between which has a negative dfw/dSw slope showing physically unstable solutions; (2) for dry injection conditions in region "C", the solutions require a constant state (IJ) between initial (I) and injection (J) conditions, forcing a shock from I to IJ by intersecting fractional flow curves, followed by spreading waves or another shock to reach from IJ to J; and (3) the location of IJ in fw vs. Sw domain moves to the left (or toward lower Sw) as the total injection velocity increases for both weak and strong foams until it reaches limiting water saturation.

Even though foams at high injection quality are popular for mobility control associating a minimal amount of surfactant solutions, foam behaviors at dry conditions have not been thoroughly investigated and understood. The outcome of this study is believe to be helpful to successful planning of foam field I/EOR applications.
New Insights on the Mechanism of Displacement Efficiency of Natural Cores by Chemical Flooding and Its Influence on the Development and Selection of Chemicals for EOR
Authors: Demin Wang , Gang Wang
Published: April 2012

Results of Newtonian Fluids flooding very homogeneous porous media show that the Displacement Efficiency (ED) of a certain system is determined by the Capillary Number (Nc) of the driving fluid.

The experience gained from Chemical Flooding natural cores and reservoirs that are all micro (pore scale) heterogeneous to some degree show that ED is influenced, besides Nc, by many other factors as explained below.

Newtonian Fluids do not have elastic properties; emulsions and gas bubbles are not formed; when flooding, there is no change in the wettability of the system; there is no imbibition; and there is no alteration in the geometry of the pores.

However, when chemical flooding, elasticity markedly effects the ED; emulsions and gas bubbles (especially when gas is injected) will often show up, which from core and field tests, could significantly increase the recovery; both w/o and o/w emulsions markedly change the phase permeability behavior and water cut; the wettability will often change and imbibition will occur; pore geometry alteration by solution and precipitation will happen, which influences the permeability, imbibition and recovery. The above factors all markedly influence the ED of the system, especially when many factors act jointly.

From the above understanding, some directions on the development and selection of chemicals for EOR are put forward.

The concept of ultimate ED and economic ED and its affect on the selection of actual field flooding systems is analyzed (many papers analyze ultimate ED, however, in the field, usually economical ED is more important).

Besides Nc, the above factors should be considered when developing and selection chemicals and flooding systems. The above insights can further deepen our knowledge of the mechanism of chemical flooding, promote further research in this area and form better selection criteria for EOR chemicals and flooding systems in the field.
Water Shutoff at Ultralow Temperatures Using Organically Crosslinked Polymer Gels
Authors: Reddy B. R. , Crespo Freddy , Eoff Larry
Published: April 2012

Use of crosslinked polymer gels employing polymeric base materials and crosslinkers for shutting off water production in a variety of situations has been amply documented at formation temperatures ranging from ambient to > 400°F. However, there has not been much work reported on chemical systems that can provide adequate gel times and gel strengths at temperatures less than 80°F. The reaction rates and gel-strength-development rates are significantly lower at low temperatures, resulting in long gel times and weaker gels. Additionally, in offshore applications, the gelling compositions must be designed to be mixable without crosslinking at warmer surface temperatures, and yet provide sufficient gel times at temperatures as low as 40 to 50°F near the ocean floor, for example, in shallow water/gas zones. Similar limitations might exist in areas known to contain gas hydrates.

In this paper, a recently developed water-shutoff system designed from polyacrylamide base polymers and polyamine crosslinkers, which provide sufficient gel times at temperatures less than 80°F, is presented. Challenges encountered in designing such a system included optimizing base polymer to crosslinker ratios and gel-strength-development rates. This paper describes optimization of gel times for the intended applications using activator chemicals and retarders, which allow designing gelling compositions that provide adequate gel times at subambient temperatures while permitting mixing at warmer surface temperatures. The activator and retarder systems also allow control of the development of rigid gels at different crosslinker concentrations.

Several practical issues and considerations for designing conformance treatments at low and ultralow temperatures are discussed. Improved temperature modeling and laboratory-testing designed to simulate the fluid-temperature profile during the operation from the wellhead to the formation bottom are also addressed.
Impacts of Timing of Crosslinker Addition on Water Shutoff Polymer Gel Properties
Authors: Shriwal Prashant , Lane Robert H.
Published: April 2012

In preparation of a gelant solution for making crosslinked polymer gels for water shutoff applications, unpublished experiments and chemical intuition suggest that, unless hydrolyzed polyacrylamide (HPAM) polymer is fully hydrated before addition of crosslinker, the final gel will have lower than optimum mechanical strength, presumably because polymer chains need to be fully unfolded before proper crosslinking can occur. When using dry polymer, which is usually the lowest cost form on a delivered basis, this may require more equipment and a large tankage footprint. However, if conditions exist where crosslinker can be added to wetted but not fully hydrated polymer, then dry polymer and crosslinker can be blended in a small continuous flow unit, with full hydration occurring as the gelant flows downhole prior to gelation.

We have evaluated gel strengths of "flowing" gels for water shut off in natural fractures and other non-matrix features as a function of time of addition of crosslinker relative to time of hydration of polymer. Gels were prepared from moderately high molecular weight HPAM crosslinked with chromium(III) acetate (CrAc) or polyethyleneimine (PEI). Crosslinker was added after either (1) initial wetting of solid polymer particles or (2) complete dissolution of the polymer.

Gel strengths were determined using a common qualitative coding system. Comparisons were made for gels prepared in an identical manner, except for the timing of crosslinker addition. Samples were prepared either in fresh water or 4% NaCl brine and then hydrated either at an ambient temperature or 122 °F. Gelant viscosity and crosslink time were also characterized with a viscometer.

Results of this work demonstrate that for most field applications using CrAc as crosslinker, optimum quality gel can be obtained using dry polymer and a small continuous mixing system for initial wetting of the polymer, after which the crosslinker can be added to the polymer solution on-the-fly. This practice can decrease the footprint and cost of large volume flowing gel treatments.
Foam Mobility Control for Nanoparticle-Stabilized CO2 Foam
Authors: Yu Jianjia , An Cheng , Mo Di , Liu Ning , Lee Robert
Published: April 2012

For miscible displacement under most reservoir conditions, due to the very low viscosity of the CO2 phase, poor volumetric sweep efficiency is a critical weakness of CO2 enhanced oil recovery (EOR). In this paper, a dynamic process for generating nanoparticle-stabilized CO2 foam is presented, which is expected to reduce CO2 mobility during CO2 EOR. This paper also describes the factors of nanoparticle concentration, CO2/brine volumetric ratio, and total injection rate effects on dynamic CO2 foam generation and foam mobility.

Dynamic supercritical CO2 foam was generated by the shearing of supercritical CO2 and nanoparticle dispersions in a glass- bead packed column. The foam image was observed in an online sapphire tube. Particle size was determined to be in the range of 60–90 nm. The experimental results showed that stable dynamic foam was generated at a shear rate higher than 1419s‒1 at 1500 psig and 25°C. The pressure differentials along the glass bead packed column and capillary tube were used to characterize the CO2 foam mobility and the corresponding apparent foam viscosity. It was found that the yield shear rate increased from 1419s‒1 to 3312s‒1 as the injection rate increased from 3.0ml/min to 7.0ml/min, and the apparent foam viscosity with nanoparticle dispersion was 1.5 to 2.5 times higher than that without the dispersion. The corresponding mobility was nine times higher. With increasing nanoparticle concentration, the normalized mixture viscosity increased and related mobility decreased. Furthermore, the apparent viscosity decreased slightly as the CO2/brine ratio was varied from 2 to 11 at the constant flow rate of 6ml/min.
Study of Adsorption and Transportation Behavior of Nanoparticles in Three Different Porous Media
Authors: Yu Jianjia , An Cheng , Mo Di , Liu Ning , Lee Robert
Published: April 2012

The revolution in nanotechnology has called attention to its many potential applications in the oil and gas industry. Nanoparticle-stabilized emulsions and foams have been proposed for enhanced oil recovery application. Understanding the transport and retention of nanoparticles in porous media is critical to their application. This paper presents the results of a study on the adsorption and transport behavior of nanosilica particles in three different porous media: sandstone, limestone, and dolomite. The results revealed that the equilibrium adsorption of the particles on sandstone, limestone, and dolomite were 1.272 mg/g, 5.501 mg/g, and 0 mg/g, respectively, in 5,000 ppm nanosilica dispersion. Coreflood tests were performed to investigate nanosilica particles transport behavior in different cores. It was observed that silica nanoparticles could easily pass through the sandstone core without changing the core's permeability. A little adsorption was noted as silica nanoparticles flooded limestone core, but the core permeability was not changed. A high particle recovery was obtained with the dolomite core. However, pressure drop across the core was observed to continuously increase, indicating core plugging occurred and core permeability was changed.
A New Look at the Minimum Miscibility Pressure (MMP) Determination from Slimtube Measurements
Authors: Amao Abiodun Matthew , Siddiqui Shameem , Menouar Habib , Herd Bob L.
Published: April 2012

Slimtube measurement is one of the standard experimental techniques used for determining the minimum miscibility pressure (MMP) of an oil and injection gas system prior to the initiation of an enhanced oil recovery (EOR) project. It is preferred because it involves actual fluid displacement in a porous medium. However, the specific criterion for determining the cut-off point during the measurement is not uniquely agreed upon in the literature. Different criteria have been proposed by researchers and this has been one of the setbacks of using Slimtube measurements.

The most commonly used criterion is the 1.2 PV criterion, which uses the recovery after injecting 1.2 pore volumes of the displacing gas as the cut-off. However, experimental observations show that even at supercritical condition, the volume of a gas is a strong function of the experimental pressure. Therefore, there is a need to develop an alternative means of determining the MMP that is not subject to particular pore volumes injected during Slimtube measurements.

This work presents different means of determining the MMP, based entirely on recovery and the particular displacement phenomenon. In this approach, two new parameters are defined - the instantaneous recovery rate (IRR) and the oil recovery rate (ORR). The maximum values for these parameters for each experiment are used as the cut-off value.

This new criteria was used in analyzing nine experimental data using oil from the Permian Basin. The results were compared with MMP prediction based on maximum recovery from each of the runs and the results were found to be in agreement.

These new criteria will provide consistent cut-off point for experimental runs because Slimtube measurements take a long time to complete. The new procedure ensures that adequate data have been gathered during each experimental run, sufficient for a consistent experimental analysis.
Calculation of Minimum Miscibility Pressure Using Fast Slimtube Simulation
Authors: Yan Wei , Michlesen Michael L. , Stenby Erling H.
Published: April 2012

Minimum misciblility pressure (MMP) is a critical parameter in designing a miscible gas injection process. It is expected that 100% displacement efficiency on the microscopic scale can be achieved provided the injection pressure is above MMP. Two approaches are usually employed for equation of state (EoS) based MMP calculation. The slimtube simulation approach is a numerical simulation of the physical slimtube experiment, which is commonly accepted as the most reliable experimental method for MMP determination. This approach carries out slimtube simulation runs at a series of pressures and determines the MMP from the recovery-pressure curve, just as in the experiment. The global approach, which is based on the method of characteristics analysis of 1D gas injection, finds the MMP by locating the pressure where a key tie-line becomes critical. Although the global approach is faster, the slimtube approach is still a necessary complementary method especially when the injection process involves complex phase behavior caused by CO2 or heavy oils. This study addresses how to improve the computational efficiency of slimtube simulation for MMP calculation. Firstly, a robust and efficient algorithm for rigorous flash forms the basis of the whole strategy. Secondly, a tie-line distance based approximation (TDBA) method has been introduced on top of the rigorous algorithm. In the TDBA method, if a new feed composition in a grid block is close enough to a tie-line previously calculated in the same block, the previous tie-line results can be used with slight adjustment. The approximation affects the final recovery very little but greatly increases the speed. Thirdly, a higher order method can be employed to use a fewer number of grid blocks to get the same accuracy in recovery. Finally, a MMP search strategy is poroposed to reduce the number of slimtube simulations needed. In addition, it is also discussed how to parallelize slimtube simulations for modern computers with multiple CPU cores to further chop the computation time.
Scale-Up of Effective Mass Transfer in Vapor Extraction Process for Heterogeneous Reservoirs
Authors: Leung Juliana Y.
Published: April 2012

Vapex (vapor extraction) is a non-thermal process using vaporized solvents with promising potential to reduce steam consumption in heavy oil recovery. The key recovery mechanism is molecular diffusion enhanced by velocity variations at different scales; i.e., dispersion. The efficiency of diffusion/dispersion depends significantly on reservoir heterogeneities, which exhibit a wide range of length scales. This paper demonstrates a procedure for quantifying the scaling characteristics of effective mass transfer accounting for heterogeneities based on the volume averaging approach.

Volume averaging is a mathematical technique to derive continuum equations at coarse scales given representative transport equations at fine scales. Although treatment of transport problems has been published in the past, application to stochastic geological systems is lacking. In the proposed procedure, results from a fine-scale numerical flow simulation reflecting the full physics of Vapex over a small element of the reservoir is integrated using the volume averaging technique to provide effective description of mass transfer at the coarse scale.

Scaling characteristics of effective mass transfer are systematically investigated for different heterogeneity distributions. Results show 1) spatial variability of effective mass transfer coefficients increases as solvent chamber advances through the reservoir; 2) mean and variance of effective mass transfer vary with length scale in a fashion similar to that of recovery statistics; 3) variability in effective mass transfer is a strong, non-linear function of heterogeneity.

An original contribution is to provide a general framework for developing scaling relationships of effective mass transfer in Vapex accounting for reservoir heterogeneities. It also presents an important potential in modeling of other solvent injection applications. Results demonstrate that effective mass transfer vary with length scale and heterogeneity; hence it should be properly represented for accurate prediction of recovery performance in simulations using scaled-up reservoir models.
Low Salinity EOR in Carbonates
Authors: Romanuka J. , Hofman J. P. , Ligthelm D. J. , Suijkerbuijk B. M. , Marcelis A. H. , Oedai S. , Brussee N. J. , van der Linde A. , Aksulu H. , Austad T.
Published: April 2012

Modifying the chemistry of injection water yields improved wettability behavior on carbonate rock surfaces. Previous work has focused on demonstrating the effect of modified brine formulation on particular carbonate samples. Here the results of a more general screening study consisting of Amott spontaneous imbibition experiments on the samples from oil-bearing zones and from outcrops of different carbonate formations are reported.

Tertiary incremental oil production due to increased water-wetness was observed upon transition to brine of lower ionic strength. Additional oil recovery from the spontaneous imbibition tests ranged from 4 to 20% of OIIP (Oil Initially In Place), reflecting a large variability in the response and indicating a high complexity of the mechanism(s). Consistent with numerous published reports, Stevns Klint outcrop chalk samples were a clear exception and exhibited increased oil recovery with increasing sulfate ion concentration. These did not respond to lowering the salinity of the imbibing brine. Tertiary oil recovery from samples containing evaporites occurred simultaneously with dissolution of salt minerals, as evident from brine analysis. However, incremental oil recovery in the same range was measured for samples without evaporites but from the same geological formation. Hence, mineral dissolution as a mechanism for enhanced oil recovery could not be confirmed.

The results show that injection of low salinity brine into carbonate reservoirs has potential as an EOR technology. However, additional research is needed to improve the understanding of the underlying chemical and physical mechanisms and improve a priori predictability.
Development of a Tool to Predict Technical Success of Polymer Flooding Applications
Authors: Rai Khyati , McComb Thais , Rodriguez Elena , Withers Robert
Published: April 2012

Quick qualitative comparison between different fields is often necessary in early phases of Chemical EOR studies when there is limited data. The tool described in this paper helps to bridge the gap between pass/fail screening techniques and more sophisticated simulation techniques, to facilitate the screening and ranking of potential candidates for polymer EOR flooding. Several studies have examined screening models for polymer flooding (PF). The models that exist in literature only assign a pass/fail response for suitability of reservoirs to polymer flooding and are insufficient for the purposes of comparative ranking. The analytical tool presented here is capable of quickly producing qualitative estimates of ‘Probability Of Technical Success’ (POTS) for polymer flooding for a set of candidate fields. This tool is useful for identifying candidates most likely to be successful polymer floods in a portfolio.

POTS number is solely a property of the reservoir characteristics and is based on parameters inherent to the field. Project design or execution parameters (such as polymer type, concentration, slug size, etc) and field implementation issues have not been taken into consideration.

POTS for polymer flood was developed using the following approach:

Important non-controllable parameters for PF were identified. A database was created with field and pilot successes and failures. The weight of parameters from step 1 was calculated based on their coefficient of variation value in the database. The weights of the parameter and parameter values are combined to give the POTS value for the field.

The results from the tool have been validated with past polymer flooded fields.
Experimental and Numerical Simulation of Surfactant-Assisted Oil Recovery in Tight Fractured Carbonate Reservoir Cores
Authors: Alamdari Baharak B. , Kiani Mojtaba , Kazemi Hossein
Published: April 2012

This paper presents experimental and numerical simulation results of oil recovery from short fractured and unfractured carbonate cores using a high speed centrifuge. The short cores are 1.5-inch in diameter and 1.5-inch long. The experiments are designed to decipher oil recoveries contributions from rock matrix in presence and absence of fractures, with and without surfactant.

This research demonstrates that surfactant oil recovery can be a viable enhanced oil recovery process in fractured carbonate reservoirs when fracture distribution and connectivity are favorable. These carefully designed experiments improve our understanding of how oil mobilization can be enhanced in fractured carbonate rocks and how the process can be modeled and solved numerically.

Three cores were selected from a Middle East carbonate reservoir, saturated with field brine, displaced with a 9-centipoise field crude, and aged to promote oil-wetness. Three different core designs were used in these experiments. One of the cores was fractured along the vertical axis and sealed with epoxy resin on the outer vertical surface. The second core was fractured and sealed on all outer surfaces except for the fracture opening. The third core was unfractured and sealed on the outer vertical surface. Using a centrifuge, these cores produced 43%, 33% and 42% in waterflood and 40%, 28% and 24% in surfactant flood, respectively.

We matched the experimental oil recoveries using two different numerical approaches: a transfer function and a 2-D finite-difference model. The results of these experiments, numerical modeling, and field observations have given us a better understanding of the mechanism of enhanced oil production in fractured carbonate reservoirs by dilute surfactant and micellar solutions. The results of this research are intended to promote field trials.
A Pilot Carbon Dioxide Test, Hall Gurney Field, Kansas
Authors: Willhite G. P. , Byrnes A. P. , Dubois M. K. , Pancake R. E. , Jyun-Syung Tsau , Daniels J. R. , Flanders W. A.
Published: April 2012

A pilot carbon dioxide miscible flood was initiated in the Lansing Kansas City C formation in the Hall Gurney Field, Russell County, Kansas. The reservoir zone is an oomoldic limestone located at a depth of about 2900 feet. The pilot consisted of one carbon dioxide injection well and three production wells. Continuous carbon dioxide injection began in December 2003 and continued through June 2005 when 16.19 MM lbs of carbon dioxide had been injected into the pilot area. Injection was converted to water on June 2005 to reduce operating costs to a breakeven level with the expectation that sufficient carbon dioxide was injected to displace the oil bank to the production wells by water injection. By March 2010, 8,736 bbl of oil were produced from the pilot. Production from wells to the northwest of the pilot region indicated that oil displaced by carbon dioxide injection was produced from five wells outside of the pilot area, to the northwest. About 19,166 bbl of incremental oil were estimated to have been produced from these wells as of March 2010. There was evidence of a directional permeability trend toward the NW through the pilot region. The majority of the injected carbon dioxide remained in the pilot region, which was maintained at a pressure at or above the minimum miscibility pressure. Although the 4-well pilot was uneconomic, the estimated oil recovery attributed to the CO2 flood is 27,902 bbl which is equivalent to a gross CO2 utilization of 4.8 MCF/bbl.
An Integrated Solution to Effective Waterflood Surveillance and Pressure Maintenance: A KOC Pilot Project of Greater Burgan Field, Kuwait
Authors: Rahman B. Abdul , Al-Naqi M. , Rajan S. , Ameen A. , Oyemakinde S. , Al-Zadjali M. , Ofrabor J. , Ali Z.
Published: April 2012

The Greater Burgan Field, in Kuwait, is the second largest field and contains the largest clastic reservoir in the world. The reservoir pressure in the Wara sands have been falling below bubble point due to insufficient pressure support from aquifer in parts of the field. As a result the Early Wara Pressure Maintenance Project (EWPMP) was begun in 2009 to pilot test the effectiveness of water injection for pressure support. The Early Wara consists of a small sector in the Southwestern portion of the field with 33 wells made up of 7 injectors, 15 producers and 11 observations wells.

A fully integrated monitoring and surveillance solution has been developed that starts with the capture, conditioning and automation of production and injection data. The surveillance solution utilizes a scalable workflow that automatically computes the required waterflood surveillance KPIs. Data from the reservoir, well and layer level are all integrated to provide feedback as to the efficiency and performance of the pilot program. The objective of this paper is to show how the waterflood surveillance workflow oriented solution has been developed to provide monitoring and analysis tool for waterflood surveillance system including appropriate inputs from the various disciplines and utilize the experiences gained towards full peripheral injection in 2014.

The end product is a multi-layered decision support system that includes data integration, workflow management, engineering analysis and diagnoses as well as visualization and performance monitoring in a collaborative environment.

The paper describes the integrated waterflood surveillance solution with the data integration, workflow automation, visualization and diagnosis layer. It illustrates how the system has become part of the daily routine and helped to promote a collaborative work environment.
Surfactant Formulation Evaluation for Carbon Dioxide Foam Flooding in Heterogeneous Sandstone Reservoirs
Authors: Bian Yu , Penny Glenn
Published: April 2012

Supercritical carbon dioxide (CO2) flooding is a widely used method in tertiary oil recovery; however, there are many challenges such as inefficient gas utilization, poor sweep efficiency and low oil recovery due to viscous fingering and gravity segregation. One recent development is the application of CO2 foam in order to reduce the CO2 mobility, especially in high permeability zones of the reservoir. However, the efficiency of the CO2 foam often decreases sharply during flooding as a result of contact with crude, adsorption of surfactants, high salinity in formation water and high reservoir temperature. Surfactant formulations which have better tolerance to these factors can greatly enhance the CO2 utilization, reduce the cost of surfactant, and improve the oil recovery. A series of formulations, including various surfactants and corresponding micro-emulsions, were evaluated as CO2 foaming agents in lab-based heterogeneous sandstone equipment at reservoir temperatures and pressures. This paper describes formulating high temperature CO2 foaming agent with co-surfactants and in a micro-emulsion system to improve crude, salt and temperature tolerance and minimize adsorption in order to place the foamer further into the formation.
Performance Evaluation of Thermally-Activated Polymers for Conformance Correction Applications
Authors: Salehi M. , Thomas C. P. , Kevwitch R. M. , Manrique E. , Garmeh R. , Izadi M.
Published: April 2012

A comprehensive laboratory study was performed to look at a thermally activated polymer (TAP) for conformance correction applications. The focus of study was to see if BrightWater® (a TAP polymer) could perform in high permeability porous media by creating flow resistance to injected fluid, hence enhancing the sweep efficiency. Furthermore, the possibility of enhancing the TAP performance by increasing the solution concentration was investigated. A set of 20-inch long slimtubes packed with acid-washed quartz sand were used to evaluate the performance of two TAP grades at 85°C in a range of 1 to 5 Darcy. Additionally, another set of short slimtubes were used to examine the performance of two low-temperature activation TAP grades at 30°C in the range of 200 to 1300 md.

Results showed that residual resistance factor (RRF) values of 2 to 12 could be achieved at 5000 ppm active concentration for the range of permeability tested here. RRF values increased by increasing the concentration to 10,000 ppm active polymer. Low-temperature activation polymers showed RRF values of 10 to 50 depending on the permeability of the short sandpacks tested at 30°C. TAP simulation approaches are also described.