bluuebunny/crossref_metadata_2025_split huggingface dataset:
History Matching with a Multiscale Parameterization Based on Grid Connectivity and Adaptive to Prior Information
Authors: Bhark Eric , Datta-Gupta Akhil , Jafarpour Behnam 
Published: October 2011

Abstract
We introduce a novel reservoir parameterization approach to mitigate the challenges associated with field-scale history matching. In this approach, the reservoir property field is mapped to and updated in a low-dimensional transform domain using a linear transformation basis. The transformation basis vectors are the eigenvectors of a Laplacian matrix that is constructed using grid connectivity information and the main features in a given prior model. Because the grid connectivity information is computed only within a small multi-point stencil, the Laplacian is always sparse and is amenable to efficient decomposition. The resulting basis functions are ordered from large to small scale and include prior-specific spatial features. Therefore, the variability in reservoir property distribution can be effectively represented by projecting the property field onto subspaces spanned by an increasing number of leading basis vectors, each incorporating additional heterogeneity features into the model description. This property lends itself to a multiscale history matching algorithm where basis elements are sequentially included to refine the heterogeneity characterization to a level of complexity supported by the resolution of data. While the method can benefit from prior information, in the extreme case where reliable prior knowledge is not available the transformation reduces to a discrete Fourier expansion with model-independent parameterization properties.
We present the derivation and theoretical justification of the proposed method and review its important properties for reservoir parameterization including efficient one-time construction of the basis prior to calibration, applicability to any grid geometry and strong compression performance. The multiscale history matching algorithm begins by updating the prior reservoir model using a parameterized multiplier field that is superimposed onto the grid and assigned an initial value of unity at each cell. The multiplier is sequentially refined from the coarse to finer scales during minimization of production data misfit. This method permits selective updating of heterogeneity at locations and levels of detail sensitive to the available data, otherwise leaving the prior model unchanged as desired. We successfully apply the parameterization approach to history match several reservoir models, including a field case, using an adaptive multiscale algorithm.
Coreflood Measurements of CO2 Trapping
Authors: El-Maghraby Rehab M. , Pentland Christopher H , Blunt Martin J. 
Published: October 2011

Abstract
We present a coreflood experiment that measures three properties that control the long-term fate of CO2 injected into the subsurface during carbon capture and storage (CCS): the residual saturation of CO2 after brine flooding as a function of initial saturation; the amount of CO2 that can dissolve in the brine; and the primary drainage capillary pressure. We employ a porous plate method to establish initial saturation, a stirred reactor ensures that the injected brine is pre-equilibrated with CO2 and we use isothermal de-pressurization to determine CO2 saturation. The fluid pressure was 9 MPa and the temperature varied between 33 and 70°C - the CO2 is in a super-critical (sc) phase at a temperature and pressure typical of likely storage aquifers with a density between 211 and 705 kgm−3. We find that significant quantities of the CO2 can be trapped, with residual saturations up to 35%; the variation of trapped saturation with initial saturation is accurately matched using the Spiteri et al. model (a quadratic function). We compare the results with experiments performed at similar conditions using decane as the non-wetting phase. More decane is trapped than CO2, suggesting that the CO2-brine systems are not completely water-wet.
We show that temperature (density) variation has no effect on the saturation of scCO2 that is residually trapped. The measured dissolution constant lies between 0.84 and 0.97 moles CO2/kg brine. The primary drainage capillary pressure is consistent with a strongly water-wet system and the same - to within experimental error - as that measured on an analogue decane-brine system.
Comparison of Oil Recovery by Low Salinity Waterflooding in Secondary and Tertiary Recovery Modes
Authors: Gamage Pubudu , Thyne Geoffrey 
Published: October 2011

Abstract
Oil recovery by low salinity waterflooding in secondary and tertiary modes was investigated in the present study. Cores from Berea outcrop sandstone and Minnelusa reservoir sandstone were used in the single phase and two phase experiments. Two types of Minnelusa crude oils were used in the two phase experiments. The single phase experiments provided the baseline for pH and pressure changes in the two phase experiments.
Set of experiments were performed by using low salinity brine for the tertiary waterflood recovery method where oil saturated cores were first flooded with high salinity brine to simulate the secondary recovery method. In the second set of experiments, oil saturated cores were directly flooded with the low salinity brine. Conductivity and pH analysis of effluent brines were performed in all the single phase and two phase experiments.
Increase in oil recovery with low salinity brine as the invading brine was observed in both secondary and tertiary modes (28% OOIP) with Berea sandstone. However, higher oil recoveries (5-8% OOIP) were observed when low salinity waterflooding was implemented as a secondary recovery method. Minnelusa reservoir cores had little to no response to low salinity brine when it was used as a tertiary recovery method. However, Minnelusa cores showed an increase in oil recovery (10-22 % OOIP) with both types of crude oils when it was used as a secondary recovery method. An increase in pH of the effluent brine was observed during the low salinity brine injection in both Minnelusa and Berea cores. However, magnitude of the pH increase was smaller with the Minnelusa cores compared to Berea cores.
The level of investigation into the mechanism of low salinity incremental production has sharply increased in the past two years. Most of the studies focus on core floods using the tertiary mode. Our work contributes systematic coupled secondary and tertiary mode experiments that offer an expanded dataset for all researchers to use in investigation of the mechanisms.
New Fracture Stimulation Designs and Completion Techniques Result in Better Performance of Shallow Chittim Ranch Wells
Authors: Pandey Vibhas J. , Agreda Aquiles J. 
Published: October 2011

Abstract
The Sacatosa Field in West Texas was discovered in 1956. Since then over 1500 wells have been drilled and completed in the main reservoir section known as the San Miguel 1. The San Miguel 1 is primarily a low permeability sandstone, with several shale layers dispersed throughout. Economic development of the field requires effective well stimulation and an active waterflood program to provide pressure maintenance. Unfortunately, the available injection water is of poor quality and can rapidly plug up pore throats with solids, resulting in significant near wellbore formation damage. When these factors are considered, hydraulic fracturing of both injector and producer wells is a viable option for improved long-term well performance. However, because of relatively shallow depths, traditional hydraulic fracturing practices can lead to a multiplane fracture system with a mix of horizontal and vertical components. A significant presence of horizontal fractures can be detrimental to fractured well performance because of their low fracture conductivities. In producer wells, this could impair production if the reservoir is laminated and has low vertical permeability. In injectors, water front movement and sweep efficiency would be greatly diminished.
This paper discusses the steps taken to plan and develop a strategy to place vertical fractures in shallow San Miguel 1 sands. These findings can easily be extended to similar shallow depth reservoirs worldwide. Some major modifications in completion design included changes in perforation strategy, redesign of the pump schedule and implementation of a staged stimulation. Fracturing treatments were pumped on a total of 26 injectors and 8 producers using a variety of methods, including Coiled Tubing fracturing. Post-fracture analysis suggests a strong vertical fracture component and analysis of injectivity tests shows fracture parameters in line with design objectives. At least a two-fold increase in production was observed in producers that were fracture stimulated using these techniques.
Kerogen Pore Size Distribution of Barnett Shale using DFT Analysis and Monte Carlo Simulations
Authors: Adesida Adelola G. , Akkutlu I. Yucel , Resasco Daniel E. , Rai Chandra S. 
Published: October 2011

Abstract
Porosity and permeability are fundamental properties of hydrocarbon reservoirs that are important to estimation of the original hydrocarbon in-place and the production rates. These petrophysical properties are often characterized by the pore size distribution. Scanning electron microscopy studies performed on organic-rich gas shale samples have provided two- and three-dimensional images of organic pores with maximum resolution of 4-5 nm. However these images also suggest that the some of the pores and the paths connecting the pores are even smaller. In this study a different set of experimental and computational procedures based on low-temperature gas adsorption measurements are used to provide information about the porous structure of kerogen. The experimental approach involved nitrogen adsorption on crushed Barnett shale samples with sizes less than 500 microns at 77°K. Following the measurements, BET, t-Plot and DFT analyses are carried out and statistical analyses were performed to determine the distribution and the effective pore size of each sample. Monte Carlo simulations are performed in the Gibbs ensemble to predict thermodynamic states of methane in model pores with the resulting effective sizes and to estimate the amounts of adsorbed and free gases under Barnett shale reservoir pressure and temperature. Analysis show that the average organic pore widths of the samples range between 5-7 nm. The amount of adsorbed gas in a pore of this size under reservoir pressure and temperature conditions constitutes about 25% of the total gas in-place. The work is important for reservoir characterization and engineering analysis of gas shales.
Steam Chamber Development In Diatomites: The Role of Microseismic Monitoring in identifying Conformance and Out-of-Zone Fracture Growth
Authors: Baig Adam M. , Urbancic Theodore I. , Seibel Margaret 
Published: October 2011

Abstract
The treatment of diatomite reservoirs with cyclic steam is intended to enhance the mobility of the oil in reservoir, thereby stimulating hydrocarbon production. With optimized array geometries, the advanced analysis of the microseismicity resulting from these treatments can yield much more information on these events, such as their failure mechanisms through the process of moment tensor inversion. When these mechanisms suggest that the strain induced by the events is occurring on natural or newly created fractures, their orientations may be gleaned from the moment tensor.
In this study, we monitor microseismic events observed during the injection and production stages of a ‘Huff and Puff’ steaming operation in a diatomite. Our focus is on analyzing the growth of two event clusters that occurred during production cycles after steaming. Since the events are located using three downhole, we can invert for the components of failure.
One cluster showed significant vertical growth and the mechanisms of the microseisms were consistent with dilatational opening of fractures, closures of the fractures, or double-couple (shear) events. While the trend of the cluster of events is reflected in the fracture orientations of some of the events, many of the events have fractures occurring at defined angles to the overall trend. This observation allowed us to infer that the stress regime under which most of the events were responding is dynamically changing as the strain induced by surrounding events evolves in the reservoir. The second grouping of events was spatially contained and consisted of inflationary or deflationary failure mechanisms, suggesting containment that reflects steam chamber development; further exemplified by the variability in fracture azimuths, suggesting that the local stress conditions played a more significant role in the observed failures.
Based on this study, we suggest that advanced microseismic analysis has the potential to outline when steam chamber development occurs within design specifications and when the regional/local stress conditions influence steam chamber development, such as observed in the example of poor containment. In both examples, the occurrence of events during production suggests that failures occur as a result primarily as a result of stress unloading and stress re-distribution locally.
Performance of a New 2.35-in. Wireline or Memory Quad Combo for Through-Bit or Small-Hole Logging
Authors: Truax Jerome , Galford Jim , Moake Gordon , Torres David , Cherry Ron , Mandal Batakrishna , Mishra Arabinda , San Martin Luis , Quintero Alberto 
Published: October 2011

Abstract
A new UltraSlim™ quad combo has been developed and deployed with log quality very comparable to that of larger tools. The suite of logging tools is backed up by a full complement of swivels, knuckles, flex joints, springs, weights, cable head, and latches adaptable to the situation. The string can be conveyed by wireline using conventional power and telemetry, either through-and-below drill pipe or in a conventional open-hole log run. The combo can also be run in the hole by slickline inside drill pipe, then pumped out and latched beneath the bit, using its downhole battery and memory.
The tool string has been logged successfully in more than twenty commercial operations in operator wells and two of Halliburton's test wells. The combo and its peripheral equipment have performed without incident. Some of these log runs were made back-to-back with standard-sized logging equipment for the purposes of certifying that the log quality is comparable. The string features an array induction log with number of coils and spacings identical to its larger siblings, array sonic with dual transmitters, deployable-pad density with PE and caliper, dual-spaced neutron, gamma ray, and borehole environmental measurements.
This paper describes the UltraSlim logging system and provides details of its reliability, repeatability, accuracy, and petrophysical performance in comparison to standard-size logging tools, by means of visual and statistical log analysis.
Laslau Mare Field, a Successful Case of Production Optimization in Brownfield Rehabilitation
Authors: Charry Lina , Blades Amanda , Strasser Ralf , Rotar Dumitru , Stancicu Sorin 
Published: October 2011

Abstract
Romgaz, the Romanian national gas company, and Schlumberger joined forces in 2003 through a 15-year collaborative agreement for the rehabilitation of the Laslau Mare gas field. One of the main focuses of the agreement is the acquisition of data in order to develop a deeper understanding of the field, and thereby optimize the field management plan. After a First Work Program campaign, executed in 2004—2005, field production was increased by 40%; the result of workover jobs performed and elimination of surface network bottlenecks.
In addition to a portfolio of rig workovers, the approved Work Program for 2009 included an aggressive and challenging campaign of rigless interventions to optimize and maintain field production. The total production from the field has increased by 17% as a result of this rigless campaign, which mainly comprises coiled tubing interventions for water unloading (identified by slick line fluid level measurements) and the verification of the mechanical status of all active wells in the field. An additional 6% production increment was achieved with optimization of well soaping schedules, which is the current continuous water lifting method in Laslau Mare field.
The encouraging results of the rigless campaign and the additionally achieved incremental production rate were realized by implementation of the production optimization workflow outlined in this paper. This workflow aims at close monitoring of individual wells, identification of production gaps and intervention opportunities. Finally, well candidates are selected based on economic analysis.
The success of the campaign is demonstrated by the production gains and the short payout times achieved. The entire rigless intervention program paid out in a couple of months.
This paper presents the optimization workflow, its implementation to select candidates for the rigless campaign and the production and economic results of the executed work in 2009.
Evaluation of the Effect of Low Salinity Waterflooding for 26 Fields in Wyoming
Authors: Thyne Geoffrey , Gamage Pubudu 
Published: October 2011

Abstract
This report evaluates the effectiveness of low-salinity waterflooding in the Minnelusa Formation in the Powder River Basin of Wyoming. The Minnelusa sandstone play constitutes a resource of over one-hundred fields with cumulative production of more than 600,000,000 barrels of oil. We conducted initial laboratory screening using Minnelusa oil and rock with synthetic brine, supplemented with geochemical models of low-salinity injection, to evaluate the potential for low-salinity waterflooding in this formation. The laboratory experiments showed little or no incremental recovery from low-salinity injection. Calculation and comparison of recovery factors for 51 Minnelusa reservoirs were used to further evaluate the effectiveness of low-salinity waterfloods at the field scale. There was no increase in recovery for fields that used low salinity injection (26) compared to fields with mixed or formation water injection (25). Since some Minnelusa fields have relatively fresh formation water, the amount of dilution was quantified using the salinity ratio (SR), defined as the ratio of salinity of injected water to salinity of formation water. This analysis showed that while some fields actually had little or any salinity reduction (13), the remaining fields with significant dilution (38) still showed no correlation between dilution and recovery factor. Since some postulated mechanisms involve change in wettability, injection of low-salinity water may produce later water breakthrough. Analysis of water breakthrough timing and watercut evolution for 23 fields found no significant difference between fields with low-salinity injection and mixed-water or saline injection.
Characterization of Microbial Diversity in Treated and Untreated Flowback Water Impoundments From Gas Fracturing Operations
Authors: Mohan Arvind Murali , Gregory Kelvin B. , Vidic Radisav D. , Miller Peter , Hammack Richarad W. 
Published: October 2011

Abstract
Operators in the Marcellus shale have a strong desire to recycle and reuse waters, particularly flowback for continued use. Recycling water provides many benefits, such as; reduced total water consumption, reduced community impact through decreased truck traffic, and energy savings through avoiding advanced water treatment technologies. With all of the benefits water recycling and reuse has presented, the practice also presents a new set of logistical challenges for the industry that demand an even greater understanding of the unique nature of flowback water.
Flowback water from the Marcellus shale often contains higher concentrations of total dissolved solids than traditional produced waters from drilling as well as some metals and hydrocarbons. When impounded prior to treatment and reuse, microbial populations arise and their activity changes the composition of the organic fractions, solubility of metals, and may result in aesthetic issues associated with the odors from gaseous sulfur and nitrogen compounds from microbial metabolism. In order to develop the type of sustainable process the industry, regulators and the communities desire, we characterized and enumerated microbial communities in treated and untreated flowback water impoundments from the Marcellus Shale to gain a comprehensive understanding of those microbial communities and how they are impacted by pre-treatment. We examined the communities at several depths in each impoundment using 16S rRNA gene clone libraries to enable description of the populations with species-level specificity. Results show that flowback water impoundments develop microbial populations that are distinctly different with pretreatment. Within each treated and untreated impoundment, the microbial communities also varied with depth. The treated impoundment was predominately enriched with bacteria closely related to known aerobic hydrocarbon degraders in the α-proteobacterial clade. Untreated impoundments were more diverse and featured populations most closely related to fermentative organisms, those associated with anaerobic sulfur cycling, hydrocarbon degradation and biogenic methane production. Quantification of 16S rRNA genes indicated higher biomass in the untreated impoundments as compared to the treated impoundment. This is the first study to characterize microbial communities in flowback water from the Marcellus shale. Specific knowledge of microbial populations that thrive in flowback water will help producers develop effective management strategies.
Numerical Prediction of Relative Permeability from MicroCT Images: Comparison of Steady-State versus Displacement Methods
Authors: Sheng Q. , Thompson K. E. , Fredrich J. T. , Salino P. A. 
Published: October 2011

Abstract
Numerical prediction of rock properties is a rapidly evolving area that has the potential to influence dramatically how core analysis is performed. In this paper, we investigate the numerical prediction of relative permeability from micro-computed tomographic images using pore network modeling. Specifically, we apply four different algorithms to a digital image of a reservoir sample that has been tested using traditional core analysis, and compare the results. The four algorithms are the following: quasi-static, unsteady-state, steady-state periodic, and steady-state non-periodic. They differ significantly in terms of the physics that they are designed to capture and their computational performance, but there is no published research quantifying how these differences affect the simulation of relative permeability. We show that the traditional quasi-static algorithm exhibits outstanding computational performance, but gives results that are the most different from the other three methods. The unsteady- and steady-state simulations give surprisingly similar results given the differences in how relative permeability is obtained. The two steady-state methods differ little under the conditions tested. This result is encouraging because the periodic simulation is significantly more computationally efficient. However, it raises questions about the ability to capture hysteretic behavior. Phase saturations are mapped from the network results onto the digital images of the pore space as a means to help interpret differences in the pore-scale behavior of the models. Finally, results are compared to relative permeabilities from laboratory corefloods.