bluuebunny/crossref_metadata_2025 huggingface dataset:
Earliest Eocene Miacidae (Mammalia: Carnivora) from northwestern Wyoming
Authors: Heinrich Ronald E. , Strait Suzanne G. , Houde Peter
Published: December 2007

Fossil carnivorans are described from earliest Eocene localities in the Clarks Fork and southern Bighorn basins of Wyoming. Three new species,Miacis rosei, Uintacyon gingerichi, andVassacyon bowni, collected from the base of the Wasatchian North American Land Mammal Age (Wa-0), are the smallest and possibly most basal members of their respective genera, and increase from one to four the number of miacids known from this faunal zone. An upper dentition ofMiacis deutschifrom slightly younger (Wa-2) deposits is also described. Previously known only from lower teeth and a single M1, the specimen ofM. deutschiincludes the left P3-M2, alveoli for the canine, first two premolars and the last molar, as well as most of the maxilla. the new material helps fill gaps in our knowledge of the dental morphology of basal Miacidae and provides insight into the functional differences of the carnassial teeth in the divergingUintacyonandMiacislineages. It also provides an opportunity to further assess the hypothesis that climactic warming in the earliest Eocene resulted in evolutionary dwarfing of mammalian species; based on three criteria for identifying dwarfed species at least one of the new taxa,U. gingerichi, is consistent with this hypothesis.
Morphometrics ofManipora(Tabulata; Upper Ordovician; southern Manitoba, Canada)
Authors: Bae Boo-Young , Elias Robert J. , Lee Dong-Jin
Published: December 2007

Multivariate morphometric analysis was applied for differentiation of closely related species and evaluation of intra- and interspecific variation inManiporafrom the Selkirk Member, Red River Formation, in southern Manitoba. Seven morphological characters were quantified in transverse thin sections of 46 coralla and statistically tested for selecting effective characters in discriminating species. Cluster analysis was performed on a raw data matrix coordinated with 46 coralla by three selected characters. Two major clusters on the resulting dendrogram were regarded as morphospecies, following comparative examination of the coralla using serial sections. Cluster analyses were also conducted on principal component score matrices obtained from the raw data set coordinated with 46 coralla by all seven characters, and from an experimental data set including the 46 coralla plus two replicates of each and six of the characters. the results agree closely with the first cluster analysis, but discrimination of morphospecies was slightly degraded. the validity of two morphospecies recognized in the first cluster analysis was verified by discriminant analyses, descriptive statistics, and bivariate plots. the results show that tabularium area is the most meaningful character for distinguishing these morphospecies; ranges of variations of the other six characters overlap between morphospecies.

Another cluster analysis like the first was performed, but with the addition of 11 type specimens and reference coralla ofManiporaspecies from the Upper Ordovician of southern and northern Manitoba and Texas. Based on this analysis, together with comparative examination of thin sections, the two morphospecies are identified as valid species:M. amicarumSinclair, 1955 andM. manitoba(Sokolov, 1955).Manipora magnaFlower, 1961 is considered to be a synonym ofM. amicarum, whileM. trapezoidalisFlower, 1961 andM. garsonensisCaramanica, 1992 are considered to be synonyms ofM. manitoba, and the hypotypes ofM. amicarumof Nelson (1963) are assigned toM. manitoba.
Permian fusulinids from the Tengchong Block, Western Yunnan, China
Authors: Yukun Shi , Xiaochi Jin , Hao Huang , Xiangning Yang
Published: December 2007

Two Permian fusulinid faunas, including nine species belonging to six genera, from the northern Tengchong Block, Southwest China, are studied and compared with the coeval fusulinid faunas from other blocks with Gondwana-affinity and South China. in the Kongshuhe section, the fauna is dominated byEoparafusulinain the lower part of the Dadongchang Formation and possibly suggests an age of Sakmarian, while in the Shanmutang section, the fauna from the middle of the Dadongchang Formation mainly consists ofChusenella mingguangensisn. sp. andMonodiexodina gigasn. sp., indicating a Wordian to Capitanian age. Study has also demonstrated that fusulinid faunas from the Tengchong Block shared similar features with the contemporary faunas from the Baoshan Block and Sibumasu Block in the low generic and specific diversities and the absence of the taxa commonly found in Cathaysia Tethys areas, such as the Pseudoschwagerinidae, Verbeekinidae, and Neoschwagerinidae. However, visible differences in species composition still exist between the faunas of the Tengchong Block and those of the other two blocks, revealing an apparent regional feature in the faunas of the Tengchong Block.
Silurian sponges and some associated fossils from the Heceta Limestone, Prince of Wales Island, southeastern Alaska
Authors: Rigby J. Keith , Rohr David M. , Blodgett Robert B. , Britt Brooks B.
Published: December 2007

A small faunule of hypercalcified agelasiid demosponges has been recovered from outcrops of the Silurian Heceta Formation on Prince of Wales Island in southeastern Alaska. Included are abundantGirtyocoeliana epiporata(Rigby and Potter, 1986), of the Girtyocoeliidae Finks and Rigby, 2004; fragments ofAlaskaspongiella laminosan. gen. and sp.,Polyplacospongia nodosan. gen. and sp., andMonolaminospongia gigantian. gen. and sp., of the Auriculospongiidae Termier and Termier, 1977, andCladospongia alaskensisn. gen. and sp.,Virgulaspongia uniforman. gen. and sp., andStipespongia laminatan. gen. and sp. of the Preperonidellidae Finks and Rigby, 2004. Also included are a few fossils of uncertain taxonomic placement, includingTurbospongia biperforatan. gen. and sp., along with a small, chambered, tubular fragment and several porous tubular stems that may be additional poriferans. Some isolated octactine-based heteractinid spicules were also recovered from the etched residues.
Temporal variation in estrogen receptor-α protein turnover in the presence of estrogen
Authors: Valley Christopher C , Solodin Natalia M , Powers Ginny L , Ellison Stephanie J , Alarid Elaine T
Published: December 2007

Estrogen receptor-α (ERα) is essential in the maintenance of cellular responsiveness to estrogen in the reproductive system. It is established that ligand binding induces downregulation of ERα protein by targeting receptor for destruction by the 26S proteasome. However, ERα is preserved in cells chronically exposed to estrogen and it is unknown how receptor levels are maintained in the continued presence of the signal that induces degradation. A modified pulse-chase analysis was developed using a tet-inducible ERα expression system to determine the rate of ERα protein decay following both acute and chronic estrogen treatments. Upon initial hormone treatment, ERα half-life is shortened from 3 to 1 h. However, ERα half-life increases over time, achieving a half-life of ∼6 h in 72 h of estrogen treatment. Analysis of ERα half-life in the presence and absence of proteasome inhibitor, MG132, revealed that the increased stability is due in part to a decreased rate of proteolysis. In addition, we observed a time-dependent increase in phospho-S118 ERα and showed that the half-life of the phosphomimetic ERα mutant, S118E-ER, is identical to that of wild-type receptor under conditions of chronic estrogen treatment. These data provide evidence that as cells adapt to chronic stimulation, ERα protein is stabilized due first to a decreased rate of proteolysis, and secondarily, to the accumulation of proteasome-resistant, phosphorylated form of receptor. This temporal control of proteolysis allows for the establishment of steady-state levels of receptor and provides a protective mechanism against loss of hormone responsiveness.
TEACHING MATH SKILLS TO AT‐RISK STUDENTS USING HOME‐BASED PEER TUTORING
Authors: Mayfield Kristin H. , Vollmer Timothy R.
Published: December 2007

Home‐based peer tutoring was used to teach math skills to 4 girls with deficits in mathematics and histories of abuse or neglect. Girls living in the same home formed tutoring dyads, and each participant served as both the peer tutor and the tutee during the course of the study. At the initiation of the tutoring intervention, an expert tutor provided multiple 3‐min tutoring sessions to the designated peer tutor on three or four mathematics skills. The peer tutor concurrently provided 3‐min tutoring sessions on the same skills to the tutee using a multiple baseline design. Results showed that participants improved their performance on all target skills. Additional interventions were implemented for some skills to improve accuracy further. Maintenance tests were also administered after 3 to 5 months of no practice on the skills. Results showed that tutors and tutees maintained their accuracy on 7 of the 12 skills assessed.
ASSESSING AND TREATING VOCAL STEREOTYPY IN CHILDREN WITH AUTISM
Authors: Ahearn William H. , Clark Kathy M. , MacDonald Rebecca P. F. , Chung Bo In
Published: December 2007

Previous research implies that stereotypic behavior tends to be maintained by the sensory consequences produced by engaging in the response. Few investigations, however, have focused on vocal stereotypy. The current study examined the noncommunicative vocalizations of 4 children with an autism spectrum disorder. First, functional analyses were conducted in an attempt to identify the function of each child's behavior. For each of the participants, it was found that vocal stereotypy was likely not maintained by the social consequences. Following assessment, response interruption and redirection (RIRD) was implemented in an ABAB design to determine whether vocal stereotypy could be successfully redirected. RIRD involved a teacher issuing a series of vocal demands the child readily complied with during regular academic programming. Vocal demands were presented contingent on the occurrence of vocal stereotypy and were continuously presented until the child complied with three consecutively issued demands without emitting vocal stereotypy. For each child, RIRD produced levels of vocal stereotypy substantially lower than those observed in baseline. For 3 of the children, an increase in appropriate communication was also observed. The children's teachers were trained to implement RIRD. Brief follow‐up probes and anecdotal information implied that the treatment had a positive impact in the natural environment.
EVALUATION OF A CLASSWIDE TEACHING PROGRAM FOR DEVELOPING PRESCHOOL LIFE SKILLS
Authors: Hanley Gregory P. , Heal Nicole A. , Tiger Jeffrey H. , Ingvarsson Einar T.
Published: December 2007

Recently, nonmaternal center‐based child care has been linked to problem behavior in young children (National Institute of Child Health and Human Development, 2003). In response, a comprehensive program to promote prosocial skills was evaluated in a classroom of 16 children between the ages of 3 and 5 years. Classroom observations were conducted during evocative situations to determine the likelihood of problem behavior (noncompliance, vocal or motor disruptions, aggression) and preschool life skills. A classwide teaching program was then implemented in a staggered manner across instruction following, functional communication, delay tolerance, and friendship skills. These four categories of preschool life skills, which included two to four related skills, were selected for classwide teaching because they were either identified by educators as important for early school success, have often been taught following functional assessments of more severe problem behavior, or both. Skills were taught on a classwide basis during typically scheduled activities (circle, free play, transitions, meals) via instructions, modeling, role play, and feedback. A multiple probe design showed that the program resulted in an 74% reduction in problem behavior and a more than four‐fold increase in preschool life skills. Similar beneficial effects of the program were evident in questionnaire data gathered prior to and at the close of the evaluation. Finally, the teachers who implemented the program reported overall high levels of satisfaction with the classwide teaching program, the target skills, and the results. Implications for the design of early childhood experiences for preempting the development of serious problem behavior are discussed.
EFFECTS OF TEACHER GREETINGS ON STUDENT ON‐TASK BEHAVIOR
Authors: Allday R. Allan , Pakurar Kerri
Published: December 2007

A multiple baseline design across participants was used to determine how teacher greetings affected on‐task behavior of 3 middle school students with problem behaviors. Momentary time sampling was used to measure on‐task behavior during the first 10 min of class. Teacher greetings produced increases in students' on‐task behavior from a mean of 45% in baseline to a mean of 72% during the intervention phase. Teacher greetings represent an antecedent manipulation that can easily be implemented in classrooms to improve students' on‐task behavior.
A Screening Model for CO2 Flooding and Storage in Gulf Coast Reservoirs Based on Dimensionless Groups
Authors: Wood D. J. , Lake L. W. , Johns R. T. , Nunez V.
Published: December 2007

Concerns over global warming have led to interest in removing greenhouse gases, specifically CO2, from the atmosphere. Sequestration of CO2 in oil reservoirs as part of enhanced oil recovery (EOR) projects is one method being considered.

This paper first presents the scaling groups necessary to describe CO2 flooding for a typical line-drive pattern, and then uses these groups in a Box-Behnken experimental design to create a screening model most applicable to candidate Gulf Coast reservoirs. By generating oil recovery and CO2 storage curves, the model estimates the cumulative oil recovery and CO2 storage potential for a given reservoir. Past screening models – Rivas et al.1 and Diaz et al.2 – focused only on oil recovery and simply assigned qualitative rankings to reservoirs. Models that did include quantitative results, including CO2 Prophet3 and the CO2 Predictive Model4, did not include the effects of dip. This model focuses on both oil recovery and CO2 storage potential, produces quantitative results for each, and includes the effects of dip.

This model quickly estimates the oil recovery and CO2 storage potential for a reservoir. Operators alike can quickly screen large databases of reservoirs to identify the best candidates for CO2 flooding and storage. The scaling groups also provide the basis for future models that may be more specific to other regions.

The results show that continuous CO2 flooding can be fully described using ten dimensionless groups - aspect ratio, dip angle group, water and CO2 mobility ratios, buoyancy number, dimensionless injection and producing pressures, residual oil saturation to water and gas, and initial oil saturation. The effects of capillary forces and dispersion were secondary effects in this model and were not included in the scaling. Dimensionless oil recovery was effectively modeled with the dimensionless oil breakthrough time and the dimensionless recovery at three different dimensionless times, while CO2 storage potential was calculated only at the final dimensionless time. The reservoir-specific parameters discussed above were calculated from response surface fits. The scaling does not work as well at small buoyancy numbers; however, it is effective in the range of values typical of Gulf Coast reservoirs.
Sand Erosion in Weakly Consolidated Reservoirs: Experiments and Numerical Modeling
Authors: Servant G. , Marchina P. , Peysson Y. , Bemer E. , Nauroy J. -F.
Published: December 2007

Allowing sand to be produced is widely known to enhance oil production rates particularly for heavy-oils fields. However, in such a situation, it is very important to be able to determine the expected sand rate as well as the amount of sand produced during the life of the well.

To address this problem, an oedometric cell specially designed to simulate a radial flow towards a well has been developed at IFP. Tests performed under CT-scan on cohesionless sand samples allow to monitor in real time the initiation of the sand production and to follow the development of the sand producing zone.

In parallel, a numerical approach is proposed to simulate the dominant sanding mechanism. The theoretical model is based on the resolution of the equations of equilibrium at the interface between the intact zone and the slurry made of eroded sand and oil. An algorithm in 2-D was developed and implemented in a finite element code. Two calculations are alternatively performed: one on the intact zone (rock mass) and one on the slurry, respectively considered as a poroelastic medium and a Newtonian fluid. For each time step, it implies an iterative process to determine the unknown fluid pressure and solid displacements at the interface. The boundary between the slurry and the porous medium evolves as sand is produced. The problem to solve has then a geometry varying with time, but no a priori assumptions are made on the shape of the altered zone.

Modeling of the laboratory sand production experiments allows the ability of this model to reproduce the observed sand production mechanisms to be assessed. The influence on the results of numerical (temporal and geometrical discretization) parameters is also discussed.
An Experimental Study of Driving Mechanisms in MIOR Processes by Using Rhodococcus sp. 094
Authors: Crescente C. , Torsaeter O. , Hultmann L. , Stroem A. , Rasmussen K. , Kowalewski E.
Published: December 2007

Microbially Improved Oil Recovery with both a surfactant producing and a non surfactant producing variant of Rhodococcus sp 094 has been tested through coreflooding laboratory tests. A goniometer was also used to measure interfacial tension and wettability for the fluid systems involved in the corefloodings. Significant reductions of interfacial tension have been measured for both variants of the bacteria. Wettabilities also changed and bacterial systems were more oil wet than their brine counterpart. The effect of bacteria concentration on overall recovery also became apparent.
Feasibility Study of WAG Injection in Naturally Fractured Reservoirs
Authors: Heeremans J. C. , Esmaiel T. E. H. , Van Kruijsdijk C. P. J. W.
Published: December 2007

The fundamental aspects of Water Alternating Gas (WAG) injection are still not well understood. There are a few applications in fractured media and these show potential1. This study looks at the sensitivity of production to reservoir and fluid properties on a pattern scale using tools derived from experimental design. Also a look has been taken into the drive mechanisms in the fractured media that play an important role during WAG injection.

Earlier studies claimed that WAG injection in fractured reservoirs is not the best improved oil recovery (IOR) method2. However when the conditions are fully understood and the injection is modeled correctly, it is optimal in some fractured reservoirs. The proper modeling of fractured reservoirs remains difficult. The standard dual porosity formulation in commercial simulators is based on a continuous matrix grid overlaid by a continuous fracture grid. The transfer of fluid from matrix to fracture is described by a transfer function. The heart of this transfer function is the shape factor, sigma. As can be seen in a fine-scale grid, the shape factor is different for different reservoir properties and injection types. The upscaling of this sigma from the fine-scale grid to the pattern scale model is important for correct modeling. This study performs several fine scale single porosity simulations to properly upscale the flow model to a dual system.

The process of determining sensitivities in an organized manner on properly upscaled models will be shown here with a limited number of parameters. Fractured reservoirs can be divided into different categories3. Based on a fine grid model of one type of fractured media, a dual porosity model with varying parameters is set up. This yields recovery outputs across a range of reservoir properties that are represented by two dimensionless numbers. These numbers represent the capillary over viscous and gravity over viscous forces. By looking into the mechanisms that are behind the recovery in different balances of forces, an insight into when and why WAG is working is given.
Unconventional EOR Program Increases Recovery in Mature WAG Patterns at Prudhoe Bay
Authors: Rathmann M. P. , McGuire P. L. , Carlson B. H.
Published: December 2007

A large scale miscible water-alternating-gas (WAG) project was implemented in the Prudhoe Bay field in 1987. Many of the original patterns are no longer receiving miscible injectant (MI) due to pattern maturity and diminishing EOR response. The EOR project is being revived in the gravity-dominated eastern part of the Prudhoe Bay Field waterflood area, Flow Station 2 (FS2), by using horizontal sidetracks to place MI at various locations within existing conventional WAG patterns which have a significant remaining EOR target.

The sidetracks are completed at the toe and then perforated sequentially along the length of the horizontal wellbore to allow up to 7 independent points of miscible gas injection. Distributing the injection points enables MI to contact additional pore volume not contacted by the original WAG injector due to gravity segregation of the MI as it moves away from the injection wellbore.

Typical WAG benefits in this area range between 0.5 to 2 MMSTB. MIST injectors (MI Sidetracks) are recovering an additional 1.5 to 4.8 MMSTB in patterns that have already been WAG flooded. Typical MIST patterns accumulate 3 to 4 times the EOR reserves of conventional vertical well WAG patterns.

This paper will explain the reservoir characteristics that contribute to such large incremental recoveries. It will also cover well design and operational issues. Based upon the success of the initial MIST program, several additional MIST patterns have been drilled, and more are possible.
Formation and Propagation of Gel Aggregates Using Partially Hydrolyzed Polyacrylamide and Aluminum Citrate
Authors: Al-Assi A. A. , Willhite G. P. , Green D. W. , McCool C. S.
Published: December 2007

A comprehensive study of the formation of gel aggregates in systems containing partially hydrolyzed polyacrylamide and aluminum citrate was completed. Under certain conditions, this system forms gel aggregates, commonly referred to as colloidal dispersion gels. Systems that formed aggregates on the exit screen of a screen viscometer also developed flow resistance when displaced through slim tubes and sand packs. A gel system containing 1000 ppm polymer and 33.3 ppm aluminum citrate was studied in sand packs 2ft and 4ft long. In the 2ft sandpack, the gelant showed no significant difference in the flow resistance when compared to polymer injection when 8.7 pore volumes were injected with at residence time 0.83 hours after mixing the gelant inline prior to injection. However, a high flow resistance developed after the sandpack was shut in for 31.4 hours. Viscosity measurements indicate that solution viscosity increases about 15 hours after mixing the solutions but a visible gel structure is not formed.

In the 4ft sandpack, gelant was injected at a slow rate so that the residence time was 19.2 hours. A high flow resistance developed across the entire length of the sandpack demonstrating the formation and retention of gel aggregates in the sandpack. Our experimental data demonstrate that gel aggregates can be formed by reaction of partially hydrolyzed polyacrylamide with aluminum citrate and propagated through sandpacks. Permeability to brine following the gelant treatment was reduced by a factor of about 9000. In-depth treatment of a porous matrix by this process is limited because retention of gel aggregates causes the permeability to decrease leading to reduction in flowrate.
A Single-Shot Method for Capillary Pressure Curve Measurement Using Centrifuge and Quantitative Magnetic Resonance Imaging
Authors: Chen Q. , Balcom B. J.
Published: December 2007

The centrifuge method for capillary pressure curve measurement involves increasing the centrifuge speed in steps and measuring the liquid expelled from a short core plug, at equilibrium, for each step. However, the traditional methods for deducing approximate solutions for the capillary pressure curve are based on the assumption that the capillary pressure is zero at the outflow end of the core. In addition, the traditional centrifuge methods for capillary pressure measurement are time consuming. A full capillary pressure curve requires approximately 10 different rotational speeds. We have observed for most sedimentary rocks that the experimental magnetic resonance free induction decay is single exponential and the effective transverse relaxation time (T2*) is largely insensitive to fluid saturation. These features ensure that Centric Scan SPRITE (single-point ramped imaging with T1 enhancement) is a quantitative magnetic resonance imaging (MRI) method, since its local image intensity is directly proportional to the local fluid content. We propose a single-shot method to measure the capillary pressure curve of a long rock core using a single-speed centrifuge experiment and one-dimensional Centric Scan SPRITE MRI to determine the fluid saturation distribution, S(r), along the length of the core. A full capillary pressure curve can be directly determined by the relation of S(r) and the capillary pressure distribution, Pc(r), along the length of the core.

The single-shot method, employing a desktop centrifuge and a desktop permanent magnet based one-dimensional MRI instrument, has been applied to measure the primary drainage, imbibition, and secondary drainage capillary pressure curves for reservoir rocks.

The proposed method for determining the capillary pressure curve is rapid, cheap, and precise. The capillary pressure curve can be obtained straightforwardly with about 40 data points. The duration of the experiment is approximately 10 times less than the traditional method. Since only a single moderate rotational speed is employed, the outflow boundary condition can be maintained, and the effect of gravity can be neglected. In addition, the long rock cores employed for the single-shot method result in a relatively small radial effect.
EOR Field Experiences in Carbonate Reservoirs in the United States
Authors: Manrique E. J. , Muci V. E. , Gurfinkel M. E.
Published: December 2007

A considerable portion of the world's hydrocarbon endowment, and even more so if resources from the Middle East are excluded, are in carbonate reservoirs. Carbonate reservoirs usually exhibit low porosity and may be fractured. These two characteristics in addition to oil-to-mixed wet rock properties usually results in low recovery. When enhanced oil recovery (EOR) strategies are pursued, the injected fluids will likely flow is through the fracture network, bypassing oil in the rock matrix. The high permeability in the fracture network and its low equivalent porous volume result in early breakthrough of the injected fluids. Infill drilling programs and well conformance strategies, mostly gas and water shutoff, have been effectively used to mitigate the early breakthrough and increase oil recovery. However, in most cases, 40 to 50% of the original oil in place (OOIP) is not produced.

A large number of EOR field projects in carbonate reservoirs have been reported in the literature since the early 70's. The field projects showed the technological capability to increase oil recovery and estimated long run costs for their operation. This increase in oil recovery would directly result in additional reserves extending the productive life of the different assets. However, the technical results were not matched by their economic viability given the price environment of the time. In some cases high upfront investments created insurmountable barriers for the technology's application despite the promise of higher returns. In other cases, the high marginal costs eliminated all benefits from the increased recovery. The latter was especially true for EOR processes based on chemical and thermal methods. Over the last three decades, many improvements have reduced the cost per incremental barrel as will be seen below. Carbon dioxide flooding (continuous or alternating with water-WAG) is the dominant EOR process in the United States, mostly due to the availability of appropriate CO2. CO2 EOR is also the stepping stone towards sequestering carbon which could become a future business opportunity if carbon trading ever is implemented.

This paper presents an overview of EOR field experiences in carbonate reservoirs in the United States, an analysis of recent efforts and discusses briefly on new opportunities for novel chemical methods. The main EOR experiences reviewed are CO2 injection, polymer flooding, steam injection and in-situ combustion (air injection).
Experimental and Modeling Study of the Transport of Chromium Acetate Solutions Through Carbonate Rocks
Authors: Chen F. , McCool C. S. , Green D. W. , Willhite G. P.
Published: December 2007

The transport of chromium acetate solutions through dolomite rock material was studied by injecting various solutions through short dolomite cores and measuring Cr, Mg, and Ca concentrations and pH in the effluent. A mathematical model was developed that describes convection, dispersion, kinetic reactions of carbonate dissolution and chromium precipitation, and chemical equilibrium for reactions between aqueous components. Experimental data and data taken from literature were simulated by the model.
Rate-Time Flow Behavior of Heavy Oil From Horizontal and Multilateral Wells
Authors: Fetkovich M. D. , Petrosky G. E. , Hughesman C. B. , Sawatzky R. P.
Published: December 2007

This paper examines the behavior of heavy oil reservoirs developed with horizontal and multilateral wells. Advanced decline curve analyses were used to characterize flow regimes and estimate the time to pseudosteady-state. Reservoir and well parameters such as the OOIP, Arps "b" exponent, decline rate, reserves, permeability and well productivity indices were also determined.

Example analyses are presented for single, dual and triple lateral wells from heavy oil fields located in Venezuela and Canada. All wells exhibit a characteristic extended transient linear flow regime followed by an exponential decline. Similar results were obtained whether the analyses were performed on single, dual or triple lateral wells. Interference between laterals was not observed.
Simulation of Gelled Polymer Treatments in the Arbuckle Formation, Kansas
Authors: Barati R. , Green D. W. , Liang J. T.
Published: December 2007

Gel polymer treatments have been carried out on a large number of producing wells in the Arbuckle Formation of Central Kansas. These treatments have been aimed both at reducing water coning from an underlying aquifer and increasing oil production. This paper describes computer simulation of two of these gel-treated wells. One is a well for which the treatment was successful and the second is a well which responded far less favorably. For each well, performance before, during and after a treatment was modeled using single porosity and dual permeability models, i.e. reservoir simulators that are based on matrix flow only or on fracture-matrix flow. For the fracture-based model, it was assumed that the producing well was connected to an underlying aquifer through a high vertical permeability fracture system.

Well performance during the polymer injection period of the treatments and the post-treatment behavior were such that there were major differences in history matching between the single porosity model (no fractures) and the fracture model. For the well that was treated successfully, behavior during polymer injection as well as post-treatment performance could be matched only with the dual permeability model. No reasonable set of parameters was identified for the single porosity (matrix flow) model that allowed a suitable history match of these same data. For the well that was treated unsuccessfully, the converse was true. An acceptable history match was obtained only with the single porosity model or with the fracture model with a very sparse fracture density. The results indicate that the presence of natural fractures connected to an aquifer is an important feature of the Arbuckle wells that respond favorably to polymer gel treatments.
Modeling Wettability Alteration in Naturally Fractured Reservoirs
Authors: Delshad M. , Najafabadi N. F. , Anderson G. A. , Pope G. A. , Sepehrnoori K.
Published: December 2007

Laboratory surfactant and hot water floods have shown a great potential in increasing oil recovery for reservoirs that are naturally fractured and have low permeability mixed-wet matrix rocks. Fractured, mixed-wet formations usually have poor waterflood performance because the injected water tends to flow in the fractures and spontaneous imbibition into the matrix is not very significant. Surfactants have been used to change the wettability for increasing the oil recovery by increased imbibition of the water into the matrix rock. The mechanisms for oil recovery are combined effects of reduced interfacial tension, reduced mobility ratio, and wettability alteration. The goal of this research is to adapt an existing numerical reservoir simulator to model chemical processes that lead to wettability alteration in naturally fractured reservoirs. Surfactants have been used to change the wettability with the goal of increasing the oil recovery by increased imbibition of the water into the matrix rocks. Reservoir simulation is required to scale up the process from laboratory to field conditions and to understand and interpret reservoir data. We have adapted the chemical flooding simulator, UTCHEM, to model improved oil recovery processes that involve wettability alteration using surfactants. Multiple relative permeability and capillary pressure curves corresponding to different wetting states are used to model the wettability alteration. Simulations were performed to better understand and predict enhanced oil recovery as a function of wettability alteration and to investigate the impact of uncertainties in the fracture and matrix properties, reservoir heterogeneity, matrix diffusion, buoyancy driven flow, initial water saturation, and formation wettability.
Optimization of Chemical Flooding in a Mixed-Wet Dolomite Reservoir
Authors: Anderson G. A. , Delshad M. , King C. B. , Mohammadi H. , Pope G. A.
Published: December 2007

Many pilot tests and several commercial field projects have been performed over the past few decades and have shown that surfactant/polymer and alkaline/surfactant/polymer floods can recovery high percentages of residual oil saturation. However, these chemical processes are sensitive to parameters such as chemical slug size and concentrations, salinity, reservoir heterogeniety and surfactant adsorption among other key parameters. In this study, a sensitivity analysis of these key parameters was performed to optimize a chemical flood design for a mixed-wet dolomite reservoir in the Permian Basin. The simulations were performed using the reservoir simulator UTCHEM, a multiphase, multicomponent chemical flooding simulator. The base case design was developed using a reservoir model provided by the operator, injection and production rate constraints from actual field conditions, brine and oil properties from the field, and chemical properties provided by the EOR laboratory at the University of Texas. An optimum design was selected based on net present value calculated from discounted cash flow analysis. The results of this study showed that chemical flooding this mixed-wet dolomite reservoir is likely to be profitable over at range of crude oil prices based upon the laboratory performance of the surfactant/polymer flood and the optimum process design determined in this study.
Scratch Testing of Drilling Mud Filter Cakes
Authors: Cerasi P. , Larsen I. , Stenebråten J. F. , Sønstebø E. F.
Published: December 2007

We adapted a scratch apparatus used to evaluate shear strength and stiffness of rocks to use on soft filter cakes, to obtain quantitative information on cake properties for modelling purposes. The modelling will help design better drilling fluids, in terms of their filter cake's resistance to oil production onset. Scratch testing of rock specimens is now a well established method to obtain reliable strength and stiffness measurements as a function of distance along the scratched surface. The apparatus consists of a rigid frame holding a cutter, being pushed at a constant velocity over a rock specimen. A micrometric screw allows the user to choose a precise cutting depth, while a bidirectional load cell monitors the shear and normal forces on the cutter. The shear force can be related to the specific energy of cutting, which in turn correlates with the Unconfined Compressive Strength (UCS) of the rock. New low-resolution load cells have been installed in anticipation of the orders of magnitude lower expected values when scraping filter cakes. Rocks were exposed to different fluids to assess the impact on filter cake quality and inner filter cake properties. The effect of the internal filter cake on the rock was also addressed by scratching the rocks prior to filtration and once again after, scratching through the filter cake, on the exposed rock face. Quantitative and detailed probing of filter cake elastic properties is now possible using the scratch method. Concerns about removing the filter cake all at once (especially when OBM systems are tested, known for their low adhesion) turned out to be unfounded; the tool was capable of scraping out clean, well-defined cake layers, down to a thickness of 0.1 mm.
Application of Artificial Intelligence in Gas Storage Management
Authors: Zangl G. , Giovannoli M. , Stundner M.
Published: December 2007

An approach is investigated, to reduce the amount of CPU time needed to execute a numerical full field model in an optimization loop.

To demonstrate the power of this approach, a real life example is presented. Data from a gas storage reservoir have been used to setup a single tank material balance program. Then, a limited number of simulation runs is carried out. These simulation runs are intended to span over the whole range of input parameter variation (app. 25 runs).

In a next step, a Neural Network (NN) model is setup. By training a Neural Network on the so gained simulation outputs, a model, which is able to interpolate between the individual simulation scenarios is created. In this way, a large variety of different scenarios can be represented with a limited amount of model runs.

The trained Neural Network model is used as a proxy function for an optimization routine. The trained Neural Network has been used as fitness function for the Genetic Algorithm to minimize the output parameter, which is in this example the RMS-error of measured and calculated tank pressure. Due to the very low CPU consumption of the Neural Network, a large number of realisations can be calculated in a short amount of time. By this, the absolute minimum of the desired output parameter (in this case the RMS-error) can be evaluated in a few seconds.

The Genetic Algorithm has succeeded to find a minimum, which is located very close to the absolute minimum of all possible solutions.
Use of Ensemble Kalman Filter With 3-Dimensional Reservoir Characterization During Waterflooding
Authors: Park K. , Choe J.
Published: December 2007

In order to estimate reserves accurately and maximize oil and gas productions, it is critical to characterize unknown properties of a reservoir. However, it is very challenging because of severe non-linearity, non-uniqueness, and large number of variables with different levels of uncertainties. In 1994, the Ensemble Kalman Filter (EnKF) was developed in ocean dynamics. Afterwards, EnKF has been successfully applied in many areas such as oceanography, hydrology, and navigation systems to overcome those difficulties in non-linear inverse modeling.

Recently, EnKF was introduced to petroleum engineering for continuous reservoir update. Although its applications look promising, there are couples of complicated problems observed for updating a reservoir model. Firstly, although there are more available measurements, the tendency to find the solution may not look satisfactory after some number of updates, especially near the boundaries. Secondly, because EnKF is based on mathematical theories, the solution sometimes includes physically unreasonable values. Therefore, we need to improve EnKF for successful reservoir characterization.

In this paper, we investigate causes of the two problems mentioned and find methods that are able to resolve them. For our objectives, we develop a reservoir characterization model using EnKF and apply to waterflooding using streamline approach for multiphase reservoir simulation. After certain number of updating, estimate error covariance of the ensemble reduces to very low, and the ensemble members become close and do not provide any ensemble effects. In order to solve the problem, we control the decrease of estimate error covariance through the regeneration of ensemble, which results in increase of error covariance.

Additionally, we examine the measurements thoroughly and use the measurement data selectively which contain helpful data for model updates. For example, the saturation data before and after the breakthrough are not sensitive to reservoir permeability or porosity distribution. However, the unnecessary measurements can make significant undesirable updates in EnKF. In a synthetic reservoir, the developed EnKF relieves the effects of the two problems and provides satisfactory solution for real-time history matching and reservoir characterization with high efficiency and reliability.
New Ways of Handling and Running C.R.A. Tubulars Prevent Corrosion in H2S and CO2 Environments
Authors: Kinzel H. , Kiess C. , Wachs T. P. , Badrak R. P.
Published: December 2007

In a corrosive downhole environment, the service life of a completion can be severely reduced if no precautions against corrosion are taken. Pipe made of corrosion resistant alloys (C.R.A.) is used to minimize corrosion. An analysis of various corrosion mechanisms shows that the surface integrity is an important factor for corrosion prevention [3].

Conventional spider and elevator inserts as well as conventional hydraulic power tong dies made of steel cause die marks that support corrosion. A gripping system named Micro-Grip distributes the required load equally onto a large number of small peaks, minimizing the indentation of each single peak [1-3]. This system is available for power tongs as well as accessories such as safety clamps.

In corrosive downhole environments, such as those that contain relevant quantities of CO2 and/or H2S at elevated temperature, C.R.A. materials with a high chromium content are often selected for the tubular and related accessories. In these environments using C.R.A., companies developed a "zero marking" policy especially for the makeup of the connections. In connection with higher torque values, this required a new gripping technology. A so-called Diamond-Grip gripping system was developed, together with a hydraulic gripping system for the power tong that delivers the required radial forces.

The paper describes this new gripping technology and a series of tests that were performed within pre-qualification processes for C.R.A. handling and running tenders in Qatar as well as in the Gulf of Mexico. The tests showed that there is no negative impact of Diamond-Grip and Micro-Grip in regards to corrosion under the severe influence of H2S and CO2.
The Relative Importance of Wellbore Pressure Drop and Formation Damage in Horizontal Wells
Authors: Hill A. D. , Zhu D.
Published: December 2007

Numerous studies have examined the roles of wellbore pressure drop and near wellbore formation damage on the production performance of horizontal wells. These studies have identified particular conditions for which these effects are important, but no quantitative general guidelines have been developed. In this paper, we present simple, analytical expressions that can be used to determine the relative effects of wellbore pressure drop and formation damage on horizontal well inflow. The equations developed are used to show how horizontal wells or laterals can be designed so that neither of these effects causes significant flow restrictions.

The relative importance of the pressure drop in a horizontal wellbore is shown to be a simple function of two dimensionless numbers, the Reynold's Number for the flow in the wellbore, and a new dimensionless number called the Horizontal Well Number. With this relationship, we illustrate how the wellbore diameter and length can be designed to insure that the wellbore pressure drop is not restricting production.

We also illustrate in this paper a technique for identifying the most critical part of the well flow system (far-field reservoir flow, near well convergent flow, or flow through the completion) from the relative sizes of different terms in the inflow equations. This analysis method shows that the importance of formation damage and the efficiency of well stimulation depend on formation thickness, well length, and reservoir extent in the horizontal plane. Guidelines are presented to show how much damage can be tolerated while still maintaining productivity within a prescribed fraction of the undamaged productivity.
Detection of Water or Gas Entries in Horizontal Wells From Temperature Profiles
Authors: Yoshioka K. , Zhu D. , Hill A. D. , Dawkrajai P. , Lake L. W.
Published: December 2007

With the recent development of temperature measurement systems such as fiber optic distributed temperature sensors (DTS), continuous temperature profiles in a horizontal well can be obtained with high precision. Small temperature changes with a resolution on the order of 0.1 °F can be detected by modern temperature-measuring instruments in intelligent completions and may aid the diagnosis of downhole flow conditions. Since in a producing horizontal well, fluid inflowing temperature is not affected by elevational geothermal temperature changes, the primary temperature differences for each phase (oil, water, and gas) are caused by frictional effects.

While gas production usually causes a temperature decrease, water entry results in either warming or cooling of the wellbore. Warmer water entry is a result of water flow from a warmer aquifer below the producing zone (water coning). In contrast, produced water can be cooler than produced oil because of differences in the thermal properties of these fluids. If both oil and water are produced from the same elevation, oil is heated more by friction while flowing in a porous medium than water, resulting in the produced water having a lower inflow temperature than the oil. Water entry by coning is relatively easy to detect from the temperature profile because of its warmer inflow temperature, but water breakthrough from the same elevation as the oil may not be obvious.

In this paper, we illustrate the range of inflow conditions for which water or gas entry locations can be identified from the temperature profile of a well from measurable temperature changes. Using a temperature prediction model1, we calculated temperature profiles for a wide range of water inflow conditions. In these calculations we assumed that one section of the well was producing water or gas, while the rest of the open section of the well produced oil. From sensitivity studies, we identified the relative water and gas production rates that create detectable temperature anomalies in the temperature profile along the well.