Theories of Arps' Decline Curve Exponent and Loss Ratio, for Saturated Reservoirs

Rate decline curve analysis is an essential tool in predicting reservoir performance and in estimating reservoir properties. In its most basic form, decline curve analysis is to a large extent based on Arps’ empirical models that have little theoretical basis. The use of historical production data to predict future performance is the focus of the empirical approach of decline analysis while the theoretical approach focuses on the derivation of relationships between the empirical model parameters and reservoir rock/fluid properties; thereby establishing a theoretical basis for the empirical models. Such relationships are useful in formulating techniques for reservoir properties estimation using production data. Many previous attempts at establishing relationships between the empirical parameters and the rock/fluid properties have been concerned primarily with the exponential decline of single phase oil reservoirs. A previous attempt to establish the theories of hyperbolic decline of saturated reservoirs (multiphase) have yielded an expression relating the Arps’ decline exponent, to rock/fluid properties. However, the values of exponent computed from the expression are not constant through time, whereas, the empirically-determined exponent b is a constant value. This work utilizes basic concepts of compressibility and mobility to justify the dynamic behaviour of the values obtained from the existing theoretical expression of the previous theory; to prove that the expression, though rigorously derived, is not the theoretical equivalence of the empirical Arps’ b-exponent; and finally, to properly to offer a new logical perspective to the previous theory relating b-exponent to rock and fluid property. Ultimately, this work presents, for the first time, a new consistent theoretical expression for the Arps’ exponent, b. The derivation of the new expression is still founded on the concept of Loss Ratio, as in previous attempts; however, this latest attempt utilizes the cumulative derivative of the Loss Ratio, instead of the instantaneous derivative implied in the previous attempt. The new expression derived in this work have been applied to a number of saturated reservoir models and found to yield values of b-exponent that are constant through time and are equivalent to the empirically-determined b-exponent

A New Theory for Interpreting Rate Decline Trends in Solution-Gas Drive Reservoirs

A number of attempts have been made to establish the theories of rate decline in solution-gas drive reservoirs with multiphase flow. However, none of these attempts have established a functional link between the empirical and the theoretical domains of decline curve analysis for such reservoirs. The absence of such a link has inhibited the formulation of simple techniques for reservoir properties estimation. The purpose of this work is therefore to establish the missing link. In this work, functional relationships between the empirical bemp and the theoretical bth were derived. The derivation was based on a novel definition of a new parameter known as time-weighted average of the theoretical exponent bth .This new parameter was found to be related to the empirical exponent bemp, thus establishing the link. A reservoir simulator was used to generate sets of production data used in verifying the derived relationships. Results presented in this paper show that the relationships derived herein are valid, even for heterogeneous reservoirs. The work also offered theoretical justifications for the various ranges of bth values, and for the first time, four distinct rate decline regimes in solution-gas drive reservoirs were identified. Sensitivity analyses were performed on the results. The effects of non-Darcy flow on decline parameters were also investigated. Lastly, this work provided a mathematical justification for the existence of the hyperbolic family of curves in decline analysis of solution-gas drive reservoir

Productivity Formulas for a Partially Penetrating Vertical Well in a Circular Cylinder Drainage Volume

Taking a partially penetrating vertical well as a uniform line sink in three-dimensional space, by developing necessary mathematical analysis, this paper presents steady state productivity formulas for an off-center partially penetrating vertical well in a circular cylinder drainage volume with constant pressure at outer boundary. This paper also gives formulas for calculating the pseudo-skin factor due to partial penetration. If top and bottom reservoir boundaries are impermeable, the radius of the cylindrical system and off-center distance appears in the productivity formulas. If the reservoir has a gas cap or bottom water, the effects of the radius and off-center distance on productivity can be ignored. It is concluded that, for a partially penetrating vertical well, different productivity equations should be used under different reservoir boundary conditions

Evaluation des produits en présence du signal cognitif pays d’origine domestique versus étranger: Une démarche qualitative auprès d’adulescents

Cet article propose une réflexion exploratoire ayant pour but, d’une part, d’étudier la ciblejuvénile des adulescents qui pourrait intéresser les marketeurs et les entreprises, et d’autrepart, d’actualiser les données relatives à l’effet « made in local versus importé » sur lesévaluations d’un produit, d’un pays en développement avec une application qualitative dans le contexte algérien. Les résultats de l’analyse de contenu du corpus issu des entretiens semi-directifs auprès d’un échantillon de convenance de 12 étudiants sont révélateurs. Ils indiquent, premièrement, qu’en dépit de la situation financière plus ou moins précaire de cesconsommateurs, ce n’est pas le prix qui est jugé le plus important. De plus, le made in,comme attribut extrinsèque, s’avère très important quand il s’agit particulièrement d’uneorigine domestique versus étrangère. Deuxièmement, les résultats montrent que lesinterviewés ne sont pas du tout ethnocentriques et affichent un sentiment de dénigrement àl’égard des produits nationaux

Variable phenotypic expressivity in a Swiss family with autosomal dominant retinitis pigmentosa due to a T494M mutation in the PRPF3 gene

PURPOSE: To characterize the clinical, psychophysical, and electrophysiological phenotypes in a five-generation Swiss family with dominantly inherited retinitis pigmentosa caused by a T494M mutation in the Precursor mRNA-Processing factor 3 (PRPF3) gene, and to relate the phenotype to the underlying genetic mutation. METHODS: Eleven affected patients were ascertained for phenotypic and genotypic characterization. Ophthalmologic evaluations included color vision testing, Goldmann perimetry, and digital fundus photography. Some patients had autofluorescence imaging, Optical Coherence Tomography, and ISCEV-standard full-field electroretinography. All affected patients had genetic testing. RESULTS: The age of onset of night blindness and the severity of the progression of the disease varied between members of the family. Some patients reported early onset of night blindness at age three, with subsequent severe deterioration of visual acuity, which was 0.4 in the best eye after their fifties. The second group of patients had a later onset of night blindness, in the mid-twenties, with a milder disease progression and a visual acuity of 0.8 at age 70. Fundus autofluorescence imaging and electrophysiological and visual field abnormalities also showed some degree of varying phenotypes. The autofluorescence imaging showed a large high-density ring bilaterally. Myopia (range: -0.75 to -8) was found in 10/11 affected subjects. Fundus findings showed areas of atrophy along the arcades. A T494M change was found in exon 11 of the PRPF3 gene. The change segregates with the disease in the family. CONCLUSIONS: A mutation in the PRPF3 gene is rare compared to other genes causing autosomal dominant retinitis pigmentosa (ADRP). Although a T494M change has been reported, the family in our study is the first with variable expressivity. Mutations in the PRPF3 gene can cause a variable ADRP phenotype, unlike in the previously described Danish, English, and Japanese families. Our report, based on one of the largest affected pedigree, provides a better understanding as to the phenotype/genotype description of ADRP caused by a PRPF3 mutation

The effect of food anticipation on cognitive function- A replication study

Several lines of evidence indicate that glucose can enhance cognitive performancewithout being ingested. Previous research has found that the effect of food anticipation can boostcognitive resources in a testing environment [1]. This study was designed to replicate thefindings utilizing the same population, examining the effect that food anticipation has oncognitive abilities among multiple weight groups. 182 students were included in this replicationstudy. In order to accurately measure the results, the study randomized the order that foodanticipation tasks and cognitive tests were performed. The results indicated that an anticipatoryfood reward effect enhanced the cognitive capabilities of individuals categorized by BMI asoverweight and obese. Furthermore, this effect shifted the attention of these individuals towardlite food options as opposed to regular. Finally, this anticipatory food effect reduced emotionalarousal regarding food for individuals in the obese BMI category. We replicated previousfindings of increased cognitive resources in the presence of food anticipation prior to test taking.These findings add to the growing literature that the presence of food can boost cognitiveresources in testing environments. Future studies should shift the focus away from weight as adriving factor in the results, and instead look at how socio-economic status (SES) and foodinsecurity may affect eye gaze behavior and the anticipatory reward effect associated with foodcues

A novel homozygous R764H mutation in crumbs homolog 1 causes autosomal recessive retinitis pigmentosa.

PURPOSE: Retinitis pigmentosa (RP; MIM 268000) is a hereditary disease characterized by poor night vision and progressive loss of photoreceptors, eventually leading to blindness. This degenerative process primarily affects peripheral vision due to the loss of rods. Autosomal recessive RP (arRP) is clinically and genetically heterogeneous. It has been associated with mutations in different genes, including CRB1 (crumbs homolog 1). The aim of this study was to determine the causative gene in a Tunisian patient with arRP born to non-consanguineous parents. METHODS: Four accessible family members were included. They underwent full ophthalmic examination with best-corrected Snellen visual acuity, fundus photography and fluorescein angiography. Haplotype analysis was used to evaluate homozygosity in the family to 20 arRP loci. All exons and intron-exon junctions of candidate genes not excluded by haplotype analysis were PCR amplified and directly sequenced. RESULTS: The proband was a 43-year-old female patient. Best-corrected visual acuity was 20/63 (right eye) and 20/80 (left eye). Visual loss began during the third decade. Funduscopic examination and fluorescein angiography revealed typical advanced RP changes with bone spicule-like pigment deposits in the posterior pole and the midperiphery along with retinal atrophy, narrowing of the vessels, and waxy optic discs. Haplotype analysis revealed homozygosity with microsatellite markers D1S412 and D1S413 on chromosome 1q31.3. These markers flanked CRB1. Our results excluded linkage of all the other arRP loci/genes tested. Sequencing of the 12 coding exons and splice sites of CRB1 disclosed a homozygous missense mutation in exon 7 at nucleotide c. 2291G>A, resulting in an arginine to histidine substitution (p.R764H). CONCLUSIONS: R764H is a novel mutation associated with CRB1-related arRP. Previously, an R764C mutation was reported. Extending the mutation spectrum of CRB1 with additional families is important for genotype-phenotype correlations and characterization of the scope of mutation

A cuttable multi-touch sensor

We propose cutting as a novel paradigm for ad-hoc customization of printed electronic components. As a first instantiation, we contribute a printed capacitive multi-touch sensor, which can be cut by the end-user to modify its size and shape. This very direct manipulation allows the end-user to easily make real-world objects and surfaces touch-interactive, to augment physical prototypes and to enhance paper craft. We contribute a set of technical principles for the design of printable circuitry that makes the sensor more robust against cuts, damages and removed areas. This includes novel physical topologies and printed forward error correction. A technical evaluation compares different topologies and shows that the sensor remains functional when cut to a different shape.Deutsche Forschungsgemeinschaft (Cluster of Excellence Multimodal Computing and Interaction, German Federal Excellence Initiative

Interpretacion de pruebas de inyeccion en yacimientos naturalmente fracturados

Este estudio presenta un nuevo método para determinar la transmisibilidad en yacimientos naturalmente fracturados usando el análisis del flujo radial en pruebas de calibración. El método se basa en el análisis del comportamiento de la derivada de la presión con el tiempo. El objetivo es simplificar y facilitar la identificación del flujo radial y la “gargantaâ€� característica que se observa en la derivada cuando se tienen yacimientos naturalmente fracturados. El método propuesto no requiere el conocimiento previo de la presión de yacimiento. Un grafico logarítmico es usado para determinar la permeabilidad, la presión promedio, el almacenamiento y el coeficiente que relaciona las permeabilidades s de la matriz y de las fracturas en el yacimiento