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The protective effect of hydroalcoholic extract of hawthorn berries (HBE) on acetic acid (AA)-induced colitis in rats was investigated. Forty-two Wistar rats were divided into seven groups, including control and test groups (n = 6). The control animals received saline, and the test animals were treated with saline (sham group), mesalamine (50 mg/kg; M group), atorvastatin (20 mg/kg; A group), HBE (100 mg/kg; H group), mesalamine and HBE (HM group), or atorvastatin plus HBE (HA group), 3 days before and a week after colitis induction. Colitis was induced by administration of 1 mL AA (4%) via a polyethylene catheter intrarectally. High-performance liquid chromatography analyses showed that HBE contained 0.13% and 0.5% oleanolic acid and ursolic acid, respectively. Elevated myeloperoxidase activity and lipid peroxidation were attenuated in the HA group. The H and HM groups showed marked reductions in colitis-induced decreases in total thiol molecules and body weight. The histopathological studies revealed that HBE decreased colitis-induced edema and infiltration of neutrophils. Our data suggest the anti-inflammatory and antioxidant effects of HBE and atorvastatin protect against AA-induced colitis. The anti-inflammatory effect of HBE may be attributable to its ability to decrease myeloperoxidase activity as a biomarker of neutrophil infiltration.

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Long-term transient linear flow of hydraulically fractured vertical and horizontal wells completed in tight/shale gas wells has historically been analyzed by use of the square-root-of-time plot. Pseudovariables are typically used for compressible fluids to account for pressure-dependence of fluid properties. Recently, a corrected pseudotime has been introduced for this purpose, in which the average pressure in the distance of investigation (DOI) is calculated with an appropriate material-balance equation. The DOI calculation is therefore a key component in the determination of the linear-flow parameter (product of fracture half-length and square root of permeability, x f ffiffi ffi k p) and the calculation of contacted fluid in place. Until now, the DOI for transient linear flow has been determined empirically, and may not be accurate for all combinations of fluid properties and operating conditions.In this work, we have derived the DOI equations analytically for transient linear flow under constant-flowing-pressure and -rate conditions. For the first time, rigorous methodologies have been used for this purpose. Two different approaches were used: the maximum rate of pressure response (impulse concept) and the transient/boundary-dominated flow intersection method. The two approaches resulted in constants in the DOI equation that are much different from previously derived versions for the constantflowing-pressure case. The accuracy of the new equations was tested by analyzing synthetic production data from a series of fine-grid numerical simulations. Single-phase oil and gas cases were analyzed; pseudovariable alteration for pressure-dependent porosity and permeability was required in the analysis.The calculated linear-flow parameters, determined from our new DOI formulations for the constant-flowing-bottomhole-pressure (FBHP) case, and the input values to numerical simulation, are in good agreement. Of the two new DOI-calculation methods provided, the maximum rate of pressure response (unit impulse method) provides more accurate results. Finally, a field case was analyzed to determine the impact of DOI formulations on derivations of the linear-flow parameter from field data.Linear-flow analysis on the basis of the DOI calculations presented in this work is significantly improved over previous formulations for constant FBHP.

Résumé -Étude de la perméabilité relative gaz-huile et de la saturation en huile résiduelle dans le cas d'une instabilité de déplacement et des nombres sans dimension s'y rapportant -Des expériences de déplacement gaz-huile ont été réalisées sur des modèles mis à l'échelle de carottes de grande longueur en faisant varier les propriétés pétrophysiques et les conditions d'écoulement. Pour ces expériences, les forces en présence, capillaires, gravitaires et visqueuses, sont comparables. Le seuil de stabilité est déterminé à partir de l'historique de production et de l'analyse d'images. Les résultats des expériences sont comparables aux conclusions de la théorie de la percolation en gradient. On étudie ensuite l'effet de l'instabilité du front de déplacement sur la perméabilité relative et la saturation résiduelle. Les perméabilités relatives déterminées par des approches analytiques et numériques indiquent qu'une plus grande vitesse de déplacement engendre une plus grande perméabilité relative au gaz et une plus faible perméabilité relative à l'huile. Les résultats indiquent que la saturation en huile à la fin est très supérieure lorsque la vitesse de déplacement se situe au-dessus du critère de stabilité. Les caractéristiques du déplacement, notamment la saturation moyenne en huile en fin de déplacement, sont ensuite décrites à l'aide de groupements sans dimension expressément le nombre de Bond et le nombre capillaire. La saturation en huile en fin de déplacement déterminée expérimentalement s'exprime respectivement par une relation directe avec le nombre capillaire et inverse avec le nombre de Bond. En conséquence, un groupement sans dimension combiné a été proposé afin de généraliser l'estimation de la saturation en fin de déplacement et résiduelle en huile dans la limite des nombres sans dimension étudiés ici. Abstract

Summary The mathematical models commonly used to describe fluid flow through porous media are dependent on various simplifying assumptions, one of them being that the permeability is independent of pore pressure. However, during fluid withdrawal, reservoir permeability may be reduced because of deformation of the porous rock. The pressure dependence of permeability is more pronounced in tight formations. When dealing with pressure-sensitive formations, the assumption of a constant permeability is inappropriate. In this study, analytical models are developed to model production from hydraulically fractured tight formations with pressure-dependent permeability, for both constant-pressure- and constant-rate production scenarios. By deriving an explicit relationship between time and pseudotime, it is shown that the analytical liquid solutions can be directly applied to pressure-dependent permeability reservoirs. This paper develops the appropriate transformation, and discusses its application by comparing the numerical solution of the nonlinear problem with the analytical solution proposed here. The close agreement between these solutions demonstrates the accuracy of the proposed methodology in forecasting the behavior of pressure-sensitive formations. We used the models developed in this work to address the following question: Is it possible that the permeability is decreased so much that a reduction in rate results when drawdown is increased? We show that the answer to the question is no. Depending on the strength of the nonlinearity, there could be a point beyond which the rate will not improve measurably as the flowing pressure is lowered. However, for a particular reservoir with a constant-permeability modulus, it is not possible to reduce the production rate by increasing the drawdown. This is contrary to previous publications that suggest that in a reservoir with pressure-dependent permeability, there is an optimum drawdown for maximum production. In a companion paper, we explore conditions where such an optimum drawdown could exist.

Summary The main objective of this work is to gain a general understanding of the performance of tight oil reservoirs during transient linear two-phase flow producing at constant flowing pressure. To achieve this, we provide a theoretical basis to explain the effect of different parameters on the behavior of solution-gas-drive unconventional reservoirs. It is shown that, with the Boltzmann transformation, the highly nonlinear partial-differential equations (PDEs) governing two-phase flow through porous media can be converted to two nonlinear ordinary-differential equations (ODEs). The resulting ODEs simplify the calculation of the reservoir performance and avoid the tedious calculation inherent in solving the original PDEs. Thus, the proposed model facilitates sensitivity studies and rapid evaluation of different hypotheses. Moreover, successful conversion of the highly nonlinear PDEs (in terms of distance and time) to the ODEs (in terms of the Boltzmann variable) implies that the saturation and pressure are unique functions of the Boltzmann variable, and as a result, saturation is a unique function of pressure. This transformation enables us to explain (a) the constant gas/oil ratio (GOR) that has been observed in some hydraulically fractured tight oil reservoirs and (b) the straight-line plot of 1/qo and 1/qg vs. t during constant-pressure two-phase production. An approximate analytical model is also developed. It is shown that the proposed approximate solution can be converted to a form similar to the well-known equations for single-phase flow, which enhances our understanding of two-phase-flow behavior. Extensive sensitivity studies are performed to examine the utility of the proposed model in predicting the performance of tight oil reservoirs. The applicability of the conclusions to the boundary-dominated flow period is investigated. On the basis of numerous simulation studies, it is shown that the impact of various parameters on boundary-dominated flow can be predicted with the transient solution, without the need for running multiple numerical simulations.