Efficiency of Horizontal and Vertical Well Patterns on the Performance of Micellar-Polymer Flooding in Anisotropic Reservoirs

There is increasing interest in micellar-polymer flooding because of the need to increase oil production from depleted and waterflooded reservoirs. Using horizontal wells for injection and production in a micellar-polymer flood process, higher sweep efficiency is expected compared with the use of conventional patterns by vertical wells. However, the use of horizontal wells is very sensitive to the well pattern designed to operate the process. This paper presents an analysis of how the overall performance of a micellar-polymer flood process in anisotropic reservoirs is influenced by the well pattern using horizontal injector and producer in different configurations. A three-dimensional numerical simulator for fluid flow and mass transport is used to analyze the effectiveness of well combinations in micellar-polymer applications. The potential for a horizontal well application was assessed through different situations in combinations of injection and production wells and degree of reservoir anisotropy. Results from the study have demonstrated that significant amount of oil can be recovered additionally and injectivity was remarkably improved by utilizing a combination of horizontal wells. The improvement of injectivity through a horizontal injection well was higher when it was combined with horizontal producer parallel to the injector. The overall performances in anisotropic reservoirs strongly depend on the type of wells considered and the orientation of the horizontal wells with respect to the permeability directions. Combination of horizontal wells placed parallel to the low permeability direction yields the best performance. In high permeability ratio reservoirs, the presence of horizontal injectors is more significant in defining the efficiency of the micellar-polymer flood than the horizontal producers.Key words: Micellar-polymer flood; Horizontal well; Anisotropy; Injectivit

Screening Effects on Nonrelativistic Bremsstrahlung in the Scattering of Electrons by Neutral Atoms

Atomic screening effects on nonrelativistic electron-atom bremsstrahlung radiation are investigated using a simple analytic solution of the Thomas-Fermi model for many-electron atoms. The Born approximation is assumed for the initial and final states of the projectile electron. The results show that the screening effect is important in the soft radiation region and is decreasing with increasing radiation. These results help provide correct information about the behavior of bound electrons in the target atom in bremsstrahlung processes

Simulation Study on Miscibility Effect of CO 2

The minimum miscibility pressure (MMP) determines the main mechanism of CO2 flooding, which is either an immiscible or miscible process. This paper examines the recovery improvements of CO2 flooding in terms of both the injection temperature and solvent composition. The results show that a lower temperature injection and LPG (liquefied petroleum gas) mixture can considerably improve oil recovery due to the reduced MMP in the swept area caused by the injected solvent. For the pure CO2 injection at the reservoir temperature, oil recovery is 59% after 1.0 PV CO2 injection. The oil recoveries by CO2-LPG mixtures are improved to 73% with 0.1 mole fractions of LPG and 81% with 0.2 mole fractions of LPG. The recovery factor from low-temperature CO2 injection is 78%, which is 32% higher compared to the isothermal case. The recoveries obtained by low-temperature CO2-LPG injection increase up to 87% of the initial oil. Heat transfer between the reservoir and the formation of over/underburden should be considered in order to describe the process more accurately. Additionally, the recovery factors from the heat transfer models are decreased by 4–12% in comparison with the original nonisothermal models

Comparison of MRI features and surgical outcome among the subtypes of focal cortical dysplasia

AbstractPurposeFocal cortical dysplasia (FCD) is the most common pathological diagnosis in patients who have undergone surgical treatment for intractable neocortical epilepsy. However, presurgical identification of MRI abnormalities in FCD patients remains difficult, and there are no highly sensitive imaging parameters available that can reliably differentiate among FCD subtypes. The purpose of our study was to investigate the surgical outcome in FCD patients with identifiable MRI abnormalities and to evaluate the prognostic role of the various MRI features and the characteristics of FCD pathology.MethodsWe retrospectively recruited epilepsy patients who had undergone surgical treatment for refractory epilepsy with focal MRI abnormalities and the pathological diagnosis of FCD. We evaluated the surgical outcome according to the pathological subtypes, and studied the prognostic roles of various MRI features. We used recently proposed three-tiered FCD classification system which included FCD type III when FCD occurs in association with other potentially epileptogenic pathologies.ResultsA total of 69 patients were included, and 68.1% of patients became seizure free. Patients with FCD type III had a lower chance for achieving seizure freedom (7/15) than in patients with isolated FCD (FCD types I and II) (40/54, p=0.044). Cortical thickness and blurring of gray–white matter junction were more common in isolated FCD than in FCD type III, but most MRI features failed to differentiate between FCD types I and II, and only the transmantle sign was specific for FCD type II. We failed to find a prognostic value of specific MRI abnormalities of prognostic value in terms of post-epilepsy surgery outcome in FCD patients.ConclusionsOur study showed that patients with FCD III have poor surgical outcome. Typical MRI features of isolated FCD such as cortical thickness and blurring of gray–white matter junction were less common in FCD type III and only transmantle sign was helpful in differentiating between FCD types I and II

Frontal lobe epilepsy: Clinical characteristics, surgical outcomes and diagnostic modalities

SummaryObjectiveTo identify surgical prognostic factors and to characterize clinical features according to the location of the intracranial ictal onset zone of frontal lobe epilepsy (FLE) in order to assess the role of various diagnostic modalities, including concordances with presurgical evaluations.MethodsWe studied 71 FLE patients who underwent epilepsy surgery and whose outcomes were followed for more than 2 years. Diagnoses were established by standard presurgical evaluation.ResultsClinical manifestations could be categorized into six types: initial focal motor (9 patients), initial versive seizure (15), frontal lobe complex partial seizure (14), complex partial seizure mimicking temporal lobe epilepsy (18), initial tonic elevation of arms (11), and sudden secondary generalized tonic–clonic seizure (4). Thirty-seven patients became seizure-free after surgery. Five patients were deleted in the analysis because of incomplete resection of ictal onset zones. The positive predictive value of interictal EEG, ictal EEG, MRI, PET, and ictal SPECT, respectively were 62.5%, 56.4%, 73.9%, 63.2%, and 63.6%, and the negative predictive value were 46.0%, 44.4%, 53.5%, 44.7%, and 51.7%. No significant relationship was found between the diagnostic accuracy of these modalities and surgical outcome, with the exception of MRI (p=0.029). Significant concordance of two or more modalities was observed in patients who became seizure-free (p=0.011). We could not find any clinical characteristic related to surgical outcome besides seizure frequency. No definite relationship was found between the location of intracranial ictal onset zone and clinical semiology.ConclusionAlthough various diagnostic methods can be useful in the diagnosis of FLE, only MRI can predict surgical outcome. Concordance between presurgical evaluations indicates a better surgical outcome

Gamma oscillation in functional brain networks is involved in the spontaneous remission of depressive behavior induced by chronic restraint stress in mice

Additional file 1: Table S1. Statistical results of the cross-correlation in Fig. 2c

Use of Nafamostat Mesilate as an Anticoagulant during Extracorporeal Membrane Oxygenation

Although the incidence of bleeding complications during extracorporeal membrane oxygenator (ECMO) support has decreased in various trials, bleeding is still the most fatal complication. We investigated the ideal dosage and efficacy of nafamostat mesilate for use with ECMO in patients with acute cardiac or respiratory failure. We assessed 73 consecutive patients who received ECMO due to acute cardiac or respiratory failure between January 2006 and December 2009. To evaluate the efficacy of nafamostat mesilate, we divided the patients into 2 groups according to the anticoagulants used during ECMO support. All patients of nafamostat mesilate group were male with a mean age of 49.2 yr. Six, 3, 5, and 3 patients were diagnosed with acute myocardial infarction, cardiac arrest, septic shock, and acute respiratory distress syndrome, respectively. The mean dosage of nafamostat mesilate was 0.64 mg/kg/hr, and the mean duration of ECMO was 270.7 hr. The daily volume of transfused packed red blood cells, fresh frozen plasma, and cryoprecipitate and the number of complications related to hemorrhage and thrombosis was lower in the nafamostat mesilate group than in the heparin group. Nafamostat mesilate should be considered as an alternative anticoagulant to heparin to reduce bleeding complications during ECMO