Integrated 3D Acid Fracturing Model for Carbonate Reservoir Stimulation

Acid fracturing is one of the stimulation methods used in carbonate formations and has been proved effective and economical. Because of the stochastic nature of acidizing in carbonate formation, designing and optimizing acid fracture treatment today still remain challenging. In the past, a simple acid fracture conductivity correlation was usually considered sufficient to estimate the overall average fracture conductivity in the formation, leading to the computation of the productivity index for fractured well performance. However, the nature of heterogeneity could not be included in the modeling. Understanding the important role of heterogeneity to stimulation performance becomes a crucial step in design and optimization of acid fracture jobs. In order to study the effect of this stochastic nature on acid fracturing, a fully 3D acid reaction model was developed based on the geostatistical parameters of the formation. It is possible to describe local conductivity distribution related to acid transport and reaction process. In this study, we have developed a new interactive workflow allowing the model of the fracture propagation process, the acid etching process and the well production interactively. This thesis presents the novel approach in integrating fracture propagation, acid transport and dissolution, and well performance models in a seamless fashion for acid fracturing design. In this new approach, the fracture geometry data of a hydraulic fracture is first obtained from commercial models of hydraulic fracture propagation, and then the 3D acid fracture model simulates acid etching and transport from the fracture propagation model using the width distribution as the initial condition. We then calculate the fracture conductivity distribution along the created fracture considering the geostatistical parameters such as permeability correlation length and standard deviation in permeability of the formation. The final step of the approach is to predict well performance after stimulation with a reservoir flow simulator. The significant improvements of the new approach are two folds: (1) capturing the geostatistical effect of the formation; and (2) modeling the acid etching and transport more accurately. The thesis explains the methodology and illustrates the application of the approach with examples. The results from this study show that the new model can successfully design and optimize acid fracturing treatments

Extended prediction rule to optimise early detection of heart failure in older persons with non-acute shortness of breath : A cross-sectional study

Objectives: There is a need for a practical tool to aid general practitioners in early detection of heart failure in the elderly with shortness of breath. In this study, such a screening rule was developed based on an existing rule for detecting heart failure in older persons with a diagnosis of chronic obstructive pulmonary disease. The original rule included a history of ischaemic heart disease, body mass index, laterally displaced apex beat, heart rate, elevated N-terminal pro B-type natriuretic peptide and an abnormal ECG. Design: Cross-sectional data were used to validate, update and extend the original prediction rule according to a standardised state-of-the-art stepwise approach. Setting: Primary care with 30 participating general practices. Participants: Community-dwelling people aged ≥65 years with shortness of breath on exertion. Methods and results: Validation of the existing screening rule in our population showed satisfying discrimination with a concordance statistic of 0.84 (range 0.80-0.85), but poor calibration. Performance measures were most improved by adding the predictors age >75 years, peripheral oedema and systolic murmur, resulting in a concordance statistic of 0.88 (range 0.85-0.90) and a net reclassification improvement of 31%. A risk score was computed, which showed high accuracy with a negative predictive value of 87% and a positive predictive value of 73%. Evaluating the improved rule in the derivation set and an independent set of patients with type 2 diabetes aged 60 years or older showed satisfying generalisability of the rule. Conclusions: Our rule resulted in excellent prediction of heart failure in the large domain of the elderly with shortness of breath, and would help general practitioners to select those needing echocardiography. Trial registration number: NCT01202006

Effect of training general practitioners in drug treatment of newly detected heart failure patients with reduced or preserved ejection fraction : A cluster randomized trial

Objective To assess the effect of training general practitioners (GPS) in the optimization of drug treatment for newly detected heart failure (HF). Design Cluster randomized trial comparing the training programme to care as usual. Participants Community-dwelling older persons with a new HF diagnosis after diagnostic work-up. Methods Thirty GPS were randomized to care as usual or the training. Sixteen GPS of the latter group received a half-day training on optimizing HF medication in HF patients with a reduced (HFrEF), or with a preserved ejection fraction (HFpEF). At baseline and after six months of follow-up, the 46 HF patients in the intervention group and the 46 cases in the care as usual group were assessed on medication use, functionality, health status, and health care visits. Results After 6 months, uptake of HF medication and health status were similar in the two groups. Interestingly, patients in the intervention group had a longer walking distance with the six-minute walk test than those in the care as usual group (mean difference in all-type HF 28.0 (95% CI 2.9 to 53.1) meters; HFpEF patients 28.2 (95% CI 8.8 to 47.5) meters and HFrEF patients 55.9 (95% CI - 16.3 to 128.1) meters). They also had more HF-related GP visits (RR 1.8, 95% CI 1.3 to 2.5) and fewer visits to the cardiologist (RR 0.6, 95% CI 0.3 to 1.1). Conclusions Training GPS in optimization of drug treatment of newly detected HFrEF and HFpEF did not clearly increase HF medication, but resulted in improvement in walking distance

Comparison of Outcomes and Intervention Among Patients With Non-ST-Segment Elevation Acute Myocardial Infarction of Those With a Left Circumflex Versus Those With a Non-Left Circumflex-Related Coronary Artery (From the ELISA-3 Trial)

Previous studies found that patients with an acute coronary syndrome (ACS) due to occlusion of the left circumflex (LC) coronary artery often present without ST-elevation, leading to a delay in diagnosis and revascularization, a larger infarct size, and a worse prognosis. In this subgroup analysis of the ELISA-3 study (early or late intervention in high-risk non-ST-segment elevation acute coronary syndromes [NSTE-ACS]) incidence, characteristics and prognosis of LC-related NSTE-ACS was investigated, and the outcome of early versus late invasive strategy was compared. In 383 of 542 patients the culprit vessel could be identified, with the LC artery in 112 (29%) of them. Patients with LC-related ACS had more often single vessel disease and underwent percutaneous coronary intervention more and CABG less frequently. The primary end point of the combined incidences of death, myocardial infarction, and recurrent ischemia at 30-day follow-up occurred in 9.0% of LC versus 16.5% of non-LC-related ACS (p = 0.057). Enzymatic infarct size and incidence of bleeding were comparable. Of patients with LC-related ACS, 62 were assigned to an early and 50 to a late invasive treatment with a median time from admission to angiography of 5.5 and 65.7 hours, respectively. The primary end point occurred in 9.7% and 8.0%, respectively (p = 1.00) with comparable enzymatic infarct size and bleeding. In conclusion, no significant differences in outcome were found between patients with an LC- and a non-LC-related NSTE-ACS. In LC-related NSTE-ACS, angiography within 12 hours of admission is feasible but not superior to angiography after more than 48 hours. (C) 2018 Elsevier Inc. All rights reserved

Het Taalportaal

Taalportaal. A new scientific grammar of Dutch and Frisian (and Afrikaans) We describe the Taalportaal, a new comprehensive on-line scientific grammar of Dutch and Frisian