Bayesian inversion of synthetic AVO data to assess fluid and shale content in sand-shale media

Reservoir characterization of sand-shale sequences has always challenged geoscientists due to the presence of anisotropy in the form of shale lenses or shale layers. Water saturation and volume of shale are among the fundamental reservoir properties of interest for sand-shale intervals, and relate to the amount of fluid content and accumulating potentials of such media. This paper suggests an integrated workflow using synthetic data for the characterization of shaley-sand media based on anisotropic rock physics (T-matrix approximation) and seismic reflectivity modelling. A Bayesian inversion scheme for estimating reservoir parameters from amplitude vs. offset (AVO) data was used to obtain the information about uncertainties as well as their most likely values. The results from our workflow give reliable estimates of water saturation from AVO data at small uncertainties, provided background sand porosity values and isotropic overburden properties are known. For volume of shale, the proposed workflow provides reasonable estimates even when larger uncertainties are present in AVO data

Alcoolização percutânea de cistos renais: revisão da literatura e apresentação de resultados Percutaneous ethanol sclerotherapy of renal cysts: treatment outcomes and literature review

OBJETIVO: Demonstrar a eficácia e os resultados práticos da alcoolização percutânea de pacientes com cistos renais simples sintomáticos. MATERIAIS E MÉTODOS: Foram revistos os resultados obtidos em dez pacientes com cistos renais simples sintomáticos (oito homens e duas mulheres), com idade entre 28 e 72 anos (média de 55 anos), submetidos a pelo menos duas alcoolizações percutâneas. A indicação do procedimento foi dor no flanco refratária nos dez pacientes, sete deles com algum grau de hidronefrose pela localização parapiélica do cisto. O volume aspirado variou entre 20 e 1.300 ml (média de 200 ml). O tempo médio de seguimento após o procedimento foi de sete meses. O procedimento foi dirigido por ultrassonografia em dois casos e por tomografia computadorizada em oito. O tempo de internação variou entre 24 e 72 horas. Foi considerado sucesso completo do tratamento o desaparecimento do cisto, e parcial a redução maior que 50%. RESULTADOS: Durante o seguimento houve redução completa do cisto em sete pacientes e redução parcial em três. Em nenhum caso foram registradas complicações e os pacientes toleraram bem o procedimento. CONCLUSÃO: A alcoolização percutânea de cistos renais sintomáticos é um procedimento seguro, efetivo e pouco invasivo e com resultados semelhantes aos obtidos por outros autores.<br>OBJECTIVE: To demonstrate the effectiveness and practical outcomes of percutaneous ethanol sclerotherapy in patients with symptomatic simple renal cysts. MATERIALS AND METHODS: The authors reviewed the outcomes of ten patients (eight men and two women) in the age range between 28 and 72 years (mean, 55 years) submitted to at least two procedures of percutaneous sclerotherapy for symptomatic simple renal cysts. Main presentation was refractory flank pain in all patients, seven of them with some degree of hydronephrosis because of the parapyelic localization of the cyst. The aspirated volume ranged from 20 to 1300 ml (mean, 200 ml). The mean follow-up period following the procedure was of seven months. Two patients had ultrasoud-guided sclerotherapy, and eight, computed tomography-guided sclerotherapy. The hospital stay period ranged between 24 and 72 hours. Complete success corresponded to total cyst regression, and partial success corresponded to recurrence of less than half the original cyst volume. RESULTS: Complete cyst ablation was achieved in seven patients and partial resolution in three. No complication was observed and the therapy was well tolerated by all of the patients. CONCLUSION: Percutaneous ethanol sclerotherapy of symptomatic simple renal cysts is a safe, effective and minimally invasive procedure, with results similar to the ones reported by other studies