Processamento de dados sísmicos para detecção de possíveis reservatórios não convencionais de gás na Bacia do Recôncavo

Abstract

Atualmente os reservatórios não convencionais tornaram-se muito atrativos para a industria, entre os não convencionais existe o shale gás (gás presente em folhelho). O objetivo deste trabalho é, através do estudo de atributos sísmicos em um cubo processado, obter uma região de interesse, o Sweet Spot . Para tanto foi realizado um processamento sísmico composto por um fluxograma simples de processamento e uma analise dos atributos de frequência média, COT e TecVA. A analise de COT foi obtida através de uma relação linear entre impedância acústica e COT, calculada utilizando o método Total Least Square (mínimos quadrados totais) para minimização do erro em ambas as dimensões. Neste Trabalho foi utilizado o cubo de aquisição sísmica 3D 0026 CEXIS da Bacia do Recôncavo e 14 poços que foram utilizados para linearização do COT. Na literatura, espera-se para reservatórios não convencionais valores de 4 % de COT, em uma região de hidrocarbonetos maturados. Com o estudo realizado foi possível identificar uma região de interesse de exploração, porem com grandes ressalvas à qualidade dos resultados obtidos comparados com o que é informado pela literatura, fazendo uma consideração para regiões de 1 % de COT.

Non-conventional reservoirs are reservoirs with very low permeability that require stimulation for the production of hydrocarbons, whose exploration has raised new challenges for geology. Currently, such reservoirs have become very attractive to the oil and natural gas (NG) market, as a way of meeting the growing demand for hydrocarbons. Among the unconventional reservoirs, there is Shale gas, a gas present in shale and which can be obtained through a cracking process, as long as the region has qualities that facilitate exploration to maintain the cost / bene t balance. The objective of this work was to nd this region of interest known as sweet spot, through the study of seismic attributes in a processed cube. For this purpose, a seismic processing was performed, consisting of a simple processing owchart and an analysis of the attributes of average frequency, total organic carbon (TOC) and pseudo-relief. The processing performed consists of static data correction, automatic gain, frequency ltering, Wiener-Levinson deconvolution, data NMO correction and stacking. The TOC analysis was obtained through a linear relationship between acoustic impedance and TOC, which was calculated using the total least square method. To minimize the error in both dimensions, the average frequency was obtained using the maximum entropy method of Wigner-Ville. In this work, we used the 3D seismic acquisition cube 0026 CEXIS from the Recôncavo Basin and 14 wells that were used to linearize the TOC. This topic is very important and current, in addition to being of interest for the development of the oil and gas industry. The study on the method for locating unconventional shale gas reservoirs, therefore, represents the main challenge of this research. This study is expected to be a relevant contribution to the debate on the exploration of unconventional gas in the Recôncavo Baiano region. In the literature, the usual for unconventional reservoirs are values of 4% TOC, in a region of matured hydrocarbons. With the data collected in this study, it was possible to identify a region of interest for exploration, but with great quali cations to the quality of the results obtained compared to what is reported in the literature, making a consideration for regions of 1% TOC.