Abstract
Subsalt carbonate rocks in Brazil’s deepwater region have broad prospects for oil and gas exploration and development. Due to the low-frequency bandwidth of the seismic data and the poor signal quality for this kind of reservoir target, there is a demand for accurate seismic prediction methods. We employ the facies-controlled inversion using a low-pass filter matrix to ensure the accuracy of the low frequency and to improve the robustness of the inversion results. We integrated the concept of adaptive regularization constraint of the Zoeppritz equation into the generalized linear inversion theory framework, which overcomes the shortcomings of the approximate equation. Making full use of the large angle prestack seismic information, Zoeppritz equation inversion improves the accuracy of the inversion results. The application of this method in carbonate reservoirs under extremely thick salts in the Santos Basin of Brazil indicates the feasibility and practicality of the proposed integrated prediction method.
Highlights
Oil and gas exploration in Brazil has experienced a significant increase in activity since the first major presalt discoveries were announced in 2007 [1,2,3]
We have proposed a strategy for the integrated prediction of carbonate reservoirs under extremely thick salts via poststack facies-controlled and prestack exact Zoeppritz equation inversion in the Santos Basin of Brazil
To reduce the errors of the poststack inversion caused by the low-frequency loss of seismic data due to the extremely thick salts, we use a low-pass filter matrix to establish the facies-controlled constraints to ensure the accuracy of the low-frequency information of the poststack inversion results and improve the robustness of the inversion
Summary
Oil and gas exploration in Brazil has experienced a significant increase in activity since the first major presalt discoveries were announced in 2007 [1,2,3]. The total proven oil reserves were 67.1 billion barrels, while the natural gas reserves were 1:63 × 108 cubic meters, meaning that Santos Basin has great potential for future production increases (according to the International Energy Agency) In this area, the water depth is greater than 2000 m, and the target layer is covered with a thick salt caprock, which seriously restricts the exploration and development process [5, 6]. The adaptive regular constraint is added to improve the inversion accuracy of the elastic parameters, and the application of real data results proves the high accuracy and strong reliability of the proposed method, which can guide the exploration and development of similar oil and gas reservoirs
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