Marco Polo Buonora

First Application of Marine Magnetotellurics Improves Depth Imaging in the Santos Basin, Brazil

Recent subsalt oil discoveries in the deep waters of the Santos Basin, Brazil, have received considerable attention due to the extent of their reserves and by the challenges in exploration and production in such environment. Recently, electromagnetic methods have re-gained attention and changes in technology are making them a powerful tool for challenging imaging environments. A first large Marine Magnetotellurics (MMT) survey was acquired in Brazil by WesternGeco Electromagnetics in cooperation with Observatorio Nacional/CNPq and Petrobras. MMT data were recorded at 96 sites along three profiles. One profile extends approximately 148 km along existing seismic. The MMT data were processed and interpreted using an advanced integrated workflow. The main objectives of the survey were to assess the response and quality of MMT data in a wide range of water depths and test the ability of MMT to enhance seismic depth imaging by providing reliable information that will be used to constrain/improve the resolution of the velocity models. We show that the MMT data can clearly enhance resolution and reduce ambiguities of depth interpretation based on seismic. Work is in progress to enhance the MMT interpretation and apply the enhanced MMT model to develop an integrated depth imaging workflow.

mCSEM data interpretation for hydrocarbon exploration: A fast interpretation workflow for drilling decision

In a hydrocarbon exploration workflow, marine controlled-source electromagnetic (mCSEM) data are usually acquired after seismic interpretation for prospect identification and close-to-the-drilling decision making. Therefore, the mCSEM interpreter must provide quick answers to the asset teams in a way that the EM interpretation can add value to that decision. To achieve that goal, Petrobras developed a fast-track mCSEM interpretation workflow that consists in identifying anomalies in the mCSEM data set by frequency normalization, and then performing 1D CMP inversions followed by 2.5D polygonal inversions. The proposed workflow was successfully applied to several mCSEM surveys offshore Brazil. We evaluated an application in a complex geologic setting where the reservoir dips toward allochthonous salt. The reservoir appears as a flat spot in the seismic section, but with no significant amplitude variation with offset response. The mCSEM analysis confirmed the seismic anomaly and extended it northward. Two drilled wells corroborated the mCSEM interpretation.

3D inversion of total field mCSEM data: The Santos Basin case study

We present a marine Controlled Source Electromagnetic (mCSEM) 3D interpretation workflow based on anisotropic inversion applied to a dataset acquired in the Santos Basin offshore Brazil as part of a co-operation project between Petrobras and Schlumberger to evaluate the integration of deep reading Electromagnetic (EM) technologies into the full cycle of oil field exploration and development. The mCSEM dataset was acquired to demonstrate the improved detection and delineation of challenging EMtargets such as “smaller and deeper” hydrocarbon filled reservoir zones in complex background using 3D total field data. The project area hosting a proven reservoir was covered by a receiver grid and an orthogonal source lines grid extending beyond the receivers in the in line and cross line directions with all receivers active throughout the acquisition of both the orthogonal sets of source lines. We show that 3D inversion of the mCSEM total field data embedded in an advanced integrated workflow improves our ability to delineate hydrocarbon, their position and thickness resolution and increases our confidence about the resistivity at the reservoir(s) level. This increased resolution can provide in subsequent integrated interpretation workflows detailed information about reservoir volume distributions.

Broadband marine controlled-source electromagnetic for subsalt and around salt exploration

AbstractSalt basins, mainly Tertiary basins with mobilized salt, are notoriously difficult places to explore because of the traditionally poor seismic images typically obtained around and below salt bodies. In areas where the salt structures are extremely complex, the seismic signal-to-noise ratio may still be limited and, therefore, complicate the estimation of the velocity field variations that could be used to migrate the seismic data correctly and recover a good image suitable for prospect generation. We have evaluated the results of an integrated seismic-electromagnetic (EM) two-step interpretation workflow that we applied to a broadband marine controlled-source EM (mCSEM) research survey acquired over a selected ultra-deepwater area of Espirito Santo Basin, Brazil. The presence of shallow allochthonous salt structures makes around salt and subsalt seismic depth imaging remarkably challenging. To illustrate the proposed workflow, we have concentrated on a subdomain of the mCSEM data set, in which a s...

Advances in marine Controlled Source Electromagnetic: The Santos Basin Project - Brazil

Summary The Santos Basin marine Controlled Source Electromagnetic (mCSEM) data were acquired as part of a co-operation project between Petrobras and Schlumberger to evaluate the integration of deep reading Electromagnetic (EM) technologies into the full cycle of oil field exploration and development. The main objectives of the survey were to calibrate mCSEM over known reservoirs, quantify the anomalies associated with those reservoirs with the expectation that new prospective location(s) could be found. Data interpretation was carried out integrating well-log resistivities and model geometries derived from seismic using advanced multi-dimensional fully anisotropic modeling and inversion technology. We show that the mCSEM response of the known reservoirs yields signatures that can be imaged and accurately quantified. A further initiative was to advance the state of the art in integrated interpretation and establish guidelines toward the development of an industry standard workflow unavailable at present.