Geotectonic Controls on CO2 Formation and Distribution Processes in the Brazilian Pre-Salt Basins

Abstract

Exploratory work for hydrocarbons along the southeastern Brazilian Margin discovered high concentrations of CO2 in several fields, setting scientific challenges to understand these accumulations. Despite significant progress in understanding the consequences of high CO2 in these reservoirs, the role of several variables that may control such accumulations of CO2 is still unclear. For example, significant differences in the percentages of CO2 have been found in reservoirs of otherwise similar prospects lying close to each other. In this paper, we present a hypothesis on how the rifting geodynamics are related to these CO2-rich accumulations. CO2-rich mantle material may be intruded into the upper crustal levels through hyper-stretched continental crust during rifting. Gravimetric and magnetic potential methods were used to identify major intrusive bodies, crustal thinning and other geotectonic elements of the southeastern Brazilian Margin. Modeling based on magnetic, gravity, and seismic data suggests a major intrusive magmatic body just below the reservoir where a high CO2 accumulation was found. Small faults connecting this magmatic body with the sedimentary section could be the fairway for the magmatic sourced gas rise to reservoirs. Mapping and understanding the crustal structure of sedimentary basins are shown to be important steps for “de-risking” the exploration process.

Issues in Energy Vulnerability Assessment: Looking for a Sustainable Choice of Natural Resource for Power Generation

“…During PDP and LDP, GHG emissions are continuous for approximately 30 years. Considering that the average life of atmospheric CO2 is over 100 years, this permanent and irreversible impact occurs at a superregional scale, consequently provoking effects on a global level [14,15,53,54]. The EIA addresses this issue: "Brazilian GHG emissions are about 4% of global emissions and Petrobras Production and Exploration emissions are 0.04% of world emissions (base year 2010), without considering that the greenhouse effect is a problem caused by the increase in atmospheric concentrations of GHG emissions due to global historical emissions" [55].…”

“…Thus, the following actions, which are essential to (or consequence of) oil and gas processing for electricity production, cause (20) permanent and long-term (and 3 irreversible) impacts on the (6) physical (14) and biotic systems: The installation of FPSOs, collection and flow systems, light and noise from operations, discharge of effluent from SRU, discharge of effluent from produced water, and atmospheric emissions.…”

“…For example, drilling wells through methods such as blasting, weight, and rotation inevitably cause irreversible damage to rock formations at the bottom of the sea. The blasting process involves the injection of drilling fluids that assist in the disintegration of rocks, which in turn are returned to the surface in the form of gravel, thus damaging all life that depends on these sites (for reasons ranging from suffocation and habitat loss to pollution/intoxication) [14]. There are also a large number of more serious potential impacts, for example in the event of a blowout (uncontrollable flow of gas, oil, or other reservoir fluids) [3,4].…”

Gas Hydrate: Environmental and Climate Impacts

“…Finally, Reference [41] analyzed the deep structures related to the high concentrations of CO 2 detected along the southeastern Brazilian Margin by using a multidisciplinary approach. Gravimetric and magnetic potential methods were used to identify major intrusive bodies, crustal thinning and other geotectonic elements of the southeastern Brazilian Margin.…”

Environmental Vulnerability in Pre-Salt Oil and Gas Operations

“…For example, drilling wells through methods such as blasting, weight, and rotation inevitably cause irreversible damage to rock formations at the bottom of the sea. The blasting process involves the injection of drilling fluids that assist in the disintegration of rocks, which in turn are returned to the surface in the form of gravel, thus damaging all life that depends on these sites (for reasons ranging from suffocation and habitat loss to pollution/intoxication) [6]. There are also a large number of more serious potential impacts, for example in the event of a blowout (uncontrollable flow of gas, oil, or other reservoir fluids) [3,4].…”