--> Key Conditions and Exploration Direction of Pre-Salt Giant Oil-Gas Fields in Santos Basin, Brazil

AAPG ACE 2018

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Key Conditions and Exploration Direction of Pre-Salt Giant Oil-Gas Fields in Santos Basin, Brazil

Abstract

The Santos basin has become a world-famous deep-water petroliferous basin with giant oil-gas fields gathering. There are favorable conditions of hydrocarbon reservoir forming with world class source rocks, large scale of lacustrine carbonate reservoirs and excellent thick salt sealing in the huge pre-salt rift system of Santos basin. Based on the analysis of tectonic-sedimentary evolution and characteristics of hydrocarbon reservoir forming in Santos basin, we systematically analyzed the key conditions of pre-salt giant oil-gas fields forming and pointed out exploration direction. The results show that: (1)The degree of reservoir development is the key factor of controlling giant oil-gas fields forming. Four types of genetic models determine layer and area of carbonate reservoir forming. Four types of pre-salt uplifts control patterns and scale of carbonate reservoir distribution. Six factors control or effect physical property of carbonate reservoir.(2)The maturity of pre-salt source rock with different geothermal gradient controlled by thickness and continuity of salt layer defines the hydrocarbon type of giant oil-gas fields.(3)the thickness and continuity of salt layer determines the forming and preservation of pre-salt giant oil-gas fields, which are favorable for delaying maturity of source rock, preservation of pre-salt primary pores and sealing.(4)The pre-salt inherited palaeo-uplift structures control the distribution of giant oil-gas fields, which are favorable for reservoir development and hydrocarbon accumulation.(5)The late CO2 influx from mantle probably transforms the giant oil-gas fields. The distribution of CO2 is controlled by thin crust, deep faults and volcanic activities. The pre-salt rift strata have become the most important exploration field and the eastern uplift zone and east part of central depression zone are the favorable exploration potential areas in Santos basin. Moreover, there are several deep-water salt-bearing basins with the pre-salt depositional system and hydrocarbon plays similar to Santos basin, which show vast exploring prospect in South Atlantic.