Caracterização dos fluidos H2S e agua em reservatorios carbonaticos
AUTOR(ES)
Monica Rebelo Rodriguez
DATA DE PUBLICAÇÃO
1993
RESUMO
Reservoir fluids from two basins - Campos and Santos - of East Brazil margin have been studied. Samples from over 16 wells have been utilized in the fluid characterization. Water and hydrogen sulphide (H_) are fluids with large distribution in petroleum fields and may provide important informations for reservoir studies. High H2S concentratios are normally associated with carbonates and evaporites, a typical association of the post-rift sediments of eastern Brazil continental margin. Three mechanisms - biogenic (BSR), thermochemical (TSR) and thermal decomposition of organic matler - have been identified in the Campos and Santos basins. Bacterial genesis of H2S (BSR) is responsible for its occurrence in reservoir A of Macaé Formation (Campos Basin). Thermal decomposition and TSR are responsible for H2S occurrence in reservoir B of Lower Guarujá Formation (Santos Basin). Reservoir A is characterized by having low temperature (65°C), presence of biodegraded oil and low H2S contents (average of 2000ppm). Reservoir B has two populations with distincts concentrations of H2S. The low H2S group (average of ISppm) shows very negative values of sulfur isotope (õ_ of -21 %o CDD, abscence of sulfate cements and waters with low sulfate, associated with high API oi!. The high H2S group, with maximum concentration around 8000ppm, is interpreted as being product of TSR. Barite, considerable quantity of methane and presence of- condensate gas in temperatures higher than 135°C are the main evidence of this processo In reservoir A (Campos Basin), heterogeneous distribution of formation water, with salinities ranging from 70000 ppm to 90000 ppm, results from natural mixing of deep saline waters with those of the oilfied aquifer. The spatial distribuition of chemical species indicates invasion of saline waters through major bounding faults
ASSUNTO(S)
campos petroliferos geoquimica gases - analise reservatorios
