TY - THES

T1 - Drilling fluid: a stochastic ROP optimization approach for the Brazilian pre-salt carbonates

AU - Nascimento, Andreas

N1 - embargoed until null

PY - 2012

Y1 - 2012

N2 - The oil & gas industry has improved in exploration for deeper areas and in areas of salt layers. Some years ago, much has been said in the field of exploration about the complexities related to activities in the pre-salt region, in Brazil, frequently located in regions of ultra-deepwater, yielding technologies challenges. Considering the scenario for 2030, it is expected an increase in the world oil demand of 34 Mbbd, and an increase in oil production in Brazil of about 4 Mbbd, which represents approximately 11% of the global demand increase. Initially, the thesis presents the context of the pre-salt of Brazil, emphasizing the particularities of the exploration activities undertaken. As case studies, it has been used, respectively, the wells 1-BRSA-329D-RJS (Parati), 1-BRSA-369A-RJS (Tupi), 1-BRSA-491-SPS (Carioca), for the carbonates drilling optimization approach. By analyzing the provided and reported well-logs from BDEP, including sonic wave transit time logs, gamma-ray logs and formation bulk density logs, rock mechanics properties are estimated and pore pressure extrapolated for the pre-salt carbonate layers for each specific well. In this way, different analysis converged for a minimum acceptable MW to be used on the system, taking into account possibilities of kick occurrence and limitation related to wellbore collapse prevention needs. Being the MW one of the most important drilling parameters that can be changed over the operation, its optimization directly reflects on the ROP optimization, methodology used for driving the results presented over the thesis. Further accomplished and supported by Monte Carlo simulations for an overall analysis, considered are as well other parameters that affect the ROP such as bit size, WOB, hydraulic jet impact force, etc., used through stochastic values generations. A wide range of ROP increasing could be easily achieved for the Brazilian pre-salt carbonates, mainly by making use of lighter MW, since just a one decimal decrease in them value reflected in almost 12%, 16% and 27% in ROP efficiency, respectively for each well. Stated could be as well that a minimum weighted mud for dealing with the wellbore wall withstand (15.2 ppg, 23.0 ppg and 13.8 ppg, to well in sequence) is innaplicable, since them lead the ROP to be very low, being almost zero from 18.8 ppg, 15.5 ppg and 13.7 ppg, respectively, for each well. Thus, stated was that the minimum acceptable limit for MW design should take into account the pore pressure plus a safety margin of 3%. Even that, the MW reported for the activities run in the Brazilian pre-salt carbonates have shown a usage of MW in 14.83%, 14.74% and 11.46% greater than necessary, which could be better designed for optimizing the ROP.

AB - The oil & gas industry has improved in exploration for deeper areas and in areas of salt layers. Some years ago, much has been said in the field of exploration about the complexities related to activities in the pre-salt region, in Brazil, frequently located in regions of ultra-deepwater, yielding technologies challenges. Considering the scenario for 2030, it is expected an increase in the world oil demand of 34 Mbbd, and an increase in oil production in Brazil of about 4 Mbbd, which represents approximately 11% of the global demand increase. Initially, the thesis presents the context of the pre-salt of Brazil, emphasizing the particularities of the exploration activities undertaken. As case studies, it has been used, respectively, the wells 1-BRSA-329D-RJS (Parati), 1-BRSA-369A-RJS (Tupi), 1-BRSA-491-SPS (Carioca), for the carbonates drilling optimization approach. By analyzing the provided and reported well-logs from BDEP, including sonic wave transit time logs, gamma-ray logs and formation bulk density logs, rock mechanics properties are estimated and pore pressure extrapolated for the pre-salt carbonate layers for each specific well. In this way, different analysis converged for a minimum acceptable MW to be used on the system, taking into account possibilities of kick occurrence and limitation related to wellbore collapse prevention needs. Being the MW one of the most important drilling parameters that can be changed over the operation, its optimization directly reflects on the ROP optimization, methodology used for driving the results presented over the thesis. Further accomplished and supported by Monte Carlo simulations for an overall analysis, considered are as well other parameters that affect the ROP such as bit size, WOB, hydraulic jet impact force, etc., used through stochastic values generations. A wide range of ROP increasing could be easily achieved for the Brazilian pre-salt carbonates, mainly by making use of lighter MW, since just a one decimal decrease in them value reflected in almost 12%, 16% and 27% in ROP efficiency, respectively for each well. Stated could be as well that a minimum weighted mud for dealing with the wellbore wall withstand (15.2 ppg, 23.0 ppg and 13.8 ppg, to well in sequence) is innaplicable, since them lead the ROP to be very low, being almost zero from 18.8 ppg, 15.5 ppg and 13.7 ppg, respectively, for each well. Thus, stated was that the minimum acceptable limit for MW design should take into account the pore pressure plus a safety margin of 3%. Even that, the MW reported for the activities run in the Brazilian pre-salt carbonates have shown a usage of MW in 14.83%, 14.74% and 11.46% greater than necessary, which could be better designed for optimizing the ROP.

KW - Salzformationen in Brasilien

KW - Carbonate

KW - Bohroptimisierung

KW - Eindringrate (ROP)

KW - Bohrspülungsgewicht

KW - stochastische Variablen

KW - Brazilian pre-salt

KW - carbonates

KW - drilling optimization

KW - rate of penetration

KW - mud weight

KW - stochastic variables

M3 - Master's Thesis

ER -