02270nmc a2200265 4500 20260520005605.0 260224s2001 xxu ing Inglés HORIZONTAL UNDERBALANCED DRILLING IN NORTHEAST BRAZIL: A FIELD CASE HISTORY SPE 69490 Dallas, Texas Society of Petroleum Engineers 2001 12/09/06 ; 09/05/2003 This paper describes aspects related to planning and execution of four horizontal wells drilled underbalanced in the Estreito Field. This field is located in Brazil’s Northeast Region (Fig. 1) and has its production zones depleted. It was discovered in 1982 and today it has more than 700 wells. Estreito field has its producing reservoir very shallow and the formation is very unconsolidated, these poses especial challenge to achieve and maintain underbalanced condition at all times during the drilling operation, requiring especial care not only during the planning, but also for the execution of the well operations. In order to achieve the required bottomhole pressure (ECD = 6.9 ppg) nitrogen was injected into the water base drilling fluid, through the standpipe. Since the wells were horizontal, it was required the use of electromagnetic MWD/GR once the regular MWD would not work properly on a gasified fluid. In these wells it was successfully tested a compact vertical gas-liquid separator with an automated control system and data acquisition system developed by Petrobras. A skimmer was used for the solids-drilling fluid-oil separation. CONGTP Cunha, J.C. 2476 Rosa, Fábio Severo 6146 Santos, Hélio 6147 Latin American and Caribbean Petroleum Engineering Conference (7th : 2001 mar. 25-28 : Buenos Aires, Argentina) 5738 Perforación bajo balance 2538 Rosa, Fábio Severo 6146 Santos, Hélio 6147 Latin American and Caribbean Petroleum Engineering Conference (7th : 2001 mar. 25-28 : Buenos Aires, Argentina) 5738 Cunha, J.C. 2476 131002 131002 https://biblioteca.iapg.org.ar/ArchivosAdjuntos/LACPEC2001/Spe69490.pdf 0 0 0 0 201924 BVIAPG BVIAPG 2026-03-03 200003056 0 200003056 2026-03-03 01:41:08 2026-03-03 ARCHIVO