Drilling Optimization in Deepwater Field Development Offshore Brazil

Abstract

ASTRACT Giant deepwater oilfields had been discovered in Campos Basin, offshore Brazil, through the eighties. After overcoming initial problems while drilling the exploratory wells, appraisal wells were drilled under regular performance standards, comparing to shallow water previous data. At that time, Albacora and Marlim field development plans were considering improved performances to occur due to the expected learning effects. The combination of the simultaneous use of dynamic positioned and deep anchored rigs with the technical improvements in well operations resulted in an outstanding overall drilling performance for the development campaign of those fields. The drilling program was concluded well ahead of schedule, establishing guidelines for future deepwater field exploitation. This paper describes Petrobras experience of planning and drilling deepwater development wells, showing the principal measures and factors that led to an update of our operational standards. Also, the ultra deepwater drilling R&D projects carried out at the moment are briefly introduced, being their aims to keep or even improve our performance and safety records as water depths up to 2,000 m are considered for oilfield developments offshore Brazil in the future. INTRODUCTION In late 1984, Petrobras started drilling the so-called deepwater wells, beyond 400 m water depth, in the Campos Basin area (figure 1), located at Rio de Janeiro State, using dynamic positioned (DP) drill ship. The first wells had striked the Marlim field and confirmed the extension of Albacora field into deeper waters. The Marlim field is located 100 km off the coast, in the eastern part of Campos Basin. Total reserves are estimated to be 1.5 billion barrels of oil in an area of 132 sq. km, straddling from 600 to 1,050 m water depth. The pilot system is composed of 10 wells, already producing 50,000 bopd to a stationary production unit (SPU). The Phase I of the field development is divided in two modules; current module 1 consists of 28 wells, being 16 production and 12 injection wells. From this total, 26 wells had been drilled and 9 wells had been completed so far. The module 1 SPU, Petrobras XVIII, has been installed at 910 m water depth, setting a new world record of stationary production unit anchoring. The Albacora field is located 107 km off the coast, in the northeastern part of Campos Basin. Total reserves are estimated to be 640 million barrels of oil in water depths varying from 230 to 2,000 m. Development Phase I consisted of 16 wells, already producing to a stationary producing unit, Petrobras XXIV. As in the Marlim field, Albacora field Phase II is also divided in two modules; current module 1 consists of 28 wells, where 22 wells had been drilled and 9 wells had been completed up to the tubing hanger so far. Seven years elapsed before the decision of developing both fields was finally taken. During this period of time, 59 wells were drilled with DP rigs up to 1,565 m water depth and other 26 wells were drilled using moored rigs up to 600 m water depth, mainly in Campos Basin area.