Abstract

Drilling exploratory wells in Campos Basin shallow water has been done before. However, if you put in place an aggressive exploratory campaign to drill 40 wells in less than 2 years, with more than 4 semi-submersible rigs new to the area and all for a recently created operating company, you are facing quite a challenge.

The lithology of the wells in block C-M-592, pore pressure profiles and the requirement for formation evaluation while drilling are challenges that needed to be addressed in the design and drilling of these wells. In addition, multiple bit trips, low ROP, and high drilling vibrations have also contributed to increased non-productive time (NPT) with the associated costs.

An integrated approach to engineering and real time monitoring has been the key to controlling the operations and understanding block C-M-592 in Campos basin. In addition, the application of appropriate new technologies along with standardized, fit-for-purpose practices that have been implemented since the beginning of the drilling campaign have resulted in performance improvements.

The drilling times have been considerably optimized through the implementation of several techniques and processes that allowed the project to achieve more than 30 percent reduction in drilling times. The main practices and technologies applied are: understanding and mitigating the shocks and vibrations environment, implementation of slender casing designs, use of the latest generation drilling bits and a clear process for the capturing of best practices and lessons learned. All this was implemented in a new company by a multidisciplinary task team working closely with geosciences support and real-time surveillance, which enabled real time decision making in an ever-changing exploratory environment.

Over the past two years, more than 14 wells have been drilled in the C-M-592 block in Campos Basin. This paper will discuss the drilling problems encountered and detail the actions taken to overcome these problems, which allowed us to achieve more than 30 percent drilling time reduction mentioned above.

Geology

The block C-M-592 is located in the Campos basin, approximately 100 km from shore, in 100-300 m of water (see Figure 1). The Campos basin is a sedimentary basin from continental margin, with a stratigraphy characterized by three phases (see Figure 2): The rifting phase occurred during the cretaceous, known as Lagoa Feia Formation, and is composed with continental lacustrine marl shale and limestone (coquina). The transitional phase (top of Lagoa Feia Formation) is characterized by conglomerates and anhydrite. The post rift phase, from the middle cretaceous (Macae Formation) to lower tertiary, initiate with Albian shallow water carbonate grading to marl and shale. The upper stratigraphy, from Palaeocene to middle Eocene, is a marine regression phase, influenced by the tectonic salt movement, composed principally of sandstone and shale with limestone beds and volcanic rock. The Albians Limestones, of the Macae formation, are the main reservoir for most of the oil reserve of the basin.

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