Claudio Lima

Staircase fractures in microbialites and the role of lamination-related mechanical anisotropy: The example of the Acquasanta Terme travertine deposits (central Italy)

This study describes a peculiar, yet common type of fracture showing a staircase trajectory, which forms in rocks with moderately weak planar anisotropies. The staircase fracture trajectory is given by alternating fracture segments oriented parallel to (LaP) or at an angle (ramp) with respect to the lamination/layering. The analyses has been accomplished on travertines, which are continental microbial/hydrothermal deposits having a typical poorly stratified yet strongly laminated texture. In these rocks, porosity and permeability have a high across-lamination variability and are mostly controlled by an interconnected and locally corroded array of permeable layers, fractures, and faults. Structural analysis integrated with analytical modeling provided a conceptual model of staircase fracture localization as a function of the travertine lamination dip. Lamination-parallel fracture segments localize within the porous laminae, mostly at the interface with tight laminae. Ramp-type fracture segments cut the lamination, connecting lamination parallel segments. Two types of staircase fracture can be modeled. The first group develops in subhorizontal to gently dipping deposits (lamination dip 30°) and corresponds to high-energy environments. Major discoveries of hydrocarbon have been recently made in continental (lacustrine) microbial carbonates in the Brazilian South Atlantic margin, some of which exhibit a texture similar to those usually observed in travertines. Understanding of the lacustrine carbonates is still at an early stage. Given that in modern rift settings, vent-related thermal (travertine) and nonthermal (tufa) carbonates are a major component, the proposed conceptual model of staircase fracture localization contributes to the preparation of a model for the potential occurrence of high-permeability pathways in hydrocarbon and geothermal microbial reservoirs.

Closing the Loop ─ Integrating Predictive Surveillance With Remote Control Operations

The oil and gas industry has had a long-time vision to close the feedback decision loops in the Integrated Digital Oilfield. Petrobras has made initial steps toward this goal by integrating Production Surveillance (for wells, equipment, and facilities) with Remote Control Operations on five platforms that comprise 15% of production operations in the Campos Basin. This represents a step change from the way Petrobras has historically operated, and has required systematic and inter-dependent changes to various sections in the organization. The first step in this direction entailed bringing remote control technical capabilities onshore, to be in closer proximity to the decision center. This ensures stronger person-to-person inter-relationships between production engineers and control operators. The decision center has been operational for over 18 months and has undergone a transformation from reactive to proactive surveillance and analysis approach on the processes supporting production operations. Now that proactive processes have been established, Petrobras has instituted combined surveillance-control processes, with each onshore team focusing on a single platform. As the project has matured, the role has changed so that now each onshore team manages multiple platforms with similar levels of operational complexity. This has led to a strengthening of the quality of remote control operations, has allowed technical expertise to be leveraged across operations, and has reduced overall HSE exposure. This paper describes the initial steps taken by Petrobras to achieve integration between predictive surveillance and remote control production operations. It also describes the benefits that have been realized, such as reducing costs and the number of people on board platforms. Based on the early success of this work, Petrobras plans to expand the program to cover all of its operations in the Campos Basin. After proving success in the Campos Basin, it is expected that this approach will guide Petrobras as it prepares for the many challenges in Pre-Salt operations: complex logistics, personnel shortages, and environmental challenges.