The crystalline composition of Portland cement clinker is commonly established by Bogue´s equations, which are based on a series of assumptions that seldom apply to oilwell cements. This is probably due to the presence of additional oxides and phase reconversion upon cooling of the clinker from the calcination temperature. Important differences are therefore observed between the numerical values yielded by the mathematical equations and image analysis quantifi cation. In this study, the concentration of crystalline phases in oilwell cement was determined using Taylor´s procedure, which consists in a system of linear equations corresponding to each one of the four main clinker phases. The results revealed an adequate relationship between this method and phase quantifi cation by optical micrography, especially concerning the contents of aluminate and ferrite.

Portland cement is by far the most important binding material used in both civil construction and oil well cementing. However, especially in the latter application, its brittle nature impairs its ability to withstand dimensional changes due to thermal gradients (RT to approximately 200°C), typical of heavy-oil recovery operations. This often results in extensive cracking of the cement sheath and debonding of the cement-casing interface, which leads to loss of zonal isolation, gas migration and production of water and oil through the well annular. Portland-Polyurethane composites have been formulated and tested in an attempt to improve the deformation ability of the cement during thermal cycles without affecting the pumping behavior or high-temperature resistance of the material. Preliminary results confirmed that the addition of small contents of polyurethane considerably improved the plasticity of the cement in approximately 50% as well as decreased porosity and permeability. No significant changes were observed in the rheological behavior of the composite slurries with respect to plain Portland cement.

After 10 years of Brazilian presalt exploration and development, the carbonate reservoirs continue to pose drilling challenges, leading to unwanted bottomhole assembly (BHA) trips due to severe shock and vibration, low rates of penetration (ROP), and premature drill-bit cutting structure damage. Today, industry efforts to improve the performance in the Brazilian presalt carbonates are driven by trial and error, which is very costly in the ultradeepwater drilling environment. The adoption of a collaborative mindset since 2012 between a service provider and operator with the desire to bring about a step change in drilling efficiency on the Brazilian presalt cluster enabled a systematic learning framework to capture, evaluate, and reuse knowledge from drilling dynamics, geological, and petrophysical aspects. The innovation of this work is the implementation of an improved, fully digital bit design workflow, integrating calibrated 4D dynamic simulation model and petrotechnical expertise from drilling engineering, geomechanics, geology, and petrophysics groups to continue to push the drilling performance envelope in the challenging Brazilian presalt application.

The pre-salt reserves offshore from Santos basin represent a great opportunity and probably the most important recent oil discovery in Brazil. These carbonate reservoirs are currently drilled with various types of drill bits, and have proven to be a challenging environment. Since their discovery, there has been an incessant search for the development of drill bits that are able to drill these hard and, in some cases, very abrasive formations in a single run and with optimized drilling rates. In this way, the costs for wells construction would be increasingly reduced, which would further increase the attractiveness of the development of these fields in Santos basin. This paper presents the technological evolution employed in drill bits, from the beginning of the exploratory campaign in Santos basin until newer developments, newer PDC bits designs, and geometric cutters currently used in pre-salt carbonate drilling. In addition, the contractual improvements and results are also presented, showing consistent evolution of ROP and perforated extension over the years, with the development and use of new drill bits in Petrobras.

The tensile strength of Portland cement may be increased by additional reinforcement. This is usually accomplished by means of steel rods, fibers or particles, which are mixed to the slurry. In an attempt of increasing toughness and tensile strength of hardened cement pastes, the present work describes the behavior of composites consisting of Portland reinforced by natural polymer particles for oil well cementing. The main purpose of the study was to select plastic and environmentally friendly powdered materials capable of filling the typical porosity developed on hardened Portland cement. Preliminary results suggested that the tensile strength of plain Portland hardened slurries could be increased by as much as 40% by adding 10% of reinforcement.