Unique Salt Drilling Steerability Test: Advanced RSS Proved Outstanding Build-up Rate Capability in Brazil Mobile Salt Formations

Abstract

Salt drilling in offshore projects has become more frequent over the last 10 years in many parts of the world. In Brazil, important oil discoveries were made in carbonates reservoirs that lay below thick salt bodies. Drilling through salt can be challenging, especially where severe salt mobility is common. Salt mobility or creep rate is mainly a function of downhole temperature, geomechanical stresses around the salt body and salt mineralogy.Today, many deepwater wells targeting hydrocarbons below the salt in Brazil are still considered exploratory or appraisal, and are drilled vertically through salt, with only a few projects in the development phase. Due to the gradual transition of deepwater projects into the development phase, the requirement for directional drilling through salt is rapidly increasing.To achieve a better understanding of the salt drillability, in terms of steerability capabilities and directional assembly stability, a pioneer directional drilling test was conducted in a mobile onshore Brazil salt formation, using an advanced rotary steerable system (RSS) and a specialized downhole drilling optimization measurementwhile-drilling (MWD) tool. This paper will show, in detail, the results and lessons learned from this unique salt drilling steerability test, along with the result of deepwater sections drilled directionally through salt formations offshore Brazil.