Moreover, minimum flow rates are required to ensure that adequate drill cuttings transport occurs.ĭownhole pressures are generated by two origins: hydrostatic forces and friction losses. Dynamic pressures should be maintained inside the operational window defined by the pore, collapse and fracture pressures, guaranteeing that no influxes, losses or rock instability issues occur while drilling. In some conditions, drilling hydraulics may limit the feasibility of the construction process. The industry has invested significantly in sensors and data transmission, but real-time interpretation is still far from the desired levels. Another important issue is to make good use of real-time monitoring of downhole pressures. The main goals of a good hydraulic project are to obtain proper hole cleaning and maintain pressures inside the operational window. The aim was to optimize hydraulic parameters to drill heavy oil reservoir sections. Monitoring Pressures during Drilling Operations Figure 2: Flow loop tests were conducted with synthetic nonconsolidated sand cores saturated in heavy oil, using CT scanning to monitor hole enlargement. Major issues in hydraulics include drilling fluid substitution and completion/ sand control, described below. A ratio of lateral departure and vertical depth greater than two is considered to be critical and challenging. This may be a good option for dry completion projects, or even to consider shallow-water vessels to drill deepwater reservoirs. Particularly in heavy oil reservoirs, to maximize the reservoir area and guarantee an economical flow rate, a big challenge is to assure sand control in horizontal sections that are longer than 1,200 meters.Īnother big challenge is drilling deepwater extended-reach wells. Horizontal sections ranging from 500 meters to 700 meters are common in deepwater developments, and these long horizontal sections pose the first challenge for well trajectory. Pre-salt cluster reservoirs are deeper (5,000 meters to 6,000 meters).ĭevelopment wells for the Campos Basin are typically directional or horizontal. Water depths in Brazil range from 500 meters to 3,000 meters while reservoir depths are typically 3,000 meters to 3,500 meters. In most offshore scenarios, Petrobras faces deepwater (greater than 800 meters) and ultra-deepwater (greater than 2,000 meters), as well as reservoir-related issues such as salt drilling, nonconsolidated sands, heavy oil reservoirs and heterogeneous carbonates.This article presents a brief history of offshore well construction in Brazil, along with a discussion of wellbore hydraulic and the main R&D efforts focusing on hydraulics that the company has undertaken in association with a number of Brazilian universities. Campos Basin is the major producing area while Espirito Santo and Santos represent relevant reserves for the future. This was one topic studied as part of Petrobras’ efforts to support its ultra-deepwater projects.Īpproximately 80% of Brazilian oil production comes from offshore fields. Waldmann, Petrobras Figure 1: Drilling fluid invasion analysis for deepwater exploratory wells is applied to minimize fluid invasion into reservoir rocks. Petrobras technology implementations pay off through field results in tough drilling scenariosīy A.L.
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