Sand-Control Aspects for Long-Horizontal-Section Wells in Unconsolidated Heavy-Oil Reservoirs

Abstract

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Abstract Gravel Packing is the most frequently applied sand-control technique for horizontal wells in the Campos and Espirito Santo basins, offshore Brazil. Because of critical conditions, such as the deep and ultradeep water and low fracture gradients, much precision is required to ensure openhole-gravelpacking (OHGP) success. An important scenario for offshore development in Brazil includes heavy-oil fields in deep water possibly requiring 2000 m of openhole horizontal sections. Gravel packing is a strong candidate for sand-control because of the wide experience acquired and the high reliability level of such applications (if pressure-loss issues can be overcome). Among the operational issues related to hydraulics, the following are critical: equivalent-circulating-density restrictions, fluid displacement while running the screens, and gravel-pack placement (if this is the adopted sand-control technique). This paper focuses on the following aspects: Petrobras experience in more than 270 OHGP completions in offshore environments, techniques for extending hydraulic limits (e.g., rathole zero, rathole bypass, multiple alpha waves, flow-divergence tools, and lightweight proppants), and a multidisciplinary approach to face challenging well designs for heavy-oil reservoirs, including research and development (R&D), tool development, and field implementation. Introduction Horizontal wells have become the main wellbore architecture for offshore development in unconsolidated oil reservoirs along the Brazilian coast. Most drilling challenges, especially concerning wellbore stability and cuttings transport, were overcome with experience. The major completion issue deals with sand control: OHGP techniques have been developed especially for Campos basin applications. More than 250 horizontal wells have been gravel packed successfully in Brazilian offshore fields (Marques et al. 2007). By 2000, Petrobras was discovering significant amounts of heavy oil in offshore turbidites. Marlim Sul, Roncador, Marlim Leste, Albacora Leste, Jubarte, and Oliva fields are examples of heavy-oil accumulations in Campos, Espirito Santo, and Santos basins. Fig. 1 highlights some of the most important heavy-oil provinces along the Brazilian coast.