Operators developing reservoirs and producing them from deep and ultradeepwater wells are pushing the technical limits regarding horizontal extension. Deepwater wells completed in unconsolidated formations usually have low fracture gradients, severe leakoff zones, and/or significant washouts. Long horizontal open holes, therefore, may become technically difficult or economically unfeasible to gravel-pack with the use of conventional fluids and gravels.Typical completions in offshore Brazil start from a 9 5 =8or 10 3 =4-in. casing, in which a 5 1 =2-in. premium screen and tubular string is hung along an open hole drilled with an 8 1 =2or 9 1 =2-in. bit. Horizontal extensions range from 980 to 4,000 ft. A variety of openhole gravel-pack techniques proved to be complex and costly, but ultralightweight (ULW) proppants have enabled simpler and more-cost-effective gravel packing in these longer horizontal open holes. The reduced gravel density allows a significant reduction in pumping rate that avoids fracturing the formation, minimizes fluid loss, and eliminates the risk of premature screenout caused by excessive gravel settling.ULW-proppant technology was introduced to Brazil in 2005 and has been applied successfully to gravel pack wells under extreme conditions such as low fracture gradient, severe fluid loss, and washed-out zones. ProppantULW-1.25 has proved to be effective for packing wells with narrow sections through the openhole interval, frequently found in horizontal wells completed through shale zones that are isolated by reactive packers and/or mechanical external casing packers. ULW-1.75 was introduced in Brazil in 2007 and has largely replaced ULW-1.25 for gravel packing wells in which an improvement in the operational pumping window is required. A combined package comprising ULW-1.75 during the alpha-wave phase and ULW-1.25 during the beta-wave phase is also discussed. This paper summarizes the procedures and results of almost 60 wells that have been gravel packed with the use of ULW-proppant technology pumped for a local operator.

The Campos basin is a sedimentary basin located in offshore Brazil, between the north coast of Rio de Janeiro State and the south coast of Espírito Santo State, encompassing many oilfields. Most of the reservoirs in the basin are high-permeability sandstones containing low API gravity oil but are without strong water drives. Long horizontal producer wells are the best economic option for field development but require water injection to maintain reservoir pressure. Horizontal sections generally range from 1000 to 2000m, which demands gravel pack as a sand control method. Gravel packing such long wells is a challenge and requires thoughtful engineering to optimize pumping techniques and technology. Presented here are best practices to overcome several challenges faced in this field to achieve overall success. The challenge for extended-reach gravel packing is that the long horizontal section develops high friction during the alpha and beta wave propagation. Increasing the pumping pressure to overcome this friction increases the risk of fracturing the formation, consequently reducing the equivalent circulation rate downhole impairing the proppant transportation. In contrast, a reduced pump rate during alpha wave propagation can lead to a premature screenout due to the increase in dune height of over 85%. To overcome these issues and place gravel packs in these wells, careful engineering and simulation, lightweight proppants, friction reducers, and thorough job planning were used to successfully perform gravel packs in more than 40 horizontal wells completed in the Campos basin from 2011 up to 2017. The experience of pumping the longest gravel pack jobs in offshore Brazil (horizontal length more than 2,000m) offer insights into best practices for gravel packs in extended-reach horizontal wells: Design considerations, specific well challenges faced, technologies deployed, and operational planning requirements. Specifically, highlighting the benefits of using lightweight proppants and optimized fluid systems to minimize screen out risks and maximize pack efficiency.

The stimulation history in offshore Brazil is undergoing into a deep transformation. The requirements of technology, before focused on sandstone reservoirs demand, are being expanded by the need for techniques to stimulate carbonate reservoirs, specially the pre-salt carbonates. In this scenario, a self-diverting acid system based on a viscoelastic surfactant (VES) technology was introduced for carbonate reservoir stimulation. The Self-Diverting VES (SD-VES) promotes viscosity development when the acid comes in contact with the carbonate formation. The mechanism of viscosity development is simple: In concentrated acid, the system presents low viscosity, which results in friction reduction while pumping; however, when the fluid reacts with the formation and the acid concentration decreases, the micelle spherical structures combine, transforming into rod-like micelles that convert to a 3-D structure, which increases the fluid viscosity. The high viscosity generates a temporary barrier across the high-injectivity zones, diverting the subsequent fluid to treat other reservoir zones. Generally the SD-VES is associated with several placement techniques that aid in achieving good treatment distribution through the entire producer interval. Regardless of the placement technique applied, the SD-VES is generally used as the main acid fluid and is bullheaded into the well. Because of its rheological behavior, the SD-VES is pumped as a single fluid during bullheading, aiming to achieve formation stimulation and good treatment distribution throuth the entire productive interval. Since the SD-VES was introduced in 2009 to treat carbonate reservoirs in offshore Brazil, more than 40 wells have been treated using the system in the various acid placement techniques presented in this paper. Three case histories are presented to better illustrate the different scenarios where the SD-VES was applied.

The Horizontal Open Hole Gravel Pack (HOHGP) is the preferred completion method employed in Campos and Espirito Santo basins, offshore Brazil. To pack the well, the proppant is pumped such that the alpha wave is propagated from the heel to the toe of the well and the beta wave then propagates from the toe to the heel. During the alpha and beta waves, the carrier fluid is diverted into and must travel through the narrow annulus between the screen base-pipe and wash-pipe to the toe, where the perforated base pipe is located. This diversion raises the friction pressure significantly. When pumping the beta wave, the friction rises even more because the fluid must travel through the gravel placed during the alpha wave before it can flow through the screen. The surface pressure required to overcome this high friction pressure can reach or exceed the formation fracture pressure, resulting in early termination of the gravel pack placement due to severe fluid leakoff to the formation. Some solutions are available, but the preferred method of dealing with pressure increases when performing HOHGP offshore Brazil is the ultra-lightweight (ULW) proppants and BOP open (return through the flow line). However, in some cases when the extended horizontal section is associated with a low fracture gradient and washed out zones, the pumping window expansion provided by ULW proppants and BOP open can be still not enough to perform the job comfortably. In such scenario a friction pressure reducer (FPR) was introduced to avoid pressure increases while pumping the gravel pack. The FPR can also minimize friction pressure increases in wells packed using intermediate-density ceramic gravels. This paper describes 3 successful case histories of circulation tests and HOHGP performed with FPR added to the completion fluid. The focuses are the challenges faced, lessons learned and advantages of using the FPR to extend the safe pumping window.

Operators developing reservoirs and producing them from deep and ultra-deepwater wells are pushing the technical limits regarding horizontal extension. Deepwater wells completed in uncosilidated formations usually have low fracture gradients, severe leak-off zones and/or significant wash outs. Long horizontal open holes, therefore, may become technically difficult or economically unfeasible to gravel pack using conventional fluids and gravels. Typical completions offshore Brazil start from a 9 5/8-in. or 10 3/4-in. casing, where a 5 1/2-in. premium screen and tubular string is hung along an open hole drilled with 8 1/2-in. or 9 1/2-in. bit. Horizontal extensions range from 980 to 4,000 ft. Ultra-lightweight proppants have enabled gravel packing in these longer horizontal open holes. The reduced gravel density allows a significant reduction in pumping rate, which avoids fracturing the formation, minimizes fluid losses and eliminates the risk of premature screen out due to excessive gravel settling. This paper summarizes the procedures and results of almost 60 wells that have been gravel packed using ultra-lightweight proppants technology pumped for a local operator.