Gravel Packing Wells Drilled With Oil-Based Fluids: A Critical Review of Current Practices and Recommendations for Future Applications

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMany of the recently discovered reservoirs in deepwater/subsea environments are prime candidates for horizontal open-hole gravel packs. Presence of multiple reactive shale breaks and penetration of different sand bodies along these holes introduce a formidable challenge for selection of proper carrier fluids, considering that most of these wells require oilbased (OB) drilling fluids.Various procedures were practiced for gravel-packing wells drilled with OB fluids, most utilizing water-based (WB) carrier fluids. Primary concern in using WB carrier fluids is the destabilization of the shales.If the displacements to WB fluids are performed prior to running in hole with the sandface completion assembly, inability to run the screen assembly to target zone is the risk. Consequently, operators were forced to use a two-step process, whereby a predrilled liner is run in hole in OB fluid environment, followed by displacements to WB fluids and gravel-packing with WB fluids. This approach introduces additional rig time and increases completion costs.If the displacements to WB fluids are performed after running in hole with completion assembly, primary challenge is the prevention of screen plugging. This necessitates a comparison of the benefits and risks of displacements to solids-free oil-based fluids and conditioning of the OB drilling fluid, considering logistics.An additional consideration in gravel packing with WB fluids in reactive-shale environments is the risk of intermixing of gravel with shales, thus reduced gravel-pack permeability. Various approaches may be taken to minimize this risk. The type of carrier fluid must also be kept in mind from a formation and gravel pack damage standpoints, should losses be experienced during gravel packing.Another approach in reactive shale environments is to use an oil-based carrier fluid and avoid exposure of the open hole to WB fluids both prior to and during gravel packing. This approach, practiced in two applications, also has its limitations.In this paper, a critical review of gravel-packing practices in oil-based drilling environments is provided, along with some of the recent developments and recommendations for future applications based on lessons learned from earlier practices.

A 20/80 Oil/Water Ratio Nonaqueous Screen Running System Successfully Employed In Equatorial Guinea

“…Parlar et al (2004) discuss the major risk associated with wellbore instability, particularly with shaly intervals. Chambers et al (2000) discuss possible fluid loss associated with contact with the filter cake.…”

“…When a nonaqueous fluid (NAF) is used to drill the reservoir section however, the use of a water-based viscous solids-free pill may not provide the best solution (Parlar et al 2004). This has led to the use, in many cases, of other techniques to prevent screen plugging.…”

“…If the system is not sheared properly, the bridging particles may not completely oil-wet and/or disperse resulting in an agglomeration of the fine particles and emulsions (Parlar et al 2004).…”

Field Implementation of Gravel Packing Horizontal Wells Using a Solids-Free Synthetic Fluid With Alpha-/ Beta-Wave Technology

“…In spite of the industry's effort to develop high-performance water-based fluids (Parlar et al 2004;Aldea et al 2005), the use of synthetic fluids guarantees superior wellbore stability, lubricity, inhibition, and drilling performance. Substituting synthetic DIF for water-based gravel-carrier fluids is a complex operation because of the potential for fluid interaction, formation damage, and problems of offshore logistics.…”

“…Another challenge is to provide a reliable sandcontrol technique in the horizontal section with operational safety and minimum formation damage. Parlar et al (2004) presented field implementations of OHGP operations considering high-viscosity nonaqueous fluid (NAF) and alternate path concepts.…”