Open hole gravel pack completions can have many advantages over comparable cased hole completions. This is especially true for horizontal well applications. However, because no perforations are present to penetrate the filtercake, borehole conditioning prior to gravel packing is critical to ensure good well productivity. To address this issue various borehole cleanup techniques have been developed. These different techniques have been adopted to address specific reservoir and economic conditions. Various levels of success have been realized for these techniques, with their development leading to an improved understanding as to which steps are critical for success under any circumstance.
This paper reports performance results from gravel packed horizontal wells completed in the East Wilmington Field. In addition, techniques applied elsewhere are reviewed. The conditions that must be met in all displacement techniques to ensure a successful completion are outlined, as will the benefits and drawbacks of each of the commonly applied methods. Guidelines for selecting a wellbore cleaning procedure to employ in specific situations are provided.
Many of the potential risks associated with horizontal open hole gravel pack operations can be traced to improper hole cleaning practices. An improperly cleaned wellbore can lead to high drag while running the gravel pack assembly, which can prevent the screen from being run to bottom. In addition, the excess polymer and drilled solids can easily plug screens, leading to high circulating pressures, prematurely stalled packs, and/or failed screens. Finally, formation debris remaining in the wellbore when gravel packing starts can result in reduced gravel pack permeability. Any of these factors can lead to elevated mechanical skin, or a completely failed gravel pack.