Method To Reduce Milling and Trip Times During the Recovery Operations of Permanent Production Packers

Abstract

There are many situations that require the removal of a production packer from a wellbore, whether it is a planned workover or a stuck packer during the completion process. In all cases, the packer must be washed over and recovered or milled up and pushed down to the bottom of the wellbore. Most of the methods used today are the same tools and techniques that have been in use for the last 30 or so years. These methods incorporate a shoe or milling head with a specific type retrieving tool to catch the packer after milling away the slips, and were designed for packers that came with millout extensions or blank bottoms. Today, however, packers are being run with seal bore extensions instead of millout extensions. Packers are being manufactured with more exotic materials and high chrome metals. These materials present a milling challenge -- not only do they create longer milling times, but they also usually require two or more trips to mill and recover the packer. A new method of milling has been specifically designed to reduce milling and trip times in these modern packers. This new method allows an operator to engage a smooth packer bore and completely remove all of the packer material and slips rather than removing only the outside material and leaving the packer mandrel. This milling procedure is quicker and produces smaller amounts of debris, therefore reducing milling times. The milling heads can be dressed with the most up-to-date cutting structures that will optimize the removal of the packer material depending on whether it is standard grade or of a high-tensile, high-chrome content. This paper will discuss the process and operational procedures pertaining to this new method, along with case histories. The paper will detail the advantages of this method and the tools used, as opposed to the conventional methods and tools that are widely used through out the world today. Introduction Many companies manufacture permanent production packers and accessories. When these packers must be removed, whether it is planned or unplanned, efficient removal will greatly benefit the producing company. This is especially important in the deepwater environment where rig rates are high. The two main processes in accomplishing this task are milling and recovery. Longer milling times or multiple trips in hole to recover debris will produce a lot of non productive time. First let us briefly discuss packers and accessories in general. The packer consists of a packer mandrel with a packing element around the outside. A set of bottom slips prevents the packer from moving downhole and a set of top slips prevent it from moving uphole. In most applications there will be accessories such as seal bore extensions that are run below the packer to allow for longer and more sealing elements to seal off inside the mandrel and seal bore extension. Between the packer element and slips there will be some type of metal rings. Also the length from the top slips to the top of the packer will vary depending on the manufacturer. These packers can also be manufactured for hostile environments and may be made out of the more exotic metals that make milling very difficult with conventional methods. These packers produce longer than normal milling times and require more trips.