Challenges and Solutions To Running Tools Through Older Well Completions Containing Significant Paraffin and Asphaltene Buildup

Abstract

Abstract Scarcity of petroleum supply is causing an industry emphasis on recompletions as well as drilling. This paper will address recompletion efforts in older wells, those drilled before 1998. In such wells, buildup of asphaltenes and paraffins presents a challenge that causes significant losses of rig time, production and revenue both onshore and offshore. A particularly difficult situation arises when trying to run tools through older completions' tubing and casing in which significant buildup is found. Though not fully predictable, the composition and causes of these buildups have already been the subject of many industry publications. This paper uses case studies from fields located in and around the Gulf of Mexico to illustrate the difficulties of using modern tools on these older well completions. Once the failure conditions under which each job was performed are established, it is shown that everything from malfunction of the equipment to not being able to run the equipment at all can be directly attributed to the presence of accumulated substances. Conversely, it is shown that the success of a job can at least in part be attributed to having produced a "clean" well condition in an older well prior to running the job. These experiences in the field serve as a means to suggest the use of different types of tools to account for the presence or absence of buildup, as well as how tools can be run to depth when there is buildup in the well. Introduction Today, though oil prices are off from their recent high of almost ﹩150/bbl, demand for oil is projected to rise in the future. To satisfy this demand, there are two options. The first is to look for and produce new fields. Since it has been accepted that most if not all of the sizable land based fields have been found, producers must go offshore to find undiscovered energy sources. Unfortunately, this is a very costly solution. Another option is to work over wells (offshore or onshore) that have been in production for some time. Since the well has already been drilled and completed, this is a far more cost effective solution. This is not to say that following this path is without challenges. For the purposes of this paper, "older" wells are those defined as having been completed initially over 10 years ago. A particularly difficult situation arises when trying to run completion tools in these older wells. If a proper maintenance schedule has not been followed, a number of challenging well conditions can arise: split or warped casing and tubing, cement sheath failure, or scale/deposit buildup. This report will focus specifically on buildup of asphaltenes and paraffins in older wells. Through the use of four case studies from the Gulf of Mexico and surrounding areas, this paper will introduce solutions to problems many operators have had when running completion tools in older wells with significant presence of asphaltene and paraffin buildup. Practical rather than technical, the aim is for this paper to be a guide to solving some common problems seen in the field. After establishing the exact well conditions under which the problems occurred, an explanation of the problem followed by some solutions and preventative measures will be given.