Deep Water Well Testing for Heavy- and Low-Pour-Point Oils - Issues, Options, Successful Methodology: Case Histories

Abstract

Abstract Testing to evaluate the potential of a new well or field is a common practice in the oil and gas industry. When performing this task in a deep-water environment, however, there are significantly more challenges for the operator and service company to address, and when testing a heavy oil reservoir, the challenges are even further exacerbated. Special consideration must be given to the following issues:High rig rates associated with deep-water operations will make job problems more costly.Producing heavy crude oil to surface, moving it through the surface production train, and finally, disposing of it in an environmentally acceptable manner.Deep-water environment exposes the crude to an extended period of heat loss and low temperatures while it is in the landing string. In order for the well test to be effective, all the above conditions must be fully understood and methodology employed that will reduce the chance that operational risks will occur. This paper will discuss the successful testing of a heavy oil reservoir in deep water. A number of different ways to assist the production of heavy crude in the deep-water environment will be presented, and the relative merits and limitations of each will be considered. The discussion will provide an outline of the necessary additions to the surface production train and the use of chemicals and heat to ensure flow. Finally, it will consider what equipment is necessary to properly dispose of the produced fluid. The testing methods discussed in this paper can be applied to heavy- and low-pour-point crudes in deep water. The equipment and methods can also be used in shallow water applications or on land. The case history data will illustrate:Why particular methods and equipment were used and why others were rejected.The success of the methods selected to address the testing needs.What conditions are inherent when testing deepwater reservoirs in heavy oil, and what is required to nullify or reduce the impact from these conditions on testing operations.The lessons learned from the jobs. Improvements that could be made to further facilitate testing of heavy oil in a deep-water environment.How careful planning can overcome the testing problems in deep water for both low- and heavy-pour-point oils. The information will show that employing proven methods and the proper equipment enables successful testing with reduced risk in difficult heavy- and low-pour-point reservoirs. Introduction For purposes of this paper, heavy oil is defined as any petroleum with an API gravity of less than 20 degrees or a high specific density. It often contains significant impurities and has constricted flow due to high viscosity. Waxes often are a significant component and contribute to difficulties in flow. Production of heavy or low-pour-point oils typically is more difficult and more expensive than with lighter oils. This fact is particularly true when it comes to short-term, temporary operations such as well testing. Well testing in deep water exposes produced crude to a significant period of time in a low-temperature environment that starts at the seabed and extends to the rig-mounted surface production package. Water temperature at the sea floor is often in the 35° F range. In addition, space constraints on exploration rigs may impact the configuration, size, and volume of the production equipment that is selected.