The US Gulf of Mexico is one of the few regions in the world where wells are completed in the deepwater Miocene and Lower Tertiary reservoirs. These deepwater plays have required constant technological improvement to equipment service capabilities in order to maintain integrity in the 30,000-psi environments and minimize risks. Although capable tools and guns have been developed, continuous assessing of reliability still remains vital in the exploratory processes.
Testing for production assessment in deep and ultra-deep water is critical, and when target reservoirs produce heavy oil, gas and condensate, or are in HP/HT environments, planning safe tests with risk mitigation that can gather high-quality data is paramount. Because of the high rig rates for deep-water operations, prolonged periods of low temperature and heat loss that can affect production or enable hydrate formation and other environmental challenges cannot be ignored. Fluid volumes and water depths can increase well-control time and expense. Also, since well tests are conducted from mobile vessels, alarm and subsea equipment philosophies are critical to success, and well-test string configurations must be flexible yet control well safety.
Obviously, all issues must be understood for the program plan to anticipate the potential challenges. The purpose of this paper is to explore these issues as well as discuss mitigation methodologies. The considerations, merits, and limitations of various solutions will be considered. Lessons learned from actual cases will compare the consequences of inadequate preparation to the benefits of proper design.
This paper explains why and how the methods and equipment suggested should be used and will include:
DP vessel testing
Well integrity at extreme depths and pressures
Functional pressure-operated tool windows
Cushion and mud-type criteria