Planning and Conducting Well Tests in Deep and Ultra-Deep Water toMitigate Potential Risks and Justify Expense for the Operator

摘要

Well testing is a critical part of potential production assessment in deep and ultra-deep water well development. When targetreservoirs produce heavy oil, gas, and condensate, or are high pressure/high temperature (HP/HT) environments, testdesigners in the operating company must not only focus on safety and risk mitigation for the operator, when planning thesetests, but also must assure that the tests will gather enough data to justify the operational expense and potential risks inherentto these types of environments. Deep-water production usually requires prolonged periods of low temperature and heat loss, which can affect productionor result in hydrate formation. Intervention can be problematic and costly. Fluid volumes, well and water depths accessed canincrease well-control time and expense for the operator. Also, since these well tests are conducted from mobile vessels, thealarm and subsea equipment philosophies are critical to the enhancement of safety and risk mitigation. Well-test design andstring configuration must have flexibility but still must be capable of efficiently controlling the conditions listed above. Obviously, these and many other issues must be fully understood by the operator if the program plan, equipment, andmethodology have the capability to assess the challenges, ameliorate the risks, and provide contingencies for unexpectedevents that could occur. This paper explores these issues as well as appropriate methodologies for mitigation. The merits and limitations ofvarious solutions will be considered along with the basic philosophy of equipment consideration. Lessons learned from actualcases will be used to compare consequences of inadequate preparation to the benefits of proper design. Also explained will be why particular methods and equipment should be used and why others are less desirable. Lessonslearned and their application will be discussed, including: 1. Red, yellow, or degraded status decision making during dynamic-positioning (DP) vessel testing 2. Coiled-tubing usage criteria 3. Defining cushion-type criteria 4. Defining mud-type criteria 5. Hydrate prevention and mitigation 6. Importance of obtaining dynamic reservoir data efficiently and economically without risking the environment and personnel safety.