Well-Completion Techniques and Methodologies for Maintaining Underbalanced Conditions Throughout Initial and Subsequent Well Interventions

摘要

Underbalanced drilling (UBD) is undoubtedly one of the "hottest" topics in the oilfield today. Although not a new concept, UBD has just recently come of age, as the benefits it offers to the oil and gas industry have been noted only within the last few years. Underbalanced drilling offers many notable advantages, which include: 1. Reducing formation damage 2. Increasing the rate of penetration (ROP) and bit life. 3. Allowing the reservoir to be tested and evaluated while drilling. 4. Reducing the number of trips into the hole 5. Minimizing differential sticking of pipe 6. Limiting lost circulation 7. Facilitating early production while drilling 8. Accessing depleted or low-pressure reservoirs 9. Selecting TD from inflow performance. The benefits of the above are obvious; therefore, they will not be discussed in depth in this paper. While UBD technology has come a long way since the early wells that were brought in via gushers that rose above the wooden derricks, underbalanced drilling can only supply part of the solution ― once drilling procedures are concluded, and the completion phase begins; the primary operational drivers change. Rather than focusing on such activities as drilling performance and formation evaluation while drilling, the completion drivers target the reduction of fluid loss and the elimination of formation damage. Thus, attaining a total solution requires that underbalanced conditions not only are maintained during the completion and for the life of the well, but also throughout any future well interventions. Unfortunately, the advances in underbalanced completion technology have lagged behind those seen in underbalanced drilling. This paper will explore the strategies, techniques and tool systems required 1) to maintain an underbalanced condition throughout the initial well completion phase and during all future remedial operations, and 2), to create a cost-effective solution that will enhance and accelerate maximum reservoir drainage. To this end, if underbalanced technology is approached as a production enhancement technique that starts at the initial stage of drilling the well and continues throughout the life of the well, the end result will be that the value of the reservoir will be increased, and will be collected within in a shorter period of time.