tailieunhanh - Reservoir Formation Damage Episode 3 Part 1

Tham khảo tài liệu 'reservoir formation damage episode 3 part 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 482 Reservoir Formation Damage where pc denotes the capillary pressure necessary for water retention Ơ is the surface tension between water and hydrocarbon 9 is the contact angle between the water and hydrocarbon and r is the pore radius. Eq. 15-1 indicates that water retention can be reduced by workover schemes reducing the surface tension and or increasing the contact angle to favor a less water-wet condition. The Mud Damage Problem Keelan and Koepf 1977 explain that drilling muds contain solid particles that form a filter cake over the wellbore wall the filter cake restricts the mud flow into the near well bore formation but some filtrate and fine particle invasion are unavoidable and usually occurs. The filtrate may react with the resident formation clays causing clay swelling mobilization and migration. The released particles and the fine particles carried into the formation by the filtrate can plug the pores and reduce permeability of the formation. The water-based filtrates increase the irreducible water saturation and create water block and hydrocarbon permeability reduction. Evaluation of Drilling Muds Damage Potential and Removal As depicted in Figure 15-11 by Amaefule et al. 1988 the face of a core sample is exposed to mud under a pressure difference across the core. As described by Keelan and Koepf 1977 test sequences can be conducted with and without the presence of mobile hydrocarbons in core plugs. Figure 15-12 by Keelan and Koepf 1977 delineates the test sequence without the presence of mobile hydrocarbons and shows the equations used to determine the magnitude of formation damage or remediation. Keelan and Koepf 1977 explain that This test indicates impairment of productivity by clay hydration and movement of fines into the formation during the drilling operation and any benefit of the fines removal when the well flow in a reverse direction into the wellbore. The core plug is saturated with the brine to be tested and may or may not contain .