Applications of Underbalanced Drilling Reservoir Characterisation for Water Shutoff in a Fractured Carbonate Reservoir - A Project Overview
- Darren J. Murphy (Petroleum Development Oman) | Ian A. Davidson (Shell Intl. E&P Co.) | _ Kennedy (PT Blade Energy Indonesia) | Rashid Busaidi (Petroleum Development Oman) | Jan Wind (Petroleum Development Oman) | Clayton G. Mykytiw (Blade Energy Partners) | Leo Arseneault (Precision Drilling UBD)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 2006
- Document Type
- Journal Paper
- 153 - 157
- 2006. Society of Petroleum Engineers
- 5.1 Reservoir Characterisation, 2.2.2 Perforating, 1.6 Drilling Operations, 1.8 Formation Damage, 5.1.2 Faults and Fracture Characterisation, 1.7.1 Underbalanced Drilling, 3 Production and Well Operations, 5.6.4 Drillstem/Well Testing, 5.8.7 Carbonate Reservoir
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Following successful implementation of underbalanced drilling (UBD) in Petroleum Development Oman (PDO), an evaluation of the value of UBD in a carbonate field was commissioned. The study showed that there was a production upside to developing the reservoir with UBD. A four-well trial campaign was conducted between June and October 2004 to assess the potential.
The trial campaign was implemented following a structured program built from PDO's previous experience. During this campaign, a reservoir-characterization (RC) system allowing identification of multiple high-permeability features was developed. Water-shutoff devices were installed in two wells on the basis of the results of the RC system. Production from the four wells was equivalent to or greater than the field average, and the campaign scope has been increased. The campaign was also a stepping stone toward the goal of integrating UBD, RC, and water-shutoff techniques.
When UBD operations commenced in this carbonate field, 46 wells had been drilled underbalanced for PDO in the preceding 2 years (Francis et al. 2003a, 2003b; Ramalho et al. 2003; Eissa and Al-Harthi 2003; Culen et al. 2003).
The field is a heavily faulted and fractured carbonate reservoir. The main reservoir is the Aptian Shuaiba formation, consisting of rudist-bearing reefal-shelf margin deposits with a complex depositional architecture. Porosities range from 14 to 26%. Matrix permeability is highly variable, ranging from 1 md to 1 darcy, with an average of approximately 20 md. The fracture system plays a substantial role, both in early high-rate oil production and in the increase in water production. In some cases, the high oil rates are believed to be a "flush production?? of oil that has accumulated in the fractures. Previous reservoir studies also concluded that the fractures were implicated in the movement of water. Post-drilling fracture systems were identified by the interpretation of formation-image logs; the conductivity of the fracture could not be determined.
A reservoir study to assess the value of UBD in this field indicated a production upside associated with drilling underbalanced. Four wells were drilled underbalanced during the campaign trial (Fig. 1).
The primary objectives of the campaign were to realize an increase in production and to evaluate the use of real-time RC to identify features, including fractures, that were believed to be responsible for water production. RC, as applied here, is the ability of UBD to statically and dynamically characterize the reservoir while drilling by collecting and monitoring surface and bottomhole (by use of a pressure-while-drilling sub) flowing parameters in real time.
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Culen, M.S., Harthi, S., and Hashimi, H. 2003. A Direct Comparison BetweenConventional and Underbalanced Drilling Techniques in the Saih Rawl Field,Oman. Paper IADC/SPE 81629 presented at the IADC/SPE UnderbalancedTechnology Conference and Exhibition, Houston, 25-26 March.
Davidson, I., Medeiros, R., Reitsma, D., and Selby, B. 2004. Changing the Value Equation forUnderbalanced Drilling. Paper SPE/IADC 91559 presented at the SPE/IADCUnderbalanced Technology Conference and Exhibition, Houston, 11-12 October.
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Mykytiw, C.G., Davidson, I.A., and Frink, P.J. 2003. Design and Operational Considerationsto Maintain Underbalanced Conditions with Concentric Casing Injection.Paper IADC/SPE 81631 presented at the IADC/SPE Underbalanced TechnologyConference and Exhibition, Houston, 25-26 March.
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