Integrated-Technology Approach Enables Successful Prospect Evaluations in Malaysia
- Chris Carpenter (JPT Technology Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- September 2013
- Document Type
- Journal Paper
- 156 - 159
- 2013. Society of Petroleum Engineers
- 1 in the last 30 days
- 69 since 2007
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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 164576, "Integrated-Technology Approach To Explore Carbonate Reservoirs in Malaysia Enhances PMCD Potential and Enables Successful Prospect Evaluations," by M. Noreffendy Jayah, SPE, Intan Azian A. Aziz, SPE, Zulhilmi Drus, SPE, Thanavathy Patma Nesan, Wong Han Sze, SPE, Abdel Aziz Ali Hassan, and Pungut Luntar, Petronas, prepared for the 2013 IADC/SPE Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, San Antonio, Texas, USA, 17-18 April. The paper has not been peer reviewed.
The central Luconia gas province located offshore Sarawak houses numerous carbonate reservoirs (Fig. 1). Some of these reservoirs are characterized by the presence of karsts and fractures, contributing to total mud losses. Implementing the variant of managed-pressure-drilling technology called pressurized mud-cap drilling (PMCD) allowed targeted total depths (TDs) to be reached on several wells. However, reaching TD alone is insufficient for conclusive evaluation. Integration of technology applications is paramount in increasing the success rate of data delivery.
Well-known for highly varying formation properties even within small sections of reservoir, the recently discovered Malaysian carbonate formations present a risk of drilling-fluid losses. Conventionally, these wells were drilled with overbalanced mud and losses were cured with lost-circulation materials (LCMs) or cement plugs to enable restoration of overbalanced condition for future drilling. Drilling a multiple total-losses zone conventionally proved to be highly uneconomical and likely to jeopardize the safety of the operation. To mitigate this inefficiency and associated safety risks, the PMCD technique was implemented and made ready for all of the operator’s carbonate drilling operations. Since 2010, PMCD equipment and personnel have been mobilized for 11 wells, but have been used only in six wells.
Introduction to PMCD
PMCD is applied in the total-loss condition. Once sufficient loss rates are encountered, the annulus is displaced from overbalanced drill-weight mud to underbalanced light annular mud (LAM). The LAM is generally designed to be under-balanced to the formation pressure at the topmost fracture by approximately 100 psi. This enables gas migration into the wellbore to be monitored closely. After casing pressure has increased to a limit, LAM is injected into the annulus to bullhead the migrated gas back into the formation. Upon each injection, the casing pressure will be restored to the original 100 psi. Drilling operations are performed while injecting seawater continuously down the drillstring and intermittently injecting LAM down the annulus. Drilled cuttings will be carried by seawater and fed into the fractures. Planning for successful PMCD operations not only revolves around equipment and engineering, but also depends on well placement and architecture, well engineering, rig equipment, training, and logistics.
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