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Abstract The North Pailin field, located in the Gulf of Thailand (GOT) had been evaluated during 1996–1997 with 15 delineation wells. Risked gas resources of 1,280 BCF (1 January 2002) will be fully developed with a Central Processing Platform (CPP) and a total of 357 development wells on 31 wellhead platforms (WP). However, thanks to a flexible performance-oriented operational philosophy, Unocal Thailand put North Pailin development on a fast track, aggressive timeline that moved the start-up project from well plan to cash flow within 9 months.
Each well of the initial first four-platform drilling program was highly deviated and followed a 3-D design in three sections: 11–3/4", 8–1/2" and 6–1/8". During this drilling campaign, many world class drilling records were achieved:In February 2002, North Pailin A-05 3D-well was directionally drilled from spud (325-ft mud line) to 11,388 feet TD in 1.9 days at $49.6 per foot.
The 12-well program on North Pailin-A was completed within 34.42 days, 115,103 feet were drilled by average 4,387 SFPD at $64 per foot.
For the entire four-platform, four rigs had drilled 618,786 feet (117 miles) out of 55 wells in the first quarter of 2002, at an average cost of $850K per well or $76 per foot.
Together with those records, 307,140 man-hours were also achieved safely without any lost time incidents.
The records achieved on the North Pailin make it the most efficiently drilled development program so far in the GOT. A brief background of the North Pailin will be presented. However, the main focus is to highlight the key performance statistics and offers insights into the success of the North Pailin drilling campaigns.
Introduction Unocal Thailand, Ltd., a subsidiary of Unocal Corporation, was the first Oil Company to win exploration rights in Thailand in 1962. The company is engaged in exploration and production of natural gas, oil and condensate in the Gulf of Thailand. As of September 2002, Unocal has set 108 platforms (81 wellhead, 4 production, 5 central processing, 1 oil central processing, 7 living quarters, 8 flare tripods, 1 gas compression and 1 riser platforms), drilled more than 1,699 wells, and produced over 4,838 BCF of gas and 174 MM bbls of condensate. Unocal Thailand's facilities are located near the center of the Gulf. (Figure 1. Thailand Concession Map)
Discovered in 1990, the Pailin field lies 90 miles east of Nakhon Si Thammarat province on the southern coast. The field is located in Concession Block B12/27, which encompasses an area of 1,200 square miles. The prospective area extends approximately 38 miles N-S, and 6–9 miles E-W. Unocal Thailand, Ltd., is operator of the Pailin field and holds a 35 percent working interest. Co-ventures include PTT Exploration and Production (PTTEP) Public Company Limited (45%), Amerada Hess Exploration (Thailand) Co., Ltd. (15%), and MOECO Thai Oil Development Co., Ltd. (an affiliate of Mitsui Oil Exploration, 5%).
Pailin is Unocal Thailand's largest and most complex single project ever undertaken and employs the latest environmental technologies. The field is being developed in two phases. Phase 1 covers the southern half of the field and had been started up on Dec 1, 1998, with a gas rate (DCQ) of 165 MMCFD. The reserve estimation for the Phase 1 (South Pailin) development is 1,426 BCF (1 January 2002).
Phase 2 (North Pailin) covers the northern half of the field with reserves of 1,280 BCF. The North Pailin project was kicked off in October 1999 during the economic crisis and a predicted oversupply market. However, with good collaboration from the co-ventures and the Petroleum Authority of Thailand, the entire difficult situation had been overcome. The North Pailin project has been start up on 1 July 2002, at a gas rate of 207 MMSCFD (DCQ of 165 MMCFD). The North Pailin will be fully developed during the next 20 years, with additional 200 development wells planned.
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