Lowering Tubing in Jonah Field Offset Production Decline
- Chinenye Excel Ogugbue (BP America) | Cody Ray Hopkins (Marietta College) | Leah Greenly (BP America Inc) | Robert K. Wilson (BP America Inc.) | Gordon Gates (BP America Production Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Americas Unconventional Resources Conference, 5-7 June, Pittsburgh, Pennsylvania USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 3.3.1 Production Logging, 5.8.1 Tight Gas, 5.2 Reservoir Fluid Dynamics, 5.1.2 Faults and Fracture Characterisation, 5.3.2 Multiphase Flow, 2 Well Completion, 3.1.5 Plunger lift, 4.1.2 Separation and Treating, 2.2.2 Perforating, 1.2.3 Rock properties, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 3 Production and Well Operations, 4.6 Natural Gas, 4.1.5 Processing Equipment, 2.4.3 Sand/Solids Control
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Declining reservoir pressure and rate in the Jonah field has led to the common problem of liquid loading. As fluids accumulate the downhole pressure increases which decreases the available drawdown that allows fluids to flow into a wellbore. Jonah wells are completed in the 2000 - 3500-ft thick Lance Formation, using 8-16 hydraulic fracturing stages. With initial end of tubing (EOT) depths set above the top perforation for most wells, this left approximately 1500-3000 feet (gross pay) of perforations below the EOT. With lifting velocities significantly greater in larger diameter casing than tubing, a liquid column was developing below the EOT and engineering and operational attention was needed to improve field performance.
Improving on the operational efficiency involved the implementation of recommended actions from a cross-functional well by well review group that received input and support from all Jonah asset members. The approach focused on how to improve liquid removal and optimize gas production from wells identified as liquid-loaded. In addition to installing plunger lift systems and injecting soaps, in 2008 a program was started to lower production tubing in wells by approximately 50-70% into perforations; the purpose was to reduce the column of fluid in the wellbore by helping more efficiently unload fluids using the reduced critical flow rate in the tubing and allowing plungers deeper access to the column of liquid covering the perforated interval.
This paper discusses the results of lowering the EOT of over 100 gas producing wells in the Jonah field. The wells showed an average sustained uplift of approximately 105 mcfd, with undiscounted payout of less than 12 months. In addition, on wells that have had the tubing lowered, their decline curves appear to flatten out, offsetting anticipated double digit decline. Practical methods of selecting candidate wells and the new EOT are presented and discussed.
The Jonah field is a tight gas field located in the upper Green River Basin in west-central Wyoming. It is a giant gas field producing from extremely low-porosity, low-permeability and fine-grained alluvial sandstones known as the Lance formation. Jonah Field is known for being one of the largest on-shore natural gas discoveries in the USA in the early 1990s (Robinson and Shanley, 2004). Bounded by the Green River on the west and the Wind River Mountains on the east, the US Bureau of Land Management (BLM) estimates that the productive area encompasses over 30,000 acres. The field is separated by a unique set of shear zones that seal the gas in place laterally and updip. (Turner et al., 2011). The Jonah field is the over-pressured area bounded by the west and south faults. The producing formation ranges from 2,000ft thick at the updip to 3,500 ft thick at the downdip, and begins as shallow as 7,800 ft and continues to nearly 12,500 ft within various locations of the Jonah field. Within this interval, the net to gross ratio varies from 25% - 40% sandstone. Sand bodies occur as both individual, 9-15 ft thick channels and as stacked channel sequences, greater than 200ft in thickness in some cases, as shown on the logs in Figure 1. Stacking of these alluvial sand-bodies has produced an extremely heterogeneous reservoir in which reservoir sand-bodies cover areal extent of a few acres to as much as a section, see Figure 2 for schematics of the type log correlation characterizing 10 acre spacing in the Jonah field. All reservoir sands are gas charged, with no water legs or significant amounts of free water production (Christensen et al., 2000).
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