Production forecast of fractured vertical wells in coalbed methane reservoirs: coupling dynamic drainage area

Numerical reservoir simulation in coal seams is different from conventional reservoir simulation because of the capacity for coal to adsorb large amounts of gas, including methane, carbon dioxide and nitrogen, and the need to model coal as a dual porosity system. These factors require specialised numerical simulators written to address these particular issues. This paper describes the development and applications of a reservoir simulator, SIMED II, to a number of applications in the coalbed methane context. SIMED II is an implicit finite-difference code developed to describe simultaneous gas and water flow in coal when there is more than one gas component present. Applications presented in this paper include (1) history matching and forecasting in vertical wells, (2) evaluation of dewatering during the cavity completion method of stimulating coal seams, (3) economic evaluation of nitrogen injection for enhanced coalbed methane recovery, and (4) application to the design and development of gassy coal mines involving gas drainage from horizontal wells. These applications have been directed at locations in the Sydney and Bowen basins in Australia, and the San Juan basin in the USA.

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CoalBed Methane Pad Wells Completion and Artificial Lift Optimizations: Case Study From Australia Surat Basin DS Gas Field

10.2523/iptc-21451-ms ◽

2021 ◽

Author(s):

Li Ming ◽

Xia Zhaohui ◽

Liu Lingli ◽

Cui Zehong ◽

Duan LiJiang ◽

...

Keyword(s):

Coalbed Methane ◽

Optimization Methods ◽

Gas Production ◽

Production Performance ◽

Vertical Wells ◽

Coal Seams ◽

Gas Field ◽

Well Completion ◽

Artificial Lift ◽

Coalbed Methane Production

Abstract The Coalbed Methane in Australia Surat Basin is main gas source for LNG project in east coast of Australia[1]. Traditionally, Coalbed Methane are drilled by vertical wells. But there are big intensively farmed land coverage in the Surat Basin, the multiple wells on single, larger pad from the surface, the bores slant away at around 70 degrees to intersect multiple, thin coal seams are applied to avoid the extra "footprint" and decrease the environment affect. Many pad wells production failure because of poor interburden isolation. Excessive solids production in pad wells resulted in new failures of holes in tubing due to accelerated erosion, which bring big challenges for the Coalbed methane production in deviated pad wells. The gas production in pad wells are analysised and the new pad wells optimization are proposed. First, the complete wire log (at least include GR and density log curves) need to acquire for correct thin coal seams correlation and locate the interburden sandstone position for future good sandstone isolation. Second the customized completion strategy and placement (swell packer) are applied in the pad wells and specialized tubing with enhanced erosion resistance to extend the run life. Thirdly ESP pumps and optimized tubing are installed in new deviated wells for good gas production. After the pad wells were put into production, the gas production was kept well for long time without pump problems. Swell able packer completion significantly eliminates sand problem by isolating in excess of or close to 80% of interburden sand. The above well completion and artificial lift optimization methods bring good production performance for the new pad wells and contribute much production for the producing gas field. The swellable packer completion also can be used in vertical wells and will be standard well completion methods for future gas development wells.

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