Greater Sierra Jean Marie Tight Gas Carbonate: Multidisciplinary Approach Drives Decade of Development

摘要

Located in Northeast British Columbia, spanning 250 km x 125 km, the Jean Marie Member has been known to industry for decades. This late-staged Devonian carbonate platform has a thick continuous linear margin reef at its western edge and an interior platform containing thinner patch reefs. The formation is characterized by low porosity (avg. ～6%), low water saturation (avg. ～20%), and low permeability (< 1 md air). The main target is reef buildups, in which porosity and permeability have been enhanced by diagenesis and fracturing. From the 1960s until the mid 1990s, prospectors were teased by gas shows, sometimes over intervals exceeding 30 meters, with potentially large gas-in-place volumes. Vertical wells were unable to unlock this massive prize. Truly, the Jean Marie needed technological advances to have its potential realized. In the mid 1990s, the first major advance came through the application of underbalanced horizontal wells. To date, Encana has drilled in excess of 1,200 horizontal wells. The rate while drilling signature is valued for geo-steering, reservoir characterization, and determining expected well performance for production forecasting and reserve bookings. In the early 2000s, a major step change was the introduction of high resolution 3D seismic. Imaging reefs and fractures aided in better planning, characterization, and predictability. Advanced seismic techniques are used to detect high permeability fairways, increasing deliverability and gas recovery. Starting in 2007, the Greater Sierra Jean Marie development began to adhere to a “gas factory” model. The Jean Marie is a large concentrated gas resource with a repeatable exploitation method of underbalanced horizontal wells. The addition of continuous improvement policy cemented the Greater Sierra Jean Marie as a gas factory. Encana has converted from nitrogen foam to drilling with natural gas. Gas is conserved by producing into pipelines during drilling and flaring is minimized. Matting and multi-well pads are utilized to load level the drilling program, minimize land use, and reduce costs. Concurrent operations on multi-well pads have been implemented, reducing cycle times by 40%. Multi-laterals, duals and tri-laterals, are now part of the development toolkit, further strengthening economic metrics. Because of these improvements, the Greater Sierra Jean Marie team achieved best program metrics ever in 2009, despite depressed natural gas prices. Keys to the successful exploitation of the Jean Marie tight gas carbonate play have been: a dominant land position on quality acreage, highly-connected multi-disciplinary team(s), repeatable yet evolving processes, awareness and application of new technologies, and rigorous tracking of results. Future development in the Jean Marie is supported by a large inventory of multi- lateral horizontals wells. A low risk drilling program executed with excellence will be augmented by the application of other new technologies, such as fracture stimulation, leading to another successful decade of development.