Talk: Development Strategies for the Morrow Formation
Speaker: Louis J. Mazzullo, Mazzullo Energy Corp., Denver, Colorado
Location: Denver Marriott City Center
Date: August 6, 2010
Abstract: Published in The Outcrop, August 2010, p. 26-27
Reservoir under-development of oil and gas resources of the lower Pennsylvanian Morrow Formation is a pervasive problem wherever the Morrow is productive, and it is related to several factors, both geological and logistical. On the logistical side, there are certain areas where the Morrow cannot be developed conventionally because of land use restrictions or resource development conflicts (e.g., Walsh, AAPG Bull. 91, pp. 1217-1229). On the geological side, there are depositional, tectonic, and diagenetic factors that make prediction of reservoir trends difficult in some places.
The Morrow records a cyclic sequence of clastics and associated, coeval carbonates in the Permian Basin of southeastern New Mexico, as it similarly does in the Denver Basin. As I will demonstrate for the Permian Basin, at least part of the Morrow Formation was affected by recurrent tectonic movement that continued after the initial late Mississippian event, which locally uplifted and eroded earlier Morrow sediments, and in other places provided accommodation space for Morrow sedimentation. Deposition of later Morrow sediments occurred above this intraformational unconformity, creating an unusual reservoir mosaic in places. Reservoirs below this unconformity may be discontinuous or exhibit geometries that do not fit the exploration or development model being used. Glacioeustatic-imposed facies changes throughout the Morrow section at any given location also make it difficult to employ a specific exploration or development approach, as reservoir geometries can change from one horizon to the next, below or above the intraformational unconformity. Diagenetic occlusion resulting from channel abandonment or clay mineralization further modifies reservoir shapes, extents, and can create localized permeability barriers that can effectively compartmentalize reservoirs, even within a specific reservoir zone. These types of effects can occur either naturally or by drilling-induced formation damage. As a result of all of these factors, reservoirs are either missed in offset wells, or inadequately drained.
Vertical wells are essential to Morrow development because often, there can be several discrete pay horizons in a given wellbore, which helps reduce risk. However, once a productive area is delineated with vertical wells, resource extraction becomes inefficient because of the number of geologic factors that can affect individual pay zones. In areas where well control is dense enough, particularly in older fields that are developed in areas where the Morrow is not very thick, it may be possible to enhance production through the use of detailed reservoir modeling and horizontal drilling. Since the better reservoirs tend to be developed in more carbonaceous-rich fluvial and transitional marine environments in the Morrow, the shales themselves may serve as both source and seal for the associated sand bodies, and can add to the resource budget in a new well. However, the geologic factors that affected those sand bodies must be thoroughly understood and reservoir geometries accurately determined before laterals can be planned. Mapping of discrete reservoir units can be done with a variety of subsurface techniques, as well as, in some cases, the use of 3D seismic. Examples from the Permian and Denver Basins will be given to illustrate these concepts.
Talk: “Unconventional” Discovery Thinking in Resource Plays: Haynesville Trend, North Louisiana
Speaker: Marvin D. Brittenham
Location: Denver Marriott City Center
Date: August 20, 2010
Abstract: Published in The Outcrop, August 2010, p. 27
Encana’s strategy for US growth was focused by the New Ventures Team, led by Brittenham, first toward the Gulf Coast Jurassic Trend. The first steps of this strategy culminated in the acquisition of Tom Brown Inc. in 2004, leading to formation of the Mid-Continent Business Unit in Dallas. Its East Texas team devised a strategy to explore the Jurassic sequence off the East Texas west shelf productive trend into an expanded shelf slope to basin sequence. This play has since evolved to the “Deep Bossier” Sandstone Play and resulted in the discovery and development of John Amoruso Field.
Using similar unconventional thinking and entry strategies on a broader scale, Encana acquired significant additional positions in the Jurassic Trend. Closely following the Amoruso success, in late 2005 and early 2006, Encana drilled the discovery wells in Red River Parish, Louisiana for the Haynesville gas shale play. Notably, Encana also recognized significant Bossier shale pay in that area. Although not widely known to industry prior to 2008, the Haynesville Play already has shifted gas shale paradigms for depth (up to 14,000 feet) pressure (up to 12,500 PSI) well productive rates (20-30 MMcfg/d) and for recoverable resource size (250 Tcfg).
For three decades, industry, academic and governmental views for natural gas production decline provided doom and gloom scenarios for US supply. It now appears that a new trend, Haynesville, has been discovered that is potentially the largest continuous gas deposit in North America. As well, with John Amoruso Field, a new play has been established with world class productive wells. Both required unconventional discovery thinking and considerable evolution of thought beyond discovery.
Discovery thinking for resource plays requires a global view of the petroleum system. All of the primary lithologies of the Jurassic sequence are potential reservoirs – even the shale/source. Deep basin over-pressured mature gas cells provide the primary setting for Jurassic gas resource trends. Economics are very robust where there is sufficient scale, repeatability and low geologic risk for gas manufacturing processes.
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