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Title: Fracture spacing in slant/horizontal cores, Mesa Verde Formation, CO: Comparison with outcrop and vertical-core data

Abstract

Core from the U.S. Department of Energy's Slant Hole Completion Test well (SHCT-1) shows an irregular but remarkably close fracture spacing in flat-lying reservoirs of the Mesaverde Formation in northwestern Colorado. Core was taken from 30 ft thick lenticular sandstones where the wellbore is inclined 60{degree} to vertical (266 ft of core), and from a 60 ft thick marine blanket sandstone where the wellbore is near-horizontal (115 ft of core), at the vertical depths of about 7100 and 7850 ft, respectively. In both zones, fractures cut across the core at a near-orthogonal angle to the core axis, with true lateral spacing averaging about 3 ft/fracture. Fracture spacing is not proportional to bed thickness. Fractures occur in swarms of up to five fractures each, and swarms are somewhat more regularly spaced at 8-10 ft, although individual fracture spacing ranges from less than an inch to 17 ft. Only one fracture was present in the same zones in 175 ft of 4 in. diameter core taken in nearby vertical wells. Outcrops of the same facies, however, show irregular spacings that average on the order of 1.5 ft (lenticular sandstones) and 3 ft (blanket sandstones). Extrapolation of outcrop fracture data, or of fracturemore » data from vertical wellbores, to engineering models of subsurface fracture spacing should be undertaken cautiously. However, subsurface fractures in flat-lying reservoirs can be more closely spaced than is commonly acknowledged.« less

Authors:
 [1]
  1. Sandia National Labs., Albuquerque, NM (United States)
Publication Date:
OSTI Identifier:
7024941
Report Number(s):
CONF-910403-
Journal ID: ISSN 0149-1423; CODEN: AABUD
Resource Type:
Conference
Journal Name:
AAPG Bulletin (American Association of Petroleum Geologists); (United States)
Additional Journal Information:
Journal Volume: 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; Journal ID: ISSN 0149-1423
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 03 NATURAL GAS; COLORADO; NATURAL GAS DEPOSITS; PETROLEUM DEPOSITS; GEOLOGIC FRACTURES; SPATIAL DISTRIBUTION; DIRECTIONAL DRILLING; DRILL CORES; FRACTURED RESERVOIRS; GEOLOGIC FORMATIONS; ORIENTATION; US DOE; DEVELOPED COUNTRIES; DISTRIBUTION; DRILLING; FEDERAL REGION VIII; GEOLOGIC DEPOSITS; GEOLOGIC STRUCTURES; MINERAL RESOURCES; NATIONAL ORGANIZATIONS; NORTH AMERICA; RESOURCES; US ORGANIZATIONS; USA; 020200* - Petroleum- Reserves, Geology, & Exploration; 030200 - Natural Gas- Reserves, Geology, & Exploration

Citation Formats

Lorenz, J C. Fracture spacing in slant/horizontal cores, Mesa Verde Formation, CO: Comparison with outcrop and vertical-core data. United States: N. p., 1991. Web.
Lorenz, J C. Fracture spacing in slant/horizontal cores, Mesa Verde Formation, CO: Comparison with outcrop and vertical-core data. United States.
Lorenz, J C. 1991. "Fracture spacing in slant/horizontal cores, Mesa Verde Formation, CO: Comparison with outcrop and vertical-core data". United States.
@article{osti_7024941,
title = {Fracture spacing in slant/horizontal cores, Mesa Verde Formation, CO: Comparison with outcrop and vertical-core data},
author = {Lorenz, J C},
abstractNote = {Core from the U.S. Department of Energy's Slant Hole Completion Test well (SHCT-1) shows an irregular but remarkably close fracture spacing in flat-lying reservoirs of the Mesaverde Formation in northwestern Colorado. Core was taken from 30 ft thick lenticular sandstones where the wellbore is inclined 60{degree} to vertical (266 ft of core), and from a 60 ft thick marine blanket sandstone where the wellbore is near-horizontal (115 ft of core), at the vertical depths of about 7100 and 7850 ft, respectively. In both zones, fractures cut across the core at a near-orthogonal angle to the core axis, with true lateral spacing averaging about 3 ft/fracture. Fracture spacing is not proportional to bed thickness. Fractures occur in swarms of up to five fractures each, and swarms are somewhat more regularly spaced at 8-10 ft, although individual fracture spacing ranges from less than an inch to 17 ft. Only one fracture was present in the same zones in 175 ft of 4 in. diameter core taken in nearby vertical wells. Outcrops of the same facies, however, show irregular spacings that average on the order of 1.5 ft (lenticular sandstones) and 3 ft (blanket sandstones). Extrapolation of outcrop fracture data, or of fracture data from vertical wellbores, to engineering models of subsurface fracture spacing should be undertaken cautiously. However, subsurface fractures in flat-lying reservoirs can be more closely spaced than is commonly acknowledged.},
doi = {},
url = {https://www.osti.gov/biblio/7024941}, journal = {AAPG Bulletin (American Association of Petroleum Geologists); (United States)},
issn = {0149-1423},
number = ,
volume = 75:3,
place = {United States},
year = {Fri Mar 01 00:00:00 EST 1991},
month = {Fri Mar 01 00:00:00 EST 1991}
}

Conference:
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