Using borehole images for target-zone evaluation in horizontal wells

Journal Article · Tue Feb 01 04:00:00 EST 1994 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:6916062

Hurley, N F; Carlson, J L ^[1]; Thorn, D R ^[2]; Eichelberger, L W ^[3]

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1. Marathon Oil Company, Littleton, CO (United States)
2. Schlumberger Well Services, Aurora (Colombia)
3. Marathon Oil Company, Tyler, TX (United States)

Horizontal wells are rarely horizontal. Instead, operators commonly try to drill such wells into particular rock layers, or target zones, which may or may not be truly horizontal. Thicknesses of target zones commonly range from a few feet to a few tens of feet (1-10 m). Target-zone evaluation concerns whether a horizontal well was successfully located and drilled in a given rock layer. Borehole-imaging logs provide a powerful tool for stratigraphic interpretation and target-zone evaluation in the Austin Chalk, Niobrara Formation, San Andres Formation, and other units. This study uses borehole images generated by Schlumberger's Formation MicroScanner (FMS), a microconductivity logging device. Open fractures and clay-rich interbeds appear as dark, high-conductivity tracers on the FMS log. These traces can be fit with sinusoidal curves and oriented on a computer workstation. The shape of the sinusoidal curve that fits a particular bedding plane tells the interpreter whether the borehole was moving upward or downward through the strata. STRATLOG (trademark of Sierra Geophysics, Inc., a Halliburton Company) software has been used to display borehole profiles by combining FMS data on fracture intensities and bedding-plane intersections with gamma-ray logs, mud logs, and borehole-deviation surveys. To aid in planning future wells, multiple penetrations of the same horizon can be detected and used to calculate highly accurate bedding-plane dips. Fault interpretation, including the detection of rollover beds, it also possible. Finally, stratigraphic interpretation can be combined with observed fractures to determine which rock layers are most highly fractured, and, therefore, should be target zones.9 refs., 5 figs.

• OSTI ID: 6916062
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 78:2; ISSN 0149-1423; ISSN AABUD2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
BOREHOLES
CAVITIES
COMPUTER CODES
DETECTION
DIRECTIONAL DRILLING
DRILLING
EQUIPMENT
EVALUATION
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
GEOLOGY
IMAGES
NATURAL GAS WELLS
OIL WELLS
S CODES
STRATIGRAPHY
TARGETS
USES
WELL LOGGING EQUIPMENT
WELLS