Core description and analysis using X-radiography and cat-scanning: examples from Sacramento and San Joaquin basins, California
X-radiographs of cores from Forbes deep basin sands, the tar-saturated paralic sands of the Temblor and the Tulare fluvial sands and silts, as well as fractured siliceous units (the Monterey Formation and equivalents) reveal geologic features that are either not visible or barely discernible to the naked eye. These features include changes in grain size, grading, ripple lamination to cross-bedding, cyclic couplets in tidal sequences, bioturbation and burrowing, and fracture patterns and filling. Forbes core x-radiography from the northern Sacramento basin clearly shows a sequence of thinly bedded sand and mudstones that are microripple cross-laminated. Partial Bouma sequences (Ta-b or Tb with Ta-c) are characteristic of the thickly bedded sands below the ripple-laminated units. Cyclic sequences of mud-turbidites and finely laminated, very fine-grained sands to coarse silts characterize a sand-poor sequence that overlies a massive to indistinctly thin-bedded sand. Most of these features described above are barely discernible without x-radiography, yet all provide major input to the interpretation of the depositional environment of the Forbes Formation, as well as information regarding reservoir continuity. Tar or heavy-oil saturation of cores can be a severe problem when cores are examined. In a Tulare Formation core sequence that was x-radiographed, essentially no bedding was visible, even using UV photography. However, extensive fluvial cross-bedding throughout the core was revealed by the x-radiography. A similar, heavy oil masking problem in a Temblor Formation core near East Coalinga was also resolved by the x-ray technique. The reservoir is divided into multiple, thin, tidal couplets (4-6 in.) of oil-saturated sand separated by 1 to 3 in. thick mudstones.
- Research Organization:
- Mesa Verde Exploration and Production Services, Whittier, CA
- OSTI ID:
- 6886929
- Report Number(s):
- CONF-8604187-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 70:4; Conference: American Association of Petroleum Geologist Pacific Section convention, Bakersfield, CA, USA, 16 Apr 1986
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALIFORNIA
SEDIMENTARY BASINS
DRILL CORES
COMPUTERIZED TOMOGRAPHY
INDUSTRIAL RADIOGRAPHY
RESERVOIR ROCK
GEOLOGIC FORMATIONS
OIL SANDS
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
DIAGNOSTIC TECHNIQUES
ENERGY SOURCES
FEDERAL REGION IX
FOSSIL FUELS
FUELS
GEOLOGIC STRUCTURES
MATERIALS
NORTH AMERICA
TOMOGRAPHY
USA
020200* - Petroleum- Reserves
Geology
& Exploration