Petrographic Analysis of Thin Sections of Cuttings and Sidewall Cores: An Effective Method for Obtaining Geologic Data

Hughbert Collier

Considerable geological and petrophysical data are needed to properly evaluate and produce a hydrocarbon reservoir. Much of this data can be obtained only by firsthand examination of cores or cuttings of the reservoir rock. Unfortunately, full-diameter coring often is not feasible. In such cases, either sidewall cores or well cuttings provide an inexpensive effective alternative.

Petrographic analysis of thin sections of cuttings and sidewall cores will identify fossils, mineralogy, clay mineral distribution, pore geometry, and factors controlling porosity distribution. In carbonate rocks, the depositional environment can usually be determined.

Case histories from north and west-central Texas (Hardeman, Young, Coke, and Tom Green Counties) illustrate the applications, shortcomings, and advantages of petrographic analysis of thin sections of well cuttings and sidewall cores. Formations considered in the study include the Cook sand, the Canyon limestone, the Mississippian limestone, and the Capps Limestone.

AAPG Search and Discovery Article #91026©1989 AAPG Southwest Section, March 19-21, 1989, San Angelo, Texas.