HARVILLE, D. G., D. T. GEORGI, and H. A. ROBERTSON, Core Laboratories, Houston, TX

ABSTRACT: The Use of Sequentially Collected Drill Cuttings in Formation Evaluation

This paper presents the results of an experiment to sequentially and accurately collect drill cuttings during drilling operations. The automated cuttings collection system consists of a mud pump, mini-shaker, seperator, elutriator, and collection vessel. This system, placed downstream of the bell nipple, is designed to minimize contamination of cuttings due to cavings and re-circulated drill solids. Drill cuttings are collected in clear plastic tubes and are available for analysis at the wellsite or in the laboratory.

Before any analyses are performed, the depth of origin of the cuttings is established by measuring gamma ray activity of cuttings and comparing this to the log gamma ray response. Gamma ray activity on cuttings is measured by taking a sample from the slabbed cuttings tube and putting the sample into a well detector. Comparison of these data to wireline gamma log showed excellent agreement and indicated that cuttings could be discriminated and identified to the log to within 1 meter.

Traditional palynological investigations were done on sidewall cores and adjacent cuttings samples. Poor to moderate success in identification of biostratigraphic markers from cuttings was achieved. Mineralogy was measured on the cuttings by Fourier Transform Infrared (FTIR) spectroscopy and was compared to mineralogy from sidewall core samples. Good agreement between cuttings and sidewall mineralogy is obtained if the sidewall (point) analyses are averaged over the same scale as the cuttings. Total clay volumes from FTIR tracked well with the wireline log gamma. Quantitative mineralogy from cuttings can be used to calculate matrix density, photoelectric factor, and sigma matrix for improved interpretation of wireline logs.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.