Application of Rapid, Integrated, Cuttings XRF, Source Rock and Trapped Fluid Analyses to Unconventional Plays
Although unconventional resource plays are highly variable in terms of geology, geochemistry and structure, many of the key factors within these disciplines are repetitively quoted as influencing successful exploitation. These include:
Often, however, available data are sparse in zones of interest, particularly in laterals typified by limited logs and no core. A rapid, substantially automated process has been developed using archived, unpreserved cuttings from historical or recently drilled vertical or horizontal penetrations to address these questions. The sample is initially cleaned of surface contamination that can affect data quality. An enhanced depth-of-field image is collected in visible and ultraviolet light using a specialized microscopy system. Samples are then crushed under vacuum to collect quantitative data on organic and inorganic volatiles trapped in the rock via direct quadrupole mass spectrometry. Finally, the crushed rock sample is analyzed for its elemental composition by x-ray fluorescence. Trapped fluid analysis is used to help predict fluid type, composition, quality and volume in tight rock, as well as identify variability along laterals that can be exploited for more effective completions. Evaluation of major, minor and trace elements can be used to document lithology and cements, produce chemical stratigraphic profiles in otherwise monotonous sections, establish depositional environments, facies and provenance, and provide some information relevant to rock behavior during completion activities. A subsample is used for source rock screening, but image, fluid and XRF data are collected on exactly the same rock material, thus preserving interrelationships among rock type, chemistry, texture, and trapped fluid type, quality and distribution. Generation of multiple data sets on the same small sample is also beneficial in instances where material is limited, or only a small amount can be acquired from government archives. As many unconventional plays have a significant number of historical vertical penetrations, rock-fluid databases can be established without drilling new wells, provided archived rock materials are available. One key advantage is that these historical wells can be evaluated without regard to age, drilling conditions (within reason) or mud system, and samples need no specialized preservation procedures. The entire data set can be produced in 5–7 days.
AAPG Datapages/Search and Discovery Article #90193 © 2014 Rocky Mountain Section AAPG Annual Meeting, Denver, Colorado, July 20-22, 2014