Comparison of Cuttings- and Core-based Vertical Geochemical Profiles & Implications for Time-Lapse Production Geochemistry in Unconventional Reservoirs
Abstract
This study demonstrates a comparison of a High-Resolution Gas Chromatography (HRGC) analysis of drilling cuttings and sidewall cores from the same oil well, with the purpose of determining how well the two sample types are correlated; and to discuss their potential implications on further geochemical analyses such as Time-Lapse Geochemistry (TLG) and more specifically Production Allocation (PA). We used HRGC to determine the peak-height ratios (PHRs) shared between the two sample types. We then compared these PHRs with produced oil samples from the same well to determine if cuttings provide the same accuracy of geochemical information as core extracts. Our results show a strong correlation of peak-height ratios, both between cuttings and core samples, as well as between cuttings and produced fluid samples, in the range of primary peaks n-C15 to n-C27. Trends in peak-height ratios also mimic petrophysical logs, which suggests cuttings are also representative of geologic characteristics, such as depositional environments and specific organic matter content. The implication of this research is such that it is indeed possible that cuttings may serve as a substitute for sidewall core samples when setting up the geochemical reference profile needed for TLG and PA. Because cuttings are a byproduct of every well (compared to core which requires specific tools and operations to extract), substituting core plugs with cuttings samples when setting up vertical reference profiles would imply a substantial cost savings for Exploration & Production (E&P) companies.
Subject
Petroleum GeochemistryGeochemistry
Time-Lapse Geochemistry
TLPG
Unconventionals
Unconventional Reservoirs
Shale
Gas Chromatograhy
GC
Citation
Scherer, John Andrew (2021). Comparison of Cuttings- and Core-based Vertical Geochemical Profiles & Implications for Time-Lapse Production Geochemistry in Unconventional Reservoirs. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /196294.