ABSTRACT PETROPHYSICS, VOL. 55, NO. 5 (OCTOBER 2014); PAGE 000–000; 22 FIGURES; 2 TABLES Kerogen Content and Maturity, Mineralogy and Clay Typing from DRIFTS Analysis of Cuttings or Core 1 Michael M. Herron 2 , MaryEllen Loan 2 , Alyssa M. Charsky 3 , Susan L. Herron 2 , Andrew E. Pomerantz 2 , and Marina Polyakov 2 Diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) has recently been introduced and is currently being evaluated. It is a rapid, robust, and efficient technique for simultaneously quantifying kerogen and mineralogy from core and cuttings samples, both in the laboratory and at the wellsite. The technique quantifies mineralogy and kerogen content by measuring the vibrational absorbance due to chemical bonds. Core and cuttings samples from wells in unconventional reservoirs in North and South America were analyzed using a technique that solves for illite, smectite, kaolinite, and chlorite, in addition to nonclay mineral components and kerogen. Samples were also analyzed for mineralogy by the more accurate but time consuming transmission dual-range Fourier-transform infrared spectroscopy technique and for total organic carbon (TOC) by LECO/coulometry. The results for both mineralogy and TOC compare very well. The DRIFTS hydrocarbon signal at 2,800 to 3,000 cm -1 is due to the C–H bond vibrational modes of aliphatic hydrocarbons. This signal decreases in magnitude faster than the TOC decreases as kerogen matures. As a result, the ratio of TOC to the DRIFTS signal can be used as a new estimate of organic maturity. Examples are presented to show the agreement with estimates from vitrinite reflectance or T max for samples with Ro ranging from 0.6 to 1.35%. Full DRIFTS analysis including sample preparation generally takes less than 20 minutes for any mud type, which allows the technique to keep up with the drilling at the wellsite. INTRODUCTION Quantitative mineral analysis is an important part of formation evaluation for all reservoirs. The mineralogy, particularly the clay mineralogy, exerts a major influence on log responses and influences most aspects of economic hydrocarbon production. The two accepted mineral analysis techniques are X-ray diffraction (XRD) and Fourier- transform infrared (FTIR) spectroscopy, including the combined mid-IR and far-IR dual-range FTIR version (Matteson and Herron, 1993; Herron et al., 1997). Accurate analysis of clay mineralogy by XRD or FTIR commonly requires several hours of sample preparation. A separate XRD run of a sample exposed to ethylene glycol is commonly used to identify swelling components, such as, smectite or mixed-layer illite smectite. The long times involved in accurate clay-mineral identification and quantification have necessitated that these techniques are only performed in the laboratory. In unconventional reservoirs, the reservoir-quality assessment also involves the kerogen content and the kerogen thermal maturity. The analysis of TOC by industry- standard techniques such as LECO and the thermal pyrolysis procedures, such as RockEval, which gives the temperature of maximum organic emission that is a proxy for thermal maturity, are also time consuming. The SGS LECO technique was vetted with samples with known TOC. The measurement of mineralogy, TOC, and maturity are each separate analyses. There is a need for a rapid technique that is capable of providing mineralogy, especially clay mineralogy, plus TOC and information on kerogen maturity. DRIFTS can quickly measure mineralogy and organic matter in sediments with minor sample preparation. Manuscript received by the Editor July 28, 2014; revised manuscript received September 22, 2014. 1 Originally presented at the 2014 SPWLA 55th Annual Logging Symposium, Abu Dhabi, United Arab Emirates, 18–22 May. 2 Schlumberger Doll Research, One Hampshire Street, Cambridge, MA 02139, USA; Email: michael.herron@slb.com; mloan2@ slb.com; susan.herron@slb.com ; apomerantz@slb.com; mpolyakov@slb.com 3 Colorado School of Mines, Chevron Center of Research Excellence (CoRE), 1516 Illinois Street, Room 143, Golden, CO 80401 USA; Email: acharsky@mines.edu