Unconventional Reservoirs · Module U2
Geochemistry a log analyst needs
Log-derived TOC only makes sense against the geochemistry behind it. This module covers what a weight percent of organic carbon means and how it converts to kerogen volume, what Rock-Eval pyrolysis reports, how kerogen type is read from hydrogen index against Tmax, and how vitrinite reflectance and the level of organic metamorphism place a rock in the oil or gas window. It ends with importing core geochemistry and fitting a maturity profile against depth.
- Level
- Advanced
- Position
- Module 2 of 8
- Video
- About 17 minutes, narrated
- Format
- Narrated video lesson with captions and slide reading view; with the certified option, a quiz whose pass unlocks the next module.
What the module covers
- Weight percent TOC and kerogen volume
- Rock-Eval S1, S2, Tmax and hydrogen index
- Kerogen types I, II and III
- Vitrinite reflectance, LOM and the maturity windows
- Tmax as a stand-in for reflectance
- Richness classes and the oil saturation index
Learning outcomes
After the module you should be able to:
- State a maturity and a kerogen type from core, with the window and richness class they imply.
- Place a sample in its maturity window from Ro, Tmax or LOM
- Explain why a maturity profile against depth beats a single typed value
A short preview
Rock-Eval heats a crushed sample and records two peaks: S1, the hydrocarbon already free in the rock, and S2, what the kerogen can still generate, both in milligrams per gram of rock. Divide S2 by TOC and multiply by 100 to get the hydrogen index. A sample with 6 wt% TOC and an S2 of 24 mg/g has a hydrogen index of 400, typical of oil-prone type II kerogen. The temperature at the top of the S2 peak, Tmax, climbs with maturity; from about 435 °C the rock is entering the oil window.
Who it is for
Petrophysicists, geoscientists and reservoir engineers who evaluate organic shales and source rocks from logs and core, and carry TOC, net pay and gas in place into appraisal and development decisions.
Prerequisites: The Intermediate track, or working experience with shale volume, porosity and water saturation; the Geomechanics course is recommended before U8. The hands-on steps use the Organic Matter workspace in Formation Evaluation, and the brittleness steps in U8 use the Geomechanics workspace, available from the Professional plan.
Take the module in the Learning Hub
Unconventional Reservoirs: Specialty course, sold separately: eight modules that evaluate an organic shale from logs and core, from TOC methods fused and calibrated to core, through kerogen-corrected porosity and net pay, to free and adsorbed gas in place and brittleness. The lesson opens in the Learning Hub once the track is purchased; graded quizzes and the certificate come with the certified option.