Experimental Quantification of the Impact of Thermal Maturity on Kerogen Density

Jagadisan, Archana (The University of Texas at Austin) | Yang, Anqi (Texas A&M University) | Heidari, Zoya (The University of Texas at Austin)

OnePetro 

Abstract

Reliable estimation of kerogen density is a requirement for dependable well-log-based petrophysical evaluation of organic-rich mudrocks. As kerogen matures, hydrocarbons are generated and the chemical structure of kerogen is transformed, which can lead to measurable variations in kerogen density. Uncertainty in estimates of kerogen density can significantly impact the reliability of well-log interpretation results.

The objectives of this research are (a) to experimentally quantify the density of kerogen isolated from a variety of organic-rich mudrocks with different origins, (b) to investigate the impact of thermal maturity on kerogen density, and (c) to investigate the impact of synthetic maturation on density of kerogen. We used organic-rich mudrock samples from four formations, to cover a wide range in kerogen thermal maturity. We isolated kerogen from these mudrock samples and estimated the density of the naturally and synthetically matured isolated kerogen samples.

The experimental results indicated that the density of kerogen varies significantly among organic-rich mudrocks with different origins. We recorded densities ranging from 1.19 to 1.77 g/cm3 in kerogen samples when the hydrogen index varied from 603 to 48 mg hydrocarbon/g organic carbon. We also observed that kerogen density increases as a function of thermal maturity. Sensitivity analysis confirmed a measurable impact of kerogen density on estimates of petrophysical properties, such as porosity and water saturation in organic-rich mudrocks. The documented experimental results and procedures can be used to enhance petrophysical evaluation of organic-rich mudrocks, by taking into account the impact of kerogen thermal maturity in the models used for interpretation of core or well-log measurements.

Introduction

Kerogen disseminated in organic-rich mudrocks presents challenges when performing well-log-based petrophysical evaluation. One such challenge is the lack of reliable estimates of kerogen density in organic-rich mudrocks. Inaccuracies in estimates of kerogen density can negatively influence assessments of porosity, mineralogy, and water saturation in organic-rich mudrocks.