Rock-Eval 6 technology: Performances and developments

The Rock-Eval 6 apparatus is the latest version of the Rock-Eval product li ne, commercialized since 1996 by Vinci Technologies. The present work descr ibes the methodology developed at IFP for reliable data acquisition and end orses the quality of geochemical parameters acquired with Rock-Eval 6. Data were obtained on 147 source rocks from various sedimentary basins, of diff erent organic matter types and maturity stages. Intrinsic correlations for two different Rock-Eval 6 apparatus were perform ed and the obtained data set shows an excellent consistency and good reprod ucibility conditions for the whole set of Rock-Eval parameters. Complete recovery of total carbon (TC) by Rock-Eval 6 was confirmed by comp arison with elemental analysis. In order to check the carbon partition (mineral vs. organic) determined by Rock-Eval 6, measurements of mineral carbon (MinC) and total organic carbon (TOC) were performed by alternative techniques. TOC measured by Rock-Eval 6 was compared to that obtained either by: the Le co apparatus for bulk rocks; elemental analysis for kerogens; and calculati on from the mass balance determined after destruction of mineral matrix and the carbon concentration determined by elemental analysis on recovered ker ogens for bulk rocks. The results display a good correlation for the whole concentration range (0-90 wt% TOC), when comparing elemental analysis and R ock-Eval 6 for source rocks and kerogens. However, comparison of Rock-Eval 6 with Leco data leads to larger deviations while correlation factors are s till good. For a subset of kerogen samples, preparative pyrolysis was performed in ord er to confirm the value of 83 wt% for the organic carbon of the total S2 pe ak for any rock with any organic type and to check the absolute value of th e S2 peak by gas chromatography analysis of pyrolysis by-product. MinC measured with Rock-Eval 6 was compared to that determined: weight loss after HCl treatment; the acidimetry technique; and calculation after TC, m ass balance from kerogen isolation and organic carbon measurement on keroge n by elemental analysis. The results displays a good correlation for the wh ole concentration range (0-12 wt% MinC), when comparing elemental analyses and Rock-Eval 6. However, comparison of Rock-Eval 6 with acidimetry data le ads to larger deviations while correlation factors are still good while com parison with weight loss is poor. As a whole an excellent reliability of TOC and MinC obtained by Rock-Eval 6 was demonstrated, and consequently, it is now possible to get at once the total organic and mineral carbon mass balance for a given rock. Recommendat ions are proposed regarding the standard samples and analytical methods sel ected for calibrating the Rock-Eval 6 over a large mineral and organic carb on range. Consistency between S2 and Tmax measured by Rock-Eval 2 and Rock-Eval 6 for Types I and II bulk rocks was also checked. A good correlation was obtaine d for S2, even though S2 values are slightly higher while measured with Roc k-Eval 2. It was demonstrated that this is due to carrier gas(nitrogen vs. helium) by running measurements with a Rock-Eval 6 under helium, the differ ence ranging from 5 to 10 relative wt% for most studied samples. For Tmax c orrelation, data are much more scattered and as a general trend Tmax obtain ed by Rock-Eval 6 are higher than T-max obtained by Rock-Eval 2 and the dif ference increases with Tmax: this is due to the fact that the probe measuri ng the temperature in the Rock-Eval 2 is located in the oven wall, conseque ntly Tmax determination is highly dependent in the Rock-Eval 6, where the p robe is in contact with the crucible containing the sample, leading to much more reliable data.