Assessment of Rock-Eval Tmax Data in Bambra-2 Well of Barrow Sub-basin, North West Shelf of Australia： A Case Study of Contaminated Rock-Eval Data

The contamination of cuttings and side-wall core (SWC) samples in the Bambra-2 well by drilling-mud additives and natural hydrocarbons may cause Ruek-Eval Tmax (℃) data to be suspect, and affect its utility in the assessment of thermal maturity. The Rock-Eval results of 284 cuttings samples, 31 side-wall core samples and conventional core samples from the Jurassic-Cretaceous sedimentary sequences in the Bambra-2 well are presented in this paper. Significantly lower Tmax values from cuttings samples compared with Tmax values from conventional core samples and solvent extracted SWC samples, from the deeper and higher maturity interval, are thought to have been caused by contamination by diesel and other drilling-mud additives. The cuttings samples in the Barrow Group of Cretaceous may be contaminated by natural hydrocarbons, resulting their Tmax values to be 2-10℃ lower than a regularly increased Tmax trend from core samples. This study indicates that more reliable Rock-Eval Tmax data are obtained from the conventional core samples and solvent extracted SWC samples. This study also indicates that the Tmax values from some SWC samples were also affected by free hydrocarbons, due to the use of diesel as a mud additive as well.

Assessment of Rock-Eval Tmax Data in Bambra-2 Well of Barrow Sub-basin,North West Shelf of Australia: A Case Study of Contaminated Rock-Eval Data

The contamination of cuttings and side-wall core (SWC) samples in the Bambra-2 well by drilling-mud additives and natural hydrocarbons may cause Rock-Eval Tmax (℃) data to be suspect, and affect its utility in the assessment of thermal maturity. The Rock-Eval results of 284 cuttings samples,31 side-wall core samples and conventional core samples from the Jurassic-Cretaceous sedimentary sequences in the Bambra-2 well are presented in this paper. Significantly lower Tmax values from cuttings samples compared with Tmax values from conventional core samples and solvent extracted SWC samples,from the deeper and higher maturity interval, are thought to have been caused by contamination by diesel and other drilling-mud additives. The cuttings samples in the Barrow Group of Cretaceous may be contaminated by natural hydrocarbons, resulting their Tmax values to be 2-10 ℃ lower than a regularly increased Tmax trend from core samples. This study indicates that more reliable Rock-Eval Tmax data are obtained from the conventional core samples and solvent extracted SWC samples. This study also indicates that the Tmax values from some SWC samples were also affected by free hydrocarbons, due to the use of diesel as a mud additive as well.