oa Variation of Biomarker Profiles in Biodegraded Oils under Subsequent Thermal Maturation and Oil-Oil Correlation in Tabei Uplift of Tarim Basin

Tarim Basin is a typical superimposed basin. The Tabei uplift had experienced uplift/erosion and then a continuous subsidence over 5000 m. Numerous biodegraded oils have been found in the Ordovician reservoirs of the northern Halahatang (N-Halahatang) and western Lunnan (W-Lunnan) of the Tabei Uplift. The biodegraded oils from W-Lunnan underwent relatively weak burial-maturation (Ro < 0.90%, < 5500m), while biodegraded oils from N-Halahatang underwent strong burial-maturation (Ro > 1.00%, > 6500m). Stronger burial-maturation may lead to alteration of biomarker profiles in N-Halahatang. Therefore, the Tabei Uplift provide us a good chance to study the superimposed secondary alteration (SSA) of biodegradation at an early stage and subsequent thermal maturation. Two relatively low-burial biodegraded oils from W-Lunnan were artificially matured to various maturities. The results showed that, except for the Pr/Ph and TT23/(TT23+TT24) ratios, most biomarker parameters related to depositional environment and oil-oil correlation were severely altered when EasyRo > 1.01%. In contrast, most biomarker parameters related to maturity (M29/H29, M30/H30, etc.) increased with maturity and maintained their applicability. Besides, the matching of biomarker parameters in deep-burial oils from N-Halahatang and heated oils from W-Lunnan under similar maturity confirmed the genetic relationship of biodegraded oils in the two areas.