关键词: 高蜡轻质油, 生物标志化合物特征, 碳同位素, 油源对比, 旅大29油田, 斜坡带, 辽东凹陷

Abstract: High-yield light crude oils and natural gases were produced in the second member of the Shahejie Formation in the LD 29
oilfield on the slope belt in the southern sag of the Liaodong Depression, showing great exploration potential. In order to clarify oil
source, depositional environment and source rock ages, systematic geochemical analyses and oil-source correlation on crude oil, oil
sands and source rock samples were carried out. Results show that the crude oils have low sulfur (0.0733%) and high wax contents
(20.77%), and are light and mature. The saturated hydrocarbon chromatograms of the crude oils have a complete distribution with the
major peak carbon at C19, indicative of non-biodegradation. In contrast, the oil sand samples which were shallowly buried are partially
affected by biodegradation, as indicated by the UCM in the chromatographic baseline. The crude oils have low C19/C23TT (0.10-0.18),
low C24 Tet/C26TT (0.49-0.53), low C27Dia/C27ST (0.30-0.43), medium Ga/C30h (0.14-0.17) and medium-high 4-MSI(0.30-0.36), and are
characterized by relatively heavy carbon isotopic compositions (-27.1‰). Organic matter is dominated by lower aquatic organisms with
minor terrigenous inputs, which was deposited under fresh-brackish lacustrine depositional environment. The crude oils in the LD 29
oilfield are mainly originated from the third Member of the Shahejie Formation in the Liaozhong depression and Liaodong depression,
with a little contribution from the fourth Member of the Shahejie Formation in the Liaozhong depression. The formation of light oil with
high wax content in the study area is mainly controlled by the organic precursors of source rock, i.e., alginite and lower organisms

Key words: light oil with high wax content, biomarker feature, carbon isotope, oil-source correlation, LD 29 oilfield, slope belt, Liaodong Depression