Hui Xiao, Ke Xuan, Qi Yalin, Shi Shuyong, Zhu Jing, Wang Yunpeng
National Engineering Laboratory for Exploration and Development of Low Permeability Oil & Gas Fields, Xi'an 710018, China.
Research Institute of Petroleum Exploration and Development, PetroChina Changqing Oilfield Company, Xi'an 710018, China.
ACS Omega. 2024 Dec 10;9(51):50377-50384. doi: 10.1021/acsomega.4c06995. eCollection 2024 Dec 24.
In recent years, new oil reservoirs have been discovered and exploited in the ninth member (Chang 9 Member, Ty) of the Upper Triassic Yanchang Formation (Ty) in the Longdong area, Ordos Basin. Some studies have shown that the crude oils of the Chang 9 Member may originate from the Chang 9 source rock in some areas, which may be related to the distribution of the source rock. However, the distribution of the Chang 9 source rock in the Longdong area is still unclear, which hinders further exploration and development of petroleum. In this study, we established a multiple linear regression model for predicting total organic carbon (TOC) based on the relationship between well-logging parameters and measured TOC values of shale core samples from 30 wells in the study area. The results show that the Chang 9 shale is mainly composed of gray and dark mudstones, which mainly belong to the interdistributary bay and front delta depositional subfacies. The TOC values of the shale core samples from this member vary in a range of 0.11-4.8%, with an average value of 0.96%. Compared with traditional and improved Δlog models, our model shows a higher accuracy of TOC prediction with = 0.9181, which meets the requirements for predicting the distribution of the Chang 9 source rock. In the map of the Chang 9 source rock predicted by our model, the thickness of the source rock (TOC ≥ 1.0%) varies in the range of 1-12 m, showing a decreasing trend from northeast to southwest in the Longdong area. The crude oil in the northeastern areas enjoys a high ratio of 17α(H)- rearranged hopane and hopane ( */ ), and the thickness of the Chang 9 source rock is also greater than in other areas. It is speculated that the Chang 9 Member tight oil in the northeast area is mainly from the Chang 9 source rock, while the oil in other areas is from the Chang 7 source rock. In our study, we presented a method for predicting the source rock distribution, which can be widely used for exploring the tight oil of the Chang 9 Member in the study area.
近年来，鄂尔多斯盆地陇东地区上三叠统延长组（Ty）长9段（Chang 9 Member，Ty）发现并开发了新的油藏。一些研究表明，长9段的原油在某些地区可能源自长9烃源岩，这可能与烃源岩的分布有关。然而，陇东地区长9烃源岩的分布仍不清楚，这阻碍了石油的进一步勘探和开发。在本研究中，我们基于研究区30口井的测井参数与页岩岩心样品实测总有机碳（TOC）值之间的关系，建立了预测TOC的多元线性回归模型。结果表明，长9页岩主要由灰色和暗色泥岩组成，主要属于分流间湾和前三角洲沉积亚相。该段页岩岩心样品的TOC值在0.11% - 4.8%范围内变化，平均值为0.96%。与传统和改进的Δlog 模型相比，我们的模型在预测TOC时具有更高的精度， = 0.9181，满足预测长9烃源岩分布的要求。在我们模型预测的长9烃源岩图中，烃源岩（TOC≥1.0%）厚度在1 - 12 m范围内变化，在陇东地区从东北向西南呈递减趋势。东北地区原油中17α(H)-重排藿烷和藿烷（ */ ）的比例较高，长9烃源岩厚度也大于其他地区。推测东北地区长9段致密油主要来自长9烃源岩，而其他地区的油来自长7烃源岩。在本研究中，我们提出了一种预测烃源岩分布的方法，可广泛用于研究区长9段致密油的勘探。
