High-quality source rocks exert primary control on hydrocarbon accumulation in continental lacustrine basins, particularly for tight sandstone oil reservoirs. The identity of the principal source rocks for Chang 7 tight oil in the Yanchang Formation, Ordos Basin, and their control mechanisms on accumulation and enrichment remain uncertain. This study integrates gas chromatography–mass spectrometry (GC–MS) analysis of mudstones, oil shales, and crude oils with hydrocarbon generation–expulsion simulations, abnormal pressure calculations, and fluid inclusion trapping pressure reconstruction to establish oil–source correlations, characterize primary source rocks, and define controlling accumulation mechanisms. Results demonstrate that: (1) Chang 7 tight oil was sourced predominantly from Chang 7 oil shales in a "lower generation–upper reservoir" configuration. (2) These oil shales are laterally extensive with substantial thickness (>15 m), high organic matter abundance (average TOC 11.36 wt.%), excellent kerogen quality (Types I and II₁), and moderate thermal maturity (average Ro 0.85%). (3) Cumulative hydrocarbon generation intensity averaged 159.46 × 10⁴ t/km², providing abundant material for tight oil accumulation. (4) Source–reservoir pressure differentials (SRPD) averaging 15.58 MPa provided the necessary driving force for efficient oil charging into tight reservoirs. (5) High-quality oil shale distribution directly governs tight oil distribution, with transitional zones between hydrocarbon generation centers and high-pressure domains representing optimal enrichment fairways. These findings clarify the fundamental role of lacustrine oil shales in tight oil systems and provide practical guidance for exploration in analogous continental basins.
Xu et al. (2026) studied this question.