Innovation and practice of the whole petroleum system theory: A new paradigm for “all strata, all types, all domains” petroleum exploration

Abstract

The whole petroleum system (WPS) theory represents a significant innovation proposed to address the limitations of the classical petroleum system theory. The successful application of this theory has propelled the oil and gas exploration in China toward a new paradigm characterized by “all stratigraphic sequences, all resource types, and all exploration domains”. Based on a review of the fundamental principles of this theory, this study provides a comprehensive analysis of 25 relevant cases from 12 basins in China. It is indicated that there exists an orderly distribution of three fluid dynamic fields in a whole petroleum system, i.e., free dynamic field, restricted dynamic field and confined dynamic field. Hydrocarbon accumulation in a restricted dynamic field primarily relies on capillary force and viscous force; however, long-term effectiveness still depends on sealing capacity and regional boundary conditions. The superposition of hydrocarbon generation from source rocks with different kerogen types or lithologies results in a broader hydrocarbon generation window, and earlier and longer hydrocarbon generation, than the traditional Tissot model, demonstrating a whole-process hydrocarbon generation across all kerogen types. The distribution and physical properties of reservoirs are generally controlled by sedimentary facies and diagenesis. From basin margin to sag center, sediment grains generally present reservoir-forming features of all facies belts and all grain-size grades from coarse to fine. A typical whole petroleum system generally follows a full-sequence, three-dimensional accumulation pattern described as “three zones laterally, three layers vertically”. Laterally, along the basin margin → slope area → sag area, conventional oil and gas reservoirs, tight oil and gas reservoirs, and shale oil and gas reservoirs develop sequentially, corresponding to the intervals of major source rocks. Vertically, in addition to shale/coal-rock oil and gas reservoirs within these intervals, tight/conventional reservoirs are also found above and below the source beds. Within the accumulation framework of the whole petroleum system, underexplored areas that have not yet achieved breakthroughs represent important potential domains for future oil and gas discoveries.