Fujie Jiang

Research advances and direction of hydrocarbon accumulation in the superimposed basins, China: Take the Tarim Basin as an example

Abstract The superimposed basins in the Tarim Basin are characterized by multiple source-reservoir-caprock combinations, multiple stages of hydrocarbon generation and expulsion, and multi-cycle hydrocarbon accumulation. To develop and improve the reservoir forming theory of superimposed basins, this paper summarizes the progress in the study of superimposed basins and predicts its development direction. Four major progresses were made in the superimposed basin study: (1) widely-distributed of complex hydrocarbon reservoirs in superimposed basins were discovered; (2) the genesis models of complex hydrocarbon reservoirs were built; (3) the transformation mechanisms of complex hydrocarbon reservoirs were revealed; (4) the evaluation models for superimposed and transformed complex hydrocarbon reservoirs by tectonic events were proposed. Function elements jointly controlled the formation and distribution of hydrocarbon reservoirs, and the superimposition and overlapping of structures at later stage led to the adjustment, transformation and destruction of hydrocarbon reservoirs formed at early stage. The study direction of hydrocarbon accumulation in superimposed basins mainly includes three aspects: (1) the study on modes of controlling reservoir by multiple elements; (2) the study on composite hydrocarbon-accumulation mechanism; (3) the study on hydrocarbon reservoir adjustment and reconstruction mechanism and prediction models, which has more theoretical and practical significance for deep intervals in superimposed basins.

Accumulation model based on factors controlling Ordovician hydrocarbons generation, migration, and enrichment in the Tazhong area, Tarim Basin, NW China

The hydrocarbon accumulation model of Ordovician reservoirs in the Tazhong area, Tarim Basin, was investigated based on the analysis of the key factors controlling hydrocarbon generation, migration, and enrichment process and history. The results show that the hydrocarbon generation processes are controlled by Cambrian–Lower Ordovician and Upper Ordovician source rocks distributed in the Tazhong area and the Manjiaer Sag. Vertical hydrocarbon migration distance is controlled by the vertical source-reservoir distribution, faults, and caprocks. Structure played a major role in the lateral hydrocarbon migration along NW-SE direction. Lateral migration pathways were governed by unconformities, transport faults, and reef-beach body reservoirs. A part from the sedimentary control, hydrocarbon enrichment is controlled by recent tectonic events. The hydrocarbon charging points refer to the intersection of northeast- and northwest-trending faults. Two types of hydrocarbon accumulation models could be retained, (a) mixed-sourced area model, in which the hydrocarbons are sourced from both the Tazhong area and the Majiaer Sag, and (b) single-sourced area model, in which the hydrocarbons are only sourced from the Tazhong area itself.

Petroleum resources in the Nanpu sag, Bohai Bay Basin, Eastern China

The Nanpu sag is an important secondary tectonic division of the Bohai Bay Basin and has an area of 1532 km2 (591 mi2), of which 1000 km2 (386 mi2) has been explored near Bohai. Recently, exploration has gradually shifted from continental to beach to shallow-marine settings, with significant exploration breakthroughs having occurred in the Nanpu 1, 2, and 3 tectonic belts, indicating good resource potential. However, a systematic resource assessment has yet to be performed, which strongly restricts the exploration progress. In this study, we improved upon the Pareto model and reevaluated the area’s resource potential using two new methods. In one method, the traps are divided into several types, including structural, stratigraphic, and buried hill traps, to predict their individual resource potential and total resources of this area; in the other method, the normalized fluid potential is used to divide the area into several accumulation systems to calculate the resource potential. The Nanpu sag resources are estimated at 1.45 × 109 t (10.6 × 109 bbl), which represents an increase of approximately 2.70 × 108 t (19.8 × 108 bbl) compared with previous evaluations because of the increase in exploration maturity and information validation. The main residual resource is distributed in beach to shallow-marine settings. The stratigraphic and buried hill traps present better resource potential using the trap-type method. Such information can guide the direction of exploration and selection of potential traps.