Classification and characteristics of tight oil plays

Based on the latest conventional–unconventional oil and gas databases and relevant reports, the distribution features of global tight oil were analyzed. A classification scheme of tight oil plays is proposed based on developed tight oil fields. Effective tight oil plays are defined by considering the exploiting practices of the past few years. Currently, potential tight oil areas are mainly distributed in 137 sets of shale strata in 84 basins, especially South America, North America, Russia, and North Africa. Foreland, craton, and continental rift basins dominate. In craton basins, tight oil mainly occurs in Paleozoic strata, while in continental rift basins, tight oil occurs in Paleozoic–Cenozoic strata. Tight oil mainly accumulates in the Cretaceous, Early Jurassic, Late Devonian, and Miocene, which correspond very well to six sets of global-developed source rocks. Based on source–reservoir relationship, core data, and well-logging data, tight oil plays can be classified into eight types, above-source play, below-source play, beside-source play, in-source play, between-source play, in-source mud-dominated play, in-source mud-subordinated play, and interbedded-source play. Specifically, between-source, interbedded-source, and in-source mud-subordinated plays are major targets for global tight oil development with high production. In contrast, in-source mud-dominated and in-source plays are less satisfactory.