New progress and prospect of oil and gas accumulation research in deep to ultra-deep strata

Abstract

There are abundant deep to ultra-deep oil and gas resources in China, but the degree of exploration is low. The deep to ultra-deep reservoirs have higher temperature and pressure than the shallow ones, and the fluid from the deep strata plays a stronger role in the deep formations. Therefore, the deep to ultra-deep reservoirs have different accumulation mechanism from the shallow ones. Through extensive research at home and abroad, the particularity and main control factors of hydrocarbon generation, reservoir-forming and hydrocarbon accumulation of deep to ultra-deep oil and gas reservoirs were systematically summarized. It was suggested that there are materials and energy in the deep to ultra-deep environment that can promote the continuous hydrocarbon generation of hydrocarbon kitchens, which can further promote oil and gas accumulation. Fluids originating from deep to ultra-deep reservoirs can play a constructive role in forming high-quality large-scale reservoirs in deep strata. The deep CO2-rich fluid flowing through source rocks and reservoirs can promote the hydrocarbon expulsion in deep strata and the hydrocarbon accumulation in shallow strata. Although these theories summarized by predecessors are still controversial in guiding the discovery of large-scale oil and gas reservoirs, it should be seen that under the unique geological conditions of deep to ultra-deep strata, when summarizing the law of oil and gas accumulation, comprehensive and full consideration of various factors will help to improve the success rate of deep to ultra-deep exploration wells and reduce exploration costs.

Keywords

• deep strata
• ultra-deep strata
• co2-rich fluid
• oil and gas accumulation