Accumulation mechanism and controlling factors of the continuous hydrocarbon plays in the Lower Triassic Baikouquan Formation of the Mahu Sag, Junggar Basin, China

Abstract

Hydrocarbon exploration in the Mahu Sag of the northwestern Junggar Basin has recently resulted in a significant discovery that defined the new “continuous oil plays” in the Lower Triassic Baikouquan Formation. This formation hosts glutenite reservoirs with oil reserves of more than hundreds of millions of tons. This resource is an example of an extensive hydrocarbon accumulation that's far from source rocks. Three conditions are necessary for this type of hydrocarbon accumulation: large hydrocarbon source, good reservoirs and effective seals, and favorable timing of hydrocarbon charge and migration. In the Mahu Sag, high-quality lacustrine source rocks are prolific hydrocarbon source, large-scale strike-slip faults enabled and facilitated long-distance hydrocarbon migration, and fan-delta glutenites are excellent reservoirs for hydrocarbon accumulation. The hydrocarbon accumulation is controlled by three factors: pro-delta sedimentary facies, structural highs, and faults. Abnormal reservoir over pressuring and fracturing has had an important impact on enhancing hydrocarbon production. The consideration of all these factors should govern the selection of future exploration targets.

Keywords

• Continuous oil and gas plays
• Fan-delta
• Lacustrine high-quality source rocks
• Highly mature light oil and gas
• Distal hydrocarbon accumulation
• Baikouquan Formation
• Mahu Sag