A major discovery of hydrocarbon-bearing layers over 1,000-meter thick in well Shunbei 84X, Shunbei area, Tarim Basin and its implications

The NE-trending strike-slip fault zones in the central Shunbei area, Tarim Basin have long been the destination of hydrocarbon migration, accumulation, and enrichment. Dilling has revealed the occurrence of faultcontrolled, fractured-vuggy hydrocarbon reservoirs along the No.8 strike-slip fault zone in the Shunbei area. Along this fault zone, 1088-m-thick hydrocarbon column has been discovered in well Shunbei 84X. The fault-controlled, fractured-vuggy hydrocarbon reservoirs are characterized by a great hydrocarbon column height, which is independent of the heights of current structures. To identify the primary factors controlling the large hydrocarbon column height of these reservoirs, we examine the characteristics of reservoirs, traps, and hydrocarbon accumulation in well Shunbei 84X, as well as the distribution pattern of fault-controlled, fractured-vuggy hydrocarbon reservoirs within. The results indicate that the tectonic fracturing of strike-slip structures plays a crucial role in the formation of tight carbonate reservoirs. Furthermore,the depth of these reservoirs is not limited by the burial depth of carbonate strata, with fault-controlled fractured-vuggy reservoirs even identified at a burial depth of nearly 9000 m. The formation of fault-controlled fracturedvuggy traps is primarily influenced by the top sealing capacities of the significantly thick overlying mudstone cap rocks, the side sealing capacities of tight limestones on both sides, and the horizontal segmentation and vertical stratification of strike-slip faults. Oil-source correlation reveals that oil and gas originate from the source rocks in the Cambrian YuertusFormation, further confirming the hydrocarbon accumulation mode consisting of multiphase hydrocarbon supply from the Cambrian source rocks, reservoir formation by tectonic disruption, in-situ vertical hydrocarbon transport,a predominance of late-stage accumulation, and strike-slip fault-controlled hydrocarbon enrichment in the east-central Shunbei area. The major discovery in well Shunbei 84X in the Shunbei area highlights the presence of strike-slip fault-controlled tight carbonate reservoirs with a large vertical depth and sufficient hydrocarbon charging in the Tarim Basin ultra-deep sequences. These findings suggest the considerable potential for ultra-deep hydrocarbon exploration in the Shunbei area.