Exploration advances and accumulation model for Neocene lithological reservoirs in Laibei Low Uplift, Bohai Sea area

Abstract

The Laibei Low Uplift locates in the southern part of Bohai Sea area, and is sandwiched by two major hydrocarbon-rich sags with a complex structural evolution history. The broken fault block traps and the model of hydrocarbon accumulation are still unclear. It is the single uplift (low uplift) without commercial development in the Bohai Sea area. Combined with recent drilling data, a "convergence-transportation-filling (CTF)" model of the Neocene lithological reservoir formation in the Laibei Low Uplift was proposed. The type of convergence determines the enrichment zone of oil and gas on the uplift, and the zones of "fault convergence type" and "structural ridge convergence type" enrichment are developed in the eastern and western sections of the Laibei Low Uplift. The vertical migration efficiency of oil and gas appeared to be determined by the activity of oil source fault. When the fracture slip of the migration fault in the drilled trap is greater than 80 m, the shallow layer is generally found to be a better reservoir of oil and gas. The relationship between fault and sand restricts the filling efficiency of oil and gas. When the contact area of fault and sand is greater than 10×103 m2, the Neocene traps generally have a better oil and gas abundance and hydrocarbon column height. By the using of established reservoir forming model, a comprehensive analysis of the undrilled lithological traps of Neogene strata was carried out by this study, 23 favorable target sand bodies were suggested and have been proved to be successful. The effectiveness of the reservoir forming model has been validated, and the first large-scale commercial oil field, i.e., Kenli 6-1 oil field, on the Laibei Low Uplift has been accordingly developed.

Keywords

• hydrocarbon convergence type
• fault activity
• fault-sand contact relationship
• lithological reservoirs
• laibei low uplift
• bohai sea area