关键词: 莱北低凸起, 岩性油气藏, 勘探历程, 思路转变, 勘探技术

Abstract: The key factors restricting oil and gas discovery in the Laibei low bulge in the Bohai Bay Basin are unclear understandings of the structural settings and the hydrocarbon accumulation model. Since 2019, by transforming exploration ideas, research on faults and structures, favorable objective strata, and oil-gas accumulation rules in this area has been strengthened. It is considered that: (1) Oil and gas accumulation in the Neogene is controlled by the development position of the “convergence ridge” of the top unconformity of the Mesozoic; (2) micro paleo-geomorphology controls the development position of favorable lithologic traps in the lower part of the Minghuazhen Formation in the Laibei low bulge; and (3) oil and gas are mainly enriched at the top of the V oil layer in the lower part of the Minghuazhen Formation. Quantitative description of sand bodies and fluid identification technology based on lithologic-constrained geo-statistical inversion have been established. Guided by new understandings and new technologies, the exploration direction has been successfully changed and a new model of superimposed and contiguous hydrocarbon accumulation in Neogene lithologic reservoirs has been established. This has led to the first commercial discovery in the Laibei low bulge, after more than 40 years of exploration. The KL6-1 oilfield is a large-scale high-quality integral Neogene lithologic oil reservoir, with the major oil layer – of large-scale superimposed and contiguous sand bodies – situated at the top of the V oil layer in the lower Minghuazhen Formation. The burial depth of the oil reservoir is generally 1200–1550 m, with oil layer thickness generally more than 8m. The porosity of the oil-bearing reservoir is 14.9%–39.8%, with an average of 31.2%. Permeability is 7.9–19721.3 mD, with an average of 2205.52 mD. DST test results show that maximum daily production of the major oil layer could exceed 180 m3.