Causes and characteristics of mudstone fracture and hydrocarbon accumulation in Dongying depression

Fractured mudstone reservoirs have been found in petro-liferous basins both in China and other countries.As one of the subtle transportation system,fractures in mudstones have been paid more and more attention.According to spa-tial relationship of fracture and rock formation in Dongying depression,hydrocarbon source rock fracture have been di-vided into vertical fracture and inclined fracture and horizon-tal fracture.Analysis of fracture characteristics shows that the mudstone fracture is mainly concerned with the magma activity and vertical difference load fracture.The magma ac-tivity related fracture is mainly distributed in the southern slope up direction of Dongying depression,and the western uplift area,the vertical difference load have an important im-pact on the fracture activities since the tertiary era.The fracture development provided favorable migration and reser-voir space for oil and gas in hydrocarbon source rocks.In the fracture,the hydrocarbon migration resistance is low under the differential pressure or drived by buoyancy forwards or in the uplift direction.In Dongying depression,the migration of mudstone fracture reservoirs are mainly distributed in tec-tonic high point,near the nose structure or faulty zone.