Reservoir Characteristics Of The Youganwo Formation Shale In Maoming Basin Of Guangdong Province

Maoming basin is one of the main producing areas of oil shale in Guangdong, where Youganwo formation is the main target stratum. Through field reconnaissance, drilling catalogue, thin section identification, scanning electron microscope observation, and combined with means of X- diffraction and high pressure mercury injection, characteristics of shale reservoir petrology, pores and cracks, organic geochemistry have been studied for Youganwo formation. Youganwo formation shale is very developed in Maoming basin, whose distribution is wide, buried depth is mainly 0-2000 m, and shale depth show a trend of increasing in basin center and declining in basin margin, especially least thickness in northwestern of the basin; Youganwo formation shale is mainly formed in sedimentary environment of semi-deep lake. Shale mineral composition mainly contains quartz(32.7%), feldspar(6.1%), clay minerals(57%), and a small amount of pyrite(3.5%), which clay minerals includekaolinite(43%), illite(10.6%), smectite mixed layer(3.7%);Transition pore is the main shale pore(about 50%), secondly microporous(39%) and mesopore accounting for only 8%, macroporous almost no developped; pore types mainly contain organic matter and clay pore, mineral dissolution pore and intergranular pore; Macro fracture and micro fracture in the reservoir are developed, but the total quantity is relatively small. The average value of shale TOC is 12.76%, with high organic matter content, kerogen belonging to type I(Humic type) and pyrolysis peak temperature with Tmax 427?-437?, specular reflectance <0.5%, organic matter is still in immature stage, the content of chloroform bitumen "A" average value is 4.31%. The characteristics of shale reservoir spatial distribution, physical properties and geochemistry are controlled by the tectonic, sedimentary environment, paleoclimate and paleogeomorphic. Maoming basin belongs to fault basin of half graben; faults of controlling basin control the depth and thickness of Youganwo formation, meanwhile reservoir fractures is not developed, due to shale formation late age and reservoir has not suffered from strong tectonic transformation, also mechanical compaction and consolidation diagenesis of shale reservoir is weak, resulting in the reservoir porosity bigger, generally more than 10%.