Analysis on Mineral Components and Frangibility of Shales in Dongying Depression

Key words: 
• shale /
• mineral component /
• shale gas /
• reservoir /
• frangibility /
• Dongying depression

Abstract: The mineral components and frangibilities of the shales of Es_4sand Es_3xof Shahejie Formation in Dongying depression were researched, and were compared with those of North America shales. The results show that those main mineral components include detrital minerals (feldspar and quartz) from land, clay minerals and non-clay minerals (carbonate rocks and pyrite) self-engendered. The average content of clay minerals is only 25%, much lower than marine shale and conventional viewpoint (over 50%). The average content of feldspar is average about 5%, higher than general marine shale. Self-engendered carbonate rocks content is rich, with average value about 37%, and changing dramatically. Short distance from origin deposition and frequently changing sedimentary facies is genesis of above shale mineral component characters. In addition, the enumerated quartz frangibility, Carbonate  frangibility and total frangibility was formulated for continental basin shale, and the enumerated quartz frangibilities, carbonate  frangibilities and total frangibilities of shales of the Dongying depression were calculated, it was founded that the content of carbonate is mainly affection factor for frangibility of the shales. The results indicate that the shale of the Dongying depression are easily to form natural fractures or easily to be crushed, and are potential reservoirs for shale gas.