Experimental evaluation of crushability of shale reservoirs in Luojia area, Shengli Oilfield

At present,there is no unified method for crushability evaluation on shale reservoirs at home and abroad.Based on rock mechanics and physical parameter tests in laboratory as well as brittleness index calculations,a systematic evaluation method of laboratory experiment has been proposed.Compared to sandstones and carbonate rocks,the tensile strength,uniaxial compressive strength,shear strength and fracture toughness of shales are lower.Along sedimentary bedding plane,the shear strength of shales is very small and the internal cohesion of vertical bedding is greater than that of parallel bedding.The cementation of sedimentary layer (natural fracture) is very fragile,easily happening shear failure.Under the action of induced stress,the greater the angle between parallel natural fracture and main hydraulic fracture,the easier the fracture initiates.When the included angle between herringbone grooving and sedimentary layer is less than 45°,it is easy to propagate along bedding plane for fractures,but when more than 45°,it can cross the bedding plane.In the end,this shale reservoir is considered to have the conditions of crushability.