The Study Of Elastic And Flexible Cement Slurry System For Shale Gas Reservoirs

The development of Shale gas provides a new opportunity for the energy industry,its business development has caught national attention and had deep impact on the development of oil industry.But the particularity of the shale gas reservoir and its development process,determines the special requirements for the cement slurry system: low elastic modulus,high folding strength,good compressive strength and good reservoir cementing performance,that means the cement should have elasticity and flexibility.On the basis of literature research,this paper analyses the characteristics of the shale gas reservoir and its performance requirements for cement stone.And in the exploration of experiment,we selected the elastic additive by the falling dynamic elastic modulus of the cement stone(rubber powder of mesh 80),and selected the flexible additives by the rising of flexural strength of the cement stone(carbon fiber of 3mm,50% of solid phase butyl benzene latex),the paper also p uts forward a comprehensive coefficient which involves the elasticity,flexibility and compressive strength of cement stone,and based on this criterion,composite performance coefficient,and based on this criterion,the plan of elastic and flexible cement slurry system was determined: oil well cement of class G + rubber powder of mesh 80(1.5% ~ 2%)+ carbon fiber of 3mm(0.4% ~ 0.6%)+ butyl benzene latex(14% ~ 18%,and the best added amount is 14%).By the experiment selecting,the types and quantity of defoamer,fluid loss addictive,dispersant,retarder,etc.was determined,and the elastic and flexible cement slurry system for the shale gas reservoir was developed.The paper takes a test for the new cement slurry system,and the flowing is the result: the density~1.739 g/cm3,initial consistency~10.2 Bc,condensate rate~0,water loss can be controlled within 50 ml,thickening time is more than 300 minutes,liquidity index > 0.6,the flexural strength of cement~6.5MPa,the compressive strength~23.2MPa,and the dynamic elastic modulus fells to 7Gpa around.The permeability of the cement stone is 0.00086 mD,the time of the static gel strength(48Pa~240Pa)<8min,so the performance of anti-gas channeling is good.The study of resist impact crushing and mechanical deformation ability shows that,this cement slurry system has good mechanical deformation ability and good resistance to impact crushing.And the study of this elastic and flexible cement slurry system lays a foundation for the development of the shale gas reservoir which needs repeated fracturing.