Ductile Nano-Cement Slurry Cementing for Slim-Hole Horizontal Shale Gas Wells

To improve the cementing quality of slim-hole horizontal shale gas wells and ensure the sealing effect of the cement sheath while fracturing and the integrity after fracturing, a ductile nano-cement slurry (DNCS) and its associated technologies were studied. The DNCS was developed by using carbon nanotubes compounded with fibers, which had the properties of low elastic modulus and high tensile strength. Compared with conventional cement, the elastic modulus of ductile nano-cement was reduced by 50.9%; the compressive strength was increased by 28.1%; the maximum tensile strength could reach 5.2 MPa. An associated carbon nanotube three-stage mixing technology was studied, which solved the problems of entanglement and difficult dispersion of large doses of nanomaterials, and the field application of carbon nanotube cement slurry was achieved for the first time. The results of the DNCS cementing test show that the qualified ratio of cementing quality in the horizontal section reaches 98%. The sealing effect of the cement sheath was evaluated by borehole microseismic monitoring technology, and the microseismic event in the off-design area during the fracturing process is 0, indicating that the cement sheath is well sealed. The DNCS provides a technical support for the efficient and low-cost development of shale gas.