Evaluation on the mechanical property of set cement of super long horizontal wells in tight oil reservoirs

Jimsar tight oil reservoirs in the Junggar Basin are characterized by extra low permeability, thick layer and developed thin interbed of mudstone and sandstone, and they are developed by using super long horizontal well. In order to realize its commercial exploitation, therefore, it is necessary to carry out perforating and multi-stage fracturing in super long horizontal sections. However, the perforating and multi-stage fracturing in super long horizontal wells leads to the irreversible damage to the integrity of set cement and results in the risk of interlayer channeling. To solve this problem, ductile expansion anti-channeling slurry system was developed in this paper. Then, the anti-channeling property of slurry and the mechanical parameters of set cement (e.g. tension strength, compression strength, elastic modulus and Poisson's ratio) were optimized by means of mechanical software and laboratory experiments. It is indicated that the optimized slurry system has stronger anti-channeling property with static gelling value rising from 0 Pa to 200 Pa within 3.5 min. The expansion ratio of set cement is 1.4%, so the micro annulus can be solved better. Tension strength, compression strength, elastic modulus and Poisson's ratio of set cement are 38.6 MPa, 4.25 MPa, 3 616.0 MPa and 0.37, respectively. The optimized slurry system and set cement are superior to conventional set cement and they can not only ensure the cementing quality of super long horizontal wells, but also satisfy the requirements on integrity and isolation of set cement after the fracturing.