Abstract:

The Daniudi gas field belongs to a reservoir of lower pressure and tight gas with a low pressure, a strong heterogeneity, a small diameter of pore and throat, a high capillary pressure, a character of multi-zone superimposed and varies gap distance between zones, which results in difficulty in reservoir protection and fracturing. A method of low damage fracture fluid with liquid N₂ is adopted, which can decrease the reservoir damage and protect reservoir. Large-scale fracturing can prolong fracture length, enlarge drainage area and increase gas rate per layer. The gas production increased from 200 m³/d to 7.23×10⁴ m³/d. Fracture operation time was reduced nearly 67%, and the cost was reduced 20.69% after separated fracturing without pulling string realized balance stimulation for multi-layer superimposed.

Key words: Daniudi gas field, low permeability, gas reservoir, multi-layer superimposed horizon, synthesical pressure-fracture