Formation Selection Criteria for Volume Fracturing in Chang 7 Tight Reservoir in the Ordos Basin

摘要

The Ordos basin possesses abundance of tight oil and it has huge commercial potential. Volume fracturing is an effective means for the exploitation of tight oil which is a significant impact by geological conditions. So far, the formation selection criteria targeting on volume fracturing of Chang 7 tight reservoir in the Ordos basin have not been established. This paper combined the experiments of rock mechanics and the fracturing simulating software Meyer, and built the selection criteria of Chang 7 tight reservoir in terms of the horizontal stress difference, the brittle index and the natural fractures. It is shown that the horizontal stress difference in Chang 7 tight reservoir is 6-12 MPa, the brittle index based on elastic parameters is 30-48, with strikingly regional natural fracture growth. The fracture geometry induced by volume fracturing is affected by the horizontal stress difference, the brittle index and the natural fracture numbers together. Complex fracture networks are likely to form in a highly naturally fractured section with the in-situ stress difference below 8 MPa and the brittle index over 40. The selection criteria is adequate for optimum formation selection and it has guide function in fieldwork which proved by field practice.