关键词: 缝网压裂, 应力场, 净压力, 分支缝, 临界压力, 缝内封堵

Abstract:

In terms of network fracturing techniques for low or ultra-low permeability reservoirs, the present paper supplemented the concept of network hydraulic fracturing by delineating network fracturing that forms multi-fractures even a “fracture network” system on the basis of forming principle fractures with the predicted supporting fracture length. Different planar models for various reservoirs and elastic hypotheses were used to analyze mechanical conditions for the formation of a fracture network. In practice, new fractures formed on the basis of primary fractures could compose a fracture network when the net pressure within fractures caused by hydraulic fracturing exceeded the sum of the difference between the maximum and minimum horizontal principal stresses and the tensile strength of rocks. Various treatment methods for network hydraulic fracturing were investigated and the one applicable to an individual reservoir with its effect prediction was then worked out. Finally, Well F1-15 was designed and fractured based on this concept of network fracturing. The oil produced by this well after treatment was much more than that of the adjacent wells. The experimental results showed that effects of network hydraulic fracturing were prominent and multi-fractures were formed. Therefore, network fracturing techniques are not only feasible and effective but also greatly promising in application to low permeability reservoirs.

Key words: network fracturing, stress field, net pressure, branch fracture, critical pressure, blocking in fracture