考虑储集层塑性变形的最小射孔深度计算

储集层被打开后，由于原地应力平衡被破坏，井孔周围的应力将重新分布。如果储集层胶结强度较低，近井带存在较大范围的塑性区。由于存在塑性区，以及钻井过程中发生钻井液的滤液及固相颗粒侵入，此双重作用导致近井带的渗透率很低，分成具有不同渗透率的３个带（含塑性作用的损害带，塑性带，弹性带）。由于塑性带宽度较大，其渗透率比弹性带小得多，因此在确定射孔深度时应将塑性带考虑在内。进行了近井周围储集层的弹塑性分析，给出了塑性带半径的计算方法，分析了影响塑性带范围的因素，在此基础上指出：射孔的最小深度应包括塑性带宽度。图３参７（段玉廷摘）

Minimum perforation depth calculation with consideration of plastic deformation around borehole.

The stress around a hole will redistribute after the formation is drilled. There exists a wide range of plastic zone around hole if the formation is poorly consolidated. There are three zones around hole, i.e. damaged zone, plastic zone and elastic zone, with different permeability because of plastic deformation and fluid invasion, after the hole is drilled. The calculation of perforation depth should take account of not only damaged zone, but also plastic zone, because the plastic zone has much lower permeability. The required minimum perforation depth is obtained on the basis of making the solution of elastic/plastic equations, and the factors affecting perforation depth are analyzed thereafter.