储层出砂、生产压差及改造压力对射孔套管强度的影响

Influences of reservoir sand producing,production pressure differential and stimulation pressure on strength of perforated casing

分析了射孔出砂形态及出砂段套管所受轴向压力;考虑不同出砂程度,建立了射孔出砂段套管三维有限元力学模型;分析了出砂分布及出砂程度对射孔段套管应力强度安全性的影响;分析了不同生产压差及改造压力作用下射孔套管等效应力的变化趋势。结果表明,射孔出砂掏空空洞的构形曲线为一个与上覆岩层压力、套管外径有关的二次曲线;空洞构形的曲率半径越大,套管所受轴向压力越大;即使轻微出砂,只要形成空洞,射孔段套管的强度会大大降低;集中出砂时套管的应力比分散出砂时的高;出砂量越大,最大等效应力越大,套管的强度安全性越低。

The configuration of sand production cavity resulting from perforation and the axial compressive force of the casing located in sand producing well section are analyzed. Three dimensional finite element mechanical model of perforated casing located in sand producing well section in which sand producing degree is considered is established. The influences of sand production distribution and amount on the strength of perforated casing are studied,and the varying trend of equivalent stress of the perforated casing under different production pressure differential and stimulation pressure is also studied. The results show that: the profile configuration of sand production cavity is a quadratic curve related with overburden pressure and casing diameter; the larger the curvature radius of sand production cavity,the greater the axial compressive force of the perforated casing; Only if a small sand producing cavity is formed,the stress of the perforated casing will apparently increase; the casing stress under central sand producing is greater than that under distributed sand producing when the number of sand producing cavities is the same; the more the sand produces,the greater the equivalent stress of the casing and the lower the strength safety of the casing.