凝析气藏返排制度优化

System optimization for gas condensate reservoir flowback

 刘林 刁素 黄禹忠 尹琅 刘琦

 中国石化西南油气分公司工程技术研究院，四川 德阳 618000

 Engineering Technology Research Institute, Southwest Oil and Gas Company, SINOPEC, Deyang 618000, China

 川西GM构造沙溪庙组气藏的气井加砂压裂后，在测试返排过程中，井口压力下降快，产凝析油，自然返排率较低，测试产量低，未能达地质预期效果。针对上述问题进行了分析，结果认为：气井井底压力降至流体露点压力以下时，产生反凝析现象，凝析油堵塞孔道是造成返排率和产能低的主要原因；另外，储层具有中等偏强的速敏和应力敏特征，压后快速返排造成井口压力下降快，导致储层渗透率下降，也会影响压后产能。文中通过PVT实验，确定了气藏的露点压力，创新性地提出了控压返排措施，避免了返排过程中井口压力的快速下降和凝析油的产出。平均返排率由前期的35.5%提高至60.1%，压后天然气产量从措施前平均1.69×104　m³/d提高至3.87×104 m³/d，增产显著。

 In the flowback process after sand fracturing of Shaximiao gas reservoir in GM structure, western Sichuan Depression, rapid wellhead pressure drops, producing condensate, low natural flowback rate and capacity are the problems. Analysis of these problems shows that when gas well downhole fluid pressure drops below dew point pressure, retrograde condensation is produced, condensate clogged pores cause low flowback rate and low productivity. In addition, the reservoir has a strong middle rate sensitivity and stress sensitivity, rapid flowback causes fast wellhead pressure drop and reservoir permeability decrease, these affect productivity after fracturing. In this article, dew point pressure is determined by PVT experiment, pressure control flowback is proposed initially, condensate precipitation is avoided in the flowback process. Average flowback rate increases from 35.5% to 60.1%, average testing capacity rises from 1.69 × 10⁴ m³/d to 3.87× 10⁴　m³/d after fracturing.

10.6056/dkyqt201504031