老井封堵技术在川东地区储气库建设中的应用

老井封堵作业是地下储气库建设的重要工作之一。四川盆地川东地区经过多年的开采，目前已进入生产中后期，天然气产量不能满足市场调峰需要，需要存储外来天然气以满足调峰要求。因此，近年来川东地区优选了部分枯竭油气藏作为调峰气藏。由于枯竭油气藏老井井筒的不完整性和复杂的地质构造，天然气在地层中窜漏，破坏了枯竭油气藏的封闭性，需要对老井进行治理。为此，针对川东气田纵向上层位多、生产层位压力系数低、老井固井质量差、套管腐蚀损伤严重等特点以及老井开采情况，提出了老井封堵的技术方案：①固化水堵漏；②注水泥浆封堵产层；③固井质量、套管腐蚀状况检测（套管段铣）；④注水泥塞+桥塞封堵。老井封堵重点是产层和井筒，主要采用暂堵技术、套管段铣技术，然后实施产层和井筒封堵。实际应用效果表明：依据封堵方案对老井实施永久性封堵作业后，井口压力为零，达到了有效治理老井的目的，从而确保了调峰气藏的安全平稳运行。

Application of old well plugging to the construction of underground gas storage in the eastern Sichuan Basin

Old well plugging is one of the most important parts of building the underground gas storage (UGS). After so many years, most gas wells in the eastern Sichuan Basin have come to their middle and later periods of production, which can no longer meet the peak shaving need in the gas market. On the other hand, more UGSs are required to store the imported gas sources. Under such a situation, some depleted oil and gas reservoirs in the eastern Sichuan Basin were optimally selected as UGSs for peak shaving need in the market. Due to the incompleteness of such well profiles and the complexity of geological structures there, gas channeling easily occurs through formations, which destroys the sealing capacity of the selected depleted reservoirs. In this respect, reconstruction is needed for those old wells. Therefore, this paper first analyzed the geological features of the depleted reservoirs like multiple vertical horizons and low pressure coefficient of pay zones, as well as the problems existing in those old wells, such as the poor quality of cementing, serious corrosion in casing pipes. Considering the status of old wells' production, we presented the following technical means: solidified water plugging, cement plugging (pay zones), examination of cementing quality and casing corrosion (casing section mill), and the combination of cementing with bridge plugging. Both pay zones and wellbores are the focus of plugging in those old wells by use of the temporary plugging and casing section milling technologies. After the above technical means were applied in practice, the wellhead pressure became zero, which proves that those old wells are successfully reconstructed enough to ensure the safe and smooth operation of the peak shaving UGSs built on those depleted reservoirs.