管外封隔器在涩北气田钻井中应用的可行性研究

Feasibility Study on ECP Application for Drilling in Sebei Natural Gas Field

摘要:

环空气窜是几乎所有天然气井固井都存在的一个潜在问题。涩北气田是第四系中浅层气田，地层成岩性差，泥岩水化分散能力强,储层易分散，具有较强的压力敏感性和水敏特性；含气井段长，气水层间互，气层薄，层数多；地层岩石抗压强度低，致使水泥环第二界面的胶结强度极低，二界面质量难以提高，容易发生气窜、水窜和层间窜槽现象。为此，如何提高环形空间的密封性，提高固井质量，保证气井井筒完整性，成为了亟待解决的问题。针对该气田特殊的地质特点，分析了影响固井质量的因素，研究了固井工艺、防窜水泥浆体系和工艺措施应用的局限性，选择了管外封隔器来解决环空窜槽问题。分析结果表明，管外封隔器不但可以有效防止管外窜槽，而且可以提高固井质量和优化井身结构，保证气井安全和延长使用寿命。管外封隔器在涩北气田钻井中应用于防气窜和提高固井质量是切实可行的，具有很好的应用价值。

Abstract:

Annular gas channeling is a potential problem in almost all natural gas well cementing. Sebei natural gas field is a middle-shallow depth gas field of the Quaternary with poor diagenesis and strong shale hydration & dispersion, strong pressure sensitivity and water sensitivity; in long gas well segment, gas layer and water layer are interbedding with multiple thin gas layers; the low compressive strength of formation rock leads to very low second interface bonding strength of cement ring, it is difficult to improve the second interface quality, gas channeling, water channeling and interstratified channeling are easy to occur. Therefore, how to improve the sealing of the annular space, improve the cementing quality and ensure the integrity of the wellboe becomes a problem that needs to be solved. In view of the special geological characteristics of the gas field, the factors affecting cementing quality are analyzed and the limitation for the application of cementing technology, anti-channeling slurry system and technological measures are studied and ECP is selected to deal with the annual channeling. The analysis results show that ECP can not only effectively prevent gas channeling cement channeling, but also can improve cementing quality and optimize casing program to ensure gas well safety and prolong service life. The application of ECP for gas channeling prevention and cementing quality improvement in Sebei gas field drill is practical.