高压气井套管回接固井预应力技术

针对套管回接固井质量不好，未能将尾管重叠段已经存在或潜在的窜流通道堵死，致使气井生产时井口带压的问题，回接固井作业时采取了很多技术措施，但都没有从根本上解决回接固井质量问题。为此，通过增加回接管柱管内外静液柱压差、井口憋回压方式，在固井施工过程中通过液柱压强转换为作用在回接套管本体上的预应力，在水泥浆凝固时该应力就迫使套管贴紧水泥石，防止水泥浆凝固时管柱和水泥环微环隙的形成，提高固井质量。几口试验井的测井结果表明：所采取的固井技术措施行之有效，能够保证套管回接的固井质量。

Pre-stress technique for casing tie-back cementing in high-pressure gas wells

Poor casing tie back cementing will lead to wellhead pressure during gas production, because the potential channeling at the liner lapping section is not stopped. The previous measures adopted cannot ultimately improve the tie back cementing quality. Herein a new method is recommended. That is to increase the hydrostatic pressure difference inside and outside the tie back string and maintain backpressure at wellhead so as to convert the fluid column pressure to the pre stress exerted on the tie back casing body during the cementing process. This stress will then force the casing to get tight with cement stones when cement is getting hard to avoid micro spaces formed between casing string and cement sheath. The cementing quality can thus be improved. The logging in several test wells show the pre stress technique is effective to ensure good casing tie back cementing quality.