Large Size Well Cementing for Underground Gas Storage in Block Shaan224 Changqing

The Benxi Formation in the Block 224 in Changqing Oilfield is mainly unstable mudstones and coal beds which always collapsed during drilling with mud density of nearly 1.6 g/cm³. The liner string commonly used had a diameter of 244.5 mm, making well cementing difficult because of large annular space and difficulty in flushing and displacing, and cementing quality of the set cementing poor. Meanwhile, the volumes of gases injected into and produced from a single gas storage well were huge, causing the cement sheath to be broken by the action of cyclical stresses, and hence annular channeling and pressure anomaly. To solve these problems, a high performance high density flushing spacing fluid and a cement slurry with enhanced toughness were developed and were applied successfully in the cementing of the φ244.5 mm liner in the Well Jingping22-4-2 in Block Shaan224, with 95.46% of the cementing job acceptable and 79.05% high quality. Subsequent injection and production of gases were operated without a hitch.