Liner Cementing the high pressure gas wells in the Block Gaoshiti-Moxi

In cementing the φ177.8 mm liner string in high pressure gas wells in the Block Gaoshiti-Moxi of southwest oilfield, problems such as active gas zones, narrow drilling windows, poor compatibility of fluids and large temperature difference at high temperatures, were encountered. Technical measures were prepared to deal with these problems, and a self-healing anti-channeling high density cement slurry was developed for cementing wells with large temperature difference at high temperatures. Laboratory study of the cement slurry showed that the cement slurry had density between 2.0 g/cm³ and 2.8 g/cm³, and in field application, the cement slurry can be prepared to have a density of 2.6 g/cm³ in one mixing circulation. This cement slurry functioned at temperatures between room temperature and 180℃. Differences between the density of the top and bottom of cement slurry column was less than or equal to 0.05 g/cm³. The fluid loss of the cement slurry was less than or equal to 50 mL. The thickening time had good linear relationship with the concentration of retarders, and the transit time for the thickening of the cement slurry was not longer than 10 min. The maximum transit time of the gel strengths of the cement slurry was 20 min. The 24-hour compressive strength of the set cement was greater than 10 MPa, and the 48-hour compressive strength of the cement top was greater than 3.5 MPa. The strength of the cement slurry developed fast at low temperatures. The set cement formed had stable non-shrinking volume, possessing a mechanical performance that is similar to that of tough cement. The cement slurry expanded when in contact with oil and gas, ensuring the quality of bonding between cement sheath with casing string and borehole wall, and the integrity of sealing, which in turn mitigating the risk of gas channeling after cementing job. High quality of cementing job with this cement slurry was obtained in cementing the well Gaoshi-X and the well Gaoshi-Y, with no pressure developed in the annular space after cementing.