Cementing of Large-sized Casing through Salt and Gypsum Interbeds in Well Keshen-243

Keshen-243 is an appraisal well located 29 km to Baicheng County, Xinjiang. The 3rd interval of this well was drilled to 5,532 m, and two-stage cementing was to be conducted to cement the hole penetrating Kumugeliemu group (salt rocks). Bottom hole static temperature of the 3rd interval was 127.6℃, mud weight was 2.43 g/cm³, and the maximum formation pressure was 132 MPa. Casing strings of φ273.05 mm + φ293.45 mm in diameter were to be run into the hole and cemented. Several problems were expected during casing running, such as low pressure bearing of the formations to be cemented which may result in lost circulation, creeping of the salt/gypsum interbeds, channeling of cement slurry and slow setting of the top cement slurry when cementing long open hole section etc. In formulating the cement slurry to address these problems, a micro powder manganese mineral and another weighting agent GM-1 were dry mixed together into the cement slurry to ensure its density, two anti-channeling agents used to improve the anti-channeling performance of the cement slurry, and a combination of high temperature and low temperature filtrate loss reducers to improve the filtration property of the cement slurry. The amount of cement retarder was reduced to avoid long retarding period of the top cement slurry under the circumstance of big temperature differences. All these selected additives, plus the cementing techniques engineered, made the two-stage cementing operation through salt-gypsum interbedded formations smoothly done even when there was lost circulation flowed by mud kick. The cementing job was qualified.