In Ordovician of Tahe Oilfield

the bottom hole temperature is high

the seam hole is developed

the leakage easily occurs

and the annular clearance of cementing is small. Therefore

the conventional low density cement slurry system cannot guarantee the sealing integrity of cement sheath and meet the requirements of exploration and development. Aiming at the above difficulties

the modified fly ash is optimized to enhance the early strength of cement

the high anti-extrusion microsphere is compounded to improve the comprehensive performance of cement slurry

the high temperature elastoplastic material is optimized to reduce the elastic modulus of cement

and the low density elastoplastic cement slurry system is evaluated co

mbined with the matching cementing additives. The density is applicable in the range of 1.25~1.50 g/cm

3

API water loss is less than 50 mL

the rheological properties is good

the right-angle is thickening

the cement slurry settlement stability is good

and the system has good mechanical properties. Meanwhile

the elastic modulus can be as low as 7 GPa and the compressive strength is greater than 14 MPa. All these things enhance the sealing integrity of cement sheath under the action of alternating stress. The applications of this system in well-Zhongtan-1 and well-TP193 of Tahe Oilfield are successful and the cementing quality are well

which indicate that the system can meet the cementing technical requirements of small clearance liner in the leaky formation of Ordovician and has a good application prospect.