超高密度水泥浆体系的研究与应用

针对中原油田超高密度水泥浆固井技术难题,通过优选加重材料、解决加重材料的沉降问题以及沉降稳定性与流动性之间的矛盾,开发出一套性能稳定的超高密度水泥浆体系。该体系采用粒径为0.154 mm、0.076 mm及0.03 mm的密度为7.0 g/cm3的铁粉,按照2∶1∶3的比例复配作加重材料,液固比取0.23~0.28时,加重材料加量为180%~390%(BWOC)时均可使水泥浆密度达2.80 g/cm3;选用胶乳作悬浮剂,其不但增大了浆体的悬浮能力,而且具有一定降失水性能。该水泥浆在30℃、常压条件下的48 h抗压强度大于14 MPa;失水量控制在50 m L以内;沉降稳定性好,上下密度差最大为0.028 g/cm3;防窜系数SPN小于3,满足了现场施工需求。研究了该超高密度水泥浆的现场混配工艺。该技术在文72-421井获得了成功应用,固井质量优良率为100%,为复杂高压油气井固井提供了技术支撑。

Study and Application of Ultra-high Density Cement Slurry

An ultra-high density cement slurry was formulated with iron powder (density 7.0 g/cm3) of different particle sizes 0.154 mm, 0.076 mm and 0.03 mm in a ratio of 3:2:1, and latex suspending agent and liquid additives. This cement slurry has density of 2.82 g/cm3 and good suspending capacity, with density difference between the top and the bottom slurry of equal to or less than 0.028 g/cm3. At 30℃ and ambient pressure, the set cement has compressive strength of 14 MPa after aging for 48 h. API filter loss can be controlled to less than 50 mL. SPN of the cement slurry is equal to or less than 3. This high density cement slurry was used successfully in the cementing operation of well Wen72-421, in combination with a special cementing technology for high density cement slurry.