1.15 g/cm^(3)超低密度水泥浆的研究与应用

Study and Application of an Ultra-Low-Density Cement Slurry

针对鄂北工区低压、易漏失地层的固井难题,中原固井公司通过研发轻质水泥,优选高强空心玻璃微珠减轻材料,与超细微硅进行级配,建立三级级配模型,确立了超低密度设计构架。选用AMPS类降失水剂、低密度增强剂、早强剂、缓凝剂等外加剂优化浆体性能,研究出一套高强度超低密度水泥浆配方,该水泥浆适用温度为60~120℃,密度为1.15 g/cm^(3),失水量为40~42 mL,游离液量不大于1.0%,稳定性密度差为0,300 min内稠化时间可调,呈直角稠化;常压40℃下72 h水泥石抗压强度为12.1 MPa,满足现场施工需求。开展混拌工艺研究,建立了分级混拌工艺,混拌大样与小样水泥浆性能符合率达到了98%,保证了水泥浆性能的稳定。通过在鄂北大牛地区块D12-P42、D17-2及DK13-FP1井等3口井的应用,固井过程中没有发生漏失,固井质量合格率为100%,实现了井筒的完整性,为低压易漏地层固井提供了技术支撑。

To successfully cement wells penetrating low-pressure easy-to-leak formations in Ebei(north Hubei)area,Zhongyuan Well Cementing Company has developed a high strength ultra-low-density cement slurry suitable for use at temperatures between 60℃and 120℃.The cement slurry was formulated with self-developed light-weight cement,high strength hollow glass beads(as light-weight material)and ultra-fine silica powder.With this three-level grading model,an ultra-low-density design framework was established.The performance of the ultra-low-density cement slurry was optimized with AMPS filter loss reducer,low-density strength enhancer,early-strength agent and retarder.The cement slurry had density of 1.15 g/cm^3,filtration rate of 40–42 mL,free water of less than 1.0%,density difference of 0,and adjustable thickening time below 300 min.The thickening curve was right-angled.At atmospheric pressure and 40℃,the set cement had 72 h compressive strength of 12.1 MPa,which satisfies the needs of field operation.Staged mixing procedure was adopted in mixing the cement slurry.98%of the bulk slurry samples had properties very close to the properties of the slurry samples made in laboratory,indicating that the cement slurry had stable properties.In cementing the well D12-P42,well D17-2 and well DK13-FP1 in Daniu block(north Hubei)with the ultra-low-density cement slurry,no loss of cement slurry happened,and pass rate of the cementing job quality was 100%,realizing the borehole integrity expected.The successful application of the ultralow-density cement slurry has provided a technical support to cementing wells penetrating low-pressure easy-to-leak formations.