窄密度窗口正注反挤低密度水泥浆固井技术

针对西南油气田分公司蓥北1井φ273.05 mm套管固井存在漏层多、分布广，油气显示活跃，低温低密度水泥浆强度低及发展慢等固井难题。开发出了密度为1.23 g/cm3的高强度韧性防窜低密度水泥浆体系，该体系稠化时间可调，静胶凝强度发展快，62℃下440 min即起强度、24 h强度高达14.5 MPa，弹性模量为5.8 GPa。通过采用低密度高强度韧性防窜水泥浆、抗污染冲洗隔离液技术、软件模拟、优化浆柱结构、结合低密度与常规密度正注和反挤等配套技术，确保了蓥北1井φ273.05 mm套管固井施工安全，固井质量合格率为85%、优质率为65%。为西南油气田窄密度窗口固井提供了技术参考。

Normal Spotting and Reverse Squeezing of Low-density Cement Slurries in Wells with Narrow Safe Drilling Windows

The φ273.05 mm section of the well Yingbei-1 (Southwest Oilfield) penetrated formations with widely distributed thief zones and active oil and gas zones. Low density low temperature cement slurries used in previous cementing operations had low strength and slow hardness development. To address these problems encountered, a high strength low density (1.23 g/cm3) cement slurry with high toughness and the ability of anti-channeling has been developed. This cement slurry has thickening time that is adjustable and fast developed gel strength. The strength of the cement slurry develops after 440 min at 62℃, and reaches the maximum value of 14.5 MPa after 24 h. The elastic modulus of the cement is 5.8 GPa. Using this cement slurry with other technical measures, such as contaminationresistant flushing spacer, software simulation, optimization of the structure of the cement slurry column, and normal spotting/reverse squeezing etc., the φ273.05 mm casing string was successfully and safely cemented. Rate of certified job was 85% and rate of quality job was 65%. The technology used in cementing the well Yingbei-1 has provided a technical reference for cementing wells with narrow safe drilling windows in southwest oil and gas field.