超细低密度水泥浆的研制及其应用

LG地区“三高（高压、高含硫、高危）”气井封固段长，复杂井眼条件下的固井给水泥浆提出了更高的要求，常规低密度水泥浆体系不能满足封固质量的要求。为此，提出引入超细水泥、微硅等材料，实现多元颗粒级配，优化各组分的粒度分布，提高密实程度使水泥浆的各项性能得到了较大的提高。水泥浆密度为1.20~1.50 g/cm3，具有良好的流变性，较短的稠化过渡时间；静胶凝强度发展形态好，具有良好的防气窜性能；API失水量小；水泥石具有高早期强度；更低的渗透率和良好的防漏堵漏功能等特点，井底压力条件下水泥浆密度恒定不变，其各项指标达到了常规密度水泥浆性能的水平。现场应用20余口井次，测井曲线显示固井质量良好。

Development of superfine and low-density cement slurry and its application in the LG gas field

The sections to be cemented in "three highs (high pressure, high H2S, highly risk)" gas wells at the LG gas field are normally long, the hole conditions are complicated for cementing job, which therefore exerts high requirements on cement slurry systems. The conventional low-density slurry cannot meet the cementing quality requirements. Therefore the superfine cement and the micro-silicon are introduced, and the performance of the cement slurry is largely improved through multiple grain gradation, and optimization of the grain-size distribution of each component, thus making the system more closely-grained. This system with a density of 1.20 - 1.50 g/cm~3 has the properties of good rheology, short thickening time, good gel strength development pattern, high gas-channeling prevention capability and low API water loss. The cement stones formed have high and early strength, lower permeability and better loss-prevention and plugging capability. And the density of the slurry system will be kept constant under the pressure of bottomhole, all other indexes are equivalent to those of the cement slurry with conventional density. The log curves of all applications in more than 20 wells show good cementing quality.