鲁迈拉油田易漏层固井技术研究与应用

Cementing of Wells with Lost Circulation in Rumaila Oilfield

鲁迈拉油田地质条件复杂,此区块的Dammam、Hartha层位地层破裂压力低,技术套管固井易发生漏失,而且地层岩性导致井眼不规则,存在大肚子和缩径井眼,固井顶替效率低,使固井质量难以保证。研制了密度为1.00～1.80 g/cm3的低摩阻塞流前置液体系,该体系以非聚合物类悬浮剂DF-1和冲洗剂DF-3为主剂,用有机溶剂DF-4作流型调节剂,可降低前置液环空循环摩阻,具有冲洗能力强、流变性可调性好的特点,提高了低返速条件下环空顶替效率。研制了密度为1.00～1.35 g/cm3的低密度水泥浆体系,该体系采用纳米硅溶胶作稳定剂,提高了沉降稳定性,体系48 h室温抗压强度大于14 MPa。优化了一系列固井配套技术,形成一套适合该区块的综合固井技术。现场试验5口井,无漏失发生,固井质量合格井段较之前提高了21%,取得了良好的应用效果。

Low fracturing pressures of the Damman and Hartha formations in the Rumaila Oilfield have been causingmud losses in cementing the technical casing strings. The existence of borehole wall washout(erosion) and tight holes have resulted in poor cement slurry displacement. To overcome these problems, a plug flow low friction prepad fluid has recently been developed. This prepad fluid, having densities between 1.00 g/cm3 and 1.80 g/cm3, was formulated with non-polymeric suspending agent DF-1, flushing agent DF-3, and organic solvent, DF-4, as flow pattern modifier. It has low flow friction, high flushing performance and easy-to-control rheology, which help improve the displacement efficiency of cement slurry at low flow rates. A low density(1.00–1.35 g/cm3) cement slurry was formulated with nano silicon sol as the stabilizer to improve the settling stability of the slurry. The compressive strength of the set cement at room temperature after 48 h is greater than 14 MPa. Cementing techniques using the prepad fluid and the cement slurry were developed as guidance for proper field operation. The prepad fluid and the cement slurry have been successfully used on 5 wells, with no lost circulation. Number of well sections cemented with acceptable job quality is increased by 21%.