一种低温低密度可固化隔离液的研制与性能评价

为适应海上“零排放”的环境保护政策，最大限度减少环空自由套管长度，同时为了提高斜井（尤其大位移井段、水平井段）固井顶替效率，改善固井二界面封固质量，研制了一种低温低密度条件下可固化的隔离液LL-CSF。对其进行性能评价，结果表明：① LL-CSF与钻井液和水泥浆具有良好的相容性，满足固井作业对前置液的要求；② LL-CSF与钻井液和水泥浆的混合液固化体抗压强度达到1.6 MPa以上，且与钻井液的混合液固化体也具有一定的抗压强度；③温度为20℃和40℃时，LL-CSF有利于提高固井二界面抗剪切强度，且40℃下可提高约3倍，但温度超过60℃时则不利于固井二界面胶结；④随着温度和时间的增加，LL-CSF固化体抗压强度先增大后降低，但随着LL-CSF密度的增大，其固化体抗压强度总体呈增大趋势；⑤ LL-CSF固化体具有较好的耐久性和稳定性。LL-CSF固化机理初步认为先是矿渣中富钙相和富硅相分解，然后各种离子和化学键重组而形成相应的水化产物。LL-CSF具有成本低廉、现场实施简便，可满足海洋固井的特殊需求，即在低温（小于40℃）且水泥浆不返到地面而又需要隔离液固化充填的固井中具有一定的应用前景。

Development and Performance Evaluation of a Low Temperature Low Density Solidifiable Spacer Fluid

A low temperature low density spacer fluid LL-CSF has been developed to satisfy the needs of “zero discharge” in offshore operations and to minimize the length of free casing string in annular space. LL-CSF can be used to increase the displacement efficiency in deviated wells (especially in the extended-displacement well section and horizontal section) and improve the cementing quality between the wellbore and the cement sheath. Performance evaluation experimental results showed that: 1) LL-CSF had good compatibility with drilling fluids and cement slurries, and can satisfy the needs of well cementing operations. 2) The solidified mixture of LL-CSF, drilling fluid and cement slurry had compressive strength of greater than 1.6 MPa, and the solidified mixture LL-CSF and drilling fluid also had some compress strength. 3) At 20 ℃, LL-CSF had the ability to increase the shear strength of the interface between the borehole wall and the cement sheath; at 40 ℃, this ability was increased by two times. When the temperature was higher than 60 ℃, the ability of LL-CSF to increase the shear strength of the interface between the borehole wall and the cement sheath was lost. 4) The compressive strength of the solidified LL-CSF first increased and then decreased with temperature and time. The compressive strength of the solidified LL-CSF increased generally with its density. 5) The solidified LL-CSF had good durability and stability. The solidification mechanism of LL-CSF is believed to be the hydration products generated by the re-combination of all kinds of ions and chemical bonds produced by the decomposition of the calcium-rich phase and the silicon-rich phase in the slag. LL-CSF is cheap and easy to use in field operation, and is able to satisfy the needs of well cementing in offshore drilling operations, in which low temperatures (< 40 ℃) are always encountered, the cement slurry is unable to return to the surface and solidified spacer fluid is required to fill the annular space.