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.