Ultra-Low-Invasion Non-Damaging Spacer System and Nano-Silicate Based High-Crush Resistant Cement Cures Lost Circulation and Established Well Integrity: A Case Study
Authors: Anwar Rameez , Elmoneim Hossam A. , Ahmed Syed Hamza , Yousuf Arif 
Published: October 2022

The paper presents the design and successful application of an ultra-low invasion non-damaging spacer system followed by nano-silicate based ultra-light cement with high crush strength to produce a competent cement sheath and ensure zonal isolation. The solution was applied in 7inch liner cementing of the candidate well where operator slightly increased the mud weight after gas kick during 8.5inch open hole drilling and encountered total losses. The job was executed with operational optimization and zonal isolation was achieved.

The severe-to-total losses (exceeding 200 bbl/hr) were experienced during drilling and liner running. Consequently, circulation could not be established before job. The ultra-low-invasion non-damaging spacer was designed to create a thin, impermeable shield over the pores and micro-fractures of weak, and under pressured formations through differential pressure. It helped to resume circulation and cement pumping even when equivalent circulating density was exceeding the fracture pressure. The 11.6 ppg nano-silicate based high-crush resistant slurry prevented post-placement losses due to early compressive strength development and provided competent cement bonding. The fluids rheology was optimized, and pumping parameters were adjusted to maintain the primary well control during the cementing operation without compromising displacement efficiency.

The technology was successfully implemented in the 7" liner cementing of the candidate well where cement evaluation was performed using sonic tools. The cement evaluation confirmed the zonal isolation along the open hole section. The proposed solution helped operator to ensure well integrity in troublesome lost circulation zones which posed well control challenges. It was later validated on four additional wells where the job was executed in similar environment and complete cement coverage was achieved in the section. The spacer system is found to be compatible with all common drilling fluid systems and can bypass the narrow restrictions of liner hanger thus offering an additional value over the conventional loss control fibrous materials. The deposited barrier on fluid-rock interface lifts off with the inflow of the well, eliminating the need for acidizing or other matrix stimulation treatments. This helped in formation impairment and simultaneously reducing time to first production. Additionally, nano-silicate based slurry having high-crush resistant lightweight additives maintained stable slurry with good fluid stability, high early compressive strength and improved bonding. Currently, well is open to production with no zonal isolation or cement integrity issues.

The proposed solution will help operators to effectively control losses and enhance zonal isolation in narrow pressure window while achieving the planned cement height along with a competent cement bond. The operators can also avoid the money and time on expensive remedial operations.