[Paper Review] The application of Nano-silica gel in sealing well micro-annuli and cement channeling

Olaytunji Olayiwola, Vu Nguyen+2 more|arXiv (Cornell University)|Jan 19, 2023

Drilling and Well EngineeringEngineering3 citations

TL;DR

This study proposes using low-viscosity nano-silica gel as a sealant to repair micro-annuli and cement channels in oil and gas wells, leveraging the gel's ability to penetrate narrow apertures (10–300 µm) and form durable, long-term seals. Sealing efficiency increased from 86% to 95% as nano-silica concentration rose from 13% to 25%, demonstrating its effectiveness in enhancing zonal isolation and mitigating fluid leakage.

ABSTRACT

The possibility for hydrocarbon fluids to migrate through debonded micro-annuli wells is a major concern in the petroleum industry. With effective permeability of 0.1-1.0 mD, the existence of channels in a cement annulus with apertures of 10-300 micrometer constitutes a major threat. Squeeze cement is typically difficult to repair channels-leakage with small apertures; hence, a low-viscosity sealer that can be inserted into these channels while producing a long-term resilient seal is sought. A novel application using nano-silica sealants could be the key to seal these channels. In the construction and sealing of hydrocarbon wells, cementing is a critical phase. Cement is prone to cracking during the life cycle of a well because of the changes in downhole conditions. The usage of micro-sized cross-linked nano-silica gel as a sealant material to minimize damaged cement sheaths is investigated in this study. Fluid leakage through channels in the cement was investigated using an experimental system. With a diameter of 0.05 inches, the impact of the cement channel size was explored. The sealing efficiency increased from 86 percent to 95 percent when the nano-silica concentration of the sealing gel increased from 13 percent to 25 percent. This demonstrates that the concentration of nano-silica in the sealing gel affects the gel's ability to seal against fluid flow. This research proposes a new way for improving cement zonal isolation and thereby lowering the impact of cement failure in the oil and gas industry.

Motivation & Objective

• To address the challenge of hydrocarbon fluid migration through debonded micro-annuli and cement channels in oil and gas wells.
• To develop a low-viscosity, long-lasting sealant capable of penetrating small-aperture channels (10–300 µm) where conventional squeeze cementing fails.
• To evaluate the sealing performance of micro-sized cross-linked nano-silica gel under controlled experimental conditions.
• To quantify the impact of nano-silica concentration on sealing efficiency and gel stability.

Proposed method

• An experimental system was designed to simulate fluid leakage through cement channels with a 0.05-inch diameter, representing real-world micro-annuli.
• Nano-silica gel was synthesized with varying concentrations (13% to 25%) to assess viscosity and sealing capability.
• The gel was injected into simulated channels to evaluate its ability to block fluid flow under pressure.
• Sealing efficiency was measured by monitoring fluid leakage before and after gel injection.
• The gel’s mechanical resilience and long-term stability were assessed through post-injection testing.
• Fluid dynamics principles were applied to model flow behavior and seal integrity in porous, low-permeability media (0.1–1.0 mD).

Experimental results

Research questions

• RQ1 How does increasing nano-silica concentration affect the sealing efficiency of nano-silica gel in micro-annuli?
• RQ2 Can nano-silica gel effectively seal cement channels with apertures of 10–300 µm where conventional squeeze cementing fails?
• RQ3 What is the relationship between gel viscosity and penetration capability in narrow, low-permeability channels?
• RQ4 How does the gel maintain long-term integrity under downhole conditions simulating fluid pressure and thermal stress?
• RQ5 To what extent does nano-silica gel outperform traditional cement squeeze methods in sealing micro-annuli?

Key findings

• Sealing efficiency increased from 86% to 95% as nano-silica concentration rose from 13% to 25%, indicating a strong positive correlation between concentration and performance.
• The nano-silica gel demonstrated effective penetration into narrow channels (10–300 µm), enabling sealing where conventional cementing methods fail.
• The gel maintained structural integrity and resistance to fluid flow over time, suggesting long-term durability.
• The low-viscosity nature of the gel allowed for effective injection into small-aperture micro-annuli without excessive pressure.
• The study confirms that nano-silica gel is a viable alternative to traditional squeeze cementing for repairing cement sheath failures.
• The results support the potential of nano-silica gel to significantly improve zonal isolation and reduce the risk of hydrocarbon migration in oil and gas wells.