Preparation and Performance Evaluation of a Supramolecular Gel Plugging Agent for Severe Lost Circulation Gas Reservoirs

TL;DR

A high-strength supramolecular gel is developed to effectively plug fractured gas reservoirs with severe lost circulation during drilling and production.

Contribution

A novel supramolecular gel plugging agent is synthesized with high compressive strength and excellent viscoelastic recovery for severe lost circulation.

Findings

The gel achieves plugging efficiencies over 95% for cores with permeabilities from 0.18 to 0.90 μm².

The gel exhibits a compressive stress of 1.43 MPa at 87% strain while maintaining structural integrity.

Swelling follows a non-Fickian mechanism due to synergistic water diffusion and polymer relaxation.

Abstract

The plugging of fractured gas reservoirs with severe lost circulation during oil and gas drilling and production has long been challenged by technical issues such as low plugging strength and short effective duration. This paper reports the preparation of a high-strength supramolecular gel plugging agent via micellar copolymerization based on the synergistic effects of hydrophobic association and hydrogen bonding. Systematic optimization determined the optimal synthesis formula: acrylamide (AM) 12%, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) 2%, stearyl methacrylate (SMA) 0.4%, sodium dodecyl sulfate (SDS) 1.5%, and potassium persulfate 0.3%, with a reaction temperature of 60 °C. Performance evaluations revealed that the gel possesses a controllable gelation time (120 min) and excellent viscoelastic recovery properties. At a compressive strain of 87%, the compressive stress reached 1.43 MPa while maintaining structural integrity. Swelling behavior analysis indicated that the gel follows a non-Fickian diffusion mechanism, with its swelling process governed by the synergistic interplay of water molecule diffusion and polymer network relaxation. Core plugging experiments demonstrated that the gel achieved plugging efficiencies exceeding 95% for cores with permeabilities ranging from 0.18 to 0.90 μm2, with a maximum breakthrough pressure gradient of up to 11.48 MPa/m. These results highlight the gel’s efficient and broad-spectrum plugging capability for fractured lost circulation zones. This preliminary study provides experimental foundations for the material design and performance optimization of supramolecular gel-based long-lasting plugging agents for severe lost circulation gas reservoirs, and further field-scale validation is required for engineering application.

Figures