# Preparation and Performance Evaluation of Gelled Composite Plugging Agent Suitable for Fractured Formation

## TL;DR

This paper introduces a new composite plugging agent that effectively seals fractures in drilling by combining rigid particles, elastic gel, and fibers.

## Contribution

A novel ternary composite plugging agent is developed with enhanced pressure-bearing capacity and adaptability for fractured formations.

## Key findings

- The rigid/elastic/fiber composite system showed the best plugging performance with 13 MPa pressure-bearing capacity.
- The optimal formulation achieved low fluid loss and high temperature resistance up to 180 °C.
- The composite agent demonstrated good compatibility with drilling fluids and adaptability to fracture roughness.

## Abstract

Lost circulation in fractured formations is a common yet challenging technical problem in drilling engineering. Conventional plugging methods often form sealing layers with poor stability and low pressure-bearing capacity. This study developed an efficient composite plugging agent composed of calcite particles (rigid particles), elastic gel particles, and polypropylene fibers. Utilizing a laboratory-scale fracture plugging evaluation apparatus and standard comparative experimental methods, the synergistic plugging effects of different composite systems were investigated. The results indicate that while single rigid particles can form a basic bridging structure, the pressure-bearing capacity of the resulting sealing layer is limited. Single elastic gel particles or fibrous materials struggle to effectively plug fractures of varying widths. Composite use of the plugging agents significantly enhanced the plugging performance, with the rigid/elastic/fiber ternary composite system demonstrating the best results. The optimal formulation (5% calcite particles + 3% elastic gel particles + 2% polypropylene fibers) achieved a plugging pressure-bearing capacity of 13 MPa for 2 mm-wide fractures, with a fluid loss of only 50 mL and temperature resistance up to 180 °C. Furthermore, the composite plugging agent exhibited good compatibility with the drilling fluid system and demonstrated excellent adaptability and plugging performance for fractures with different roughness levels, indicating promising potential for field application.