Degradable Thermoset Composite Frac Ball for Offshore Well Stimulation

Abstract

Degradable frac balls are used widely in unconventional stimulation operations for sleeve activation. The objective of this work was to develop a new degradable frac ball product for challenging offshore multistage fracturing systems where conventional degradable metal frac balls have challenges due to high hydrostatic pressure or lack of suitable degradation fluid. The scope of work included creating a new blend of material and accompanying test methods to meet application requirements. These requirements were that the degradable frac balls i) exhibit no degradation in the ball launcher during stimulation operations, ii) are able to degrade at high pressures (up to 15000 psi) in the presence of oil below the ball and iii) create by-products that do not plug or adversely affect the completion/production. In this paper, we report the development and testing of thermoset polymer composite balls designed primarily for offshore well stimulation applications. This polymer consisted of a cyanate ester thermoset composite that exhibited excellent mechanical properties (compressive strength 37 ksi; tensile strength 14 ksi and tensile modulus 2 Msi). Frac balls with sizes ranging from 1.30″ to 3.18″ were compression molded and pressure tested to ensure a pressure differential rating of 5,000 psi across a ball seat with approximately 0.16 % engagement at 150°F. This material was found to degrade in fresh water and various brines when exposed for two or more days at temperature>250°F, making it applicable to deep-water completions. The residual products of the degraded composite balls were tested for production screen plugging and demonstrated no risk of plugging to the test equipment. These results demonstrate the feasibility of this new material to be used for deepwater hydraulic fracturing operations.