Swellable elastomer packers are the preferred choice for openhole zonal isolation for many applications due to their cost-effective and interventionless deployment. For drilling long laterals, customers prefer to drill in oil-based muds (OBM) because the OBM acts as a lubricant and helps deeper and faster drilling. The swell packers are deployed in OBMs up to total depths (TD) of 36,000ft and require sufficient time to run liner to bottom, pull out of hole with running string, and run a displacement string to total depth (TD) to displace the OBM mud to a completion brine and breaker prior to the swell packer contacting the 8.5-in. open hole. Thereafter, upon exposure to produced or injected fluid, the packer must hold pressure to a wash out an openhole diameter of 9 in. > 1,000psi. Commercial oil swell packers meet the differential pressure requirements, however, their fast swell rate, especially in high-temperature applications, presents a significant challenge in getting these packers to the required depth/distance. In this paper we report the development and testing of 11-day delay oil swell packers to compartmentalize an 8.5-in. openhole, seal a 9.25-in. washout zone, and hold a minimum differential pressure of 1000psi at 220° F. Swell delay was conducted on 20-in. × 8.15-in. OD donuts (dunk packers) on a base pipe 6.625-in. OD in oil-based mud (NAF) at 200 to 207° F. Pressure testing was performed as per API190H standard on packers (4 ft × 8.15 in. and 5.5 ft × 8.15 in.) on a 6.625-in. base pipe that was pressure tested at 225° F by applying pressure from top and bottom annulus. These packers held a steady differential pressure of 1100 to 1300 psi for 30 minutes. This development enhances the ability to reliably compartmentalize larger open holes with potential washout sections by using a delayed swell oil packer.
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.
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