Q: What is a resin?
A: Resin is a compound that begins in a viscous (liquid) state and hardens with treatment and/or time. Resins are either synthetic or naturally occurring. A naturally occurring resin is pine sap; synthetic resins are generated in a laboratory. WellLock resin is a synthetic thermosetting polymeric material. There are many classes of resins and many different applications ranging from nail polish to the aerospace industry. The application of WellLock resin is for the oil and gas industry to help provide wellbore architecture integrity. Unlike other resins, WellLock resin is non-flammable and tolerates water. It has been designed to work with aqueous-based fluids (i.e. water-based muds, cement slurries).
Q: What is the specific gravity of WellLock Resin, and what is the density range?
A: The density of the base WellLock resin ranges from 9.2-9.4 lb/gal. With the addition of lightweight additives or weighting agents the density can be adjusted anywhere from 6.5-18.0 lb/gal, respectively.
Q: What is the cost versus the benefit of WellLock Resin?
A: One must consider the cost of remediation and/or alternative annular barriers such as a casing packer. While WellLock resin has a higher cost than conventional cement, a relatively small amount can provide extreme benefit. WellLock resin is an impermeable, flexible barrier with high compressive strength. It is designed to serve as a gas-impermeable barrier to complement the cement sheath or as a means of achieving successful remediation.
Q: What is the wait on resin time with WellLock resin?
A: This is strongly dependent upon temperature and placement time. Low temperatures and long placement times lead to a long wait on resin time (48 hours). High temperatures and short placement times develop strength much faster, and the wait on resin time is reduced (24 hours). In critical applications this should be determined on a case by case basis by measuring the time for strength development of a representative sample. However, if the resin is used as a lead slurry in conjunction with cement, the wait on cement time would take precedence since it is lower in the well bore.
Q: What is the static gel strength, transition time and ability to transmit hydrostatic pressure of the WellLock resin?
A: Unlike cements which exhibit Bingham Plastic or Hershel Bulkley rheological behavior and have a yield stress associated with flow, WellLock resin exhibits much different flow profiles. At low molecular weights or low degrees of crosslinking, resins behave as Newtonian fluids. As molecular weight increases resins behave as power law fluids, until they set into a completely crosslinked three dimensional network. Hence, WellLock resin does not gel but rather builds viscosity, and as a result, transition time is not an appropriate method of measurement for this resin. WellLock resin transmits hydrostatic pressure while it is a viscous liquid until the system reaches a point known as the crossover point where the loss modulus of the material is equal to the storage modulus. Once this point is crossed the WellLock resin begins to take on solid-like behavior allowing the gradual build-up of a pressure gradient across the column of resin. Once fully cured, no pressure is transmitted through the cross-linked resin. Force is balanced by the shear bond of the resin to the formation and the casing.
Q: What happens during the transition time of resin?
A: Since WellLock resin does not gel like cement, the concept of transition time (time from 100 lbf/100 sq ft to 500 lbf/100 sq ft) should be approached in a different manner. For a resin, the transition time could be viewed as the time from the crossover point to full cure. However, in recent experiments, WellLock resin in this state of transformation from a liquid to a solid not only resisted any and all gas influx, but continued to transfer hydrostatic pressure.
Q: How far can resin flow into a small space? And how small is the smallest space it can invade?
A: An unfilled (unweighted) resin can readily penetrate into micro-porous materials. For filled systems (a resin system blended with weighting agents, for instance), the particle size of the filler is the limiting factor since bridging may occur.
Q: What is the influence of temperature on the resin?
A: Increases in temperature increase the reaction rate of WellLock resin leading to shorter pump times but faster compressive strength developments. Also, increases in temperature reduce the viscosity of WelLock resin. The temperature range of WellLock resin is 60°F-200°F BHCT (16°F-93°C). Note, up to 250°F (121°C) for BHST.
Q: Once set, how is the WellLock resin influenced by temperature?
A: Due to its thermal expansion coefficient being greater than both steel and rock, WellLock resin will expand to further seal the well bore. If the temperature exceeds 200°F, there will be little impact on the resin. If the temperature exceeds the glass transition of WellLock resin (300°F), the material will transition into a rubbery like material with low mechanical properties. However, no degradation will occur below 300°F. In addition, if WellLock resin is heated then cooled under pressure it can self-remediate.
Q: What is the effect on WellLock resin of corrosive chemicals and corrosive environments?
A: For a crosslinked and cured resin, there is little effect below the glass transition. Above the glass transition, chemical resistance is lowered.
Q: What is the sensitivity to water and spacers? Is there an issue with the WellLock resin in regards to contact with water?
A: WellLock was designed to have low sensitivity to water and water based fluids. In any case, fluid compatibilities should still be performed.
Q: What is the effect of inefficient well cleaning and poor mud displacement on the WellLock Resin?
A: WellLock resin has been observed to form a competent material with high compressive strength with up to 30% contamination by drilling mud.
Q: Are we able to identify successful placement of the WellLock Resin using a conventional logging tool and log analysis?
A: Yes, conventional acoustic bond logs with ultrasonic pulsed echo tools have been used to log resins, historically. WellLock resin has been run on a UCA to determine the transit time (acoustic impedance) to more fully determine how to interpret the bond log of a well in which WellLock resin has been used.
Q: What is the API standard in regards to resin systems?
A: Currently, API does not have standards regarding resins.
Q: In the past resins were used exclusively for disposal wells using corrosion-resistant casing; can the WellLock Resin adhere to conventional casing?
A: WellLock resin can adhere exceptionally well to conventional casing.
Q: Is there data showing that the WellLock Resin can, in fact, prevent gas migration? What is the testing methodology and what are the results?
A: In pressure transmission experiments with WellLock resin, a gas pressure is applied to a column of resin and pressure transmission is diminished over time. The resin formed a gas (nitrogen) tight seal with a pressure differential of 450 psi.
Q: What considerations should be given during placement operations of WellLock resin?
A: Pump time and compressive strength are not independent of each other. If a long pump time is required, long compressive strength development occurs. This is more dramatic at low temperatures (<125°F) but less of an issue at higher temperatures (>125°F). WellLock resin can be placed using alternative placement methods such as reverse, squeeze, and a cap on the backside. Volumes and mechanical properties should be designed for the challenges of each well.
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