Hexion
Fall 2008
 
fracline
 
Low Temperature Applications of
Resin Coated Proppants

Decreased productivity due to loss of conductivity in the fracture is an important consideration in lower temperature applications. For the past twenty-five years, external chemical activators have been used to effectively shorten the consolidation time for curable resin coated proppants (RCPs) at temperatures below 140°F (60°C). However, it is common practice in many field applications to flow wells back immediately following the completion of the hydraulic fracturing operation. In this situation, external chemical activators can be run with curable RCPs even at temperatures up to 160°F (71°C). Without the use of an external chemical activator, proppant pack consolidation strength development of conventional partially cured phenolic resin proppants in water at temperatures below 140°F (60°C) can take up to five days as the temperature approaches 100°F (38°C). This bond strength development is dependant on proppant mesh size, which directly correlates to the number of contact points within the proppant pack.

Low Temperature Areas
Key areas where large amounts of RCPs are used at low temperatures include: the Permian Basin in West Texas and New Mexico; Alaska; Northeast U.S.A.; Alberta, Canada and western Siberia in Russia. The combination of shallow depths and water flooding or CO2 flooding of mature oil producing reservoirs provides challenges that make it difficult to develop the necessary proppant pack bond strength without the aid of an external chemical activator.

Chemical Activators
Most field strength chemical activators contain a flammable solvent component that helps initiate the bond of the phenolic resin coating where the grains contact, and also helps provide lower freeze points for the activator material during storage. The addition of chemical activator to the proppant slurry requires frac fluid compatibility testing to ensure that the fluid system will perform properly. Also, the excessive use of external chemical activators may cause oversoftening and sloughening of the resin coating.

Internal Activator
In recent years, there have been many advances related to low temperature RCP applications. Although external chemical activator is still a viable option, it is no longer the only solution to proppant pack consolidation issues in the wellbore. Low temperature cure systems have been developed to provide superior proppant pack bond strength without the use of external activation at temperatures as low as 100°F (38°C). To make this possible, the bond strength development curve has been shifted to allow the pack strength to be developed much faster at lower temperatures without the use of the external chemical activator. The upper usable temperature range is still comparable to the standard products used in these closure applications for RCPs. Eliminating the need for external activators not only decreases fracturing treatment complexity, but it also reduces the amount of time, money, and need for chemical transportation as well as the associated potential hazards. With the addition of an external chemical activator, the lower operating temperature limit of this resin chemistry can be extended even further.

Case History: Increase Well Production
A Canadian operator working in the Keg River Formation in Northern Alberta was experiencing proppant flowback and proppant pack consolidation issues in a low temperature 104°F (40°C) well. After switching to SiberProphl™ 20/40 and a slow forced closure at 1-2 barrels/min (6.29-12.58 m3/min), a consolidated proppant pack was formed and proppant returns were greatly reduced. SiberProphl 20/40 is a specially formulated low temperature cure resin system designed to bond without the use of external chemical activators. This frac design modification not only led to a 10-15% production increase in offset wells, but it also reduced the need for workovers and well clean-up.

Case History: Minimize Proppant Flowback
A West Texas operator working in the Permian Basin required a proppant solution that would provide superior bond strength in a low temperature [125°F (51°C)] and low pressure [5,000 psi (35 MPa)] environment. They elected to use approximately 160,000 lbs (72,575 kg) of SB Excel™ 20/40 with Activator (1% Activator loading) per stage. This activated proppant used in conjunction with a slow forced closure allowed the stress bond resin system to activate. As the fracture closed and exerted a differential pressure on the proppant pack, grain-to-grain bonding occurred. This operator has used this stress bond resin system on over 45 wells in the Clearfork formation to substantially reduce proppant flowback, as well as minimize the need for well clean-up.

 
 
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