This paper presented at the Fourth Symposium on Formation Damage Control of the Society of Petroleum Engineers of AIME held in Bakersfield, California, January 28–29, 1980. The material is subject to correction by author. Permission to copy is restricted to an abstract of not more than 300 words. Write: 6200 N. Central Expwy., Dallas, Texas 75206.
Results of field tests and laboratory evaluation have shown that a plastic pre-coated gravel system is a successful method of sand control for both non- thermal and thermal wells. Significant improvements in this process have been made which provide higher compressive strengths, increased quality of coating, greater chemical and thermal stability and higher permeability of the consolidated gravel. These permeability of the consolidated gravel. These results have been obtained by using higher quality gravel, an improved coating process and improved placement techniques. placement techniques. Full scale pumping tests and actual field results indicate that this system provides a consolidated gravel pack capable of controlling sand production without impairing fluid production. The use of this type of material even prior to the improvements has provided good sand control in both injection and provided good sand control in both injection and production wells in the offshore Gulf Coast region for over production wells in the offshore Gulf Coast region for over a year. Field results in the San Joaquin Valley, California have demonstrated that it is also well suited for sand control in moderate temperature thermal wells. Wells using both steam drive and huff-and- puff methods of stimulation which have employed this puff methods of stimulation which have employed this improved plastic coated gravel have increased production and virtually eliminated bailing of sand. production and virtually eliminated bailing of sand
Plastic coated gravel systems were first successfully used during the 1960's although a moderately successful system of plastic coated walnut hulls was used in the late 1950's. All of the systems basically were slurries of gravel and liquid plastic in a viscous carrying fluid such as a refined neutral oil. Other systems placed the gravel and plastic with diesel oil by pumping at relatively high rates until the pack was complete, then a catalyst solution was injected to harden the plastic after any excess gravel had been removed from the wellbore. The plastics were commonly epoxies, phenolics or furans with plastics were commonly epoxies, phenolics or furans with a catalyst or accelerator designed to cause the plastic to consolidate the gravel after the slurry was plastic to consolidate the gravel after the slurry was placed in the well. placed in the well. Some of the problems with these systems are as follows:
Some liquid plastic from the slurry may be flushed into the formation sand and reduce the permeability of the sand. permeability of the sand.
When a screen or slotted liner is used excess plastic may reduce its flow capacity. plastic may reduce its flow capacity.
Successful placement and consolidation of the gravel depends on accurate measurements of the bottom hole temperature, volume of plastic, volume of catalyst and other ingredients for control and completion of the necessary chemical reaction. It is also critical that no chemical contaminants are present. present.
In slurries that are internally catalyzed there is a possibility of the plastic hardening before it is completely pumped in place.
Externally catalyzed slurries usually require washing out excess gravel from the wellbore before the catalyst solution is injected. This may disturb the gravel and there is always the possibility that some of the plastic may not be completely catalyzed.
With the advent of pre-coated gravel systems, the above problems are virtually eliminated.(8) The pre-coated gravel can be placed like a gravel pack. pre-coated gravel can be placed like a gravel pack. Since this system requires only heat to produce a consolidated gravel pack, no catalyst or additional chemicals are needed. The heat to set the resin coated gravel can be supplied externally by steam generators or hot water or by the natural bottom hole temperature.
This new and unique approach to obtaining a consolidated gravel pack has many applications in the oilfield. Prepacked screens using this material could be used in deviated wells to eliminate the possibility of voids in the gravel pack causing possibility of voids in the gravel pack causing failure. It can be used in injection and disposal wells as well as thermal injection and production wells where moderate temperatures are encountered.
