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 compressive strengths, increased quality of coating, greater chemical and thermal stability and higher permeability of the consolidated gravel. These results have been obtained by using higher quality gravel, an important coating process and improved placement techniques.
Full scale pumping tests and actual results indicate that this system provides a consolidated gravel pack capable of controlling sand provides a consolidated gravel pack capable of controlling sand production without impairing fluid production. The use of this type 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 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 improved plastic coated gravel have increased production and virtually eliminated bailing of sand.
Plastic coated gravel systems were first successfully used during 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 (1–7). All of the systems basically were slurries of gravel and liquid plastic in a viscous carrying fluid such as oil The plastics were commonly epoxies, phenolics or furans which contained a catalyst or accelerator designed to cause the plastic to consolidate the gravel after the slurry was placed in the well. Some systems placed the gravel-plastic-carrying fluid slurry without a catalyst which was followed by an overflush that included a catalyst.
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.
When a screen or slotted liner is used excess plastic may reduce its flow capacity.
Successful placement and consolidation of the gravel depends on accurate measurements of the bottomhole temperature, volume of plastics, 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.
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, these problems are virtually eliminated. The pre-coated gravel can be placed like a 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 bottomhole temperature.
This new and unique approach to obtaining a consolidated gravel pack has many applications in the oilfield. Prepacked screens 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 failure. It can be used in injection and disposal wells as well as thermal are encountered. This material could also be used for repair of cut out liners and for placement of gravel packs in short lap situations.
The purpose of this paper is to present findings that show that parameters which affect the performance of consolidated gravel packs parameters which affect the performance of consolidated gravel packs formed using a pre-coated gravel. Parameters such as compressive strength and permeability have been shown to be a function of both resin concentration and gravel mesh size. Setting conditions have also been shown to be an important factor in the effectiveness of this type of system. Production data has shown that even in some of the most severe conditions, a pre-coated gravel can provide a consolidated gravel pack which can control sand production.
One of the most apparent uses of pre-coated gravel is for sand control in injection or disposal wells. Such wells often require sand control when they are backflushed or shut-in to prevent the wellbore from filling with sand. However, during longer term injection of fluids a conventional gravel pack may be destroyed either due to imperfect packing of the gravel when it was installed or softening of the formation sand by dissolving the natural cementing agent and pushing the formation sand away from the wellbore.
Several injection wells have now been successfully packed with precoated gravel around a wire wrapped screen using a gelled brine precoated gravel around a wire wrapped screen using a gelled brine slurry packing placement technique. Some of these wells have now been on injection for over a year with good injectivity or sand problems. problems.