A method for delivering a chemical composition downhole into a wellbore includes forming a cylindrical body including a treatment chemical, where the cylindrical body includes a flow channel therethrough. The method further includes positioning the cylindrical body into a fluid conduit of a wellbore, and flowing a release fluid through the flow channel to release at least part of the treatment chemical into the release fluid. The release fluid causes the release of the treatment chemical by dissolving the chemical, and/or by removing a coating on the chemical through dissolution, response to pH adjustment, and/or response to an abrasive material in the release fluid. Examples of a treatment chemical include a cross-linker, breaker, fluid loss pill agent, and an encapsulated chemical.