Abstract
American Petroleum Institute (API) has led for more than 85 years the development of equipment and operating standards in petroleum and petrochemical industries. API maintains 685 standards and recommended practices which have been also followed by international organization for standardization (ISO). Currently, there are no established guidelines in the industry to evaluate stability of cementing-mix fluids with time prior to mixing and pumping with cement.
API specification is not the same as API recommended practice. Specifications apply to pure materials while recommended practices are used on daily basis for cement slurries. Recommended practices can be modified and altered to be more suitable to field cementing operations and this is the main topic of this paper, to establish guidelines addressing stability of mix fluid in terms of thickening time, fluid loss, and most importantly the stability of latex and polymers within the mix fluid to ensure proper resistance against temperature and pressure cycling. To the best of the authors’ knowledge this is the first study to establish such guidelines.
API objective is to have a group of tests that produce consistent, reproducible results from test to test and from one lab to another. API only consider small part of testing so we should not be disqualifying additional tests because they are not API.
In addition to standard tests such as thickening time, rheology, and fluid loss. New and quick tests were designed to evaluate polymer and latex stability within the mix fluid that can be performed in a quick and an effective way to support the operator decision of dumping or maintaining the mix fluids with time for the cementing operations. Such a critical decision can not only be achieved by the standard API testing such as thickening time, rheology, fluid loss, etc. The consequence can definitely affect wellbore isolation and well performance. If the stability is not tested properly, then the cementing pumping operations can be achieved however we might end up with improper zonal isolation when changing mud weight or conducing fracturing operations.
