Have you ever wondered what tests you should (or could) ask the lab to run when you are preparing for a cement job? Have you ever been part of an argument around a lab test result because it may or may not reflect the conditions of your current well?
API STANDARDS
All operators around the world refer to lab procedures specified by the American Petroleum Institute (API) standards, most of which are also International Standard Organization (ISO) procedures today.
These standards don’t cover all available test apparatuses widely used today, but they offer a way “to promote standardization and uniformity and to eliminate discrepancies and misunderstandings relative to cement slurry behavior in the laboratory as well as in actual cementing operations.”
The norms are not an invention of recent days. They were a result of close collaboration between O&G operators and their service companies with the API organization. They reflect the newest advances in slurries evaluation and the current tendencies as a basis for the design of competent cement systems for well integrity.
API AND ISO PRACTICES AND STANDARDS
Along the years, the API continue to develop standards to cover other aspects of the cementing process, below is a list of the recommended API and ISO practices and standards related to cementing lab testing as they exist today:
- API RP 10B-3 (ISO 10426-3) Recommended Practice on Testing of Deepwater Well Cement Formulations
- API RP 10B-4 (ISO 10426-4) Recommended Practice on Preparation and Testing of Foamed Cement Slurries
- API RP 10B-5 (ISO 10426-5) Recommended Practice on Determination of Shrinkage/Expansion of Well Cements.
- API RP 10B-6 (ISO 10426-6) Recommended Practice on Determining the Static Gel Strength of Cement Formulations.
- API 10A Specification for Cements and Materials for Well Cementing.
ARE ALL THESE STANDARDS UP FOR USE EVERY TIME YOU PREPARE FOR A CEMENT JOB?
- The short answer is: No.
Two of these standards aim at certain types of operations:
- Standard 10B-3 is specific to wells in deep-water environments, addressing the cool-down effect caused by low seabed temperatures.
- Standard 10B-4 is specific for wells where foam cement will be used. Foam cement is used to address cementing across low frac gradient formations.
The other two standards are intended to address wells that suffer from two particular kinds of downhole conditions:
- Standard 10B-5 aims to measure and control cement changes in volume after setting. Typically measured in wells where expanding agents were added to the cement slurry (to obtain about 1% radial expansion after setting and sealing micro-annulus) or wells that are susceptible to the creation of micro-annuli due to the cement natural contraction (4 to 6%).
- Standards 10B-6 is intended to evaluate the slurry ability to provide gas migration control. The test assesses the ability of the slurry to control gas percolation during the transition time (change from liquid to gel/solid). During the transition time, the slurry loses its ability to transmit hydrostatic pressure to the formation when gels exceed 100 lbf/100ft2 making it susceptible to gas invasion. Then, when gels reach 500 lbf/100ft2, the slurry regain enough resistance to prevent gas migration. If the transition from one gel strength to the other happens quickly enough (< 45 mins) the risk of gas migration is considered negligible.