Ongoing Development of Cementing Practices and Technologies for Kuwait Oil Company's Deep HP/HT Exploration and Gas Wells: Case History

Abstract

Summary Exploration activities in Kuwait have been focused on the search for high-quality oil from the Jurassic formations and gas in the Triassic/Permian series. The wells drilled to these prospects are very challenging because of high-pressure/high-temperature (HP/ HT) conditions, large casing sizes, oil-based mud, the presence of high levels of H2S and CO2, and a narrow pore-/fracture-pressure window. In particular, the cementing of the deep strings in these wells has been extremely challenging. Over the last 8 years, a concentrated effort has been made to introduce new technologies and materials to improve the cementing practices both from operational and safety aspects. In 2003, the success ratio for deep cementations was highly variable. The Kuwait Oil Company (KOC), along with one of their cementing service providers, worked on a series of changes to practices and materials with the aim of improving job quality with high repeatability. This was based primarily on the technologies being developed in HP/HT wells around the globe, especially in the North Sea, and it resulted in a notable improvement in cementing performance. Technologies and practices that had been developed include spacer technology, application of synthetic retarders, fluid-loss and antigas-migration additive improvements, development of finegrained weighting additives, use of HP/HT rheometers, systematic product control, the minimizing of handling, and safer mixing practices at the wellsite. This paper will discuss the application of these technologies, materials, and practices over an 8-year period as a case history to illustrate the improvements made in achieving consistent cement quality and final slurry placement for the deep-casing and liner strings, and will conclude with recommendations and lessons learned during this process.