An Enhanced Microfine Cement Design for Special Squeeze Applications

Abstract

A new and enhanced microfine cement system is presented in this paper which can be used in challenging cement squeeze applications. There are numerous cement squeeze jobs conducted during workover operations every year within the State of Kuwait to prevent water influx. A very common challenge encountered during these applications is either low or no injectivity scenarios. Conventional cement slurries at 15.8-lb/gal density have more often than not resulted in failures while performing post job positive and negative pressure tests, even when the pressure tests are repeated multiple times. These failures can often be attributed to the fact that effective squeezing is not possible due to the larger cement particle size across a limited number of perforations due to early bridging of the cement. Similarly, conventional microfine cement systems which have also been used in these applications have had only limited success. To overcome these challenges, an improved and enhanced microfine cement design has been developed which is able to obtain higher compressive strengths at lower slurry densities (e.g. 12.5 to 13.0 lb/gal) versus the 15.8-lb/gal conventional slurries. This microfine cement design can be further modified to be used in high, low, and zero injectivity scenarios. It possesses several unique features including thixotropic, expansion, anti-gas migration, and strength retrogression properties. Initial field trials of the system have been very successful. The application of conventional microfine slurry systems in low injectivity scenarios is relatively common in the industry; however the enhanced microfine slurry design can be utilized in a variety of injectivity scenarios, or even in loss situations across perforations, casing leaks, or across the casing shoe. The new microfine cement slurry design has the potential of avoiding multiple squeeze jobs by achieving successful positive and negative pressure test results in a minimum number of attempts.