As the global demand for energy increases, operators are being forced to drill in increasingly challenging environments. In the northeastern United States, that often means exploring unconventional reservoirs such as the Devonian Shale or lower-pressured sandstone reservoirs such as the Big Injun or Berea sands (and drilling through the associated Sunbury Shale). Economic limitations in these areas often require operators to attempt single-stage production cement jobs with associated fills of 3,000 ft or more. Achieving zonal isolation above these low-pressure zones requires low-density cements that are pushing the limits of current cementing technology. If the cement is made light enough to circulate, but cannot withstand the stress of fracturing or other downhole conditions, the initial seal will only be temporary. If cement cannot be successfully circulated or fails to function shortly after placement, this can have a great impact on drilling costs usually designed with very tight economic constraints and can cause delays in production delivery because of required remedial work. Most of these wells require stimulation treatments to become economical producers. If zonal isolation is not initially achieved, remedial work may not be enough to effectively isolate the downhole formations, resulting in a complete loss of the well or zones within the well. Historically, lightweight slurries have been applied in these reservoirs in an attempt to successfully achieve zonal isolation in both single- and multiple-stage cement jobs; however, previous cement solutions were found to be lacking in one way or another. Problems ranged from price to poor bonding results, poor zonal isolation, or more typically designed cement fills not being attained.

As cementing solutions become more advanced in technology, the associated costs often increase. When choosing a cementing solution, the operator should balance price with the potential well productivity and the cost of using a cheaper solution. In this case study, we examine various examples where an effectively priced, high-quality, low-density cement was used to overcome numerous cement challenges, delivering zonal isolation that can allow effective post-cementing stimulation treatments that result in a positive return on investment (ROI).

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