Ultralightweight Cementing Technology Sets World Record for Liner Cementing With a 5.4 lbm/gal Slurry Density

摘要

In an effort to meet increased demand for petroleum products, operators are drilling in more challenging environments. In Mexico, meeting the new challenges is requiring more skills and innovative materials from oilwell cementing providers. Nowhere else in the world have service providers attempted cementing across more depleted zones or weaker formations. Current cementing technology may not ensure successful circulation and an effective seal, which can have a great impact on (1) the cost of drilling a well and (2) the productive life of the well. In addition to the easily quantified cost of often-required remedial work, additional costs that are more difficult to quantify can be incurred from delays in production delivery and early water production. Traditionally, the industry has relied on two very different technologies for the creation of ultra-light (densities < 10 lb/gal) cement slurries. The current technology involves either (1) the creation of a foamed cement using nitrogen or (2) the addition of lightweight microspheres (LMS) (sg < 1.1) into the cement. While both of these technologies are capable of producing very light cement slurries, neither of them has been used in an oil well to form an effective seal at densities below 7.3 lb/gal. In these most difficult Mexican formations where fracture gradients range from 7.3 down to 6 lb/gal, current cement densities of 7.3 lb/gal or greater have reduced chances of successful circulation. This paper presents case histories from Mexico showing how a melding of both of these technologies, foam and microspheres, were required to stretch current lower slurry-density limits, allowing us to meet extreme operational demands. Along with the case histories and laboratory data, guidelines are provided for the best use of these technologies at densities down to 5 lb/gal. Details provided from the case histories illustrate how the advantages of both technologies were maximized, while their limitations were minimized.