Conversion of Drilling Fluids to Cements With Blast Furnace Slag: Performance Properties and Applications for Well Cementing

Abstract

A new method of obtaining improved zonal isolation using drilling fluid solidification technology has been developed. A water-base drilling fluid is converted into a cement using a hydraulic blast furnace slag. Hydraulic blast furnace slag is a unique material which has low impact on rheologid and fluid loss properties of drilling fluids, can be activated to set in drilling fluids which are difficult to convert to cements with other solidifrcation technologies, is a more uniform and consistent quality product than Portland well cements, and is available in large quantity from multiple sources.Because of its low impact on drilling fluid properties, blast furnace slag may be added to a drilling fluid at low concentrations during drilling operations. The Glter cake and drilling fluid in washed out sections thereby contain a hydraulic materiaL ARer reaching casing point, a mixture of drilling fluid containing chemical activators and higher concentrations of slag may be usedto cement the casing string. Chemical activators from this mixture cause the slag in the filter cake and any bypassed drilling fluid to set. The result is a more complete seal for the annulus. Fluid and hardened solid properties of blast furnace slag and drilling fluid mixturm used for cementing operations are comparable to properties of conventional Portland cement compositions. The design, testing and field application for this technology are similar to conventional cementing methods. Fluids with densities between about 1198 kg/m3 (10 lblgal) and 2397 kg/m3 (20 lblgal) may be prepared. The mixtures have been applied in web where temperatures range from about 4' C (40°F) to 315°C (600°F).This new solidification method provides the proper combination of fluid and solid properties, simplicity of design and application, improved zonal isolation, and broad applicability to bring drilling fluid solidification technology into widespread use.A fundamental weakness of the conventional cementing process is the uncertainty of establishing atrue, reliable seal at the borehole w a l l and cement interface. In many cases, alayer References and tables at end of paper.

Drilling Fluid Conversion: Selection and Use of Portland or Blast-Furnace-Slag Cement

“…Combine drilling mud and required dilution water and mix for 5 minutes; dilution requirements are determined experimentally as described by Cowan et al 3 and Wilson et al 4 Dilution of the drilling mud to achieve an active clay content of 15 to 20 lbm/bbl has been applied as a rule of thumb. (When applicable, add pretreatment materials and mix for 1 hour before next step.)…”

“…However, as a rule, BFS cement can be introduced to drilling muds with less effect on rheological properties and filtrate volume than Portland cement. 3 The additional flocculative effect of Portland cement is the result of the calcium oxide (quicklime) content of the material. If calcium oxide or calcium hydroxide (lime) is used as a BFS activator, flocculation of the drilling mud is nearly identical to that of Portland cement.…”

Solidifying Mud Cake to Improve Cementing Quality of Shale Gas Well: A Case Study

“…As a trail, the technology of mud to cement (MTC) emerged in the early 1990s [17,18]. The integrated solidification and cementation of the cement-interlayer interface were achieved using multi-functional drilling fluid.…”

Cementos petroleros con adición de escoria de horno alto. Características y propiedades

“…La eliminación efectiva de los lodos de perforación y el efecto de la contaminación de la lechada por los lodos de perforación o los lodos de lavado son dos de las variables más importantes que determinan el éxito del aislamiento zonal desarrollado por la capa de cemento. Sin embargo, garantizar estas condiciones es casi imposible (5).…”

“…The efficient elimination of drilling sludge and the effect of slurry contamination by drilling or cleaning sludge are two of the most important variables that determine whether the layer of cement successfully establishes the necessary separation. Guaranteeing these conditions is nearly impossible, however (5).…”