Weldon M. Harms

Cementing of Fragile-Formation Wells With Foamed Cement Slurries

Substantial regions of hydrocarbon production in California consist of formations that are very fragile, which imposes a density limit on the cementitious system used to cement the well pipe. Also, troublesome fallback problems have been experienced for years in these areas. Fallback can possibly reduce production by causing formation damage. Usually, the use of foamed cement offers a low-density cementitious material that develops adequate compressive strength while avoiding fallback problems that are caused by density. After hardening, foamed cement has reduced density, and it usually provides the advantages of temperature stability and heat insulation properties. In this paper, the properties of foam cements are discussed and more than 60 cementing jobs completed with foam cement are summarized.

Study of Continuously Mixed Crosslinked Fracturing Fluids With a Recirculating Flow-Loop Viscometer

Continuously mixed gel fracturing fluids were successfully prepared with polymer slurries of guar, derivatized guar, and derivatized cellulose. The authors describe the rheological behavior of the continuously mixed fluids measured on a recirculating flow-loop viscometer over a temperature range of 80 to 300{sup 0}F (27 to 149{sup 0}C). Rapid and complete base-gel hydration required proper pH control and high mixing energy. Oil-based polymer slurries allowed rapid hydration rates sufficient to achieve performance from a crosslinked fluid prepared during a completely continuous operation. Water-based polymer slurries required a short holding period for complete hydration. Delayed-crosslink-gel viscosity was influenced by shear rate and the degree of base-gel hydration. Chemical factors influencing viscosity development included base-gel concentration, crosslinking-agent concentration, fluid pH, and ionic strength. Hydration time and pH requirements may differ for specific polymer/crosslinker pairs.