fax 01-972-952-9435. AbstractFormation fluid influx into cement slurries immediately after placement presents not only a short-term problem, for example losing the slurry due to shallow water flows, but also presents a long-term problem, for example gas flow and pressure buildup behind the casing. It is critical that cement slurries be designed carefully when such problems are anticipated. Cement slurries that often offer the best solution to resist the formation influx are those that do not gel while being pumped then gel/set and gain strength rapidly once placed. These are sometimes referred to as "right-angle set" cements and should possess the following attributes in laboratory design testing:• Maintains a low rheological profile while pumping for lower ECDs. • Predictable thickening and set times.• Retains the ability to transmit hydrostatic pressure under static conditions until the cement is ready to gel/set. • Short gel to set time under static conditions, often termed "transition time." • Short waiting on cement (WOC) time.This paper shows that although a cement slurry having a "right-angle set" may ensure the first two benefits, it does not always guarantee the latter two when present behind a casing. For example, some slurries might reach thickening time and become unpumpable rapidly, but strength development may not occur until long afterward, due to a time lag between thickening and hydration time (set time) of cement. In such cases, slurry should be designed such that the thickening time and hydration time are essentially identical. Novel slurries that maintain low rheological profiles while the slurry is being placed, then set and gain strength quickly due to cement hydration afterward, have been developed for a variety of densities and downhole temperatures. Results from laboratory and related field case histories will be presented.

fax 01-972-952-9435. AbstractFormation fluid influx into cement slurries immediately after placement presents not only a short-term problem, for example losing the slurry due to shallow water flows, but also presents a long-term problem, for example gas flow and pressure buildup behind the casing. It is critical that cement slurries be designed carefully when such problems are anticipated. Cement slurries that often offer the best solution to resist the formation influx are those that do not gel while being pumped then gel/set and gain strength rapidly once placed. These are sometimes referred to as "right-angle set" cements and should possess the following attributes in laboratory design testing:• Maintains a low rheological profile while pumping for lower ECDs. • Predictable thickening and set times.• Retains the ability to transmit hydrostatic pressure under static conditions until the cement is ready to gel/set. • Short gel to set time under static conditions, often termed "transition time." • Short waiting on cement (WOC) time.This paper shows that although a cement slurry having a "right-angle set" may ensure the first two benefits, it does not always guarantee the latter two when present behind a casing. For example, some slurries might reach thickening time and become unpumpable rapidly, but strength development may not occur until long afterward, due to a time lag between thickening and hydration time (set time) of cement. In such cases, slurry should be designed such that the thickening time and hydration time are essentially identical. Novel slurries that maintain low rheological profiles while the slurry is being placed, then set and gain strength quickly due to cement hydration afterward, have been developed for a variety of densities and downhole temperatures. Results from laboratory and related field case histories will be presented.