国外用水基泥浆的很多，否则成本是怎么降下来的？比如Haynesville页岩开发，现在基本都是采用水基泥浆，当然是特别研制的，是针对高温高压的（200度，102Mpa)。
Most of the technologies developed specifically for Haynesville have emerged in response to the extreme
HPHT conditions of the formation in comparison with other producing shales. An instructive example of this
is Newpark Drilling Fluids' Evolution water-based drilling fluid system, developed in 2009 as an alternative
to the oil-based muds (OBMs) that had become the default in the play. A number of operators had attempted
different water-based muds (WBMs) in the Haynesville in order to reduce the high costs of drilling in the play
(oil-based muds are more expensive, and more difficult to dispose of after use), but these attempts had failed.
After considerable sampling and analysis of the shale, Newpark determined that the shale was not
particularly reactive, as had previously been hypothesized. Rather, the major issues were the high temperature
and carbon dioxide content. At the high temperatures found in the Haynesville, the standard viscosifying
polymer of choice, xanthum gum, deteriorates rapidly.
"We also discovered a significant amount of CO2 in with the gas, such that if you use a conventional
bentonite mud, it flocculates severely, giving you a viscosity hump that significantly limits your lubricity," lab
manager David Breeden told World Oil. "The only way to treat out the CO2 is with lime, and at bottomhole
temperatures of 350[degrees] and above, you don't want very much lime because you'll make cement.... So
you're constantly going over the two viscosity humps of CO2 and calcium." The high mud weights required
in the Haynesville, exceeding 15 lb/gal, further complicated the search for alternatives.
Newpark went to work to formulate a water-based polymer system that exhibited thermal stability at
temperatures in excess of 400[degrees]F, provided contaminant resistance to CO2 and drilled solids, and
provided lubricity comparable to that of OBMs. The resulting system, incorporating a polymeric viscosifier
and suspension agent, an HPHT lubricant, a rheology modifier and a general-purpose fluid conditioner,
performed successfully in the field and became the first water-based system used repeatedly in the
Haynesville.
