Summary
Drilling activity has increased dramatically in unconventional shale gas
reservoirs. The drilling fluid of choice in these shale plays is often
nonaqueous-based fluid (NAF). While NAFs can provide advantages such as shale
stabilization, lubricity, and contamination tolerance, environmental
consequences and associated costs are an issue. These disadvantages cause
operators to seek water-based muds (WBMs) for drilling many of these gas
reservoirs.
Despite some operational similarities, a wide variety of unique downhole
conditions can be found in the shale plays. Shale mineralogy and bottomhole
temperature (BHT) represent just two highly variable critical factors in
unconventional gas reservoirs. Therefore, a single water-based solution for
addressing shale plays globally is not a realistic option. Instead, a
customized approach that delivers WBMs formulated specifically for a given
shale play has been pursued.
Customization relies on detailed analysis of the well parameters of a given
shale play. This analysis includes not only the shale morphology and lithology
but also well drilling program plans, environmental factors, and other
reservoir-specific considerations. Applying appropriate drilling-fluid
chemistries on the basis of this detailed analysis has led to the successful
field deployment of a number of new shale fluids.
Details of the process used for customizing a WBM for a shale play, as well
as specific examples of new fluids developed for the Barnett, Fayetteville, and
Haynesville shales, are presented in this paper. Full laboratory development
and testing are described. Additionally, field-trial results are presented that
show that specially designed WBMs can provide performance comparable to that of
NAFs, but with enhanced environmental and economic benefits. Application of the
customization process to develop WBMs for other shale plays around the globe is
also discussed.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
28 June 2011
- Meeting paper published:
11 April 2011
- Revised manuscript received:
7 September 2011
- Manuscript approved:
22 September 2011
- Published online:
22 December 2011
- Version of record:
27 December 2011