Development of Water-Based Drilling Fluids Customized for Shale Reservoirs

Abstract

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.

South Africa’s Technical Readiness to Support the Shale Gas Industry

“…Because every shale is different, WBMs have to be optimised for each area, whenever the mineralogy changes and especially if the shale contains water sensitive components (Deville et al, 2011).…”

“…For hydraulic fracturing operations the range of water use is from 3 500 m 3 up to 26 000 m 3 per well, with an average of 15 000 m 3 (Deville et al, 2011). The flowback is in the range of 20% to 80% (Boschee, 2014;Smistad, 2013).…”

Evaluation of polyacrylamide/clay composite as a potential drilling fluid additive in inhibitive water based drilling fluid system

“…The plastic viscosity, apparent viscosity, yield point, and gel strength were optimized as per the parameters required for the drilling of shale formations after considering several research papers on case studies of various shale formations like Haynesville shale, Fayetteville shale, Barnett shale, Mancos shale samples, Algerian shale formations etc (Khodja et al, 2010;Deville et al, 2011;Onuoha et al, 2011). The plastic viscosity values (20-29 mPa-s), apparent viscosity (33.5-49.5 mPa-s), yield point (13.5-20.5 Pa), gel strength (3/5-5.5/10 Pa) of the developed drilling fluid combinations were found to be in acceptable range for the drilling of shale formations (Ji et al, 2012;Guo et al, 2006).…”

Evaluation of polyacrylamide-grafted-polyethylene glycol/silica nanocomposite as potential additive in water based drilling mud for reactive shale formation

“…The rheological parameters like PV, AV, YP, and gel strength were optimized as per the parameters required for the drilling of shale formations after considering several research papers based on case studies of various shale formations like Haynesville shale, Fayetteville shale, Barnett shale, Mancos shale samples, Algerian shale formations etc (Li et al, 2012;Deville et al, 2011;Onuoha et al, 2011). The plastic viscosity values (20e29 mPa-s), apparent viscosity (29.0e47.0 mPa-s), yield point (9.0e18.0 Pa), gel strength (3.5/5.5e4.5/8.5 Pa) of the developed drilling fluid combinations were found to be in acceptable range for the drilling of shale formations (Ried et al, 1992;Ji et al, 2012;Guo et al, 2006).…”

“…Generally, water based drilling fluid accelerates physical and chemical reactions with the reactive shale formations inside the wellbore. The situation becomes more severe in the presence of smectite and illite clay minerals as they get hydrated easily in presence of water and causes swelling and dispersion of shale (Liang et al, 2014;Oort, 2003;Deville et al, 2011;Patel, 2007;Simpson et al, 1961). Studies on the interaction between the shale and drilling mud confirm that wellbore instability is due to the water adsorption, osmotic swelling, and disintegration of the cuttings which in result alter the in-situ stress regime of shale formations and properties of the drilling mud (He et al, 2014;Lyons, 2010;Lummus and Azar., 1986).…”