An increase in drilling activity in deep oil and gas reservoirs has created industry demand for stable water-based drilling fluids capable of withstanding high-temperature environments in cases where invert emulsion fluids were preferred. Conventional biopolymers fail near 300 F over short periods, and standard synthetic polymers could be stable at high temperatures but do not provide the low-end rheology to suspend sol-ids. Drilling fluids that do not maintain stability in high temperatures require extensive fluid conditioning.
VeraTherm high-temperature, water-based drilling fluid from M-I SWACO, a Schlumberger company, delivers stability above 400 F, exhibiting excellent low-end rheology for hole cleaning and suspension while providing minimal fluid loss at high temperatures. The fluid is compatible with most oilfield completion fluids, from freshwater to near salt-saturated brines. The ability to prepare the fluid at the rig site adds flexibility to operations.
The fluid is applicable in high-temperature, water-based scenarios including drilling, logging, screen running, deep water, coiled tubing (CT) drilling, and fluid loss control pill or suspension pill. The water-based drilling fluid withstands up to 400 F without any treatment or property reduction over time and enables multiple logging runs without circulation, eliminating conditioning trips and a day of rig time with each avoided trip in high-temperature applications. It is compatible with common drilling fluid additives such as shale inhibitors, corrosion inhibitors and H2S scavengers.
The VeraVis branched synthetic polymer viscosifier and fluid loss additive, the main component of VeraTherm fluid, provides dual function, delivering rheological properties and fluid loss control. By offering excellent solid suspension properties even at higher temperatures, it eliminates sag issues. Unlike synthetic polymers that have been used in different applications within the oil and gas industry for more than 50 years, the VeraVis additive contains unique chemical modifications. The branched nature of the synthetic polymer provides drilling fluid properties similar to conventional biopolymers such as xanthan, diutan and starch. This feature enables a significant reduction in formation damage compared to the linear synthetic polymers available in the market.
Many conventional water-based drilling fluids contain clay, which causes gelation issues at higher temperatures. Because the high-temperature, water-based drilling fluid is a clay-free system, no gelation issues occur across the full temperature and density range. The addition of proper lubricants produces drilling performance comparable to oil-based mud (OBM) and synthetic-based mud (SBM) systems.
The high-temperature, water-based drilling fluid pro-vides excellent drilling fluid parameters performance, which includes high low-end rheology, low pump pressure, excellent fluid loss control, inherently low coefficient of friction and superior shale inhibition properties. It remains stable for longer durations at high temperatures (Figure 1 below).
Using the fluid in place of SBM reduced the opera-tor’s overall drilling fluids cost. The use of one system through intermediate and reservoir sections reduces the environmental footprint.