Case Study: Argentina: MEGADRIL Allows The Operator to Drill Successfully With High MW and Lower Oil-Water Ratio

Challenge: For exploration well CLX-1, operator Tecpetrol required an oil-based drilling fluid which could be managed effectively at high density as it would have to penetrate a pressurized zone. Additionally, the operator requested that the system will initially deliver a low oil/water ratio (OWR) to reduce diesel consumption. The ratio would be adjusted upon entering the target zone. Ideally, the client wanted to convert a conventional oil-based mud (OBM) stored from a previous job to a system with optimum rheological properties and OWR to drill the planned CLX-1 well.

Solution: M-I SWACO recommended the operator to convert its used conventional VERSADRIL oil-base drilling fluid to a MEGADRIL system, by incorporating the MEGAMUL stabilizer, emulsifier and wetting agent. The system was formulated to deliver the required parameters for an OWR between 70/30 and 80/20, much lower than the OWR necessary for a conventional OBM of thus lowering inventory requirements, diesel consumption of and the rheological profile. The MEGADRIL OBM, will also be required to be stable at the high density required to penetrate a pressurized zone.

M-I SWACO supported its recommendation with MEGADRIL system testing performed in its regional laboratory. Once the optimum physical and chemical characteristics were achieved the client elected to deploy the modified system in its exploration well.

Result: The results justified the selection. Losses in the poorly consolidated sands of the 17 ½ in. section were controlled easily with lost circulation materials (LCM) while the rheology and OWR were maintained easily 70/30 for the entire well. The system maintained stable properties during drilling, cementing and casing run. The 9 ⅝ in. casing was run and cemented trouble free.

In the 17 ½ in. interval from 353 m to 1,640 m, mud losses were experienced during drilling poorly consolidated sand sections. Mud losses were successfully controlled with LCM. The rheology and OWR of the system were kept between 65/35 to 70/30. The addition of MEGAMUL emulsifier combined with an effective solids control permitted to maintain a lower fluid rheology and deliver a clean fluid, with MW between 1,090 to 1,190 g/l and electric stability (ES) between 350 to 400 V. Drilling was stopped to address rig problems, but resumed trouble free after a prolonged shutdown.

In the 12 ¼ in. interval formation drilled consisted of gypsum, sandstone and shale sections. The OWR was increased from 70/30 to 75/25, while the ES trended between 450 and 580 V. MEGAMUL emulsifier was added as per programmed at the ratio of 1 gal/bbl of hole drilled.

In the 8 ½ in. section, the OWR was adjusted, with an increase of MEGAMUL emulsifier to which worked with mud weight ranging from 1,560 to 1,680 kg/m³ and ES from 580 to 800 V. Salt and limestone formations were drilled successfully with no fluid-related problems.

While the well was abandoned for not reaching the geology objective, the MEGADRIL system was credited with remaining stable throughout the project. The use of MEGAMUL helped to improve HTHP filtration , ES and maintain a lower-rheology profile when compared with a conventional OBM.

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“Introducing the MEGADRIL system in North Argentina allowed us to minimize the use of diesel while improving the chemical and physical properties of the fluid.”
Miguel Velez
M-I SWACO Project Engineer

MEGADRIL vs. Conventional OBM

Megadril Argentina
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