Overview
Clear Solutions were asked to help provide an alternative to a standard drilling fluid which was causing problems for a customer drilling geothermal wells in Europe. A Pure Bore® based fluid was proposed and successfully met all of the requirements, removing the issues that had previously been seen.
Challenges
Multiple deep geothermal wells up to 3,000m TVD/4,100m MD with BHT of 100°C were drilled to provide green energy to city districts within Europe. The first two wells (Well 1 & Well 2) were both drilled with a standard Potassium Carbonate/Xanthan/PAC based drilling fluid and both wells encountered several drilling and fluid related issues. High levels of clay dispersion, excessive rheology, foaming, excessive solids loading, bit balling issues, low ROP, high dilution, disposal volumes and a stuck pipe event on one well, led the operator to look at alternative drilling fluid solutions to deliver a technically more effective and cost efficient drilling fluid.
Solutions
Given the issues experienced on the first two wells, and considering that the use of chlorides are prohibited in this area, a Potassium Carbonate Pure-Bore® based fluid was proposed for Well 3, combined with the unique properties of the Pure-Bore® products to overcome all of the issues. The proposed Potassium Carbonate/Pure-Bore® system has several advantages such as a highly shear thinning rheology, no bit balling, improved ROP, significant shale encapsulation, improved solids control efficiency through finer shaker screens hence reduced dilution volumes. These features would eliminate the issues seen previously with the Potassium Carbonate/Xanthan/PAC system, facilitating good hole cleaning and minimised clay dispersion.
Conclusion
The efficiency of the Pure-Bore® system aided in reducing the concentration of low-gravity solids which in turn decreased the dilution and disposal volumes, delivering a 35% project cost reduction and requiring fewer days to successfully complete the well.
