Overview
Removing complete, undamaged cores can be a very difficult process for Geologists. Clear Solutions were able to help a University in the UK to successfully complete their coring project by suggesting a KCl/Pure Bore®/Pure Bore® ULV fluid. This enabled them to achieve a fantastic core recovery of 98-99%.
Challenge
Coring sedimentary rocks is a slow, laborious process and geologists know that their targets of complete, undamaged material recovery are not often achieved. The mechanical stress of coring can break cores, the well bore can collapse with time and drilling fluid can invade the core, altering its composition and affecting the acquired data quality. Given the sedimentary nature of the rock column, a significant percentage was made up of water sensitive clays. The upper cored section was expected to be open for 15 days and the lower 400m section for 33 days. These time periods have a potential to result in hydration induced instability when in contact with WBM.
Solution
Clear Solutions proposed a Potassium Chloride based Pure-Bore® system. The formulation provided rheology, fluid loss and encapsulation with only two polymers, Pure-Bore® and Pure-Bore® ULV. The system proved quick to mix with minimal logistical requirements. The Pure-Bore® polymers created a competent filter cake to reduce invasion of silts and a coating on the reactive clays to reduce hydration. Mud properties were managed for coring requirements using forecasted quantities of products.
Conclusion
The primary project objective of coring to 650m was achieved, with consistently good core recovery of 98-99%.
