Well Recovery in Expansive Marl
Granada, Spain
“We thought we’d lost the well. Quimacer’s technical solution allowed us to clear the blockage within a few hours and continue drilling.”
A drilling client specializing in groundwater extraction for agricultural operations contacted QUIMACER from a job site located in the province of Granada.
The project involved drilling a well approximately 90 m deep, with a diameter of 220 mm, using direct-circulation rotary drilling.
During the first few meters, drilling proceeded normally, but at a depth of 25–30 m, the drill bit encountered a formation of highly plastic clayey marl, typical of several areas in southern Spain. The initial drilling fluid system was based on water and conventional bentonite, without any specific inhibitors or friction-reducing additives.
After several hours of downtime, the customer contacted QUIMACER, facing a real risk of losing the borehole, the drill string, and a full day of machine time.
Problems Identified
- The rigging became entangled at a depth of about 32 m.
- Gradual increase in torque and overload of the rotating head.
- Partial closure of the borehole's effective diameter due to hydration and swelling of the clays.
- Difficulty in passing stool due to an accumulation of plastic material in the annulus.
- High economic risk: abandonment of the well, forced mechanical extraction, or loss of the tool.
Our Intervention
- QUIMACER's technical team conducted an immediate remote assessment, reviewing the depth, lithology, drilling method, fluid type, and symptoms observed by the driller.
- A clear incompatibility was identified between the base fluid and the clay formation: the free water was hydrating the marl and increasing the plasticity of the soil.
- An intervention strategy was defined along two lines: inhibiting the clay to reduce its reactivity and lubricating the rod-wall contact to reduce torque.
- It was recommended to gradually replace the existing fluid with an inhibited, dispersant, and lubricated WBM system, avoiding abrupt extraction maneuvers.
- We worked closely with the client during the treatment's initial implementation, adjusting the dosage based on the results of the monitoring.
Solution Implemented
- Reformulation of the fluid with BENTONITE QE at 20 kg/m³ to provide structure, gel, and wall stability.
- Addition of QUIMAGEL AS-950 at a rate of 1.5 kg/m³ as a PHPA inhibitor to reduce the hydration and dispersion of the clays.
- Add 1.25% QUIMAFLUX ST to make plastic clays more fluid, reduce stickiness, and improve annulus cleaning.
- Add 0.5% QUIMALUBE 906 to reduce friction, torque, and heat buildup during operation.
Target control parameters: Marsh viscosity 45–55 s, approximate density 1.05–1.10 g/cm³, slightly alkaline pH, and return with a lower plastic load.
Results and Improvements
Gradual release of the rod system within less than 4 hours after treatment application.
Estimated torque reduction of more than 40% compared to the initial condition.
Restoration of water flow and a visible improvement in sediment transport.
Drilling continued to the final depth without any further critical incidents.
Estimated savings of more than 15,000 euros by preventing well abandonment, tool loss, and prolonged equipment downtime.
| Parameter | Technical Details |
|---|---|
| Sector | Water well / agricultural water intake |
| Soil | Expansive clay loam |
| Method | Direct-Circulation Rotation |
| Critical depth | 25–32 m |
| QC Products | BENTONITE QE, QUIMAGEL AS-950, QUIMAFLUX ST, QUIMALUBE 906 |
| Recommended dosage | 20 kg/m³; 1.5 kg/m³; 1.25%; 0.5% |
| Key Improvement | >torque reduction of 40% and well recovery |
WHY QUIMACER?
- Rapid response to critical construction incidents.
- Specific knowledge of expansive clays and problematic loams.
- A formulation tailored to the specific site, not a one-size-fits-all solution.
- Direct reduction in the total cost per meter drilled.
