Solids Control in Drilling Operations: Maximizing Efficiency and Sustainability

In the ever-evolving world of drilling, where costs of drilling fluids and their disposal continue to rise, solids control has emerged as a critical and enduring concern. The primary objective is clear: maximize the use of drilling fluid while minimizing the volume that needs to be disposed of. Solids control equipment plays a pivotal role in achieving this goal, particularly for contractors operating larger rigs where such equipment is typically integrated from the outset. However, even mid-size rigs can benefit, contingent upon their specific tasks and locations. In this editorial, we will delve into the essential aspects of solids control and why it’s imperative to make informed choices when selecting and operating solids control systems.

For seasoned operators of larger rigs, the fundamentals of solids control equipment are well-understood, making equipment selection relatively straightforward. Yet, smaller operations must tread carefully, assessing their specific requirements before making a purchase, steering clear of the temptation to opt for the cheapest available unit. In fact, oversizing the unit, within reason, may prove advantageous since manufacturer ratings often assume constant flows and perfect mud conditions, which are rare in the field. Conversely, under sizing the unit can lead to poor fluid quality returning to the borehole, resulting in drilling issues and operational delays as the cleaning system struggles to keep pace.

Efficient drilling and production depend on good mud properties, and these properties should not be constrained by the solids control system. It is crucial to maintain the required viscosity and flow volume for cutting removal. An effective drilling fluid program must strike a balance between efficient drilling and recyclability. Collaborate with your fluid supplier, keeping in mind that the solids control system’s capacity plays a pivotal role in this equation. The geological formations you encounter will also influence the additives used and adjustments to the solids system settings. Properly sizing screens is essential to manage the flow of material through reclaimers, preventing overloading and system inefficiencies.

Understanding the basics of drilling mud and its purpose is pivotal to success. The primary goal is to have mud with the viscosity necessary to transport cuttings out of the borehole and into the return pit, where solids can start settling out before reprocessing. The sequence when mixing mud is water, soda ash, bentonite, dry polymers, and liquid additives. Water quality is critical, as it comprises 97% of the drilling fluid. Aim for a pH of 8.5 and minimal total hardness. Soda ash can raise the pH, particularly important when using water sources like fire hydrants, which typically have a pH of 7. Bentonite, a cost-effective viscosity builder, should be added based on anticipated drilling conditions. A PAC polymer often follows to provide good gel strengths, fluid loss resistance, and compatibility with reclaiming systems. If needed, a biopolymer can further enhance viscosity for specific conditions. Liquid clay inhibitors, lubricants, or detergents can be added once the desired viscosity is achieved but be mindful of their impact on mud rheology.

Now, let’s turn our attention to the reclaimer itself. It’s paramount not to underestimate the importance of having adequate solids control capabilities on-site. Knowledge of your system’s limitations is crucial to prevent drilling operations from outpacing mud reclamation. Reclaimers employ shaker screen filtration, de-sanding, and de-silting cones in a cyclone-like process. Proper screen sizing is essential, considering the material coming up from the borehole. Scalping screens require larger mesh sizes (e.g., 60 or 80), while de-sanding and de-silting cones should have finer screens (160-320 mesh). Regular screen inspection is necessary, as sand and silt can wear screens over time.

Understanding the clean tank and dirty tank, as well as how to combine and recirculate them, is equally important. By recirculating mud within the system during downtime, you can remove the next largest particle size, enhancing overall efficiency.

The final piece of the solids control puzzle is testing. Regular testing for viscosity, mud weight, sand content, pH, and total hardness is vital to monitor the health of your drilling fluid. A basic mud testing kit should be available, and all reclaiming systems typically include one. Communicate these findings with your mud engineer to fine-tune a mud program that aligns with your specific requirements.

In conclusion, solids control is not merely a matter of equipment; it’s a science that blends drilling efficiency with environmental sustainability. Contractors, regardless of rig size, must grasp the intricacies of solids control, from mud composition to reclaimer operation and routine testing. By doing so, they can ensure that drilling operations are not only cost-effective but also environmentally responsible, helping preserve our natural resources for future generations.