Case Study Significant Reduction of Ultrafines in Synthetic-Based Mud Leads to Successful Mud Recovery
Offline mud treatment using RHE-USE centrifuge system overcomes contaminated mud challenge, saves more than USD 90,000 in dilution, Argentina.
Two-stage centrifuge system
The RHE-USE system enables operators to reuse invert emulsion drilling fluids over multiple wells without relying on reclamation through high rates of dilution. The process treats oil-based drilling fluid, reducing solids below 1% while drilling.
Before the introduction of the RHE-USE system, combating the buildup of ultrafine, low-gravity solids required using dual centrifuges and dilution. With the RHE-USE system, staged centrifugation accompanied by chemically enhanced treatment renders both low-gravity solids (LGS) and drill solids manageable. The system can easily be adjusted to produce relatively ‘dry’ cuttings, reducing drilling wastes.
Conventional mechanical separation methods are unable to extract ultrafine low-gravity solids from an oil-based drilling fluid, requiring operators to dump the expensive fluid. The chemically enhanced RHE-USE system has been field-proven returns the fluid to the loop at the same weight as the mud was originally built. After the mud is run over the drying shakers, a low-speed centrifuge makes a separation then returns the barite slurry with the large LGS particles back to the mud system. This slurry is adjusted to match the original mud weight.
The liquid phase from the low-speed centrifuge is run to an effluent tank where it is polished using a mid-speed centrifuge. Base fluid is added until the target volume is met. Then the fluid is passed through the high-speed centrifuge and the RHE-USE system chemicals are added to further remove the LGS. By delivering clean fluid, the RHE-USE system also dramatically improves drilling performance.
The RHE-USE system delivers tremendous savings in mud-related costs, including reducing the amount of solids-laden fluids transported for disposal. By reducing the amount of LGS in the fluid, the RHE-USE system also reduces the amount of dilution required to return the drilling fluid to a usable state. This saves on resources, such as barite, base fluids, and chemicals associated with building invert emulsion drilling fluids. High-quality barite is increasingly scarce and expensive. The RHE-USE system enables operators to reduce the quantity of barite and other materials in their fluid systems, providing 25–30% savings.
Using the readily available CD-500 HV high-volume, high-speed precision-balanced centrifuge, the RHE-USE system makes a separation of the fluid from the LGS using low speed centrifugal separation. The slurry is then balanced to match the weight of the mud system. Once the slurry is in the effluent tank, it is pumped to the high speed centrifuge, which is typically set at around 2,400 rpm. Base fluid may be added at this point to help lower the plastic viscosity. A second pass in the centrifuge, this time at 2,900 rpm, mechanically cleans the effluent prior to the chemical stage.
Then a single tote chemical that contains dual surfactants and a polymer in a water-based carrier is added. Once the cuttings are water-wet, they develop a charge. The polymer envelops them and causes the ultrafine solids to grow to a size that is readily removable by a final pass through the high speed centrifuge at 2,900 rpm, resulting in a fluid that can be returned to the main drilling fluid system free of LGS.