Traditional primary solids control methods use high energy, high G-force shakers to "shake" the fluid off the drilled solids on multiple static screens, and drilling fluid losses are typical 1 barrel of fluid for every 1 barrel of rock drilled. The new approach described in this paper replaces shakers with a vacuum-based system, to optimize the separation of drilling fluid and cuttings as they return from the wellbore. During this trial, a high-flow vacuum and rotating filterbelt (screen) system was configured to safely recover more drilling fluid from the cuttings, with the intention of reduce drilling waste. The goal is to validate the performance and HSE benefits of using vacuum-based primary solids control technology versus traditional shale shakers. Success criteria for the trial on two land wells were compared to common shale shaker performance and included: reduce fluid on cuttings by 30% (no more than 0.7 barrels of mud per 1 barrel of rock drilled); reduce screen consumption; and reduce noise level below that of the existing shale shakers.
A third-party cuttings flowmeter was used to measure the rock recovered by the vacuum-based system. The following results were recorded during the trial on two wells: fluid-on-cuttings was only 29%, versus the 70% target for the trial; average filterbelt life exceeded the trial target by 54%; and sound pressure level was measured at 74 dBA, at least 3 dBA less than common shakers. Based on retort analyses, Oil On Cuttings averaged 8.39% wet weight. Total rock recovery for the vacuum-based system was 91% of the theoretical hole drilled. During the fluid/cutting separation process, the unit is operated as an enclosed system, eliminating operator exposure to harmful vapor and gases. Finally, it was noted that changing the filterbelt (screen) could be performed by one person in approximately 3 minutes. In conclusion, the trial demonstrated that 71% less drilling fluid was lost versus a typical shale shaker, at the same time reducing overall drilling waste volumes and providing a safer working environment for personnel.
Vacuum-based primary solids control systems represent a step change in performance over the decades-old shale shaker concept. The production of significantly dryer cuttings can eliminate the need for traditional de-sanders, de-silters, centrifuges and cuttings dryers. In addition, benefits related to transportation, storage, and processing of drilling waste, can be dramatically obtained.
