The increasing need to reduce costs and minimize the environmental impact associated with drilling has fueled the adoption and expansion of solids control. The primary goal of solids control is to maximize the number of contaminants and particulate matter eliminated from the drilling fluid or effluent flow as they pass through the solids control equipment or system.
An effective solids control system minimizes the amount of solids remaining in the drilling fluid improving drilling fluid rheology and increasing drilling fluid life. It also reduces the need to dump, dilute and mix new drilling fluid which greatly reduces drilling costs and environmental impact.
A good solids control program reduces overall operational costs by:
- Removing abrasive contaminants that damage high wear items
- Improving drilling fluid properties
- Extending drilling fluid lifespan
- Lowering fluid dilution rates
- Minimizing the number of additives required
- Facilitating higher flow and penetration rates
- Facilitates simple byproduct disposal process
- Reduces regulatory and compliance issues
Shale Shakers
Shale shakers are the first phase of a solids control system and depending on your exact goal you have some choices. Usually effluent type, process flow rate, solids loading, solids removal cut point and desired dryness of removed solids are considered in the selection process. Some shale shakers are designed to convey large amounts of solids while others are designed to dry large amounts of solids. In either case, the shale shaker will remove larger solids from effluent streams allowing secondary and third phases of solids control to work more efficiently while helping to reduce high wear solids and solid by-products found in the effluent stream. Shale shakers are comprised of the following three major components:- Possum Belly: A effluent flow catch box designed to allow free flow of effluent while deadening fluid velocity and delivering effluent evenly to the shaker deck.
- Shaker Deck: A two-sided structure with open top and open bottom designed to hold both the vibratory motors and shaker screen. The shaker deck is one of the most integral parts of the shale shaker as it secures the vibratory motors which transfer motion through the shaker deck causing removed solids to convey over the shaker screen while effluent falls away from removed solids.
- Skid: A base for securing and supporting both the possum belly and shaker deck. The skid is usually constructed with either an open bottom or enclosed catch pan with side discharge.
- Screens: A woven wire mesh with varying hole sizes between wire mesh strands that allow distinct size solids to pass through the screen. Shaker screens are secured to the shaker deck and can be removed and changed when needed.
- Vibratory Motor: Usually electrically or hydraulically driven with acentric weights causing linear, orbital or elliptical motion to occur. The vibratory motor is affixed to the shaker deck forcing its energy through the shakers desk causing vibration.
How Shale Shakers Work
Whether pumping effluent or using gravity fed effluent the slurry/fluid will first flow through the possum belly where the velocity is deadened and allowed to flow evenly to the shaker deck where shaker screens are secured. Shaker screens can be changed allowing for changes in screen mesh/micron sizing which will affect effluent flow rate, solid removal cut point and dryness of removed solids. As effluent flows over the shaker screen the vibratory motor produces energy/ motion moving the shaker deck causing the effluent and solids to shear. The removed solids are conveyed along the shaker deck and discharged over the open end of the shaker. The effluent falls away from the solids through the shaker screen and into a tank and/ or catch pan where it is routed to the next step or process.Desanders
Desanders consist of hydrocyclones larger than 5″ in diameter. They come in 6”, 8”, 10”, or 12″ standard diameters. Due to their large size, they remove sand-sized particles, larger drilled solids, and small amounts of liquid that have passed through the shaker screen. Desanders eliminate solids in the range of 45-74 μm.How Desanders Work
When drilling fluid passes through the centrifugal pump and flows into the desanders, the larger solid particles are forced to the sides of the hydrocyclone where they then spiral down to the bottom of the container. They’re then discarded from the bottom flow hole and land on the mesh for separation. The other lighter fluids flow by cyclonic action into the third class separation equipment desilter for further cleaning. Desanders remove abrasive solids that shakers can’t remove.Desilters
Desilters use smaller hydrocyclones, often 4″ or 5″ in diameter, to remove smaller particles from the drilling fluid. The smaller hydrocyclones allow desilters to eliminate the smallest particles from the drilling fluid of the separation equipment. Desilters are designed to remove solids in the range of 15-25 microns.How Desilters Work
Drilling fluid from the desander flows into the desilter for further cleaning treatment. Desilters remove tiny particles from the drilling fluid.Mud Cleaners
A mud cleaner is a cleaning and purifying device in a drilling system. It consists of hydrocyclones mounted over a shale shaker with a fine mesh screen. A mud cleaner uses a two-stage separation process to eliminate solids from drilling fluid and serves as second and third-phase solids control equipment.How Mud Cleaners Work
When mud is fed into the drilling system, it passes through several hydrocyclones of varying sizes. The smaller cones or desilters remove finer silt-sized solids, while the larger desanders remove coarser sand-sized particles. The underflow from the hydrocyclones passes through the vibrating screen, which further discards even larger particles. Mud cleaners are designed to eliminate drilled solids larger than 74-15 microns to prevent viscous build-up. Mud cleaners can effectively:- Control weighted drilling fluid solid content
- Remove drilled fluids from unweighted drilling fluids
- Reduce the drill string
- Prevent differential pressure sticking
- Filter cake thickness on bond issues
- Reduce both drilling fluid expenses and disposal costs
Steps Involved in Water Treatment
Wastewater treatment has several steps that eliminate contaminants and ensure that the final overflow discharge complies with regulatory standards. The process includes:- Elimination of solids
- Hydrocarbon removal
- Chemical treatment
- Testing and discharge
