Before solids control, drilling fluids were processed using a series of processing pits. As the fluid passed through these pits, solids were sucked out of them by the force of gravity. The liquid was channeled to pumping stations and sent to the drilling equipment.
Processes Involved in Solids Control
The drilling industry relies on solids control to keep drilling fluids clean and safe for drilling. Drilling rigs typically have a series of stages for solids control, including a mud tank, shale shaker, vacuum degasser, desander, and desilter. The process is also crucial to the safety of the drilling rigs and equipment.
Proper solids control techniques like the ones used at Diamond T services can minimize drilling waste, reduce hauling costs, and improve drilling fluid recovery. The oil industry has long recognized this. In the late 1800s, drilling companies used open earthen pits to separate cuttings from boreholes, allowing solids to settle naturally. They then suctioned clean mud into a suction pit.
Modern solids control techniques have evolved. Shale shakers, for example, were initially borrowed from the mining industry and have been used in the oil and gas industry ever since. Other solids-control systems include hydrocyclones and centrifuges.
Geology of Drilling Fluids
Drilling fluids are diverse substances used in oil and gas production. Their composition varies depending on the type of formation and depth of the borehole. Some are water-based, while others are oil-based. These fluids are formulated to modify specific properties of the formations to facilitate drilling.
Drilling fluids are essential materials used in the oil and gas industry. Water-based drilling fluids are often the most common type, as they are inexpensive and non-hazardous. However, they may not be suitable for a wellbore with water-sensitive geology because water may compromise the stability of the formation. Oil-based fluids may be needed for water-sensitive geological occurrences such as shale or sandstone. Oil-based fluids must be appropriately formulated to minimize water movement in the rock pores.
The ability of a drilling fluid to carry rock excavated by a drill bit depends on several factors, including the cuttings’ size, shape, and density. It also depends on the speed of the fluid traveling up the well. It is analogous to how sediment moves up a stream: large sand grains settle down to the stream bed while small sand grains are carried along with the water. Another important property of drilling fluids is the viscosity of the liquid. If a drilling fluid is too viscous to move a rock, the cuttings will sink to the bottom of the well.
Equipment Used
The modern solids control system comprises improved versions of the original equipment introduced in the oil industry years ago. While the core technology hasn’t changed much, the equipment has become more durable and efficient. Proper utilization of solids control equipment is crucial for the cost savings that can be obtained.
Solids control equipment must be hydraulically balanced and capable of the scalp and fine cutting. It also needs to have the requisite mixing and recirculating capacities. It should be allowed during drilling. The shakers should be able to handle different mesh sizes. The operators must be familiar with various screens to ensure the optimal removal of solids.
The solids control system has several stages, each with a different purpose. The first step is to separate the drilling solids from the mud. Shale shakers remove the larger cuttings from drilling mud, but they don’t remove the smaller solid particles, which are turned into silt and become part of the mud. The resulting silt and sand can increase the weight of the drilling equipment.
Costs Associated with Solids Control
When evaluating solids control equipment, you should consider several factors, including how much it will cost to purchase and maintain the equipment. Depending on the size of your operation, you may need to buy large pieces of equipment that can be costly to carry and store. Moreover, solids control equipment is often leased, which can reduce the costs associated with ownership.
The costs associated with drilling fluid maintenance are significantly reduced when drilling companies implement proper solids-control practices. While it is possible to remove 100% of the drill solids, this is often uneconomical. Instead, achieving a balance between mechanical solids separation and dilution is better for accomplishing an acceptable drill solids level at the least cost. This will result in reduced clean-up costs and a decreased SPTA bill.
Drilling fluids are expensive, and solids control is essential to minimize waste and the volume of drilling fluid. It is important to select solids control equipment that can effectively remove large cuttings without affecting the quality of drilling fluid. Ideally, solids control equipment should be able to process up to 125 percent of the drilling mud circulation rate.
