According to the different characteristics, there are different classification methods in the solid phase of drilling fluid. According to the density of the solid phase can be divided into: high density of solid phase and low density solid phase. The former is based on the drilling requirements of the heavy materials, in order to increase the density of drilling fluid. The drilling fluid with heavy material is added to increase the drilling fluid or worsen the mud.
The low density solid phase includes common drilling cuttings; the bentonite and the treating agent are required to configure the drilling fluid. A drilling fluid that does not contain a heavy material, is called a non - increasing drilling fluid or non - increasing mud. According to the American Petroleum Institute (API), the size of the solid particles can be divided into three major categories of solid phase in drilling fluid:
The grain size of clay (or gum) is less than 2 m
Mud particle size is 2 ~ 74 M
Sand (or API) grain size >74 M
The size of the solid particles in the drilling, and the content of various particles are also different. The size of the solid particles is known as the particle size (and thickness). The percentage of all kinds of particles in the solid phase is called graded. In the drilling process, the type of the rock drill and the different parameters of the drilling parameters are different, and the solid content of the drilling fluid and the grain size distribution are not the same.
Over the past twenty years, with the development of the technology of jet drilling, drilling, drilling, high quality drilling fluid and oil layer protection, the technology has been developed rapidly. Solid control task is: 1 from the drilling fluid to remove harmful solid, so that the solid content is not beyond the requirements. 2 reduce the proportion of fine particles in the drilling fluid, maintain a reasonable size and gradation of the solid phase.
Commonly used methods of solid control are: dilution method, substitution method, natural sedimentation method, chemical deposition method and mechanical removal method. Red mud method: is to maintain the solid content of the basic constant, to the high solid content of the drilling fluid in the water or other liquid, diluted into a low solid content of drilling fluid (at the same time should also be added to the chemical treatment agent). Replacement method: is to keep the total volume of drilling fluid, the drilling fluid with high solid content from a part, then the treatment agent for the solution into the same amount and low solid drilling fluid, mixing after use. Natural sedimentation method: the drilling fluid in the well is in the process of the surface circulation, because of the large size of the ground drilling fluid, the flow rate is low, and the debris particles in the drilling fluid are separated by the gravity action. Chemical deposition method: in the drilling fluid to add a small amount of chemical precipitation agent to make a contact with a small amount of debris, a contact with these chemicals to produce a larger particle, and rapid settlement. Mechanical removal method: the use of mechanical equipment to remove harmful solid, change the solid phase gradation.