The cut point is used to indicate the separation characteristics of the solid control equipment at a given time. In the evaluation of separation point data, it is necessary to consider not only the performance of solid control equipment, but also the performance of drilling fluid. The separation point curve can be drawn based on the collected data, which characterizes the probability of a specific size solid phase passing through or being removed by a solid control device at a certain determined time when the data is collected. Therefore, the separation point curve is a function of the physical properties of the solid phase (such as density), the particle size distribution of the solid phase, and the condition of the solid phase equipment (such as sealing ability) and the performance of the drilling fluid.
The separation points of all solid control equipment can be determined by comparing the mass flow rates of solid phases of different sizes discharged from the solid control equipment and the mass flow rates of solid phases of the same size entering the equipment. When testing specific solid control equipment, you should know the injection flow rate of the solid control equipment and the discharge and underflow flow rates of the solid control equipment. Obviously, the sum of the mass flow rate of the equipment discharge must be equal to the mass flow rate of the equipment injection. Typically, part of the effluent stream is discarded, while another part remains in the drilling fluid. Before measuring the solid phase size of various liquid flows, you should first check whether the mass balance equation is satisfied, that is, the volume flow rate balance and the mass flow rate balance.
The solid control equipment only removes a part of the solid phase in the drilling fluid entering the equipment. For example, a 4-inch cyclone in a desilter has a processing capacity of 50 gal / min, but can only remove about 1 gal / min solid phase material. The ratio of the discharged solid phase material to the treated amount is so small that it is difficult to measure the difference between the retained liquid and the injected stream. Therefore, in order to obtain a more accurate concentration of the injected solid phase, the concentration of the solid phase in the discharged stream plus the concentration of the solid phase in the bottom stream is used to calculate the solid phase concentration in the injected stream.
In order to determine the mass flow rate of a specific size solid phase in an injection stream and the mass flow rate of particles of the same size in a waste stream, the flow rate and solid phase concentration need to be measured. Although the waste volume flow rate is generally relatively low, measuring the injection flow rate requires the use of a flow meter or metering pump.
For a drilling fluid shaker , the flow rate of the shaker is equal to the rate of drilling fluid in the annulus of the wellbore. The drilling fluid pump displacement can be controlled to provide accurate injection flow rates. When drilling, move the drilling pump from the suction mud tank to the weighted mud tank, and measure the descending speed of the drilling fluid weighted mud tank. Drilling fluids in weighted mud tanks contain liquids and gases. Therefore, the volume of gas must be subtracted from the volume of drilling fluid that is drawn when the mud tank is weighted. The gas volume fraction is obtained by dividing the difference between the pressurized drilling fluid and the non-pressurized drilling fluid by the volume of the pressurized drilling fluid and multiplying by 100. If the desilter or drilling fluid centrifuge uses a sand pump as the slurry pump, other types of flow meters are needed to accurately measure the flow rate. The anemometer can be replaced by a large scale container and a stopwatch. Due to the high particle content in the underflow of centrifugal sand pumps, it is difficult to measure the underflow volume flow rate of the equipment. Draw a calibration line inside the container for volume measurement. Inject a large amount of water into the mud tank and connect the mud tank to a centrifuge installed on the top of the mud tank. When the drilling fluid in the mud tank flows into the drilling fluid centrifuge, the stopwatch starts timing and you can observe the change in water level. Divide the known volume between the two lines by time to get the discharge volume rate. Typical samples of underflow or high-density drilling fluid are used for underflow density measurement. Once the mass and volume flow of the confidence measurement is balanced, the particle size in waste and underflow can be determined.
Measuring the rate of drilling fluid shaker and desilter injection and discharge flows requires larger vessels, and their volume cannot be directly weighed or measured. Remaining in the drilling fluid must use typical samples to determine the mass of particles of different sizes.
For drilling fluid centrifuges and desilters, micron-scale instruments must be used to measure the size of the solid phase. Drilling fluid vibrating screens can be measured using screens because the separation point range is within the screen level determined by the American Society for Measurement Experiments (ASTM). Different diameters require different instruments for measurement. Smaller diameter particles must be measured with more accurate experimental equipment. The laboratory needs a laser.
Solid and liquid phases contained in waste drilling fluid samples. For the waste stream of drilling fluid shakers, the mass of particles left on the ASTM test screen can be measured directly by weighing the dried solid phase. For desilter underflow and underflow (heavy drilling fluid) waste fluid from a drilling fluid centrifuge, the density of the solid phase must be used to determine the mass fraction of the particles.
Using a series of standard drilling fluid shakers, the separation point of the drilling fluid shaker can be measured by measuring the solid phase particle size in the injection stream, the waste stream, and the underflow. Once the flow rates of the bottom stream of the injection stream and the waste stream are determined, the mass flow rate of the particles in each screen discharge liquid of each stream is different from the mass flow rate of particles of the same size in the injection solution.
With this method, the sample injected into the flow is only a small part of the total flow, because errors can lead to unconserved mass. A better method is to use the waste stream and the underflow as samples, and combine the particle distribution in the two streams to establish a more accurate separation point curve. This method can be used for solid control equipment where the flow rate of the injected liquid is much greater than the flow rate of the waste liquid.
Take waste liquid and underflow samples from solid control equipment for analysis. Measure the density of all streams. The volume flow rate of the waste liquid stream is measured by placing all waste liquid in a container, which is a part of the trench intact in the working state of the drilling fluid shaker waste section. The mass flow rate of the waste fluid divided by the density of the waste fluid or the drilling fluid density is the volume flow rate of the waste fluid. The displacement of on-site drilling solid control equipment is the injection volume flow rate. The injection mass flow rate is used to clean the excess drilling fluid from the liquid phase of the drilling fluid, thoroughly dry the screening sample, and the measurement is the injected volume flow rate. The injected mass flow rate is calculated by multiplying the drilling fluid density by the circulating fluid velocity. Use a series of widely distributed sieving wet samples, clean excess drilling fluid with the liquid phase of the drilling fluid, thoroughly dry the sieved samples, measure the mass of solid particles under the sieve, and calculate the flow rate of the injected waste and underflow . To determine the screen separation point curve, the amount of particles of a particular size in the waste stream must be compared to the amount of particles of the same size entering the screen. Although all waste streams can be collected, the mass of all waste-specific particles can also be determined. However, while the waste stream is being collected, it is impractical to try all the fluids of the cell phone screen. For example, if the circulating flow in the wellbore on site is 500 gallons per minute and the mobile phone wastes the sample for 3.5 minutes, then the exhaust flow through the drilling fluid shaker should be 1750 gallons. If the drilling fluid density is 9.2 lb / gal, it means that 16,100 lb drilling fluid passes through the drilling fluid shaker. The total solid phase processed by the drilling fluid shaker in 3.5 minutes was 113.75 gallons (6.5% of 1750 gallons). It is considered impractical to collect and screen such a large amount of solid phase, so it is more practical to determine the particle concentration and size distribution of the drilling fluid shaker through the bottom fluid oxygen pump of the drilling fluid shaker as a sample. The flow rate of the underflow sample and the mass of the solid phase of each screen must be measured. The flow rates of the above dry solid phase are only used for calculation, not for the reason of collecting all particles in a specific time.
The mass flow rate of the injection stream corresponding to each screen cloth can also be determined, and the flow rate of the waste liquid stream and the injection stream of the underflow screen cloth can determine the percentage of the waste solid phase in the solid control equipment. The size of the solid phase is plotted against the percentage of solid phase removed.
The separation point curve shows the fraction of solid particles of various sizes entering and being removed by the solid control device. For example, the D50 separation point is the intersection of a 50% point on the Y axis and the corresponding particle size on the X axis of the separation point. This separation point indicates that there is a 50% chance that the particle size injected into the solid control equipment will pass through the equipment and a 50% chance that it will be excluded from the equipment. Usually the solid phase distribution curve is incorrectly marked as the separation point curve. The separation point curve indicates the classification of the particles of different sizes that are separated. They largely depend on the drilling fluid parameters and indicate the performance of the solid control equipment at the time of mobile phone data. The separation point of solid control equipment depends on the performance of the equipment and the performance of the drilling fluid.
The following distribution introduces the method of analyzing particle size and calculates the separation point using the separation point curve. Then, the drilling fluid shaker is taken as an example to describe how the data is collected and processed, and a lot of useful information is obtained from the example. This method is most suitable for the analysis of the separation point of the drilling fluid vibrating screen. Since the drilling fluid vibrating screen cannot be very fine, it can be analyzed to the API 400 mesh screen.
The non-screening method should be used to draw the curve of the separation point of the cyclone in the desilter and the sand separator and the centrifuge in the drilling fluid. Approximately 635 mesh sieve measurement of solid phase particle size is the limit of sieving analysis.