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Drilling is a vital process in the oil industry, and the infiltration rate plays a crucial role in ensuring efficient completion of drilling operations. Various factors such as Weight on Bit (WOB), Rotating Speed (RPM), drill bit type, formation characteristics, and mud properties significantly impact the infiltration rate of a drilling bit. Accurate determination of the sand content in drilling mud is essential because sand particles can be highly abrasive, leading to excessive wear and tear of pump components, drill bits, and pipe connections.
Excessive sand can also result in the formation of a thick filter cake on the hole's walls or settling within the hole around equipment when circulation is temporarily halted, disrupting drilling tool operations or casing placement. The sand content test is a critical method for determining the sand content in drilling mud. In this experiment, a sand content kit with a 200-mesh screen, a funnel, and a measuring tube was employed to determine the sand content of mud samples.
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The mud samples were prepared with similar materials and measurements, with the only variation being the type of bentonite used. The results of this experiment were assessed to determine their practical utility.
Understanding the sand content of drilling mud is essential to prevent issues like the formation of a thick filter cake on the hole's walls or settling of sand around equipment when circulation ceases, which can disrupt the effective operation of drilling tools and casing placement. High sand content can also lead to excessive abrasion of pump components and pipe connections.
The sand content kit is designed to determine the volume percentage of sand-sized particles in drilling fluid. API defines sand-sized particles as any material larger than 74 microns (200-mesh) in size. This test can be performed on low-solids fluids as well as on weighted fluids.
Drilling fluids play a critical role in oil rig operations, serving as the first line of defense for the wellbore. Their functions are of utmost importance, especially in supporting and stabilizing the wellbore. However, if not managed correctly, contamination, particularly an excessive presence of sand during the drilling process, can pose a significant challenge. Gravel packing is the most widely used sand-control technique for well completions, accounting for more than 90% of all sand-control operations. Gravel packing offers versatility and can be applied to almost any well at any deviation angle.
The experiment involved measuring bentonite and barite using an electric weighing balance, water using a graduated cylinder at room temperature, and preparing mud samples using a mixer. The sand content of the drilling fluid was determined using a sand content kit. All measurements were conducted in the laboratory and at room temperature.
The experiment was conducted at room temperature and under normal atmospheric pressure. Therefore, the results obtained reflect the behavior of drilling mud at low temperature and pressure conditions. These findings may not directly represent the sand content of drilling fluid in the wellbore at high-temperature and high-pressure conditions.
The sand content equipment comprises a specially developed sieve with a mesh size of 0.08mm (200-mesh), a high-quality plastic funnel, and a specially designed measuring tube. The measuring tube features markings to indicate the volume of the filled drilling fluid, allowing direct reading of the sand percentage, which is graduated from 0 to 20%. Sand-sized particles in drilling fluid are defined as those larger than 74 microns (200-mesh). The volume of sand added to the void space between grains is typically expressed as a percentage. Sieve analysis is the recommended method for determining sand content due to its reliability and ease of testing.
High sand concentrations in drilling mud can have adverse effects, such as the formation of a thick wall filter cake or settling at the bottom of the hole when circulation is interrupted. Additionally, high sand content can lead to abrasion of pump parts and pipeline connectors. The sand content equipment consists of a sieve with a unique mesh size of 0.08mm, a suitable plastic funnel, and a specially developed measuring tube with markings to indicate the filled drilling fluid and water levels. The sand proportion in the measuring tube can be directly read from 0 to 20%. The quantity and type of solids in drilling fluid are critical factors for controlling the rheological and filtration properties of the mud.
Most mud engineers prefer a sand percentage of less than 1%. Achieving this ratio can be challenging in excavated pits and virtually impossible in small steel pits without assistance. To address this, one approach is to use at least one desander cone to reduce the finer cuttings before they have a chance to recirculate. While this method is effective in small-diameter, shallow holes, it becomes inadequate as the hole diameter and depth increase. As a result, cuttings may continue to be recirculated and reground by the bit until they are too fine to be removed even by a desander. This situation leads to an increase in mud weight, water loss, and the risk of reduced circulation.
The only way to maintain consistent mud weight, viscosity, and sand concentration for optimal drilling results is through mechanical treatment, which involves removing the cuttings before they are recirculated. In water well drilling, a scalping shaker and a desander system large enough to handle more than 100% of the mud volume in circulation are commonly used. These systems can reduce the sand content to less than 1% before returning the mud to the rig.
The experiment involved the use of various apparatus and materials for measuring the viscosity of mud in the laboratory:
Report the sand content of the mud in volume percent and specify the source of the mud sample (e.g., above shaker, suction, pit, etc.). Note that coarse solids other than sand, such as lost circulation material, coarse barite, coarse lignite, etc., will be retained on the screen, and their presence should be documented.
After each use, thoroughly wash any sand or drilling fluid from the screen, funnel, and tube. Ensure that all equipment is completely dry. Pay special attention to cleaning and drying the 200-mesh screen.
Using the scale on the graduated tube, read the volume percent of sand obtained from the experiment.
Drilling fluids are essential fluids used during well drilling, playing a crucial role in maintaining primary well control by managing subsurface pressures through a combination of density and additional pressure on the annulus or surface. They are circulated down the drill string, flow out of the bit, and return to the annulus before reaching the surface, facilitating the removal of drill cuttings from the wellbore.
In this experiment, three different mud samples (Sample A and Sample B) were prepared, and the sand content of each sample was measured. The following table presents the measured sand content for each mud sample:
| MUD SAMPLES | SAND CONTENT (%) |
|---|---|
| SAMPLE A | 0.9 |
| SAMPLE B | 0.5 |
As depicted in the table above, two distinct types of bentonite (samples A and B) were used to create drilling mud, with the density increased by the addition of barite and further thickened by the addition of NaOH.
The sand content in the mud was tested using sand content equipment, which effectively filtered out sand-sized particles. To ensure accuracy, the sand should be thoroughly cleaned from the mesh screen, leaving no residual particles. Additionally, it's crucial to note that sand content has limitations in certain drilling locations and should not exceed a range that can damage equipment, especially pipelines.
The results showed that the sand content's volume percentage in the drilling mud increased with the amount of sand supplied. Furthermore, due to differences in bentonite types, sample A exhibited higher viscosity than sample B, as sample A had a greater sand percentage.
This experiment highlights the presence of sand-sized particles in drilling mud, emphasizing the importance of their removal if they exceed a certain range. The utilization of sand content equipment enables the measurement of sand content's volume percentage. By reducing sand content, the volume of slurry returning to the drill bit can be minimized, thus reducing drilling mud wastage and cost. In conclusion, regardless of the type of mud system employed, striving for a sand concentration of less than 1% is advisable. A compact and affordable sand content kit, readily available from mud companies, is a valuable tool for drillers.
Analysis of Drilling Fluids Sand Content. (2024, Jan 04). Retrieved from https://studymoose.com/document/analysis-of-drilling-fluids-sand-content
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