LSU Oil Inc.
Date: October 26th, 2016
To: Jack Worrysome, Drilling manager
From: Nicholas Perez-Lasala, Jason Jaume, Rafael Morales
After arriving at LSU #6, two procedures for weighting up the current drilling mud were performed. Adding barite and a barite/water mixture were the two procedures executed.
After completing and analyzing both procedures and results, we recommend adding a mixture of Barite and water to the drilling mud. This method will allow a lower pump pressure to be maintained by providing a lower viscosity. If the mud is weighted by adding barite directly, the density and viscosity would be too high. This would cause the mud to be too thick and heavy, which would cause pump pressure to rise. The recommended procedure would also give a lower gel strength and yield point.
In this case, when faced with a high percentage of cuttings, dilute the mud. Once the dilute mud is ready, adding barite will make a heavier mud.
When faced with limited mud volume, the available must be placed in the mixer and the weighting substance must be added carefully and slowly. The quality of the mud must be continually monitored as to not create a viscosity that is too high.
- Experiment Data
Mud density is dependent on the components in the mud and their volume fraction. Bentonite is a typical clay used in muds and has been used extensively in previous experiments. Bentonite was used as the base mud in this experiment. Additives like barite can be used to weigh the mud and increase the density. When adding bentonite, other properties change other than density, such as viscosity and API water loss. These properties should be watched to ensure they stay within the optimal ranges. In certain cases, where viscosity needs to be lowered, a proper amount of water may be added with the additive to obtain the results desired.
A 9 ppg base mud was supplied in this specific experiment. The density of the mud was determined by a mud balance. Readings were taken at 300rpm and at 600rmp to determine both the plastic viscosity and yield point. The ten second gel strength was also obtained from the viscometer. A retort was performed on the base mud as well as a sand content test on the base mud to determine the portion of the mud that was solids and liquids. Finally, the API water test was conducted.
The amount of barite and a combination of barite and water was calculated to weigh the mud up to 12 ppg. The barite and water were added at the beginning of mixing the mud and all of the tests listed above except the retort and sand content tests were performed on the two 12 ppg muds.
The needed amount of calculated additives was determined. Based on these, a 12.4ppg density was measured for barite, and a density of 12.45 ppg was measured for barite/water mud. The raw data measured in each test is located on the attached data sheet below. It is important to notice the additives resulted in a higher water loss than the base mud. It is also noted that the retort test showed the mud with barite to have a much higher solids volume fraction than the base mud; which makes sense since it is added to increase density. The yield point and the gel strength for the mud with barite is substantially higher than that of the base mud. These two muds are in the acceptable range.
- Adding barite increases Fann readings at both 300 rpm and 600 rpm. The raised difference between these reading increases both the plastic viscosity and yield point of the mud. Properties that decrease with the addition of barite are the gel strength and the API Water Loss.
- Adding water with barite reduces the gel strength when compared to adding just barite. While the plastic viscosity remains the same with water addition with barite, the yield point increases when water is added simultaneously with barite as opposed to just adding barite. The API water loss for both muds stayed constant. In general, many of the properties stayed constant due to a slight difference in barite and a small amount of water was added.
- 6. Adding water with barite creates a more viscous mud (raising both 300 rpm and 600 rpm Fann readings by 10 cp –a 10-20% increase). For mud that does not need high gel strength, mixing water with the mud will lower the gel strength. The density will also decrease so it is vital not to add too much water to reduce the pressure too much.
- When faced with limited mud volume, the available must be placed in the mixer and the weighting substance must be added carefully and slowly. The quality of the mud must be continually monitored as to not create a viscosity that is too high.
When faced with a high % low gravity solids, it is proposed to dilute this mud with water to reduce the mud to a low % low gravity solids. Once the dilute mud is ready, adding barite will make a heavier mud.