Calculation of Evaporation loss rate of drilling fluids during drilling/circulation
17 January 2019
I am trying to find a method to calculate evaporation losses of drilling fluid from the tanks during drilling. I have found a graph which relates the evaporation rate with the flow line temperature but it does not consider the surface area of mud tank system. The problem is that number of tanks in the active system and their area has major effect on evaporation rate. that's why I cannot calculate the correct results by using this graph. I would appreciate if someone can help me in this calculation.
I missed your post explaining why you needed this information.
In your circumstances, I would definitely concentrate on the solids control equipment.
The importance of the shakers cannot be emphasised enough.
If the original manufacturer has not inspected them within the last year, get them to mobilse an inspector to service and test them - it is surprising how often these throw up poor service or operating practices by the Rig.
In fact, given your circumstances, I'd recommend having a solids control expert on the Rig at all times.
They only have to save a few bbls of mud per day to pay for themselves, while greatly increasing the standard of reporting - not just of mud useage and losses, but also retorts showing exactly how much mud is being lost on the cuttings from the shakers and centrifuge underflow.
This quality information can make it much easier to justify capital expenditure, for example, upgrading the shakers, or retro fitting an additional shaker, or adjusting the way the centrifuges are run.
Always use an approved supplier shaker screens - preferably OEM. Beware of cheap copies (especially 'metal frame' screens from China). Trying to save money by buying cheap screens will end up costing you a lot more in mud losses in the long run.
Remember that shakers and screens are designed to work together as a system - you wouldn't replace a broken gearbox in your Mercedes with one from Ford, would you?
Avoid using the mud cleaner - the centrifugal pump breaking up of cuttings in the hydrocyclones will just add more fines to the system and make the centrifuges work harder.
All the best
The evaporation rate of your fluid on surface is not just down to air temperature, humidity or the size of your pits.
The temperature of the mud is the major factor. The spreadsheet here can be a good guide.
To reduce your evaporation rate , consider using mud coolers.
Thanks a lot for all of you who took interest in my silly question and came up with valuable answers.
Let me explain some detail of what I want.
I am working on the idea to improve solid control equipment efficiency in order to reduce overall drilling fluid cost. We are working with diesel based OBM and the wells depth ranges from 4,000 m to 5,500 m. The northern area of Pakistan is famous as one of the most difficult zones in the world. The strong tectonic forces have destroyed the area in such a way that sometimes the actual formations sequence is only 50-60% matches the prognosis.
Drilling a well takes 8-12 months. This long period of time makes the surface losses a nightmare (Last year we lost 16,000 bbls of OBM as surface losses during a single well).
I want to precisely measure each component of surface losses to discover actual room for improvement in each part of the mud system (shaker loss/mud cleaner loss/ centrifuge loss/evaporation loss/tripping loss/equipment maintenance loss/Mud hidden in hole washouts etc). Usually no proper calculation is done while reporting the surface losses which results in misleading information.
I want to avoid investment of unnecessary money in upgrading the equipment without knowing whether it is really beneficial or not.
This is an issue for the waterbased sections of many wells drilled in desert environments. No one that I know has an accurate solution. There are just too many variables. At a minimum you have losses on cuttings and to the formation. The suggestion to observe losses in a reserve pit would get a non-swag number to consider. You could also try measuring the relative humidity just above the surface of the mud and comparing to atmospheric humidity. I have also observed how the O:W ratio in oil mud changes with no water additions. But, absent a completely enclosed system to "capture" the evaporation it will still be an estimate at best. Good luck!
Great unusual answer to an unusual question. The mainframe culture has killed acquired intelligence. Time to get some artificial intelligence so there is augmented intelligence with decision quality. Note with a mud system the loss of liquids can be analysed in a number of ways but viscosity reading and solids concentration are a couple. Don't for get filtration loss and hydration impact free water. Point being we should care why such a question has to be asked once someone has graduated from high school. The reward for care is joy and wisdom. Imagine what life in the oil industry would be like if folk cared intrinsically Vs the current extrinsic. CARE "Competency Assessing" "Risk Ethics HESQ" "Respect Empathy" "Relational Equity"
To answer your question - at least from my perspective; in hot, dry, land environments, unaccounted for mud losses in the system can amount to 10's of bbls per day.
These are often logged as "evaporation losses", especially if there are no indications of downhole seepage losses.
However, it's a SWAG as to how much is really being lost on cuttings over the shaker vs. how much is really being evaporated and in the past I have seen the figures, shall we say, 'massaged' if permits limit how much mud can be disposed of with the cuttings.
A reserve tank of mud can be used to get an approximate evaporation rate, if you can leave it alone for a suitable period of time.
One application of knowing ahead of time could be if you are looking at a Rig with uncovered mud tanks, but water is expensive.
An evaporation calculation could be used to work out the rough cost of water lost due to evaporation vs. the cost of getting the tanks covered.
In over 50 years in the industry, I have never heard this question. Why do you care?