What is a trip tank and its roles for drilling operation?

A trip tank serves as a compact, calibrated tank typically holding between 20 to 50 barrels, employed in drilling operations to monitor the flow of drilling fluid into and out of the wellbore whether pulling out (tripping out) or running in (tripping in) drill pipe or any tubular in the hole.

As each section of pipe is pulled out, the resulting void must be filled with drilling mud equivalent to the removed steel volume. This process, known as “pulling dry,” prevents a decrease in hydrostatic pressure, which can lead to unwanted wellbore events. The volume of mud pumped in is meticulously recorded on a trip sheet.

Trip tanks help detect potential kicks (inflow of formation fluids) by comparing the actual mud volume pumped in with the calculated displacement volume. If the actual volume is significantly lower, it suggests the well is swabbing and fluids are entering, a key indicator of a potential kick. Conversely, while running pipe in, any excess mud displaced should equal the steel displacement. The image below shows the typical trip tank diagram.

Trip tanks come in various configurations, but all prioritize accurate volume monitoring. The typical design is tall and narrow, allowing for easier detection of even slight changes in fluid level. This ensures precise measurement of fluid gain or loss within the wellbore.

The ability to continuously fill the hole and simultaneously capture returns in the trip tank is highly beneficial. This eliminates the need for constant driller attention, reducing the risk of hydrostatic pressure fluctuations. Comparing the actual trip tank volume changes with the calculated displacement volumes helps identify discrepancies and ensures the well is receiving the appropriate amount of mud. Trip tanks can also be utilized for dedicated wellbore monitoring. By diverting wellbore returns to the tank, even small fluid gains or losses can be identified, providing valuable information during flow checks and other critical operations. The image below shows the actual trip tank on the rig.

Trip Tank

Trip Tank

Rigorous maintenance of trip tanks is essential. Regular cleaning prevents solids buildup, while inspections ensure proper valve and pump functionality. Additionally, floats and instrumentation require calibration at specified intervals to maintain accuracy.

For even greater accuracy, especially during stripping operations, a separate tank with a smaller capacity (3-4 barrels) can be used. This “strip tank” allows for precise measurement of small fluid volumes before transferring them to the main trip tank for cumulative volume analysis.


Trip tanks are indispensable tools in drilling operations, ensuring accurate wellbore pressure maintenance, kick detection, and overall wellbore status. By prioritizing reliability, accuracy, and meticulous maintenance, these vital pieces of equipment contribute significantly to a safe and efficient drilling process.


Cormack, D. (2007). An introduction to well control calculations for drilling operations. 1st ed. Texas: Springer.

Crumpton, H. (2010). Well Control for Completions and Interventions. 1st ed. Texas: Gulf Publishing.

Grace, R. (2003). Blowout and well control handbook [recurso electrónico]. 1st ed. Paises Bajos: Gulf Professional Pub.

Grace, R. and Cudd, B. (1994). Advanced blowout & well control. 1st ed. Houston: Gulf Publishing Company.

Watson, D., Brittenham, T. and Moore, P. (2003). Advanced well control. 1st ed. Richardson, Tex.: Society of Petroleum Engineers.

What You Need To Know About Drilling Bit Balling Up and How To Troubleshooting It

Bit balling is one of the drilling operational issues which can happen anytime while drilling. This issue can cause several problems such as reduction in rate of penetration and surface torque, increase in stand pipe pressure. Personnel may eventually need to pull out of hole the BHA in order to clear the balling issue at the bit. This article will teach you about the bit balling and how to prevent it in the planning phase and how to effective detect and clear the balled up bit before it becomes a worse problem.


How You Recognize the Bit Balled Up While Drilling

Drilling Torque – Drilling torque will be lower than normal drilling torque since most of the cutters are covered up by cuttings.

Rate of Penetration – The ROP will decrease more than projection. If you drill 100 fph and later on the ROP drops to 50 fph without any drilling parameters changed, this might be this problem.

Standpipe Pressure – Standpipe pressure increases with no changes in flow rates or drilling parameters. Balling up around the bit reduce annular flowing area resulting in increasing pressure.

Factors Affecting Drill Bit Balling Up

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Mechanical Blind Back Off Drill String and Tubular

Mechanical blind back off is the procedure to intentionally break out stuck drill string by applying left hand torque and transmitting down hole. This is the last method to recover drill string because back-off position cannot exactly determine. One situation that I used to do the blind back of is when the perforating gun cannot be run into tubing string.


Procedure to Perform Blind Back Off Operation

1. Determine drilling parameters prior to get stuck if possible.

Pick up weight __ lb

Slack off weight __ lb

Rotating weight __ lb

2. Pick up drill string at 10% over the rotating weight. Apply 50% of make-up torque with left hand turn and lock TDS. Record how many turns. Slowly work string down for 5-10 minutes to transmit surface torque to the bottom. Weight while working should be between pick-up and slack off weight.

3. Repeat step#2 with 70%, 90%, 100%, 110% make up torque

4. The string should be back off while working down.


Note: The concept is to have overpull tension applied at each connection while left hand torque is transmitted into the drillstring. Once the drill string is worked, the torque will be transferred to the bottom connection of the well.


Fishing Drill Pipe Procedure – Screw in Drill Pipe

Sometimes drillpipe is accidentally dropped into the well and you need to fish it out of the well. One easy option that may be feasible to perform is to use a drill string to screw into the drill pipe in the well.


Before going into a detailed procedure, you may need to check the following conditions.

• Tight clearance between hole and tool joint

• Tool joint at the top of fish is in a good condition

Data that you need to know before going to fish the drill string

• Fish length

• Top of fish

• Weight of fish in the mud

• Actual turn to fully engage when screw in

Detailed procedure for fishing drill pipe by screwing into the fish

Fish length = xxx ft

Expected TOF = xxx ft

Weight of the fish (BHA + DP) = xx Klb


1. Trip in hole 1 stand

2. Count the actual turn of drill pipe

3. Run in hole to xxx MD (200 ft above the Top Of Fish)

4. Make up top drive

5. Break circulate with 160 GPM using current drilling fluid in the well

• Record pressure

6. Record pick up and slack off weight without rotation

7. Record pick up and slack off weight with 20 RPM

8. Record torque with 20 RPM

– In the steps 5-8, you will get the base line values when the drill string does not engage with another part.

9. Slowly run in hole without rotation

10. Tag top of fish while pumping with 160 GPM

11. Pick up 5 ft

12. Slowly run in hole with 20 RPM

13. Attempt to screw into the top of fish (tool joint)

14. Indicators if the fish is engaged.

– Increase in pumping pressure, torque, weight on bit and pick up weight.

– When picking up drill string, increment of pick up weight should close to buoyed weight of the fish (dropped drill string).

15. Flow check

16. Pull out of hole to surface.

 Note: This is the generic guideline. You may need to adapt some parameters/steps to match with your rig operation.


Deal With Soft Clay Formation in Sea Water

The well was drilled with sea water and the formation is soft clay formation. Then, the bit was totally plugged. We did not have any chance to displace well with water based mud prior to coming out of the hole. We flow checked and came out of hole to change the bit.

Because the formation is clay which will react with seawater resulting formation swelling, we need to develop specific rig procedure to deal with when tripping in hole.

What are the foreseeing issues?

• Clay formation swell

• Pack off due to formation instability

• Soft formation tends to get side tracked easily with mud motor

What is the objective?

• Attempt to condition the well before running back in hole with motor assembly to minimize chance of side track.

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