A drill pipe float valve, also recognized as a non-return valve, is a specialized valve installed in the bottom hole assembly (BHA) and its primary function is to serve as a check valve, permitting the downward flow of drilling mud through the drill string but preventing any unwanted fluid from flowing back up into the drill string.
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
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.
Conclusion:
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.
References
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.
The Valve Removal Plug (VR Plug) is a specialized one-way check valve designed for threaded installation through an outlet valve on a casing head, casing spool, or tubing spool into a female thread in the outlet. This configuration effectively isolates the valve from pressure, enabling the convenient removal of the outlet valve for repair or replacement. After the necessary maintenance, the valve can be reinstalled, and the VR Plug can then be removed. It is important to note that VR Plugs are intended for short-term use and should not be considered a permanent substitute for wellhead valves. The image below is a VR plug.
A choke is a special valve used in well control situation and its primary purpose is to generate back pressure in a well, effectively increasing bottomhole pressure to manage formation flow during the removal of an influx. Chokes come in two types: positive or non-positive sealing, with adjustable features necessary for well control applications, as opposed to fixed chokes used in production or testing. These components are offered in various sizes and pressure ranges, and adjustable chokes can be either manually operated or hydraulically controlled from a remote console.
There are two main categories of chokes: manual chokes and hydraulic chokes.
Manual Chokes:
Operated by hand using a handwheel, manual chokes are not the primary choice for well control operations. The manual adjustment process is less effective for controlling pressure in the wellbore during circulation.
Manual Chokes
Hydraulic Chokes:
Hydraulic chokes provide easy adjustment and enable precise remote regulation of choke pressure. A notable feature of most hydraulic remote chokes is their placement in the choke manifold, while control occurs remotely from a panel displaying casing and drill string pressures.
Hydraulic Choke
In scenarios with multiple chokes, the manifold design should facilitate the isolation and repair of one choke while another remains active. Additionally, it is crucial to have spare parts for the chokes readily available at the rig site.
References
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.
Learn key differences between Back Pressure Valve (BPV) and Two-Way Check Valve (TWCV) so you can choose the right one for a particular operation.
