Trip Tank for Drilling Rig:Not included in the mud recycling system, the design fortrip tankis to protect the inner wall of drilling hole when the drilling stem out and in the hole and prevent the kick off. Trip Tank is always equipped with a level gauge so that the operator could control the mud capacity on the operation board. To some extent, trip tank is a independent tank from the mud cleaning system.Trip Tankis a small metal tank with small capacity about 20-40 bbls with 1 bbl divisions inside and it is used to monitor the well. There are several operations that we can use the trip tank to monitor the well as follows;Trip Out Of Hole (TOOH):While tripping out of hole, the trip tank is used to track volume of mud replacing volume of drill string. The volume of mud should be equal to displacement volume of any kind of tubular tripped out of hole.1. Trip In Hole (TIH):While tripping in hole, the drill string (bit, BHA and drill pipe) is ran back in the hole, the trip tank must be use to keep track volume gain. The expected volume gain should be equal to the displacement volume of whole string.2. Flow check:The trip tank is utilized to determine well condition in order to see if the well is still under static condition.The importance of trip tank is as follows:Provide sufficient hydrostatic pressure to prevent influx from reservoir.When TOH, mud hydrostatic will be lost because mud volume must substitute drill pipe volume pulled out of hole. If hydrostatic pressure decreases too much, influx from reservoir can come into the hole and make a trouble in well control. For this reason, mud in trip tank must be filled into hole to maintain hydrostatic pressure.

Kick Indicator:Volume of mud from the trip tank is pumped in the hole can be an indicator that relates to a situation occurring in wellbore as kick. If the volume of mud measured by trip tank is less than the expected volume of drill pipe volume tripped out of hole, the suspect problem is kick because volume of kick substitutes volume of mud.The Circulation System While Tripping:

To show the circulation system while tripping out of hole therefore you will be more understanding about how trip tank works.While Tripping Out of Hole (TOH), a trip tank pump will circulate mud into a bell nipple in order to keep the hole full all the time and the over-flow mud will return back to the trip tank. Once every stand is pulled, the mud volume in the well will decrease because the drill pipe is pulled out of hole. Since the trip tank pump is always run while tripping, the annulus will be full all the time (see figure below).

Figure 1- The diagram of trip tankTrip Tank and Its Importance to Well Control:Trip tank is a small tank which has a capacity of 20 50 bbl and its shape is tall and shallow because it can effectively detect volume changes. The trip tank system has the ability to continuously fill the well and take return back to the tank. With this capability, it will keep the hole full all the time and the volume changes either increasing or decreasing can tell the condition of the well.The diagram (Figure 2) below demonstrates how the trip tank is lined up:

Figure 2 Trip Tank Line Up To Continuously Fill The Hole

Each trip tank has a pump which will suck the fluid from the tank and pump into the well via the fill up line connected to a bell nipple under the rig floor. The fluid return will flow back via a return line and back to the trip tank. The float in the trip tank is connected to the wire and the position of the float will represent the trip tank volume indicator. Whats more, nowadays several rigs have installed the electronic instrumentation for the accurate volume measurement. This will help personnel on the rig track what is going on the well very quickly and accurately. As you can see, the complete system allows personnel to monitor the well.The trip tank must be maintained in order to avoid solid build up, pump and valve failure, leakage, etc. Moreover, it is very critical to frequently check the float and the electronic instrument to see if they are in good condition.Stripping operation requires a separate trip tank which has very small capacity of 3 to 4 bbl therefore it is not recommended to use the normal trip tank for this operation. The small volume tank, called strip tank, has more accuracy and suite for the operation.

How The Trip Tank Monitor The Well For Well Control:Trip Out of Hole:While pulling out of hole, each stand of drillstring pulled out must have the same amount of drilling fluid to replace the drillstring volume. For instant, each stand should take around 0.8 bbl. If you pull 10 stands out of hole, you should see at least 8 bbl of mud volume decrease in the trip tank. If you see the volume displacement less than what it should be, it indicates that the well is swabbed in.

Figure 3 Trip Tank While Tripping Out

Trip In Hole:While tripping in hole, mud will be pushed out of the well to the trip tank because steel displacement will replace the drilling fluid in the well. The volume displacement should be the same as the steel displacement. If the volume displacement is more than the steel displacement, the well may has some unwanted kick in the well.

Figure 4 Trip Tank While Tripping In

Flow Check:While flow checking, the volume in the trip tank should be at the same level. There should not be any changes. Increasing volume in the trip tank means the well is flowing. Conversely, if the volume decreases, the well has static loss.

Figure 5 Trip Tank While Flow Checking

Hole Monitoring Procedures While Running Casing or Tubing:This is the example of hole monitoring procedure while running casing and this will give you some ideas only. You need to adjust it to suit with your operation. Perform pre-job safety meeting with personnel involved in operation. A Full Opening Safety Valve (FOSV) and a closing handle with correction bottom connections that fit with of drill string which is being used must be available on the drill floor at all time. Driller must check this equipment. It must leave in an opened position.It may be required to have cross over from FOSV to casing connection. The Driller is responsible for well monitoring while tripping. The driller has the right to shut the well in if there is an indicator of well control or any doubt while tripping out. Trip sheet must be prepared with correct drill string/ tubular displacement. The Driller is responsible for well monitoring while tripping. The driller has the right to shut the well in if there is an indicator of well control or any doubt while running casing or tubing. Shut In Procedure Running Casing or Tubing for Well Control Situation must be posted in the driller cabin where the driller can see it easily at all time.Note: shut in procedure depends on requirement on each company. Kick detection devices as flow show, Pit Volume Totalizer monitor, and alarm must be tested properly and regularly. Mud logger kick detection devices must also tested in the same way as rig instrumentation to confirm an accuracy and readiness. Set the trip tank gain/loss and the flow show at required level. Use mud pit to monitor the well if larger casing is ran. Use a trip tank to monitor the well if a smaller casing or tubing is ran. This depends on the rig system. Track volume displacement with two separate systems if possible (one from the rig system and another one from mud logger system). Verify all well control equipment is properly lined up to shut the well in. Confirm the correct line up for well monitoring via a trip tank. Confirm the correct line up from mud pumps to the rig floor. Review shut in procedure while running casing or tubing. Review any foreseeable issues with Tool pusher and Customer Representative Ensure correct casing or tubing tally while running in hole Trip sheets must be recorded every stand of casing / tubing ran. Assistant Driller has a responsibility to accurately fill a trip sheet while running casing/tubing. Trip sheets must be kept in a tool pusher office after tripping operation completed. While running casing/tubing, if the volume discrepancy is seen, Assistant Driller must inform Driller, Tool Pusher and Company Representative. The running casing/tubing operation must be stopped for further evaluation and a Full Open Safety Valve must be installed. Ensure shut in while running casing/tubing procedure is posted on the rig floor closed to the driller console While tripping, if the volume discrepancy is seen, Assistant Driller must inform Driller, Tool Pusher and Company Representative. The tripping operation must be stopped for further evaluation and a Full Open Safety Valve must be installed.Hole Monitoring Procedures While Tripping:This is the example of hole monitoring procedure while tripping and this will give you some ideas only. You need to adjust it to suit with your operation Perform pre-job safety meeting with personnel involved in operation. Ensure a trip tank is clean without any barite sag or solid that can cause a trip tank pump failure. Trip sheet must be prepared with correct drill string/ tubular displacement. AFull Opening Safety Valve (FOSV)and a closing handle with correction bottom connections that fit with of drill string which is being used must be available on the drill floor at all time. Driller must check this equipment. It must leave in an opened position.It may be required to have cross over from FOSV to drill string connection. The Driller is responsible for well monitoring while tripping. The driller has the right to shut the well in if there is an indicator of well control or any doubt while tripping out. Shut In Procedure While Tripping for Well Control Situation must be posted in the driller cabin where the driller can see it easily at all time.Note: shut in procedure depends on requirement on each company. Kick detection devices as flow show, Pit Volume Totalizer monitor, and alarm must be tested properly and regularly. Mud logger kick detection devices must also tested in the same way as rig instrumentation to confirm an accuracy and readiness. Set the trip tank gain/loss and the flow show at required level. Track volume displacement with two separate systems if possible (one from the rig system and another one from mud logger system). Verify all well control equipment is properly lined up to shut the well in. Confirm the correct line up for well monitoring via a trip tank. Confirm the correct line up from mud pumps to the rig floor. Review shut in procedure while tripping. At the following events, flow checks must be performed; At the bottom of the well prior to tripping out. At the deepest casing shoe. Anytime that there is any doubt in the well condition. Anytime that the hole displacement is not correct. Prior to pulling HWDP or Drill Collars through the BOPs. If the monitoring or circulating system does not work properly. Review any foreseeable issues with Toolpusher and Customer Representative Check and maintain accurate pipe tally Do not trip when filling up a trip tank Perform trip drill with crew every trip if possible Toolpusher should be on rig floor for at least first 10 stands to monitor the operation. Trip sheets must be recorded every stand of drill pipe pulled. Assistant Driller has a responsibility to accurately fill a trip sheet while tripping. Trip sheets must be kept in a tool pusher office after tripping operation completed. While tripping, if the volume discrepancy is seen, Assistant Driller must inform Driller, Tool Pusher and Company Representative. The tripping operation must be stopped for further evaluation and a Full Open Safety Valve must be installed. Ensure shut in while tripping procedure is posted on the rig floor closed to the driller console Record pick up weight and maintain a trend in a data sheet to observe any hole issue. Do not attempt to pull if you see abnormal drag 30 Klb over a current pick up weight. Any abnormal dram must be informed to Toolpusher and Customer Representative. If a slug is planned to pump, driller must determine volume gain from slug.

Barrels of slug required for desired length of dry pipe Weight of slug required for desired length of dry pipe with set volume of slug: The U-Tube effect must be discussed with team prior to pumping slug. Ensure the well condition before pumping slug. Inform Toolpusher and Customer Representative before pumping slug. After pumping slug, it is required to wait until the well is stable prior to continuing the tripping operation.

What Are Differences Between Possible and Positive Well Control Indicators?Many people tend to confuse between possible and positive well control indicators therefore we would like to differentiate between these two well control indicators. These two concepts are vital for well control because one indicate the possibility of the kick but another one shows definite signs that the well is taking back to you. In this article, we summarize all information regarding the possible and positive kick indicators so you can use for your work.Possible Well Control (kick) Indications:Possible well control (kick)indicators : Mean that there is possibility to get influx into wellbore. ItMAYorMAY NOTbe a kick.The indications can be either kick or just formation react while drilling. You need to remember that just only a single possible indicator cannot may not good enough to identify underbalanced condition in wellbore and the possible kick indicators must be used collectively. Therefore, drilling team on the rig needs to closely monitor the well and prepare appropriate action plans.The Possible Well Control (kick) Indications are as Follows:Change in Drilling Breaks (ROP Change): If the differential between formation pressure and hydrostatic pressure created by drilling mud decreases, there is possibility to increase rate of penetration because the hold down effect is decreased.Increase Drag and Torque: Increasing in drilling torque and drag are usually noticed while drilling into overpressured shale formation because underbalanc hydrostatic pressure exerted by drilling fluid column cannot to hold back the formation intrusion into wellbore. Shale normally has low permeability so formation fluid will not come into wellbore. Anyway, if we drill ahead pass high shale pressure into overpressured high permeability zones such as sand or carbonate, the formation fluid will flow into wellbore resulting in kick. This is very important to record frequently drilling torque and drag because it could be your well control indicator.Decrease in Shale Density: Typically, shale density will increase as we drill deeper. If we see decrease in shale density, it may indicate that your well is in underbalance condition because high pressure zones (abnormal pressure) develop within large shale section. Practically, density of shale must be measured frequency and plot against drilling depth. You can see from a chart if there is any deviation in trend that could be an indication of change in pore pressure.Increase in Cutting Size and Shape: Pieces of formation may break apart and fall into wellbore because of underbalance situation. Because rocks pieces broken by underbalance condition are not ruined by bit, they will be more angular and bigger than normal cutting. Larger of cutting size will be result in difficulty to circulate them out of wellbore, hence, there will be more hole fill and torque and drag will increase. In addition, without a proportional increase in ROP (rate of penetration), cutting volume coming over shale shakers will increased noticeably.Decrease in d-Exponent Value: Normally, trends of d-Exponent will increase as we drill deeper, but this value will decrease to lower values than what we expect in transition zones. By closely monitored d-Exponent, d-Exponent chart will be useful for people on the rig to notify the high pressure transition zones.Read and understand about d-Exponent and learn how to calculated-Exponentandnormalized d-Exponent (corrected d-Exponent).Change in Mud property: Without any chemical added into drilling fluid system, its property change due to increasing in water and/or chloride content indicates that formation fluid enters into the wellbore.For some drilling mud, when salt water enters into the wellbore and mix with drilling fluid, the mud viscosity will increase.In water base mud with low Ph salt saturated, the mud viscosity will decrease because of water from formation mixing with mud. On the other hand, water contamination in oil base mud will result in viscosity increases.Increase in Temperature from Returning Mud: By observing trend of temperature coming from mud return, temperature trend showing deviation from the normal temperature trend can be an indication of abnormal pressure zones, especially while drilling into transition zones.There are some factors that you need to account for when you try to evaluate mud temperature changes as listed below; Surface temperature conditions. Elapsed time since tripping. Mud chemicals used. Wellbore geometry. Circulating rate. Cooling effect when drilling fluid flows through a long riser (deep water consideration).Increase in trip, connection and/or background gas:Gas in mud, normally called gas cut mud, does not be a sign of a well flowing because it could be gas coming from formation. Nonetheless, personnel on the rig should keep in mind as a possible kick indicator. Hence, flow show and PVT (pit volume total) must be closely monitored.Gas in the mud can come from one or more of the reasons listed below: Drill into a formation that contains gas or hydrocarbon. Temporally reduce in hydrostatic pressure due to swabbing effect. Pore pressure in a formation is greater than the hydrostatic pressure provided by drilling fluid in a wellbore.Positive Well Control (kick) Indications:Positive well control (wellbore influx):- Indications mean indications showingalmost 100% kick(wellbore influx) into wellbore. We can classify the positive indicators the following categories.Positive Well Control Indicators While drilling:Increase in flow show Without any increasing in flow rate in, increase in return flow indicates something coming into wellbore while drilling. Therefore, flow show instrument provided by the rigs or service companies must be checked and calibrated frequently.Increase of active pit system (Pit gain): Because drilling fluid system on the rig is a closed system, increasing in flow show without adjusting flow rate in will cause pit gain in a pit system. Nowadays, with high technology sensors, detecting change in pit level is easily accomplished at the rig site. However, visually check the pit level is importance as well for double checking figure from the sensors. Sometimes, change in pit level may be detected after the increase in flow show because it takes more time to accumulate volume enough to be able to detect by pit sensors.Continue Flowing While the Pumps are Off: When pumps are turned off, bottom hole pressure will decrease due to loss of equivalent circulating density (ECD). If there is any flow coming after pumps off, it indicates formation influx into wellbore.Positive Kick Indicators While Tripping:Trip log deviation:such as short fill up while tripping out and excess pit gain while tripping in. For tripping operation, it is very important to have a filling system via trip tank that provides continuous hole fill all time. With utilizing that system, we can compare fluid that is filled in or returned from wellbore with steel volume of tubular (drill pipe, drill collar, BHA, tubing, casing, etc). If drilling fluid volume is less than theoretical pipe displacement while tripping out or more return fluid while running in, you need to flow check and monitor the well. If flow check indicates wellbore influx, crew must quickly shut the well in. If flow check does not show any influx, drill string must be run back to bottom in order to circulate at least bottom up to ensure hole condition.Positive flow when pipe is static:Every time that pipe in static condition. Trip tank with correct filling system must be monitored all time by both rig personnel and mud logger. If volume in trip tank increases, personnel must confirm flow check and prepare to shut the well in.Hole Monitoring Procedures While Drilling or Milling Operation:This is the example of hole monitoring procedure while drilling or milling and this will give you some ideas only. You need to adjust it to suit with your operation. Perform pre-job safety meeting with personnel involved in operation. The Driller or the toolpusher on the break is responsible for monitoring a well condition and identifying when a well must be shut-in with safe and correct practices. If the driller sees a hole problem, the drilling operation must be stopped and inform the following people: Toolpusher, Senior Toolpusher and Company Representative. Shut In Procedure While Drilling or Milling for Well Control Situation must be posted in the driller cabin where the driller can see it easily at all time.Note: Shut in procedure depends on requirement on each company. The Driller has a responsibility to check all well control equipment and record into the sheet at the beginning of tour. The Driller must review the schematic for line up and ensure the correct line up for required operation. A drilling parameter trend sheet will be updated every hour during drilling operations. The parameters are as follows; RPM, active pit volume, % return flow, Rate Of Penetration (ROP), drilling torque, off bottom torque, pickup weight / slack-off weight, mud density, gas units or percentages, pumping pressure, Equivalent Circulating Density (ECD), etc. The driller must monitor any drilling break and inform Tool pusher and Customer Representative if there is drilling break. Kick detection devices as flow show, Pit Volume Totalizer monitor, and alarm must be tested properly and regularly. Mud logger kick detection devices must also tested in the same way as rig instrumentation to confirm an accuracy and readiness. Set the PVT gain/loss and the flow show at required level. Discuss with pump man, shaker man, centrifuge engineer and mud engineer to have a proper communication prior to transferring any drilling fluid. Driller and mud logger must be informed prior to making any changes in the mud pit level. Any changes in centrifuge parameters must be also informed a driller and a mud logger. A full opening safety valve and a closing handle with correction bottom connections that fit with of drill string which is being used must be available on the drill floor at all time. It must leave in an opened position. Driller must check this equipment. The driller must confirm a current space out diagram and ensure the correct height. Monitor drilling mud properties and ensure that personnel involving in drilling fluid as mud engineer, pump man, shaker man and centrifuge engineer to communicate to the drilling if there is any changes in mud properties, especially mud weight. Discuss with shaker man to closely monitor cuttings over the shale shakers. If excessive cuttings and/or change in casing size/shape are observed, inform the Driller, Tool pusher and Customer Representative. It is a possible well control indicator. If one of thepositive well control indicatorsis seen, the driller must shut the well in as per a shut in procedure. Then inform Tool pusher, senior Tool pusher and Customer Representative. If one of thepossible well control indicatorsis seen, the driller must stop drilling and flow check the well. Then inform Tool pusher, senior Tool pusher and Customer Representative. If there is any doubt in the well condition, the driller has the right to shut the well in. Then inform Tool pusher, senior Tool pusher and Customer Representative. Do not try to contact any supervisors first.