What’s a Poor Boy Degasser (Mud Gas Separator)?

Poor Boy Degasser or Mud Gas Seperator, located downstream of the choke manifold, is a vertical vessel used to separate any gas from drilling fluid during well control situation. Once the gas has been separated, it can pass through the vent line in the derrick. Alternatively, as long as it’s a safe distance from the rig, it could even be vented.

Figure 1 - Poor Boy Degasser (Courtesy of H-Screening)

Figure 1 – Poor Boy Degasser (Courtesy of H-Screening)

With mud’s separators, there are two main types. Also known as a ‘poor-boy’ and a ‘gas buster’, the more common of the two is called an atmospheric mud/gas separator. However, some mud/gas separators are designed to operate at moderate back pressure. Although these will mostly operate under 100 psig, it’s possible to come across those that work at the atmospheric gas vent line pressure plus the vent line friction drop. The simple diagram of poor boy degasser is show in figure 2.

mud-gas-seperator-1

Figure 2 – Poor Boy Degasser (Mud Gas Separator) Diagram Continue reading

What is a degasser on a drilling rig?

A degasser is equipment used to remove entrained gas in drilling fluid so it prevent or minimize reduction of hydrostatic pressure due to gas cut mud. When drilling mud passing over the shale shakers while drilling, gas will normally be released. However, the wellbore could receive additional volumes of gas and these need to be removed from the mud. If not removed from the circulating system properly, recirculation of mud containing gas will reduce the well’s hydrostatic head. With a degasser, this can eliminate or minimize loss of hydrostatic pressure.

Figure 1 - Degasser (Courtesy of NOV)

Figure 1 – Degasser (Courtesy of NOV)

Mounted over the active pit, degassers are essentially a one-stage liquid/gas separator. With a maximum lift to the inlet of around ten feet, mud vacates the submerged pipework in the mud pit and enters the degasser. From here, a three hp electric motor will power a vacuum pump and this should be mounted atop the degasser itself. By the pump, the vacuum is then applied to the vapor space.

Ultimately, the range applied by the vacuum will depend on the density of the mud passing through. In most cases, it will offer between 2-5 pounds per square inch (between 8 and 15 inches of mercury). In terms of extracting gas from mud flows, 900 gallons per minute is likely to be the maximum rate. Continue reading

Common Problems and Complications During Well Kill Operation

During well kill operation, crews should always be vigilant since complications can actually occur at any stage. If there’s a discrepancy in the kill plan, it needs to be noted immediately. For example, pressure gauges may stop working; they therefore should be monitored carefully. If there’s a failure, back-up gauges need to be made available during a well control operation.

In this article, it will describe common problems and complications during well kill operation which are plugged bit nozzle, plugged choke, choke washout, pump failure and string washout.

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Possible Kick Indicators in Well Control

The alertness in determining early possible kick indicators in well control is of the utmost importance to prevent a well control incident. Careful observance and positive reaction to these signs will keep the well under control and prevent the occurrence of a well control situation.

The various signs that have been recorded as early warning indicators are not consistent in all situations. The signs however may have to be used collectively as one indicator may not accurately provide the warning of getting into an underbalanced situation. Even though the series of signs may change between wells, early warning indications can be found from the following list.

  • Increase in drilling rate of penetration.
  • Increase torque and drag.
  • Decrease in shale density.
  • Mud property changes.
  • Increase in cutting size and shape.
  • Increase in trip, connection and/or background gas.
  • Increase in the temperature of the return drilling mud.
  • Decrease in D-exponent.

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What Cause Insufficient Mud Weight Leading to a Well Control Situation

Known as an underbalanced condition, this occurs when, in the wellbore, formation pressure is higher than the hydrostatic pressure and this lead to a well control situation. To overbalance formation pressure, the required hydrostatic pressure is normally provided through an adjustment in drilling fluid density. Hydrostatic pressure loss can occur for a number of reasons;

  • ECD loss
  • Surface drilling fluid dilution
  • Cement density reduction
  • Drilling process releasing formation fluids
  • Weighting material movement from mud cleaning equipment
  • Drilled cuttings or mud weighting materials settling

Since a reduction in the density of mud returns is sometimes happened, most wells are designed to have sufficient overbalance to encounter the small reduction of mud density and this should prevent a kick. However, if there is significant mud weight reduction, an investigation shall be performed to find any root cause and provide any preventive actions.

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