Killing Method: Bull heading Method

Bull heading is a shut-in well control technique to be used to pump fluids underground without returns. This method is typically used in situations where circulation cannot be performed, such as when a packer in the wellbore is set, or when an annular influx blocks standard circulation. The bullhead is an operation focused on forcing kill-weight fluid into the formation, displacing the influx and controlling the well.

This article will describe the bull heading operation in details giving its general requirement, alternate conditions, preparation steps and the operational procedure. Also discussed will be important safety concerns and best practices for implementing them safely and safely.

Bull heading Operation General Requirements

During a bull heading operation, various important parameters need to be assessed to ensure effective well control.

Assessment of Key Factors

Prior to undertaking a bull heading operation, the following parameters must be, established and assessed:

ESTIMATED MAXIMUM SURFACE PRESSURE – It is important to know how high a pressure the well might see to avoid equipment failure.

Type of influx – Knowing if the influx gas, oil, or water, will help define the kill fluid and strategy.

Squeeze mud ahead of influx — If the influx has migrated or has been circulated up, it is important to squeeze mud ahead of the influx to correctly displace it.

Mud gas separator capacity – Evaluation of separator capacity, vent line size and killing rate effect on system

Formation fracture risk – Establishing the risk of formation fracture during routine killing operations to avoid unintentional losses.

Formations Data Training

As a result, contractors must estimate the pressure required to fracture formation via its strength at the kicking zone. So the applied pressure is guaranteed, never exceeds the safe limit, etc.

Pressure Data Recording

All pressure data should be documented during well killing But when everything is at stake, and you need to have that well under control as soon as possible, data acquisition might go to the background because safety is your priority.

Proper Use of Killing Lines

When installed according to the pre-processing program, both the inlet killing line and the outlet killing line must use a hard line.

Fluids Killing Compatibility

Therefore, the kill fluid shall be formation compatible to minimize formation damage and fulfill geological and operational parameters.

Adequate Kill Fluid Volume

The kill operation and any subsequent testing or fracturing will require sufficient well-killing fluid available on location.

Pressure Assessment

Maximum allowable treating pressure is to be determined by a complete review of working pressure for all components (i.e., what the well head and respective equipment down hole can withstand.

Gas Invasion Monitoring

No gas is leaking into the well, which must be verified. Gas shall be routed to the poor boy degasser and flare line bled, with personnel at flare outlet.

Venting and Ignition Planning

A ventilation and ignition plan should be developed that is based on the wind direction. If hazardous gases such as H2S are present in the emitted gas, then they should be flared.

Hazardous Gas Monitoring

Monitoring for toxic gas (natural gas, H2S, CO2) should be continuous and the data recorded. Make sure if this is the case, proper signage and barricades are placed to mitigate risks.

Fire and Explosion Prevention

Open flames and hot work shall be prohibited.

Ensuring correct protection of electrical facilities.

Any other potential secondary hazards should also be neutralized (i.e. relocating flammable items like fuel tanks upwind of the explosion).

Conditions Under Which Bull heading is Used

Bull heading is employed throughout any situation where normal circulation is not feasible — for example: Tubing in the well with a packer set –The tubing is not communicated with annulus.

Tubing in well, influx in annulus – Cannot circulate through tubing.

No tubing is present in the well. Influx is already in the casing, which makes bullheading the simplest and most rapid.

Depleted formations — With low formation pressure circulation is challenging.

H2S Influx – Surface handling is dangerous.

Surprisingly high surface pressures – Results in device operating beyond stress levels.

Constrained casing pressure – Bull heading may be required due to well pressure.

Minimize or mitigate risk to rig and equipment due to high surface pressures – Standard killing methods may pose significant danger

Training for Bull heading Operation

Preparation is the key to safe and effective bull heading. You should do the following steps:

Pre-job Safety Meeting

Discuss its responsibilities, operational risks and safety control measures.

Confirm that everyone involved understands the steps to operate and the safety precautions.

Killing lines and valves inspection

Assurance Line Validate killing line and valve system integrity and work before starting

The making of Kill Fluid and Spacer

High volumes of well-killing fluid and spacer should be provide in accordance to the well-killing program.

Clearing High-Pressure Areas

Prior to operation, ensure evacuation of non-essential personnel from high-pressure areas.

Procedure for Bullheading Operations

Systematic bullheading needs to be followed to make bullheading a success. The key steps include:

Calculate pump rate and total volume

Loss of circulation occurs in the geological environment when the pump rate surpasses the upward path taken by the gas bubbles.

Pressure Testing

Balance systemby connecting the pump line and performing a pressure test.

Control Bleed-Off Pressure

Bleed off pressure in stages prior to kill in order to stabilize conditions.

Pump Spacer

As per program requirement, pump a spacer fluid to ensure an effective kill operation.

Ongoing Pressure Assessment

Keep a check on the pressure during the entire operation.

Keep pressure less than the minimum working pressure of wellhead equipment, casing strength, and formation fracture pressure.

Flow Check and Observation

To ensure the well is under control, make sure the outlet is free of overflow.

Conclusion

Well killing is a vital operation process when conventional circulation is impossible, and with bull heading method be used extensively. Due to the adherence of strict safety procedures, careful assessment of the critical parameters during the well control operation ensures that this method provides a successful well control operation with minimum harm to formation and operational hazards.

The Bull heading method is one of the important and mostly applied techniques on well killing, oil and gas well control, kill-weight fluid, formation fracture pressure, how to handle H2S gas, and well intervention for well control operations guidance.