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Well Control Standards

This article describes the standards applicable for Well Control.

General Standards

  • All wells drilled shall comply with the guidelines as specified in API RP 53.
  • All pressure containing well control equipment shall comply with API RP 53 and NACE MR-01-75.
  • The standard shut in procedure to be used in all well control situations is the ‘hard shut in’.
  • Accumulator volumes shall be sufficient to satisfy the requirements of API RP 53.
  • Bullheading techniques shall only be used after approval from the Drilling Manager.
  • As a minimum the shoe shall be tested to the expected maximum pressure experienced at the shoe while circulating out a swab kick from the deepest open hole section TD below the shoe.
  • Shallow gas shall be considered and addressed in all well planning.
  • All Drilling Engineers shall follow Company’s Offshore and Onshore Emergency Procedures.

Personnel Qualifications and Training Requirements

Primary and secondary control training of crews shall not be confined to on the job training only. API RPT-3 entitled 'Training and qualification of personnel in well control equipment and techniques for drilling on offshore locations' should be consulted. API RPT-3 provides criteria for the training of drilling personnel in the use of well control equipment and procedures.

The International Well Control Forum (IWCF) should be adopted. Examinations as its standard certification for rigsite and office supervisory staff.

The following personnel shall be in possession of a valid IWCF certificate:-

At “Driller” level:-

  • Drilling Contractor Drillers
  • Drilling Contractor Assistant Drillers

At “Drilling Supervisor” level:-

  • Drilling Superintendent
  • Senior Operations Engineer
  • Operations Engineer
  • Company Drilling Supervisor
  • Drilling Contractor Rig Manager/Superintendent
  • Drilling Contractor Toolpusher
  • Drilling Contractor Night Toolpusher
  • Drilling Contractor Drillers.

Drilling Blind

  • Drilling ahead with total losses is an accepted practice in Company after approval from Drilling Manager.

BOP Tests and Drills

  • Well control drills shall be held weekly with each crew, or more frequently depending upon crew performance.

Mud Gradient

The drilling fluid used must provide a minimum of 100 psi overbalance at expected top of any potentially productive formation.

Maintenance of Mud Densities

The drilling programme is based on knowledge or prediction of formation pressures, and shall recommend the appropriate mud gradient required for drilling under normal conditions.

  • When drilling, the mud should provide an overbalance (100 - 200psi) at expected top of any potentially productive formation.
  • During workover (cased hole) operations, brines should give an adequate over balance with trip margin (normally 100 - 200 psi) at top perforations.

 

Monitoring of Mud Density

  • The gradient shall be checked at regular intervals and maintained at the correct value.
  • The circulating system should be consistent: no 'light spots' should occur due to erratic dilution.
  • If gas/oil cutting is observed it may be necessary to run the degasser to maintain the correct density.  Such shows indicate that a hydrocarbon bearing formation has been penetrated and signals the possibility of an influx. Additionally if gas/oil cutting is observed, mud density measurements shall be made with a pressurised mud balance.

Formation Leak-Off Tests

Leak-off tests shall be scheduled in exploration and appraisal wells below intermediate casing and liner shoes, when drilling has to be done below that casing / liner string. The tests may be restricted in the following circumstances and will be fully documented in the drilling programme :

  • Reliable formation strength data is available.
  • If it is thought that due to the high strength of the formation below the casing shoe there is a risk of introducing micro fractures in the cement bond behind the casing before leak-off occurs.
  • If a loss/weak zone is known to exist below the casing shoe.

Formation Limit Tests

Limit tests shall be carried out in development wells to confirm that an adequate shoe strength exists to safely drill the next hole section. The design basis for the specified limit shall be discussed in the Drilling Programme.

Mud Systems Monitoring

Active Mud Volume

  • Active system volume shall be continuously monitored.
  • The hole will always be kept full except for the following two cases
  • While drilling surface hole and losses are expected
  • Drilling blind as per programme
  • In the event returns are lost and mud tanks are depleted the hole will be filled with water.
  • The pit level shall be closely observed.  Any change shall be reported to the Toolpusher/Drilling Supervisor.  The Driller shall cross check that this is done.

 

Trips

  • During tripping the trip tank shall be used for accurate measurement of mud volume changes using electronic and manual floats. This is the responsibility of the Driller or Assistant Driller on the brake. It shall not be delegated to the Mud tester or other personnel.

 

Drilling Breaks

  • When a drilling break occurs, drill no more than 2 ft into the break and then carry out a  flow check.

 

Mud Properties

Lost circulation should be minimised by:

  • maintaining suitable mud properties (lowest allowable density, reasonable PV, YP).
  • drill string design.
  • nozzle configuration.
  • circulation rate (minimising annular friction losses)
  • pipe running speeds.

Flow Checks

Flow checks shall be carried out in the following instances:

  • drilling breaks
  • prior to pulling out of hole
  • with the bit in the shoe whilst POOH
  • prior to pulling the bottom hole assembly through the rotary table
  • at any time that standard kick indicators are observed.

Flowchecks whilst drilling (in response to standard kick indications) and prior to and during tripping operations should be a minimum of 10 minutes duration

Note :  Should flow be observed during a flowcheck then the well should be closed in immediately.

 

 

Annulus Pressure Monitoring

 

A daily check shall be made on all casing annuli while operations are in progress.  Any pressure observed shall be recorded and reported daily in the allocated section of the morning report.

Note:   A comprehensive check for annuli pressures shall be made prior to removing any mechanical barrier (eg., Xmas tree, Tubing head spool or casing head spool/housing). Gauges pre-installed on wellheads, or by other departments must be checked to ensure correct operation.

Equipment Requirements

Degassers

  • Degassers should always be in operational condition and used as required.

Note: Running of the degasser should be reported in the IADC daily drilling report

 

Diverter

  • The need for a diverter shall be assessed during the pre-planning stage for each drilling proposal.

 

Trip Tank

  • It is essential that the trip tank and its related equipment are in good order.  Two quantitative measuring devices shall be located on the drill floor and be visible to the Driller.
  • The system shall be designed in such a way that it can be isolated so that it is impossible to have accidental gains or losses from or to the main mud system.
  • In case the tank cannot hold the required amount of fill up mud, then it shall be filled up again before the level becomes too low for the measuring system to function accurately.

 

Volumetric Stripping

Whilst stripping may not be a primary well control technique, all rigs shall be equipped for volumetric stripping and crews shall be trained to be familiar with the technique.

Kick Control Work-Sheet

A kick control worksheet shall be used to pre-record the data required for secondary control and shall be kept updated while maintaining primary control.

Slow Pumping Rate Pressures

Well control operations are performed at reduced pump speeds.

Well Shut In Philosophy

The Company standard shut in procedure is the ‘hard shut in’.

Barite Mixing Capacity

In order to be able to implement the method recommended for controlling an influx, i.e. in one circulation, the mud mixing facilities have to be capable of raising the existing mud gradient to that required for killing the well as the mud is being circulated.

It is therefore important to determine the rate at which barites can be added over a prolonged period as this will control the pumping rate when circulating to the higher gradient mud.

Contingency Stock Levels

Minimum Stock Levels shall be in place to ensure losses can be controled for Well Control.