Well control equipment falls into five basic working pressure classifications:·13,800 kPa (2000 psi) WP,·20,700 kPa (3000 psi) WP,·34,500 kPa (5000 psi) WP,·69,000 kPa (10,000 psi) WP,·103,500 kPa (15,000 psi) WP. The BOP stack rating of used BOP”s (> 5 years old) should be at least 10% higher than the maximum expected surface pressure that could … Classification of BOP and well control equipment.
If secondary control cannot be properly maintained, emergency procedures can be implemented to prevent the loss of control. Two common procedures involve the use of barytes plugs and cement plugs. 1. Barytes plugs A barytes plug is a slurry of barytes in fresh water or diesel oil which is displaced through the drillstring. If conditions … Well Control – barytes and cement plugs.
If an overbalance existed prior to pulling out of hole, then the only reasons for the well to flow are:·swabbing;·failure to keep the hole full;·losses induced by surge pressures. Early detection of kicks off bottom can be achieved by observing whether the hole is taking the proper amount of fluid during roundtrips. This can be … Well Control – Kick whilst tripping
Pre-recording of information.Proper secondary well control follows a planned course of action. Pre-recording relevant information avoids unnecessary delay. The following aspects concerning the pre-recording of information are discussed: Kick control worksheet. Checking pump pressure at reduced pump speeds. Establishing the weighting material mixing capacity of the rig. Relationship between bottom hole pressure, formation strength at … Well Control – Preliminary record of information
Complications during well control operations Stopping the control operation, Plugged chokes, Change in circulating kill rate, Plugged bit nozzles, Kick caused by loss of circulation below production zone, Complete power failure during the controlling operation 1 Stopping the control operation Control operations may have to be stopped because of equipment failure or for checking static … Complications during well control operations
Kick control when drilling high pressure wells (philosophy, drilling procedure and well control equipment) 1 Well control philosophy The BOP and surface system, including the drillstring, should be pressure rated (and tested, except for the drillstring) to safely withstand pressure conditions created by a full gas column originating from the highest pressure zone exposed in … Well Control – High Pressure Wells
A non standard well control method is to attempt to bring the well under control by circulating heavy mud to overbalance the surface pressures. The theory behind this method is that the well can then be opened and the string run deeper. This method is not reliable since there is no proper control of bottom … Well Control – Circulating heavy mud (bit off bottom)
A kick is generally recognised by an instantaneous increase in the rate of mud returns and/or an associated gain in mud volume in the active mud tanks. A flowline show (gas cut or fluid contaminated mud) does not necessarily mean that the well is kicking. Flowline shows can be: drilled shows; swabbed shows; high pressure … Well Control – Flowline Shows
Slim Hole Drilling which, for the purpose of well control, means hole sizes of 4 3/4″ and smaller, will impose certain restrictions on well killing techniques and will require well planning to take care of these limitations. 1 General Annular friction losses are an important aspect in Slim Hole Drilling, especially with regards to well … Well Control – Slim Hole Drilling
All hydrostatic pressure-related calculations should be based on true vertical depth values. This means that the standpipe kill graph of a deviated well has a different curve as compared to the graph prepared for a vertical well due to the behaviour of Pdp. It applies only for phase I (balanced method), since the standpipe pressure … Well Control – Deviated and Horizontal wells