Technical analysis of the causes of blowout in BiBi Hakimeh well No. 76

Fractures are the most common geological structures which might occur in every reservoir rock. Regarding the importance and significance of the fractures properties it can be mentioned their effective role in porosity and permeability increase and consequently the production of an enormous amount of oil especially in the carbonate reservoirs. The evaluating and studying of the fractures, recognizing their situation, distribution pattern over the entire reservoir may noticeably help in the development plan of the field, locating suitable areas for drilling new wells, lifetime increase and significant oil production from the reservoir. Although the existence of fractures in the production formations has many benefits, it has some disadvantages. Severe and complete drilling fluid losses may lead to blowout, which is one of the greatest challenges associated with drilling industry during the drilling of fractured formations. BiBi- Hakimeh oilfield is one of the greatest oilfields in Southwest of Iran. The analysis of provided data and maps from this field indicates the existence of fractures all over it. The drilling rig 43- Fath of National Iranian Drilling Company which had been moved in for repairing the well number 76 of BiBi- Hakimeh oilfield due to the problem of additional gas production, suddenly was encountered the problem of total fluid loss, during the drilling of Asemari formation with 5 7/8" bit size at the depth of 1884 meter. The rate of fluid loss was so excessive that the pumping of a great amount of loss control materials could not assist in solving the proposed problem. In the following for pulling drill bit and directional drilling motor out of the well and raising and running R.T.T.S for installing cement plug, drill string was in the progress of making an apparently normal trip to the depth of 300 meters, while well began to flow unexpectedly, on October 28, 2011 (Friday) at 5:30 o'clock in the morning. As the result of the flowing gas high pressure (approximately 1600 psi) and the light weight of drill strings, they were blown from the hole like piston. Regarding mentioned tough situation and sudden rising of drill string through the well, the attempts to control the well and to close-in blowout preventer valves were failed. As drill strings were blown from the hole and hit the derrick together with the flow of gas and reservoir hydrocarbon fluids to the surface and due to the friction caused by that, the well erupted unexpectedly and consequently the drilling rig was on fire for a few minutes. While the well was burning, Proper actions were taken to control the well by National Iranian Drilling Company's operation crew including Tool Pusher, Tour Pusher, Driller, Assistant Driller, Derrick man, Floor men and National Iranian South Oil Company's representative, and finally after pumping a large amount of water with required pressure and flow rate they could kill the well and control its blow out.

کلیدواژه ها:

fracture ، losses ، blowout