Trends Extracted From 800 Gulf Coast Blowouts During 1960-1996

The cost of blowouts and the loss of life incurred from blowouts warrant the study of past occurrences in order to reduce number of future blowouts. Even though we continuously learn more about how to handle an unstable well, it seems that the problems of detection, handling kicks and loosing control do not change much with time in the real world out on the rig, The small changes and improvements that do occur are first of all seen thorough statistical data. A new data base resently compiled will soon contain extensive data on more than 800 blowouts from the Gulf Coast area and adjoining states duting the period 1960 through 1996. At the moment the compiling work has not been completed. However, at the 1998 [ADC/SPE Drilling Conference an updated version of this paper will be available. Five agencies contributed blowout report information. The State Oil and Gas Boards/Conservation Office of Alabama, Mississippi and Louisiana, The Railroad Commission of Texas and the Mineral Management Service (MMS) of the Dept, of Interior. At the moment the Texas blowouts makeup approximately 50V0of the blowouts in the data base but range below the average blowout frequency of 0.15 blowouts pr. 100 well-ft. drilled. The three major operations in progress when blowouts occurred were exploratory drilling, workover and development drilling. Most frequently blowouts occurred during the activity of actual drilling, tripping out and circulating/killing. The analysis indicated also that the major causes were related to swabbing, drilling into a high pressure zone or formation break down while the secondary barrier after a kick has occurred which most often failed were either failure to close BOP, failure to stab string valve or BOP failed after closure, Introduction Control of the formation pressure is an important concerr both in the planning phase and during execution of the drilling operations. Improper procedures with respect to detection and handling of kicks may result in loss of control. The cost of blowouts and the loss of lives incurred from blowouts warrent the study of past occurrences in order tc reduce the possibilities of titure blowouts. We are hoping to see that operating experience in general and experience through required blowout schools especially is slowly paying off. Technology changes may however override these effects in both directions. Examples 01 technology changes are diverterless drilling combined with drilling in deeper water and pushing the surface casing deepel and deeper/fewer casing strings, thus causing a changing risk and not necessarily accompanied by a corresponding reassessment of the kick detection/killing procedures. Since the shallow gas hazard and consequences are above normal, large improvements have been noted the last decade or twc with respect to shallow seismic and kick detection systems for floaters. Method of Analysis On basis of data from five data sources ●State Oil and Gas Board of Alabama ●Louisiana OffIce of Conservation ●Mississippi State Oil and Gas Board ●Texas Railroad Commission (RRC) ●Minerals Management Service (MMS) (Outer Continental Shelf)