Gilles Guerin 1 , Ann Cook 1 , Stefan Mrozewski 1 , Timothy Colle 2 , & Ray Boswell 3 Green Canyon 955 LWD Operaons and Results Gulf of Mexico Gas Hydrate Joint Industry Project Leg II: 1 Borehole Research Group Lamont-Doherty Earth Observatory of Columbia University Palisades, NY 10964 E-mail: Cook: acook@ldeo.columbia.edu Guerin: guerin@ldeo.columbia.edu Mrozewski: stefan@ldeo.columbia.edu 3 Naonal Energy Technology Laboratory U.S. Department of Energy P.O. Box 880 Morgantown, WV 26507 E-mail: ray.boswell@netl.doe.gov 2 US Geological Survey Denver Federal Center, MS-939 Box 25046 Denver, CO 80225 E-mail: tcolle@usgs.gov Introducon Three holes, Green Canyon 955-I (GC 955-I), Green Canyon 955-H (GC 955-H), and Green Canyon 955-Q (GC 955-Q) were drilled in the Gulf of Mexico Green Canyon Block 955 to test the potenal occurrence of gas hydrate in sand sediments associated with a channel/levee system at the mouth of the Green Canyon (Hutchinson et al., 2009). Hole GC 955-I was drilled in what was thought to be a thick part of a channel levee with a high potenal for sand occurrence. Holes GC 955-H and GC 955-Q were drilled within a four- way closed structure which was thought to trap gas sourced along numerous local faults. A complete assessment of the Green Canyon 955 sites and a full descripon of the drilling operaons are provided in McConnell et al. (2009) and Colle et al. (2009). Operaons Logging-while-drilling (LWD) operaons at the Green Canyon Block 955 Site were conducted using a state of the art boom hole assembly (BHA), using the Schlumberger MP3, geoVISION, EcoScope, sonicVISION and PeriScope tools. For detailed descripon of the BHA, of each tool and of the tool measurements, see Mrozewski et al. (2009). Hole GC 955-I Aſter tagging the seafloor at a driller’s depth of 6822 ſt below rig floor (rf), Hole GC 955-I was spudded at 11h15 on April 22, 2009. Following a spud protocol designed to maintain good condions at the top of the hole (Colle et al., 2009), the first 95 ſt below seafloor (sf) were drilled while circulang 200 gallons of sea water per minute (gpm) and rotang the drill bit with only 15 rotaons per minute (rpm). Between 95 and 160 sf, the drilling fluid flowrate was increased to 225 gpm and rotaon rate to 75 rpm, aſter which they were increased to 350 gpm and 90 rpm, respecvely. The rate of penetraon (ROP) averaged ~ 250 ſt/hr. Drilling connued smoothly with drilling fluid sweeps every couple stands unl 1275 sf when ROP was reduced to 180 ſt/hr for the target zone of interest. At the same me, drilling fluid was swapped over to 10.5 pound per gallon (ppg) water-based drilling fluid to facilitate cungs removal and borehole stability as the hole deepened. At 1310 sf, rotary speed increased to 140 rpm, and at 1875 sf, ROP was restored to 250 ſt/hr for the remaining of the well. The total depth of 2203 sf was reached at 05h45 on April 23. The hole was not displaced with heavy drilling fluid since the deepest part of the hole had been drilled with a 10.5 gpm drilling fluid, but an LWD downlink was performed to slow the tools’ record rates before the boom hole assembly (BHA) was pulled out of hole and suspended in open water for the rig move to the next drill locaon. Subsequent visual monitoring of the GC 955-I wellhead with the Q-4000‘s ROV revealed that the well was flowing water (no evidence of gas). To stop the observed water flow it was decided to place a cement plug in the well (for further discussion, see Colle et al., 2009). The LWD BHA was brought to surface by 23h30 and laid down shortly aſter. A simple BHA, without the LWD tools, was run back into the hole to place the cement plug. Hole GC 955-H Aſter compleng operaons in Hole GC 955-I, the Q-4000 was moved to the next drill locaon: Hole GC 955-H. Operaons started at 2130 hr on April 24, with rigup and running the drill pipe and the LWD BHA to the seafloor. Aſter tagging the seafloor at a driller’s depth of 6721 rf, Hole GC 955-H was spudded at 06h30 on April 25, 2009. Following a spud protocol designed to maintain good