The cement inside the casing is now being drilled out to just above the casing shoe, after which the calcium chloride drilling mud in the hole will be replaced with fresh water (plus corrosion inhibitor) before the rig is demobilized. On-site documentation, scanning and archiving of the cores were completed today, and this information is now being uploaded to the ICDP for inclusion on the SAFOD web site. This ends the work of the on-site core handling team; thus, this will be the last regular message on this web site. We would like to thank you for your support of and interest in SAFOD over what has been a very exciting summer. More information on the fascinating cores obtained this summer will be posted on the SAFOD web site over the coming months, culminating in a SAFOD Sample Party to be held at the USGS in Menlo Park, CA, on Dec 9, 2007 (just before the Fall AGU meeting). If you are interested in attending this Sample Party and are not already on the SAFOD Samples Team mailing list, please send an email to hickman@usgs.gov.
Today we installed and cemented the 7-inch casing. Although we had hoped to install casing to the maximum depth reached during yesterday's hole conditioning operations (10,960 ft), borehole stability problems prevented this and, after pushing and circulating the casing through some tight spots, it encountered an obstruction at a depth of 10,546 ft MD and had to be cemented at that depth. Fortunately, the casing is set through the actively deforming fault at 10,485 ft MD. Thus, we are in an excellent position to perforate the casing directly within this fault and install monitoring instrumentation (seismometers, accelerometers, tiltmeters and a fluid pressure transducer) in the immediate vicinity of the the M2 ""Hawaii"" target earthquakes over the coming year.
Today we went in with a rotary drill bit to clean out and condition the hole in preparation for running the casing early tomorrow morning. Work continues on site to complete core processing and scanning and entering these data into the ICDP Drilling Information System.
Early this morning, the drill-pipe-deployed logging string were returned to the surface, at which point we discovered that the lower portion of the string had fallen off in the well, presumably when we got stuck and had to pull free at a depth of about 10,700 ft. Today we went fishing for these lost tool components, but were unscuccessful. Since the well has already reached its total planned depth and further fishing attempts were deemed to have a low probability of success, we abandoned fishing operations and are now starting in the hole with a drilling assembly to condition the well for casing installation. Also, today was the last day for Steve Pye as the on-site representative of the prime drilling contractor, Thermasource. Steve has served the needs of SAFOD with skill, dedication and good humor over the much of the summer and will be missed by us all. He is being repalced by Jerry Hamblin (also with Thermasource) who served as drilling contractor representative earlier this summer and will help us finish up SAFOD Phase 3 drilling operations over the coming week.
Beginning at approximately 8 AM, we began drill-pipe-deployed logging of the open hole. We collected resistivity, spectral gamma and sonic logs while tripping in the hole, and intended to collect these logs again (but in tool centralized mode) as well as an electrical image log (the Formation MicroScanner) while tripping out. However, the tool encountered strong resistance starting at about 10,700 ft MD, so we started to pull out of the hole and log up from there. At this time, high tensional loading was observed on the tool string and the drill pipe also got stuck. We started circulating drilling mud through the tool-head circulation sub, which freed both the drill pipe and the logging tools. Unfortunately, the lowermost module on the logging string -- containing the Formation MicroScanner and the tool orientaion sensor -- stopped functioning at this time. However, the rest of the tool continued to funcion properly and we were able to collect good-quality resistivity, spectral gamma and centralized sonic logs while pulling out of the hole. The logging assembly is now being tripped out of the hole and the Schlumberger crew has began demobilizing.
After conditioning the hole for logging for much of the day, we are now running in with a drill-pipe-deployed logging run of the open-hole section, including the two active fault zones we just cored. The tools being deployed are a high-resolution electrical imaging tool (the Formation MicroImager), a bulk resistivity tool (Laterlog), a spectral gamma tool and a dipole sonic tool. While this is going on, the on-site core science team continues to clean, realign and label core before scanning them on the Multispectral Core Logging System.
Rotary drilling has continued since yesterday evening and should arrive at terminal depth of 11,000 ft tonight. Geophysical logging will begin tomorrow. The core-handling team has continued to process the core this weekend. This is the last day that Dr. Thomas Wiersberg of GFZ Potsdam will be on-site collecting gas data and samples. He has been working on-site since the start of drilling in June and is returning home to be with his family. We thank him for his hard work this summer, his significant contributions to the success of the project, and wish him the best on his return to Germany.
The borehole was opened and reamed, last nigth, at the depth interval from the last 3 coring runs. We are now tripping back into the hole to drill another 100 ft, to ensure enough room for the geophysical logging tools.
Our effort to retrieve a 4th core from the 10830 fault zone was unsuccessful last night. We were unable to circulate mud once the core barrel was on bottom so the decision was made to trip out of the hole and prepare the hole for geophysical logging. Core from the 10830 fault zone is still being processed.
We got it! Today we returned 36 feet of core from the heart of the ''10830"" ft. fault zone to the surface. The core contains many highly fractured shear zones and at least one major interval of fault gouge. The science team is working overtime to describe and curate these samples as we prepare for one final coring run and the open hole geophysical logs.
The first of three core runs through the 10830 ft fault zone arrived on deck at 8:30 AM this morning. Nearly 18 feet of core were recovered. Although we had only a short time to work on the core today, there appear to be many exciting structures and fault rocks present in it. The next core is being drilled as of 7:30 PM and should be on deck tomorrow morning.
After successfully coring across the 10480 fault zone, we have rotary drilled (dashed line in figure) to the measured depth to begin coring of the ""10830"" fault zone. After changing over to a coring assembly this afternoon, we should begin coring this evening. The first core should show up on deck tomorrow morning. Three core runs are currently scheduled for this fault zone.
Drilling has made steady progress today, and we are currently at 10740 feet. If we continue at the same rate, we should reach the target depth in approximately 12 hours.
Directional drilling continues. We are at 10650 ft as of 6:00pm and are drilling at an average rate of 3 to 4 ft per hour. The processing of core from the ""10480"" fault zone continues.
Directional drilling to the ""10830"" fault zone began last night and slowly made approximately 80 feet of new hole. The [pipe is now being tripped to replace the current bit with a new bit which will hopefully drill faster. Coring will hopefully commence Monday night or Tuesday. Today was the last day that crew member Tim Keenan of Saint Louis University worked with us (Tim is second from the left in the photo). He worked diligently for the past three months to insure that the cuttings and core were collected, processed, and archived properly. We thank him for his hard labor.
More core from the ''10480"" fault zone arrived on deck this morning. The cored interval is now being reamed, and directional drilling will begin this evening to reach the next coring depth of approximately 10820 feet.
Mark Zoback and Steve Hickman examine a core from near the actively creeping fault encountered at 10,480 ft (MD) in the SAFOD main hole. Fourteen feet of core were obtained in this run. A second coring run is now being conducted. This core was obtained near one of the fault zones that is slowly deforming the main hole casing. The ''Hawaii"" microearthquake cluster appears to be on this fault, approximately 100m below the depth at which the core was taken. This cluster occurs on a strand of the San Andreas fault that is located along the southwest border of the 250 m-wide ""damage zone"" that hosts multiple active faults.
Directional drilling was successfully completed late this morning. Following a change in bottom-hole assemblies and bits, we are currently tripping back into the hole to core the ""10475"" fault zone. Coring will commence at midnight and continue until mid- to late morning. By this time tomorrow, we will hopefully be looking at core from a creeping segment of the San Andreas fault zone!
Directional drilling has continued today and is currently at a depth of 10390 feet as of 6 PM. We have approximately another 50 feet of directional drilling before we reach the depth of the next core run.
The time drilling has successfully started the new side track. The crew is now tripping in the new bottom-hole assembly to directional drill approximately 150 feet.
Time drilling of approximately 1 foot per hour commenced last night at approximately 7 PM at a depth of 10245 feet (measured depth). Tomorrow, once the side track is well established in the sandstone formation away from the concrete plug, the bottom hole assembly will be changed over to allow for more rapid directional drilling to the target depth..
Last night's reaming trip was successful in clearing the hole obstruction. We are now on top of the cement plug at 10250 ft. with the bent-sub assembly and are just starting our second attempt to sidetrack around the lost core barrel. The sidetrack will start with drilling at a constant penetration rate (time drilling) to be followed by directional drilling until we reach the starting depth for the next core run.
Today we ran in the hole with the bit, mud motor and bent-sub assembly in an attempt to start the side track off the cement plug at 10,245 ft MD. However, the bit stopped before reaching the top of the cement plug, either due to a bridge in the hole or landing on a ledge. We have now tripped out of the hole with this assembly and are rigging up for a reaming trip to the top of the cement plug, after which we will make another attempt to kick off and start the sidetrack.
Cementing was completed successfully yesterday. The plug was then tagged at 10,081 feet and polished off to 10,150 feet. The cement is now curing and will be checked again this evening. If cured, time drilling will begin tomorrow morning.
The sidetrack is now in the process of being cemented. We will then back up the hole approximately 100 feet in order to rotary drill around the fish and reach the next coring target at approximately 10480 feet.
The sidetrack was unsuccessful and now there will be another attempt to drill away from the plugged hole. Rig crews are tripping out of the hole for preparation.
Time drilling continued today and the new open-hole sidetrack was successfully started. Cuttings showed increasing amounts of shale with decreasing amounts of cement, indicating that the drill bit had kicked off the cement plug and into the shale formation. At 5:00 PM, tripping began to change the bottom hole assembly. Once completed, we will trip back into the hole and continue drilling to the next coring point at 10440 ft.
After placing a cement plug on top of the lost core barrel yesterday afternoon, today we waited for the cement to cure hard enough to begin the sidetrack. As of 6 pm this evening, the cement was not fully cured, so we will wait a few more hours before testing the cement again with the drill bit.
The milling bit, which was pulled out of the hole late last night, was heavily worn down especially on the side of the bit. This unexpected wear pattern necessitated a change in strategy from fishing out the obstruction to going around it. The hole is now being cemented and a new open-hole sidetrack will be started at approximately 10350 feet.
Milling of the outer core barrel continued today in preparation for another fishing attempt using the overshot. The milling bit is being pulled out of the hole this evening and a new overshot assembly will be tripped in tonight. The wear on the surface of the milling bit will hopefully be symmetrical, consistent with the core barrel being centered in the open hole and in good position for being grabbed by the overshot. If so, we have a reasonable chance of retrieving the core barrel tomorrow. Stay tuned.
Efforts continue to fish out the remaining core barrel at the bottom of the hole. Multiple attempts have been made to mill down and catch the top of the core barrel. Although progress is slow, the fishing operations continue with reasonable probability of success.
Our initial attempt to retrieve the lost core barrel recovered only a portion of the aluminum inner liner, which was found to be resting on top of the outer core barrel. After a separate trip to mill out the aluminum liner, we are now tripping in with an overshot for our second attempt at retrieving the lost core barrel. If this fishing operation is successful, then we will conduct hole cleaning operations before we start to core the first of two active traces of the San Andreas Fault.
Just as coring was to get underway approximately 5 m from the ""10480"" fault zone, it was evident that there was a problem downhole with either the motor or core barrel. It was decided to trip out of the hole for inspection and replacement of the malfunctioning components. When the equipment came to the surface, it was discovered that the core barrel had detached. It is not clear how this happened as the threads were tightened to the prescribed torque prior to running in the hole, there was no reverse rotation of the drillstring and there appears to be no damage to either set of threads. Fishing is now underway to retrieve the core barrel.
Characterization of the two core runs from 10306 to 10340 feet continue. The cores are in excellent shape and contain many well preserved features including numerous faults with thin cataclastic zones. Pictures of the cores will be uploaded in the next couple of days. Drilling operations continue in preparation for coring of the ""10480"" fault zone.
We are drilling ahead to the next interval to be cored. This will be the ""10480"" fault zone which is deforming the casing and appears to be the fault responsible for the ""Hawaii"" earthquakes, located approximately 100m below the point of intersection. The geophysical logs across this faut zone indicte that it is an approximately 1m thick zone of weak gouge. As this fault zone has caused considerable drilling difficulty, we are proceeding with caution.
12+ feet of core were successfully recovered in the second core run. The second core also contains arkosic sandstones that show increasing amounts of fracturing with depth. The coring assembly has been laid down and preparations are underway to rotary drill approximately 100 feet to the next coring target, and active trace of the San Andreas Fault.
22 feet of spectacular core were recovered yesterday and are now in the process of being scanned, described, and archived. Overnight, a second core was cut to a depth of 10,346'. We expect this core on deck by late afternoon with processing to continue into the evening.
Seven meters of hard arkosic sandstone and conglomerate with multiple faults and fractures was recovered today. The frequency of faulting increases with depth. A second core will be retrieved in an attempt to sample the contact between the arkose and the siltstone and shale associated with the Great Valley formation.
Rotary drilling was successfully completed last night to a measured depth of 10306 feet while still within the arkosic sandstone unit. The coring assembly is now being tripped down and coring should begin this evening. If all goes well, we should have core tomorrow.
Milling was successful last night! Following a trip out to replace the milling bit with a tricone, we have drilled ahead nearly 40 feet. The crew will trip out the bit after 15 feet more of drilling and prepare the coring assembly. If all goes well, we should be coring tomorrow!
The new tricone bit arrived at bottom early this morning and rotary drilling commenced. Unfortunately, parts of the previous bit have remained at the bottom of the hole and prevented forward progress. The new bit was tripped out and a milling assembly with a junk catcher was tripped in. The milling assembly, which has just arrived at bottom as of 6 PM tonight, will mill through the old bit. This should be completed tonight, and drilling should commence tomorrow.
Rotary drilling reached a measured depth of 10259 feet last night, and was within 30 feet of completion when the tricone bit gave out. This necessitated tripping out of the drill string, replacement of the bit, and tripping back in. The crew is currently reaming out the open hole as they progress downwards. By tomorrow morning, the last 30 feet of the hole should be drilled, and then operations will commence for the coring phase of sidetrack two.
As sidetrack 2 nears the start point for coring, Scientific Drilling is running a final gyro survey and gamma log. The gamma log will be used to tie together a broad suite of logs collected over the history of the SAFOD project. Rotary drilling continues through the arkosic sands toward the coring start point, just shy of the geologic plate boundary.
Rotary drilling progressed well down to 10,000 feet MD. Due to a hydraulic problem with the top drive, there was no drilling for much of the day. The problem is fixed and drilling is currently at 10,060 feet and will continue for approximately another day.
Directional drilling through the arkosic sandstone (cuttings shown to the right) has been progressing well over the past two days. We are currently at 10,000 feet measured depth, and will continue drilling until we reach approximately 10,300 feet. The first target for coring will be the apparent boundary between the Pacific plate (as characterized by arkosic sandstones) and the North American plate (as characterized by the siltstones and shales of the Great Valley formation).
After successfully kicking off, directional drilling of sidetrack 2 began this morning. We anticipate multiple days of directional drilling prior to starting the first coring run. During drilling, cuttings will be collected every 10' and preparations for core will continue.
Sandstone cuttings crossed the shaker table as the milling of the casing was completed. Pipe is currently being tripped out of the hole to change the bottom-hole assembly. Directional drilling will begin tonight.
