Operational
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An Alternative to Wireline and/or MWD Measurements
The South Africa Mine Rescue Operation, shown above, rescued 27 trapped coal miners.
Engineering geologists are often asked to descend in caisson borings in a similar apparatus to visually map the geology of the side of the boring.
Fortunately, wireline and MWD measurements have eliminated the need to do this for deeper wells.
Potash Logging, Canada
This was supposed to be a winterized drill rig! That was cold comfort to the slim-hole logging engineer and me, as we spent 18 hr, huddled in his camper shell logging unit running the logs for this borehole.
After a short nap, I prepared the Multiple Log Potash Assay, presented it to the client and then drove through an ice storm to the airport for my trip home.
The major difference between slim-hole logging and major vendors wireline logging operations is the crew size (1 man) and the logging sonde sizes (2.5 ” x 3 – 20 ‘). Slim-hole logging vendors also usually need a little more care and handling than major venders.
It has been my experience, however, that I can get slim-hole wireline logging vendor products with quality comparable to those of the major logging vendors.
Making up a Sonic Tool, South America
The logging crew shown here are making up a combination tool in the borehole, because the derrick tower is too short for the completed tool to hang above the rotary table.
The man in back is holding the make-up plate which will suspend the bottom of the partially completed tool combination in the top of the borehole while the next section is screwed into place.
In this case, the orange coveralls are for visibility and do not indicate a particular vendor’s work uniform.
Buying Logging Cable By The Pound, Oceania
Bad things can happen quickly, during logging operations. A stuck tool – A bad decision by the Tool Pusher and the next thing you know…
You’re retrieving 3.5 miles of logging cable by balling it up on the drill bit, cutting it off with an acetylene torch, and buying logging cable by the pound.
The Story Behind These Pictures:
The well pictured above was an extended reach directional well drilled from an isolated drilling island in dense jungle.
The Logging Engineer became concerned about the possibility of sticking the formation testing tool, based on cable pulls encountered in earlier logging trips for this job.
My weevil, the Wellsite Geologist, did the right thing. He communicated the Logging Engineer’s concerns to his management. After careful consideration of options, the Operator elected to risk sticking the formation test tool, in order to obtain formation pressure information.
During the formation test logging operation, the Logging Engineer’s fears were realized and the formation test tool stuck. Attempts to free the stuck tool by collapsing the calipers and “yo-yoing the cable” were unsuccessful. At this point, the Tool Pusher intervened and decided to use the rig traveling block and draw works to free the tool, by clamping the logging cable at the surface with the drill pipe elevator “ears”.
A wireline logging system is designed such that the cable “weak point” is at the cable head on top of the logging tool. This is accomplished by breaking off half of the double wrap cable armor strands and using only the remaining half to attach the cable head. Locating the cable weak point at the cable head allows the logging cable to pull free from the cable head of a stuck tool, clearing the borehole of debris, so that the tool can be recovered, using an overshot tool on a drill string.
When the logging cable in this well was clamped at the surface, the clamping point became the “weak point” and the cable parted at the surface, filling the borehole with approximately 3.5 miles of logging cable on top of the stuck formation test tool.
Once the logging cable parted at the surface, there was nothing for the Wellsite Geologist to do but retire to one side and photographically record the ensuing recovery operation.Story Behind These Pictures:
The well pictured above was an extended reach directional well drilled from an isolated drilling island in dense jungle.
The Logging Engineer became concerned about the possibility of sticking the formation testing tool, based on cable pulls encountered in earlier logging trips for this job.
My weevil, the Wellsite Geologist, did the right thing. He communicated the Logging Engineer’s concerns to his management. After careful consideration of options, the Operator elected to risk sticking the formation test tool, in order to obtain formation pressure information.
During the formation test logging operation, the Logging Engineer’s fears were realized and the formation test tool stuck. Attempts to free the stuck tool by collapsing the calipers and “yo-yoing the cable” were unsuccessful. At this point, the Tool Pusher intervened and decided to use the rig traveling block and draw works to free the tool, by clamping the logging cable at the surface with the drill pipe elevator “ears”.
A wireline logging system is designed such that the cable “weak point” is at the cable head on top of the logging tool. This is accomplished by breaking off half of the double wrap cable armor strands and using only the remaining half to attach the cable head. Locating the cable weak point at the cable head allows the logging cable to pull free from the cable head of a stuck tool, clearing the borehole of debris, so that the tool can be recovered, using an overshot tool on a drill string.
When the logging cable in this well was clamped at the surface, the clamping point became the “weak point” and the cable parted at the surface, filling the borehole with approximately 3.5 miles of logging cable on top of the stuck formation test tool.
Once the logging cable parted at the surface, there was nothing for the Wellsite Geologist to do but retire to one side and photographically record the ensuing recovery operation.
Geothermal Logging Operations, US
Intermediate depth temperature holes are drilled on a 7/24 schedule much like deep, produceable geothermal wells. In this case, “Bull Dog”, the Tool Pusher, called out a major logging vendor to run a complete suite of wireline measurements.
The major differences between intermediate depth temperature holes and produceable geothermal wells are the bit size (6.25″), the drill rig (the racked drill pipe are double 20′ joints, and they are standing on the ground), the drilling crew (a driller and two helpers), and the crew schedule (2 Tours/24 hr). I have had very good success running normal (i.e., not HEL) major logging vendor tools in these small diameter boreholes.
Also, like deep wells, the logging jobs seem to start and end after dark.
The Tool Pusher is Your Friend
Sometimes, in the rush to “get the well down and protect it with casing”, the object of drilling it in the first place – to evaluate a reservoir – is overlooked.
Decisions about mud type, mud chemistry and drilling rates can effect the condition of the borehole and, subsequently, the quality of the wireline and/or MWD petrophysical measurements.Using dispersive muds (e.g., lignosulfonate) to drill expansive clay shales risks stuck logging tools, severe borehole wash-outs, and caving.
Attempting to keep a borehole open by “weighting up the mud” may be counter productive, as the increased borehole fluid pressure will drive the mud chemicals into any cracks in the borehole wall.
“Making hole too fast” runs the risk of building insufficient mud cake to keep the borehole open for wireline operations and running casing.
I will work with your Drilling Department and drilling contractors to provide the best possible environment for Wireline and/or MWD petrophysical measurements.
Uranium Logging Operations, US
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Uranium exploration usually involves slim-hole coring and wireline measurements. This particular property was a candidate for in-situ leach mining, so we brought in a major logging vendor for comparison of porosity tools.
The above tableau (an analog logging van, a digital recording truck, a derrick truck, three logging engineers and three operators) is what resulted for a 900 ft corehole. Much to everyone’s relief, the slim-hole logging vendor’s porosity tool results agreed very well with those of the major logging vendor.
The major logging vendor tied up all of that equipment and personnel for a week. The client was upset with the $1,500 logging charge for three coreholes and need to ream out the coreholes to accommodate the major logging vendor’s tools.
Needless to say, I sent a flowery thank you note to the major logging vendor operations manager with a cc to the client’s sister oil & gas E&P company Petrophysicist.
I doubt very much that the major logging vendor became involved in this exercise for the income from this particular job.
Swamp Drilling Operations, West Africa
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Swamp drilling operations look much alike, regardless of where they are. A canal is dredged to the drillsite and the drill and crew barges brought in to drill the well. Once the well is completed, the dredged canal allows service equipment access to the wellsite. Unfortunately the dredging spoils are often silty and the water different salinity from that of the surface waters resulting in, at least, temporary damage to the swamp vegetation.
This particular oil field brought into play the adage about the map of Africa being drafted on the drawing tables of Europe. The field was located within the province of a different tribe from that of the local village. The local village chief was very upset about oil revenues not going to his tribal homeland province and acted accordingly. His actions disrupted and delayed the development of this oil field until an accommodation could be reached.