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Hydraulisk frakturering udført ved vandret boreteknik - Design og anlæg

Bilag G:
Feltjournal

Dana Brocks feltjournal

November 30, 1999

Presented below are summary notes of field activities for the installation of two hydraulically fractured groundwater extraction wells near Naestved, Denmark in November, 1999.

Friday and Saturday, November 5 and 6, 1999

Flew British Airways to LHR, then to CPH. Arrived Saturday afternoon 1500. Lisbeth picked me up and drove me to The Cottage Inn, B&B near airport for overnight stay.

Sunday, November 7, 1999

Lisbeth picked me up at B&B and took me to NIRAS Allerød. Worked in office for 4 hours and then drove to Karrebæksminde in the evening.

Monday, November 8, 1999

On-site at 08:00. Cool (+4C), radiation fog. Set up office equipment in field trailer. Chemicals for fracturing not yet on site. Fracturing apparatus at machine shop in Køge.

Tuesday, November 9, 1999

On site at 0700. Cool (+3C), some fog. Truck from Esbjerg (Slumbergers) on-site with frac mixing tank and pumps. Mixing tank is huge (1-2 cubic meters just to reach the bottom of the paddle), far larger than the Chem-grout 550 mixer and pump system I had specified. I suggested we contact a well drilling company or a grouting company to find a more appropriately sized mixing plant. The pumps are double diaphragm and air driven. It is not possible to tell from the nameplate what working pressure and flow ranges are appropriate so we will need to talk to Schlumberger.

Traveled to Optiroc to observe grout mixer. The several large mixers at their facility are the approximate size we need (300-700 liters).

Met Flemming from the County of Storstrom. Met with Kim Radmer and Karsten Haslund (H&S) at 1300 to discuss project logistics. Karsten brought "Borax", KCO3. Sand, breaker and Guar already on site. Schumberger guys show up to check in. Kim says come back tomorrow.

We discussed:

Grooving tool

I asked for a 3/8" NPT threaded fitting for the jets for this tool based on past similar equipment. They use 1/8" NPT plug for their jets so we changed to reflect this. I asked for a 0.065" (~ 1.7mm) hole in each jet. They made a 1.5mm hole – OK. The Vermeer drill rig D16/20 is good for approximately 1500 psi (103 bar) pressure. I had hoped for higher pressure although I had stated 1200 psi in specs.

Double diaphragm pumps

The Sandpiper pumps are air driven and used for transferring liquids and sludge. Each diaphragm produces 0.8 liters per stroke. The outlet pressure is same (minus minor losses) as the air pressure available from the compressor driving the pump. I said we needed at least 8 bar and optimum delivery rate would be in the range of 20-30 liters per minute. They said the pumps could operate in these pressure and flow ranges but that the flow characteristics could be better maintained if we had an 8 cubic meter capacity compressor rather than the 3 cubic meter compressor at the site. The pumps are rated for 0-20 bars but need adequate compressor capacity.

Mixing tank

There is a misunderstanding regarding the capacity of mixing tank needed for the project. Although we will mix approximately 3000 liters per well, the fluid couldn’t be stored until it needs to be used. Once the breaker is added, it is imperative to pump the fluid down hole as soon as possible. Even the guar should be fresh and the cross linking fluid added a few minutes before pumping. Therefore a capacity of 150 liters minimum to about 600 liters maximum per batch is appropriate.

The mixer supplied by Schlumberger will not mix quantities this small (propeller is too high and tank is too big). New mixing tank must be found.

Wednesday, November 10, 1999

On-site at 0700. Drilled pilot hole without problems. Began mixing frac fluid test batches. Cross-linker works well using typical concentrations, breaker is a little sensitive. Added tracer dye, which may make the Guar a little more salty than typical. Came up with reasonable consistency and subsequent break after 3 trials.

Thursday, November 11, 1999

Mixed 10 batches (for 300 liter frac fluid batches) of cross linking fluid and placed in Schlumberger container (with workbench) (to keep out of night cold).

Friday, November 12, 1999

On-site at 0400. Stirred cross-linking fluid. Weighed out guar for grooving (and first fracturing), 3.4 kg/950 liters. Connected grooving tool to rods at exit pit. Pulled in a meter or so to observe effectiveness. Groove is approximately 4mm x (at least) 10cm. Looks good. After checking the groove location with Jan, pulled into place and began grooving.

Horizontal Boring #1 (Well completed as well no. A-A)

Observations during grooving are as follows:

Completed grooving at day break. Schulumberger guys arrived at 0700am.. I asked them to set up pumps and run small compressor for packers. Began exercising packers in 1 bar increments to 8 bars. Then held pressure at 5.8 bars for ½ hour.

Pulled packers into place and hooked up to drill rods on exit end. After protracted discussion about correctly positioning the packers, pulled them into hole for first fracture.

Observations during fracturing are as follows:

Fracture #1 (frac A1):

Flemming and big group from County on site during 1^st fracture interval.

Pressured packer set to 5.8 bar for five minutes. Pumped mix as designed at 20 l/m for 300 l. Pump pressure at 5 to 8 bar. Mixed second identical batch and pumped into formation at 15 l/m at 7-8 bar. At ~150 l pumped, pressure dropped to 3-4 bar, then increased back to 7-8 bar. At ~400 l pumped observed ~5 l Guar outside of exit end of hole. Pressure still at 7-8 bar. Later observed a surface vent in the garden 16m down line of well toward exit pit. No change in levels reported.

Fracture #2: (frac A2)

Pressured packers at 5.8 bar for five minutes. Pumped design mix at 4-6 bar and 20 l/m for 3 minutes. Pressure dropped to 2-4 bar briefly, then 4-7 bar for remainder of pumping. Mixed 2^nd batch. Added 50% more breaker. Pumped 300 l. Some clear liquid, then green liquid, then sand and frac fluid mix into exit pit. Otherwise, no other indications of extent of fracturing. No change in levels reported.

Fracture #3: (frac A3)

Pressured packers at 6 bar for five minutes. Design mix, except 50% more breaker. Pumped 300 l at 1-4 bar, occasional spikes to 6 bar. Pumped 300 l at 1-6 bar, 20 l/m.

Maximum pull barely moves packer set out of position # 3 to position #4, so mixed fresh guar and pumped 100 l down hole to packers (with packers deflated). Packers then easily pull to position #4.

Fracture #4: (frac A4)

Pressured packers at 6+ bar for five minutes. Added 50% more breaker. Pumped 300 l standard mix at 6-8 bar at 20 l/m. Mixed second batch, also with 50% more breaker. Pumped 150 l at 7-8 bar, pressure began rising to 8+ bar. Pump using both diaphragms ceases to work. Switched to single diaphragm pump with similar results. Attempted pumping for 10-15 minutes. Checked lines, sand bridge in pipe just downstream of pump, sand bridge at transition between grout hose and plastic pipe, both cleared. Tried to pump again. No response. Cut blue pipe so only 9m showing out of hole. Appears to be plugged.

Attempted to pull packers forward. Stopped. Attempted to pull back. Also stopped. Hooked up pumps to grout hose and attempted to pump. After >100 liters, packer set began to move. Pulled out of hole. Lead packer damaged. Grout hose pulled off of EZ Flex joint on back of back packer. Air line broken.

Washed off packer, secured equipment and chemicals and left site at 0030, Saturday morning.

Saturday, November 13, 1999

Traveled to Copenhagen by car in AM. Took train back to Naestved and bus to Karrebæksminde in evening.

Sunday, November 14, 1999

Spent day in Karrebæksminde.

Monday, November 15, 1999

Arrived on site with Lisbeth at 0700. Clear, cold (-4C). No one else on site yet. Crew showed minutes later. Brief discussion about approach to today with Lisbeth. Requested tools for rebuilding packer from H&S. About 1030 an packer set moved inside Larsen’s shop on site. We removed lead packer and Christian and I rebuilt it. It was difficult to remove the sliding sub because sand had lodged in it. I was not sure about grease supplied with replacement element, but later confirmed with TAM that it is meant for the replacement rebuild. Reassembled but not tested by 1300.

Observed core drilling that Lisbeth was conducting in afternoon. First push 2 1/2m west of boring encountered 10 cm sand lens from fracturing. Second push, approximately 1m east of fracture #4 encountered very thin lens, 2-3mm, probably infilling of an existing fracture at 4 ½m (this one displayed color of dye tracer). Also, 4m away 3.4m depth, 15mm fracture.

Called TAM at 1545 to request a replacement (new packr) element in DK by Wednesday. He will call back about shipping.

Tuesday, November 16, 1999

Exercising packers and preparing equipment for next fracturing attempt. Obtained new air line from Køge.

Wednesday, November 17, 1999

On-site at 0400. Cool (+3C), cloud cover. Weighed guar for four 950 liter batches. Mixed tracer (50g/l, 100ml per 300 liter batch). Started pulling back at 0520. Hard spot (rock?) at 24-27m back from exit pit. Worked past with grooving tool. Rig went down due to pump problems at 0620, snowing lightly. Mud filter clogged with guar. Tanks have clumps of guar. Started again at 0640, filter clogged again at 0645, then again completely at 0700. Mixed new batch of guar, started grooving again at 0740. Completed grooving and pulled out of hole at 0810.

Horizontal Boring #2 (Not completed as a well, later abandoned)

Observations during grooving are as follows:

At 1000, set up to ream but pump clogged again. Began reaming at 1030. Tight spot before first fracture point, Klaus worked past. Stopped at 1120 to repair rod clamp. Reaming again at 1145. Completed reaming just before lunch time. At 1430, pulled in packer assembly to Fracture interval #1. The assembly broke apart with relatively low pullback pressure (<3 tons) – surprising. Later inspection indicates that assembly broke at coupling behind lead packer. Mandrel on lead packer is scored. Some white flint is in clay plug pulled out ahead of lead packer. All other components are retrieved from hole intact (portion ahead of the break pulled out of entrance pit, portion behind the break pulled out of exit pit).

Thursday, November 18, 1999

On-site at 0800. Overcast, cool (+2C). Crew preparing to pull casing into Well #1. I travel to Køge to rebuild packers at 1000. Arrived at 1130. Rebuilt lead packer using TAM replacement element that arrived Wednesday. Completed at 1400. Drove back to site.

No progress since I left the site (it is now 1500). Starting solenoid on D16/20 broke, Vermeer came out to fix it.

H&S pulled shelter casing into hole in evening. Installation and removal of shelter casing went smoothly.

Friday November 19, 1999

On-site at 0700. Cool (+2C), overcast. Rig was down all day and did not drill pilot hole for boring #3. Grouting company on-site to abandon boring #2 with cement/bentonite mixture (I suggested 5% or less bentonite to Lisbeth).

I went to Køge to pick up fracturing apparatus. I arrived just before noon and had one of the welders grind a bevel in the couplings between packers and on the back of the trailing packer to make less of a kink in the air line. Tried airing the packers and discovered that the air line we removed with the assembly on Wednesday is clogged. Shop closed down at noon but Kim stayed on until a new air line (154m) was shipped down from Copenhagen. Installed fittings and aired up line. It held tight at 5.8 bars. Loaded up truck and returned to the site about 1630. It was raining lightly. Unloaded packers (and aired them up twice), checked out grouting operation, got things organized for Monday and left site in PM. After dinner, traveled to Copenhagen with Lisbeth Walsted.

Saturday, November 20, 1999

I stayed in Copenhagen. Klaus and Jens on site installed pilot boring #3 (well B-B) in preparation for fracturing attempt on Monday, November 22, 1999. We learned from them Sunday night that the pilot bore encountered difficult conditions just beyond the first and last planned fracture intervals.

Sunday, November 21, 1999

I stayed in Copenhagen. Returned by train to Naestved in afternoon. Lisbeth drove me to Karrebæksminde.

Monday, November 22, 1999

Arrived on site at 0400. Cold (-8C), snowflakes falling occasionally. Jens filling truck with water. Klaus setting up rig. While I am in shop exercising new lead packer element, Klaus come in with mud transfer hose for rig, which is frozen solid. I help Klaus with hose, keep exercising packers, three (3) hours to thaw and get rig operational.

Began pulling in grooving tool at 0710. Stopped to repair hydraulic oil leak (20 minutes down). Next, bearing in rack broke. Bearing fixed by 0800, pulling back grooving tool. Grooving completed at 0840 with following results:

Horizontal Boring #3 (Completed as Well no. B-B)

Observations during grooving are as follows:

Lisbeth meeting with DEPA at 0900. Klaus set up 250mm reamer to open first portion of boring from the exit pit to within three rods of the first fracture interval. We are doing this because of Klaus and Jans’ report of rocks or other obstruction that caused steering difficulties when installing the pilot boring on Saturday.

Completed reaming with the 250mm to within three rods of first fracture, then pushed reamer back out of hole to exit pit with no problems (H&S had been initially concerned about pushing the reamer backwards). Pulled 122mm reamer into exit pit end of boring and pulled back to rig. Completed pulling back in late afternoon. Set up for fracturing.

Began pulling fracturing apparatus into place after 1630. Once in place, mixed first batch of fracture fluid and attempted to pump down casing. Sandpiper pumps will not pump. Schlumberger guy having difficulty troubleshooting. I suggest he call his office. It is a critical time and he needs to fix the pumps. Klaus pitches in to take a pump apart. Schlumberger guy calls his office. He suspects he needs a little positive suction head and that we should reconfigure the mixing unit and hopper so they are above the elevation of the pumps. Jakob and others start moving components. Pumps are taken and apart and reassembled. We mix a new batch of fracture fluid and try again (I am not sure of timing of any of this.

Observations during fracturing are as follows:

Fracture #1 (frac B1):

We pump 300 liters fluid plus 120 liters sand into first interval. Pressure at 6-8 bar. Venting noticed in garden so we limit injection to 300 liters (+120 liters sand) and plan to inject this amount for all subsequent fractures (1/2 the amount injected into the fracture intervals for Well nr. A-A). Deflated packers after 20 minutes, then waited 10 minutes and pulled to next interval. Rotated reamer and injected guar in front of packers and injected guar down grout hose behind packers. No problems moving packers.

Fracture #2 (frac B2):

Second fracturing 300 liters (+120 liters sand). One small venting next to pond.

Fracture #3 (frac B3):

Third fracturing same as second, except no venting noticed.

Fracture #4 (frac B4):

Fourth fracturing similar to third, also no venting.

Fracture #5 (frac B5):

We did not attempt a fifth fracture because the pumps, once again, had difficulty moving the fluid/sand mixture and the fracturing apparatus got stocked. Klaus and Jens pulled out fracturing apparatus beginning about 0030 Tuesday morning.

Tuesday, November 23, 1999

Left site at 0100. Slept at house in Karrebæksminde until 0400. Drove to CPH for 0815 flight on British Airways to LHR. LHR to SFO, arrived 1500.

Closing

Thanks for the opportunity to contribute to this project. I will be very interested to hear about the progress of the remaining drilling and casing installation as well as the performance of the system.

If you have any questions, concerns or other needs, please call, write or e-mail.

Best regards

Dana J. Brock

Consulting Engineer / Geologist

224-001