Reducing)Tubing)Failures)inWolfberry)Wells) …mapleleafmarketinginc.com/pdf/COG SPE...
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Reducing Tubing Failures in Wolfberry Wells Michael Beggs COG Operating Abstract Reducing tubing failures in Wolfberry wells is a main priority for COG Operating. A study was performed that placed boronized tubing across failure points. An in depth look at the boronized tubing process is reported, and the EndurAlloy benefits are discussed. Failure rates were calculated before and after the installs. A 28% reduction in failure rates was found and associated savings are reported in the paper. Introduction COG Operating is a Permian Basin operator based in Midland with over 1,600 wells in the Wolfberry play. Concho’s acreage is in the Midland Basin stretching south of Midland to the cities of Crane and Rankin. The acreage covers parts of Midland, Ector, and Upton counties. Figure 1: Basin Map Operators call the producing interval from the Spraberry formation down to the Wolfcamp, the Wolfberry play. The typical Spraberry depth is around 7,000 feet and the Wolfcamp can be as deep as 10,500 feet. The wells are usually drilled in about 14 days. Pay intervals are picked and up to 11 stages are perforated. These wells are fracture stimulated using approximately 100,000 pounds of proppant
Transcript of Reducing)Tubing)Failures)inWolfberry)Wells) …mapleleafmarketinginc.com/pdf/COG SPE...
Reducing Tubing Failures in Wolfberry Wells
Michael Beggs COG Operating
Abstract
Reducing tubing failures in Wolfberry wells is a main priority for COG Operating. A study was performed that placed boronized tubing across failure points. An in depth look at the boronized tubing process is reported, and the EndurAlloy benefits are discussed. Failure rates were calculated before and after the installs. A 28% reduction in failure rates was found and associated savings are reported in the paper.
Introduction
COG Operating is a Permian Basin operator based in Midland with over 1,600 wells in the Wolfberry play. Concho’s acreage is in the Midland Basin stretching south of Midland to the cities of Crane and Rankin. The acreage covers parts of Midland, Ector, and Upton counties.
Figure 1: Basin Map
Operators call the producing interval from the Spraberry formation down to the Wolfcamp, the Wolfberry play. The typical Spraberry depth is around 7,000 feet and the Wolfcamp can be as deep as 10,500 feet. The wells are usually drilled in about 14 days. Pay intervals are picked and up to 11 stages are perforated. These wells are fracture stimulated using approximately 100,000 pounds of proppant
and 3,200 barrels of fluid per stage. Frac gradients average from .85 psi/ft in the Wolfcamp to .5 psi/ft in the Spraberry. Because of this, the required frac rate in the Wolfcamp is 70 bpm and 40 bpm in the Spraberry. The average frac is 9-‐11 stages and takes approximately 2 days to complete. The stages are separated by plugs and are drilled out after the frac to prepare for production. Producing a well with over 3,500 feet of pay interval can be very challenging.
Figure 2: Midland Basin Stratigraphic Map
One challenge facing operators is tubing failures. COG’s Wolfberry target total failure rate for 2012 was .33 f/w/y. The failure rate calculation is shown in Equation 1.
Equation 1:
f/w/y = (number of failures)/(number of wells)/(1 year)
Tubing failures made up about half of the total. In one specific area the tubing failure rate for 2012 averaged .41 f/w/y. There are several factors that make tubing failures detrimental.
• More costly than pulling for a rod part or pump problem • Take longer to repair resulting in more deferred production and rig costs • Tripping tubing can be operationally challenging
The 2012 average cost to repair a hole in tubing was over $36,000. Because these failures are so costly, COG is committed to find a solution to make a drastic reduction in the failure rate.
Figure 3: Failure Rate Chart
Most of the tubing failures were comprised of rod on tubing wear.
Figure 4: Rod on Tubing Wear Image
0 0.05
0.1 0.15
0.2 0.25
0.3 0.35 0.4
0.45 0.5
0.55 0.6
F/W
/Y
Total Wolfberry Composite Failure Rate
Target Total Pumps Tubing Rods
Measures were taken to reduce the amount of buckling in the rods including reducing fluid flow through restriction in the pump and sinker bar sections, but with no significant impact on failure rate. A chemical program was utilized to minimize corrosion and scale problems. Another option was to run hardened tubing in rod cut areas. Boronized tubing, specifically EndurAlloy was chosen to be run at the failure locations.
EndurAlloy Process
The high strength process is an alloyed surface created on the tubing by diffusing boron into the substrate of carbon steel. The surface is comprised of one atom of boron and one atom of iron, which combine to create a molecule of iron boride.1
Figure 5: EndurAlloy Process Image2
This process provides excellent protection against rotating or stroking rod wear, erosion caused by abrasive fluids, corrosion, and other factors that cause premature tubing failures. There are several advantages in utilizing EndurAlloy over IPC (internally plastic coated) tubing including retaining the original internal diameter of the tubing, and it is stable up to 900 F.3
The boronized steel retains the mechanical properties of the original J-‐55, and has a hardness rating of 73-‐90 Rockwell C equivalent. For comparison, regular J-‐55 is less than 20 HRC.
Figure 6: Hardness Scale Chart4
Well Installation
Pumping Unit:
Weatherford 320-‐305-‐100
Surface stroke of 100”
Average pumping speed of 8 spm
Pump plunger diameters from 1.25” to 1.5”
1.25” pump capacity: 140 x 80% efficiency = 112 bpd
1.5” pump capacity: 200 bpd x 80% efficiency = 160 bpd
Rod String Design:
Wells pumping above the perforations:
• 0-‐4500” Weatherford EL’s on top • 4500-‐7500’ Weatherford KD’s on bottom • 300’ 1.5” Grade C sinker bars
Wells pumping below the perforations:
• 0-‐7000” Weatherford EL’s on top • 7000-‐10000’ Weatherford KD’s on bottom • 300’ 1.5” Grade C sinker bars
Tubing String Design:
Wells pumping above the perforations:
• 3600’ of 2.375” L-‐80 tubing on top • 3900’ of 2.375” J-‐55 tubing on bottom
Wells pumping below the perforations:
• 3600’ of 2.375” L-‐80 tubing on top • 7000’ of 2.375” J-‐55 tubing on bottom
Tubing failures were documented and the joint number of the failure was tracked to determine the optimal installation location for the boronized tubing. On average most of the failures occurred between joints 180 and 280.
Figure 7: Failure Location Chart
After each failure, the joint number was documented and if several were in close proximity to each other EndurAlloy was run across that interval. Because of the cost on average 10 joints were placed across the failure location. The difference in cost/ft between a regular joint of J-‐55 and 1 joint of EndurAlloy is about 8.29 times higher. From June to December of 2012 COG has installed 831 joints of EndurAlloy tubing in 82 wells. Failure rates were calculated 1 year before installation date and after. The average failure rate 1 year before EndurAlloy installation calculated out to 1.27 failures/well/year. The average failure rate after installation date calculated out to .92 failures/well/year.
100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Joint #
Wells
Failure Rate Loca3on Chart
Minimum Joint Failure Locafon
Maximum Joint Failure Locafon
Individual Well Example: Amacker 88A #5
The Amacker 88A #5 is located in the South area of Concho’s acreage. This well was spud 3-‐25-‐12 and put on production 5-‐4-‐12. The tubing and rod details are outlined below. The left part of figure 7 is pre-‐installation, and the right part is post-‐installation.
Figure 8: Tubing and Rod Detail
The 1.5” pump is set approximately 139 feet above the top perforation at 7,120 feet. The Amacker 88A #5 average production is 40 BOPD, 200 MCFD, and 30 BWPD. This well ran 117 days from the time it was put on production to the first failure on 8-‐29-‐12. During that repair 25 joints of EndurAlloy were installed above the IPC tubing and seat nipple. The current time between failures as of April 1 is 215 days, and it is still running. That is an 84% increase in the time between failures.
0
50
100
150
200
250
Pre-‐install Post-‐install
Days Between Failure Chart
Figure 9: Days Between Failure Chart
Conclusions
Figure 10: Failure Rate Chart
No failures in the 831 joints of EndurAlloy tubing have been found. All failures were typically in the J-‐55 tubing above or below the EndurAlloy. It appears that the boronized tubing transferred the failure to the J-‐55, and prolonged the time between failures. There is probably still rod on tubing contact on the EndurAlloy, but it is much harder to wear a hole in. One point needs to be considered in this calculation. All of the installation dates were within a year time period, so a calculated yearly factor was used to adjust the failures/well/year. The yearly factor formula is shown in Equation 2.
Equation 2:
Yearly factor = days between failures/365
That being said, there may be failures that occur after the study since only a small snapshot was taken. This is an ongoing project and the results will be continually evaluated. The before and after failure calculations result in a decrease in failure rate by 28%. There is also an associated drop in deferred production. That means that if a well is down with a failure, then it is not producing hydrocarbons. The associated drop in deferred production is 5,281 bbls of oil and 15,138 mcf of gas reduced by 28% calculates out to a savings of $158,118 assuming $84/bbl oil and $8/mcf gas.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Pre-‐install Post-‐install
Failure Rate Chart
Tubing failures for Concho in 2012 totaled over $9.3 million.
Figure 11: Tubing Failure Costs
• A 28% reduction in work over costs calculates out to $2.6 million in savings and netting $2 million after taking out the EndurAlloy costs and adding deferred production.
• Since most of these installations are new and may fail again, the percentage could drop to 10% and COG would still net $260,000 on the program.
Based on these results EndurAlloy tubing
• Increases run time between tubing failures • Reduces expenses and increases revenues by eliminating rig jobs and lost production.
$0
$1,000,000
$2,000,000
$3,000,000
$4,000,000
$5,000,000
$6,000,000
$7,000,000
$8,000,000
$9,000,000
$10,000,000
Tubing Failures
2012 Tubing Failure Costs
Failure Rate Calculations
Quantity # joints Well Name
# HIT failures 1 year prior to install
date yearly factor
f/w/y prior to install
date install date
# HIT failures
after install date
yearly factor
f/w/y after
10 LAURA #3919 0
0 12/7/2012 0
0 10 HASEL28 #2 0
0 12/6/2012 0
0
10 CHRISTINE #8 1 0.2995 3.34 11/29/2012 0
0 20 HASEL29 #2 0
0 11/28/2012 0
0
10 LYNCH26 #3 0
0 11/26/2012 0
0 11 CADEN #4328 1 0.2253 4.44 11/20/2012 0
0
20 NEAL RANCH "97" #1 2 1 2 11/19/2012 0
0 10 AMACKER23SW #2 0
0 11/19/2012 0
0
3 HALFF12 #1 1 0.2912 3.43 11/15/2012 0
0 10 KYNDALL #5412 2 1 2 11/13/2012 0
0
2 LEAH #19 0
0 11/12/2012 0
0 23 ELLIE #1406 2 1 2 11/10/2012 0
0
10 HASEL55 #2 1 0.5385 1.86 11/9/2012 0
0 10 CCP L53 #2 1 0.6712 1.49 11/9/2012 0
0
2 Railway Ranch "18" #2 0
0 11/8/2012 0
0 10 LYNCH NORTH 30 #4 0
0 11/6/2012 0
0
10 HALFFYATES12 #2 1 0.3709 2.70 11/6/2012 0
0 8 SLOAN #4111 0
0 11/6/2012 0
0
10 HASEL6 #2 0
0 11/5/2012 0
0 10 JESSE #6 0
0 11/1/2012 0
0
10 MEREDITH #6 0
0 10/30/2012 0
0 10 DAWN #6 0
0 10/30/2012 0
0
10 AMACKERADAM #2302 1 0.6712 1.49 10/29/2012 0
0
20 POWELL 31 #14 5 1 5 10/26/2012 0
0 10 LORA LYNN #10 0
0 10/25/2012 0
0
10 COWDEN2 #2 0
0 10/25/2012 0
0 20 HASEL2 #2 1 0.211 4.74 10/22/2012 0
0
2 LYNCH27 #2 0
0 10/18/2012 0
0 10 JESSE #4 0
0 10/18/2012 0
0
2 TXL 21 #12 0
0 10/16/2012 0
0 2 DIANA153 #5 0
0 10/11/2012 0
0
10 CASEY LYNN 4105 1 0.5824 1.72 10/11/2012 0
0 10 JESSE #27 0
0 10/10/2012 0
0
15 MANN17 #4 1 0.261 3.83 10/8/2012 0
0 1 POWELL 31 #14 4 0.9863 4.06 10/5/2012 1 0.0577 17.33
20 CASEY LYNN 4101 0
0 10/3/2012 0
0 10 LYNCH52 #2 1 0.3654 2.74 9/27/2012 0
0
10 JENNIFER #2 0
0 9/25/2012 0
0 10 MADELINE KATE
#4007 1
1 9/21/2012 0
0 10 FLORENCE 3915 1
1 9/21/2012 0
0
20 LYNCH NORTH 30 #1 1 0.4 2.5 9/19/2012 0
0 10 CLAYTON #6 0
0 09/13/2012 0
0
20 COWDEN50 #2 2 0.4863 4.11 09/13/2012 1 0.1566 6.39 10 CLAYTON #3 0
0 09/10/2012 0
0
10 MADELINE KATE #4026 1 1 1 08/31/2012 0
0
10 JESSE #5 0
0 08/31/2012 0
0 10 LORA LYNN #11 0
0 08/30/2012 0
0
25 AMACKER88 "A" #5 1 0.3214 3.11 08/28/2012 0
0 10 POWELL 31 #10 4 1 4 08/24/2012 1 0.3123 3.20 2 COWDEN2 #2 0
0 08/22/2012 0
0
10 AMACKER #8405 1 0.3123 3.20 08/21/2012 0
0 2 TXL 15 #3 0
0 08/20/2012 0
0
2 POWELL 36 #3 0
0 08/20/2012 0
0 2 TXL 9 #1 0
0 08/14/2012 0
0
10 LYNCH50 #3 1 0.2363 4.23 08/09/2012 1 0.2685 3.72 2 AMACKER60SE #2 0
0 08/08/2012 0
0
2 MANN14 #1 0
0 08/03/2012 0
0 20 NEAL RANCH "47" #4 4 1 4 07/31/2012 0
0
10 AMACKER 19SW #3 0
0 07/30/2012 0
0 10 JOY #4 0
0 07/30/2012 0
0
10 LYNCH17 #2 2 1 2 07/26/2012 0
0 20 KYNDALL #5409 1 0.2335 4.28 07/25/2012 0
0
10 CCP L53 #2 1 0.3489 2.87 07/24/2012 1 0.3049 3.28 2 TXL 23 #6 0
0 07/24/2012 0
0
10 LORA LYNN #6 0
0 07/23/2012 1 0.1923 5.20 2 POWELL 36 #4 0
0 07/23/2012 2 0.2335 8.56
10 DOLORES #11 0
0 07/19/2012 1 0.2802 3.57 2 TXL 35 #11 0
0 07/18/2012 0
0
10 VANESSA #9 0
0 07/18/2012 2 0.2912 6.87 2 TXL 9 #5 0
0 07/13/2012 0
0
20 NEAL RANCH "38" #5 1 0.533 1.88 07/13/2012 0
0 10 MORGAN 3815 0
0 07/11/2012 0
0
10 NEAL RANCH "57" #14 1 0.6923 1.44 07/11/2012 0
0 10 POWELL 31 #14 3 0.7418 4.04 07/11/2012 2 0.294 6.80 10 TXL 31 #12 1 0.3242 3.08 07/10/2012 0
0
10 CHEVRON 43 #21 0
0 07/09/2012 0
0 10 CHEVRON 35 #9 1 0.4588 2.18 07/09/2012 1 0.3104 3.22 20 LYNCH NORTH 30 #2 1 0.261 3.83 07/09/2012 1 0.2335 4.28 10 TXL 27 #15 0
0 07/06/2012 0
0
10 VANESSA #7 0
0 07/05/2012 0
0 10 DOLORES #11 0
0 06/25/2012 1 0.2802 3.57
10 AMACKER47 "A" #3 0
0 06/15/2012 0
0 5 POWELL 31 #13 2 0.3984 5.02 06/12/2012 0
0
831
Averages 1.27
0.92
-28.04% Reduction in failure rate
Figure 12: Failure Rate Calculations
References
1. Endurance Technologies Inc. EndurAlloy Corrosion Applications October 2012 2. Endurance Technologies Inc. EndurAlloy Corrosion Applications October 2012 3. Endurance Technologies Inc. EndurAlloy Tubing Presentation October 2012 4. Endurance Technologies Inc. Comparative Hardness Scale, October 2012
