2004 Drilling Engineering Association Workshop

“Step Changes in Drilling Technology 2004”

June 22-23, 2004

Moody Gardens Hotel -- Galveston, TX

The Development of the First “TRUE”

Oilfield Air Hammer

John Adam Meyers, Diamond Air Drilling Services;Rainer Beccu, Drillco Tools S.A.; and

Tommy Taylor, Fasken Oil & Ranch Ltd.

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Abstract

Percussion drilling tools (air hammers) have proven to significantly increase the drilling rate of penetration[1]on many Oil and Gas wells. However, these air hammers were typically designed for mining, water wells or industrial applications, so their performance has not been optimized for the specific conditions of a deep-hole Oil and Gas well.

Deep-Hole drilling (below 8000 feet) typically requires a higher amount of air volume (SCFM) to clean the annulus[2], higher air pressures (above 350 psi) to overcome formation water influx, as well as the capability of drilling under hot-hole conditions (above 250ºF). This paper describes the specific design features of the first “True” Oilfield Air Hammer that has significantly improved the drilling performance over the conventional air hammers when encountering such harsh conditions.

Field test data is reviewed including the World Record Single Run performance (12,480 feet in 167 hours = 74.7 ft/hr) for an8 ¾” hole size which was accomplished in May 2004 in Val Verde County, TX. Application specific problems that were encountered on other field tests are documented and future work is described on how these problems have been or can be solved.

Introduction

The development of new technologies will often take many years due to the technical hurtles, but limitations in financial support due to the up and down business cycles within the Oil and Gas industry will often prevent worthwhile projects from being started. One example of new drilling technology that has taken far too long to develop has been the design of the first “TRUE” Oilfield Air Hammer. Air hammer drilling tools designed for the mining and water well industries have been used within the oilfields of North America since the 1980’s because they drill fast as well as straight holes[3].

However, air hammers have typically been limited to shallow (< 8000 feet) and dry (Dusting) drilling applications becausetheir performance reduces with depth as well as with formation water influx. Many natural gas wells have deeper production zones which require the use of a mist or a foam circulating medium[4] to improve annular hole cleaning. Industrial hammers typically do not drill very well with Mist or Foams because they were designed to be efficient with dry air as well as with low air volumes. Therefore, these hammers do not work effectively with a high amount of mist rate (because of the incompressibility of the water) or with a high annular back pressure.

Thus, the development of an air hammer that eliminates current design weaknesses as well as drills more reliably and effectively with mist and/or foam applications would be a welcomed improvement to the Air Drilling areas of the U.S. These areas include the Val Verde Basin of West Texas, the San JuanBasin of the Rocky Mountains, the Appalachian Basin of the Northeast U.S., the ArkomaBasin in Southeast Oklahoma as well asa relatively new air drilling market in the Fort WorthBasin (north-central Texas).

Fig. 1 Conventional Hammer

(Ingersoll Rand QL8)

New Design Concept

In order to improve the performance of any drilling tool, we must first understand the reasons that the original design has been limited for a particular application. In this case, the conventionalair hammer is designed with a Foot Valve assembly (Fig. 1 Ingersoll Rand QL8 hammer) which utilizes a plastic tube on the top of the bit as a valve to “seal” the bottom chamber of the hammer. Upon sealing the bottom

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chamber, high pressure air pushes the piston upwards, thus starting the piston’s cycle. It should be noted that the bottom chamber must be “sealed” in order for the piston’s cycle to begin. In other words, if the Foot Valve is missing or broken the hammer will not operate.

Although the Foot Valve mechanism has worked quite well in mining and industrial applications (Dusting), it is less reliable when operating with Mist or Foam circulating mediums. It is thought that this general design concept allows water to accumulate in the bottom chamber because the air and water must “climb” above the Foot Valve to exhaust the bottom chamber through the bit (Fig. 2 Bottom Chamber exhausting).

Fig. 2 Bottom Chamber exhausting for

conventional Air Hammers

NOTE: The accumulation of any

incompressible fluid in the lower

chamber of an air hammer could

reduce the impact energy of the piston

on the bit.

Thus the major design concept of this “Oilfield” Air Hammer is to eliminate the Foot Valve mechanism while still maintaining a seal for the bottom chamber. The design should minimize the accumulation of water (non-compressible fluid) in the bottom chamber so that the impact energy of the piston would not be

compromised when Mist or Foam drilling.

Fig. 3 FAMUS 8 Hammer

This “Oilfield” Air Hammer(Fig. 3 FAM-Us 8 Hammer) incorporates a “small nosed” piston design which allows for the bottom chamber to be sealed on the OD of the piston instead of the ID as with the Foot Valve sealing mechanism. When the piston lifts off of the seal area, the entire bottom chamber exhausts easily through the bit. (Fig. 4 - Bottom Chamber exhaustingFAMUS 8) Thus, the accumulation of water (incompressible fluid) in the bottom chamber should be minimized.

Fig. 4 Bottom Chamber exhausting

FAM-Us 8 hammer

However, the most popular reason that this hammer will be famous (FAM-Us) is because of the elimination of the plastic Foot Valve (also known as a Blow Tube) which can be amajor nuisancewhen causing hammer trips. The conventional air hammer is infamous for breaking “Blow Tubes” occasionally and thus causing an expensive trip out of the hole to replace a $30 piece of plastic. As you would expect, this occasional problem is very hard for the customer to accept.

Technical Review

From a technical point of view, this design concept dramatically changes the compression ratio of the lower chamber. In the case of the conventional air hammer the lower chamber is compressed by as much as 87% (See Fig 5), while the FAM-Us hammer only compresses the lower chamber by 42% (See Fig. 6).

Fig. 5 Conventional QL8 Air Hammer

Bottom Chamber Compression (87%)

Fig. 6 New FAM-Us 8 Air Hammer

Bottom Chamber Compression (42%)

The lower compression ratio will lower the pressure in the bottom chamber and thus reduce the amount of deceleration of the piston which occurs just before the impact with the bit. Thus, the piston strikes the bit with a higher velocity, which is directly related to the impact energy. Remember

E = ½ m v ²

proves that if the velocity of the piston is increased (or decreased less), then the energy level (impact) is increased significantly due to the velocity being squared. Therefore, the new FAM-Us hammer has the potential to drill faster with the same operating pressures or operate with lower pressures while delivering the same ROP.

Thus with this design concept supported by the above mathematical formula, it is conceivable that when drilling with a significant amount of non-compressible fluids (Mist or Foam), the piston’s velocity will be dramatically reduced with a conventional air hammerdesign because of the small lower chamber volume at the point of impact.

Field results using a conventional air hammer support this theory because the ROP is typically reduced by nearly 40 % when converting from Dust to Mist drilling.Thus,if the theory is correct, then the new FAM-Us hammer should will have a much lower reduction in piston velocity, and therefore it should drill faster than the conventional air hammer under the same operating conditions when Misting or using Foam. (See Field Test Results).

Field Test Results

Field Test 1 -- The original field test of this “Oilfield” Air Hammer was run in Edwards County, Texas in June 2003 in a “Dusting” (dry air medium) application to see how it would compare to the standard conventional air hammer. To our delight, the hammer drilled 8293 feet in 98.5 hours (84.2ft/hr) which was significantly above average (28% in footage, 23% in hours, as well as 12% in ROP).

Misting Field Tests -- In Misting applications, this hammer has performed quite impressively with the Rate of Penetration (ROP) increasing by approximately 30% over conventional air hammers. Under typical operating conditions, the rate of penetration of an industrial air hammer will decrease from 80 feet per hour (Dusting) to 45 feet per hour (Misting) which is a 40+% reduction. This ROP reduction can be directly contributed to the piston’s impact energy as described earlier. The field test data (See Table 1) for the FAM-Us air hammer thus far shows to have significantly improved ROP while Misting.

Table 1 - Dust VS Mist Run Data*

Hammer
Type / Air
Type / Water
Volume / ROP
(Ft/Hr) / % Diff.
Conv. / Dust / N/A / 80 - 90 / Base
Conv. / Mist / 14bbls / 45 -55 / - 41%
Conv. / Mist / 22bbls / Watered Out / N/A
FAMUs / Dust / N/A / 90-100 / +12%
FAMUs / Mist / 14bbls / 60-65 / - 26%
FAMUs / Mist / 22bbls / 50 - 55 / - 38%

* Data from Terrell County, TX

It should also be noted that the general trend has been to increase the Mist Rate which enhances hole cleaningand reduces the time for each connection which can be significant for deep-hole drilling. Typically past experience has shown that the conventional 7” OD Air Hammer (used in 7 7/8” thru 8 ¾’ holes) could “water out” if more than 14 Bbls/hour (10 gpm) of water ispumped down-hole. The FAM-Us 8 hammer has been used with as much as 25 Bbls/hour (18 gpm) of water and continued to deliver acceptable rates of penetration (ROP).

World Record Performance -- After making several minor design changes to improve the reliability of this hammer’s components, the 3rd version FAM-Us 8 hammer has been drilling in the field since February 2004. The results thus far have been very good, in fact, in May 2004, the World Record Single Run Record for an 8 ¾” hammer bit was shattered by this hammer with a run in Val Verde County, TX of 12,480 feet in 167 hours (74.7 ft/hr).

Additional Design Features Address Specific Application Problems

Hot Hole Applications --By eliminating the Foot Valve (Blow Tube) as well as upgrading several other components (i.e. O-Rings, clearance dimensions, Rock Oil, etc.), this “Oilfield” air hammer can now drill at much higher temperatures (+320ºF).

Conventional air hammers have typically struggled when approaching depths near 12,000 feet and/or temperatures near 250ºF, due to the plastic Foot Valve (Blow Tube) having numerous failures. Typically air hammers were replaced by roller cone bits when temperatures caused premature hammer failures due to “melted” Foot Valves (Blow Tubes).

High Tech (very expensive) materials such as Vespel® have been used to replace the standard Delrin® plastic material for Foot Valves but with limited performance improvements. Table 2 shows an example of the number of trips (bits) and days required to drill a well in Val Verde County, TX using the conventional industrial air hammer verses the new FAM-Us air hammer to depths where the bottom-hole- temperatures approached 300ºF.

Table 2 -- Hot Hole Well Data*

Year / Hammer / TD / #Trips / #Days
2000 / Conventional / 11,080 / 3 / 9
2003 / Conventional / 11,762 / 2 / 10
2003 / Conventional / 13,410 / 4 / 16
2003 / FAM-Us / 14,500 / 3 / 15
2004 / FAM-Us / 14,335 / 1 / 9

* Data from Val Verde County, TX

Bottom Hole Temperature 260 - 320ºF

below 12,500 feet.

Deep Hole Applications -- this hammer also incorporates a By-Pass Choke system which allows continuous air flow to the annulus that improves hole cleaning especially when drilling deeper hole sections. It is important to note that the piston’s frequency and the Rate of Penetration can be directly related to the air volume that is circulated through the hammer’s power section. However, using excessive air volumes can cause excessive impact energy which has led to broken pistons and shanked bits. Thus, it was impressive to find that this new hammer has equaled or improved ROP when “Dusting” while By-Passing as much as 25% of the air volume, which in-turn also lowered the air pressure versus a conventional air hammer that did not have a By-Pass choke (See Table 3). This appears to confirm that higher annular back pressure (depth) can significantly affect the efficiency and/or impact energy of a conventional air hammer.

Table 3 -- Pressure & ROP Comparison

Hammer
Type / Vol.SCFM / PSI / Avg.
ROP / %
CHANGE
Conventional / 2100 / 400 / 81.0 / Base
Conventional / 2700 / 475 / 90.0 / +11%ROP
FAM-Us* / 2100 / 350 / 93.0 / +15%ROP
FAM-Us* / 2700 / 400 / 100 / +23%ROP

* FAM-US hammer using a 3/8” choke

Reliability Improvements -- Most industrial hammer designs have a significant number of removable parts in an effort to make the overall hammer cheaper to maintain (i.e. smaller “consumable” parts are used instead of larger more complicated and expensive parts). These small consumable parts (i.e. air guide, inner sleeve, lower bearing sleeve, snap rings, etc) often have a short life expectancy in tough oilfield applications (i.e. High Air Volumes, High Pressures, Brine-Water Mist, etc.). Therefore in our effort to improve reliability, this “Oilfield” air hammer has also been designed with a reduced number of parts which last longer in the harshest environment.

Rig Operations -- It should also be noted that the conventional air hammer has a very short (4-5”) Top-Sub section which makes the make-up and break-out of the connection slow and difficult on the rig floor. This hammer has a longer Top-Sub which allows for easier make-up on the rig floor as well as having a standard “Oilfield” length fishing neck.

Conclusions --

1)The Small Nose Piston’sdesign has a lower compression ratio as well as better exhausting of the bottom chamber which improves ROP when Misting.

2)The elimination of the plastic Foot Valve allows the FAM-Us hammer to drill in deeper hot-hole applications where conventional hammers have had problems.

3)The FAM-Us hammer drills faster than conventional air hammers with lower air pressures because of the By-Pass choke system. The By-Pass choke evidently helps improve annular hole cleaning which in turn increases the actual differential pressure across the hammer.

Future Efforts --

Although the performance of this hammer has been outstanding, several reliability problems were noted during the 2003 – 2004 Field Tests,which included broken pistons and shanked bits. The piston has received geometric design changes which increased its durability in most applications but it may also require a material and/or heat treatment modification to further improve its reliability when drilling intough environments such as Brine-Water Mist applications.

The occasional shanked bit situation appears to be impact energy level related, so more work is required to determine if application specific designs and/or operating parameter changes may be needed to optimize this hammer’s overall performance.

The Oil & Gas industry continues to request whether a hammer can be used in directional and horizontal holes. Therefore, future work should also include determining how to directionally drill with a conventional air hammer and/or the development of an air hammer that can steer the well bore in a desired direction.

Acknowledgements --

The development of any new drilling tool takes clever and/or focused engineers and designers, but as mentioned earlier, without the support of management many projects are subject to dramatic changes because of the dynamic business cycles of the Oil & Gas industry. The authors would like to thank the following individuals for there continuous support and patience during the development of the FAM-Us hammer.

Rolando CarmonaDrillco Tools

Jimmy Davis, Jr.Fasken

Greg Hawley Diamond Air

Wayne JoinerNewfield

Doug KeithlyNewfield

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[1] Reinsvold, C.H., Clement, J., Oliver M., Witt, C., and Crockett, J., “Diamond Enhanced Hammer Bit Reduce Cost Per Foot in the Arkoma and Appalachian Basins”, SPE/IADC 17185, 1988 SPE/IADC Drilling Conference, Dallas, TX, Feb 28 – Mar 2, 1988

[2] Cooper, L.W., Hook, R.A., and Payne R.R., “Air Drilling Techniques”, SPE 6435 presented on April 17-19 at the 1977 Drilling and Production Symposium in Amarillo, TX.

[3] Johns, R.P., Witt, C. and Fredrick, M., “Hammer Bits Control Deviatiopn in Crooked Hole Country”, SPE/IADC 18659 presented at the 1989 SPE/IADC Drilling Conference in New Orleans, LA., Feb. 28 – Mar. 3, 1989.

[4] Okpobiri, L.W., and Ikoku, C.U., “ Volumetric Requirements for Foam and Mist Operations”, SPE 11723 published in Drilling Engineering Feb. 1986.