Drilling with Air
Contents
1. food grade EP type lubricant for water well hammer drilling Wear nose and mouth filters when drilling with air to minimize your intake of solids and the airborne oil mist parti cles which can be hazardous to your health NGWA org control which is automatically pneumatically controlled by the air tank pressure F gt SZ ie gt eed yp ra ee 1 e The Water Pump Drilling with air stirs up a lot of dust To control the dust in dry holes water can be added to the airstream at a higher pressure than the compressor The water converts the dust into mud balls When drilling with air be sure to wear eye and ear protection Yes you can still hear the hammer operation Put in as little water as required by the hole condition water may be hard to get at the drill site A small pump at 8 gpm means 480 gallons per hour four hours of drilling is nearly 2000 gallons The pump must be variable volume de livery The best drive will be a variable speed hydraulic drive With a fixed drive part of the delivery is piped back to the tank through valving This is a waste of energy The air motor concept is good however it does take away from the drill air cfm Some of the pumps frequently used are the old twin piston Myers pump designs are now owned by Fred s Water Service The model A08 4 produces 0 to 8 gpm at up to 400 psi The pump shaft eccentric provides a stroke of 0 688 inch and runs at maximu2. A Simple Cycle of Compression Rotary Screw Compression is a Continuous Pulse free Process cycle of compression The complete cycle of compression is as simple as the rotary screw principle itself As the rotors tum the compres 1 Air Filter 2 Inlet Control Valve rotary screw compressor In the casing direct there are only two moving parts the rotors The male lobes functioning as pistons that roll not slide in the female cylinders The male does the compressing the female is the idler For clarity we ve illustrated just one Compressor Unit air end Oi stop valve engine runs at 2100 rpm with the tranny in to 1 Maximum speed for this oil flooded screw 1s about 4700 rpm The basic dry screw compressor was designed in the 1940s by SRM Svenska Rotor Mask iner in Sweden Then came the oil flooded screw with the development of a coalescent filter that is able to separate the oil out of the compressed air But strangely enough we add special oil back into the air to lube downhole equipment Functions of the compressor oil are e Cooling of compressor e Lubrication of screws bearings and gearbox e Sealing clearances between screws avoiding steel to steel contact NGWA org sion chamber is flooded with oil This contact cooling removes the heat af compression seals clearances and lubricates the rotors and bearings The compressed air oil mixture passes into the receiver where most of the
3. tion jumps possibly landing in even more trouble Put a screen guard around these items Air and Mud Combination Piping This is a difficult one Even double swing brass checks and ball valves will eventually leak mud and sand into your air tank This mud will work its way into the unloader valves on piston com pressors and cause extreme pressure buildup and pop the safety valve When mud is detected in the condensate either replace the checks and ball valves or isolate the air to mud connection If a rig is equipped with this dual hookup we recommend that a small slobber pot be installed on the tank to trap the mud and keep it from going into the unloader system lines Service and Operation Suggestions e Check when the compressor was last serviced with fresh lubricant and filters e Ifthe compressor delivers oil with the air change the coalescent filter immediately e Clean or replace the air intake filters 52 September 2010 Water Well Journal Resolutions to Make Today l Check your drilling program and see Have adequate filters and compressor Determine what hammer lubricant Invest in a bit grinder and dress those Figure 25 A Ewbank M 100 RD develops a very large well with a 750 350 Sullair compressor Note the enormous difference in water flow meaning a much larger downhole screen surge Photo by Gerry Neubecker Ill Check your pipe dope specs to make sure it can be used for water
4. CLOSED i GRA a AA J amp 6064606506 66 IIA APAA Ma tf ID gt LETT Te N N SS A Z EA RE RE O EC a le oe LE YAOI el ck fe VE oe lee WEL METAT F74 EFS SWA A IX H ws WL NGWA org So 460 2 31 199 psi A larger compressor is needed with reference to the pressure rating 250 psi would break the water column blow out the water and drilling continues An experi enced driller will not shut down for lunch however if the situation de scribed in the example happens for some reason he would then pull 200 feet of pipe and try again The water column would now be 260 feet above the bit or hammer 260 2 31 112 psi The 125 psi compressor would break the water pressure and blow out the water Quick connections and blowing after each joint will get that bit back to the bottom of the hole to continue air drilling Before selecting a compressor the pressure must be considered for e Pressure required by the downhole hammer e Maximum water column to be expected in the hole e Cleaning of the bit TRANSFER OF TECHNOLOGY continues on page 42 dd d REMOVE 2 1 0 CUSHION RUBBER FOR SHORT FLOATING SHOCK SUB NOTE i SLL ff fi fi LA TI N 2 3 8 REG BOX TO 3 1 2 REG BOX OTT ff ADS 7 AB F DEEANN INN Lt af It Water Well Journal September 2010 41 Figure 6 The LeRoi 250 series S2 two stage and SDS single dual stage are Table
5. TRANSFER OF TECHNOLOGY continues on page 40 Figure 1 Many drill manuals include this chart to determine compressor size We prefer our simple formula AIR VELOCITY DETERMINATION CHART VAT Zavaraue AT HOLE R ANGIR NGWA org Table 1 Maximum Diameters for Some Popular Compressor Sizes Using 4 4 Inch Pipe d Inch D Max Inch TRANSFER OF TECHNOLOGY from page 38 e Mix water foam and try to float the chips out e Get a duplex pump to pump the hole clean e Geta crane large enough to pull your pipe past the breaking point and hope that it breaks close to the bit e Fill the hole properly and start over The uphole velocity is strictly a func tion of the volume of the compressor in cfm The compressor capacity is expressed as cfm psi 900 350 Please be aware that the cfm is the intake cfm and not the volume at the rated pressure Atmospheric pressure equals 14 7 psi At 100 efficiency ignoring altitude humidity and temperature the com pressed package would be 900 x 14 7 350 37 8 cfm Air Pressure As stated previously the compressed air is forced to either the button bit tri cone or the DTHH down the hole ham mer The hammer does not eat the air it simply takes the energy stored in it and then turns it loose into the borehole Obstructions in the annular space usu ally chips and water will maintain some pressure on the air reducing this as it comes to the top of the hole 1
6. oil drops to the sump Virtually all remaining oil is removed from the air by a coalesc ing filter The oil is pumped from the sump first through a filter then through a compressor oil heat exchanger to the compression chamber and bearings 1 Atmospheric air is drawn axially into the compressor as the rotors turn past the intake port of the housing 2 The rotors have been turned past the intake port air is trapped in the compressor housing and rotor cavities 3 As the rotors continue to turn the lobes reduce the volume in the cavities compress ing the trapped air 4 The process is completed as compressed air is discharged through the outlet port of the housing The Basic System I A 3 Two screws rotate within a chamber Chamber is flooded with oil Coalescent removes oil and lets air through Oil must be cooled in cooler Oil must be filtered and controlled flow of oil will maintain operating temperature Throttle valve controls amount of intake air and thus output cfm Air with oil comes into the tank separator tangentially spinning out most oil like a centrifuge Drive clutch powers compressor rotation A closed throttle valve allows the clutch to stay engaged while no air is produced There are no unloader valves like on a piston machine Because a rotary screw has a contin uous rotary motion it may be driven by hydrostatic motors without any prob lems of pressur
7. the director of engineering for the George E Failing Co in Enid Oklahoma John was born in the Nether lands and moved to Enid in 1969 He is the founder owner and president of Enid Drill Systems Inc He received the 2003 NGWA Technology Award 38 September 2010 Water Well Journal then a 750 cfm compressor will be re quired Actual uphole velocity at 100 efficiency will be 750 721 x 3000 3120 fpm Yes hole cleaning time before con nection is still a requirement Drilling at a depth of 500 feet the chip flying time will be 500 3120 x 60 seconds 10 seconds As soon as you cut off the air supply the chips start falling down Many drillers will have one or more compressors and typically a 4 4 1inch flush joint pipe is used Do not use a square shoulder tool joint style drill pipe for air drilling See Drill Pipe and Col lar Designs April 2009 Water Well Journal page 54 for more information The question arises Just how big a hole can I drill D d x 16 5 cfm converts into D V d2 cfm 16 5 For direct circulation air drilling without foam consider Table 1 as gospel Many drillers brag on drilling larger holes with their compressor Some of them will have enough integrity to call me and say John I hate to admit that you were right We are stuck bad how can I get my hammer out My suggestions were e Get one or more compressors to get at least 5000 ft min velocity
8. wells Never use grease on tool joints Send the correct hammer oil with the rig Design a system that turns off the water foam and oil injection when the compressor tank pressure drops below 25 psi Be sure and thoroughly clean oil flooded wells Service related equipment such as the water foam and oil injection system Check your air reservoir condensate water for color rust and mud Write a drill air section on mainte a 6 Contact the hammer manufacturer nance and stick with it to get proper lube specs and air vol ume pressure for the DTHH if you have enough too little or too much air Watch out for diameter changes in the borehole 7 Review if you need a shock sub 8 Switch to nontoxic hammer lubes Coming next month Drilling with augers and buckets No extra mud or air for these holes Why do some augers have a hole on the centerline and can you get a patent on a hole in a tool fluid on hand with clear instructions on how to add the fluid should be used Unless otherwise noted all photos taken by John L Espoir bits before sending them to the field Interested in the book Transfer of Technology It is available in the NGWA Bookstore The member rate is 75 the nonmember rate is 87 50 Call NGWA at 800 551 7379 to order your copy today NGWA org TRANSFER OF TECHNOLOGY APPENDIX here must be thousands of re ciprocating piston compressors Figure 1 Courtesy of
9. 2 found on many rigs for well developing three cylinder models and drilling with LeRoi Air Compressor air six cylinder series Courtesy of Comp Air Model 256 S2C hp Capacity cfm 125 445 510 TRANSFER OF TECHNOLOGY from page 41 Penetration Rate Let s look at two basic but different types of air drilling conventional with collars and button type tricones and down the hole jackhammer known as DTHH drilling The conventional three cone bits Figure 2 for hard formation are either a short tooth type or a tungsten carbide button tooth A lot of drill collar weight is required to get proper chipping ac tion Weight of up to 8000 pounds per inch of diameter may be needed An 8 inch hole would require 8 x 8000 64 000 pounds of drill collars Add the drill pipe to get the string load and it Le Roi Model 256S2 Stationary Air Compressor becomes obvious that a rig with a mini mum hookload of 100 000 pounds is re quired Air drills are not this big and most rigs would have trouble putting more than 30 000 pounds of pulldown onto the string due to their limited rig rear axle weight The DTHH is nothing more than a jackhammer operated by air to get chisel action at a slow rotary speed A typical air drill will have a very slow rotary speed Years ago the hammers commonly used required 0 to 10 rpm and 250 psi With the introduction of the variable speed hydrostat drives the rpm has a range from 0 to 125 rpm whereas th
10. D S M Austin Texas on drilling rigs today The TRAT uy Yr major brands are Gardner Den he s ver and LeRoi while there are a lot of t Quincy and Joy units as well Switching over to the rotary screw type usually means a contractor with a lot of deck space can put on a compressor package with its own engine Typically a new trailer mounted compressor will be re quired which is costly with serious fuel consumption Of course the new com pressor will have more cfm and or psi as compared to the on board piston machine Some of the reasons why a screw compressor does not fit as a replacement are e insufficient space e limited horsepower of engine e limited horsepower of drivetrain e inadequate speed of driveline e incorrect input rotation of driveline The above reasons are powerful rea sons to maintain your compressor prop erly repair it as required and use the proper lubrication Figure 1 shows a Gardner Denver model 580 WCG The rating is 580 cfm at 50 psi at 870 rpm The compressor has six cylinders all producing single stage compression This unit had been in service for 30 years CompAir LeRoi is now owned by Gardner Denver Their service manual spells out a single viscosity nondeter gent super refined oil with rust and oxi dation inhibitors Grades of Oil Ambient temperature range e SAE 30 above 60 F e SAE 20 from 32 F to 60 F e SAE 10 below 32 F A mineral based oil will break dow
11. Figure 19 CAT model 2020 on Ewbank M 100 C in Egypt Variable speed hydraulic drive plus the additional foam injection assembly The capacity is up to 20 gpm and 800 psi TRANSFER OF TECHNOLOGY from page 48 inserted into the holes in the tool until they are flush with the outside diameter Then they are welded in place making sure they are tangent and perpendicular to the circumference of the circle and taking care to protect the threads on the inside of the collar Flat plates are usually welded on the top and bottom of the tool It is best to cut these plates just a little smaller than the outside diameter so that when the plates are welded to the casing it will give a natural bevel to the corner instead of a square corner that has to be ground and beveled The top plate should have a hole cut in it to accommodate what ever threaded connection the driller will be attaching to it 50 September 2010 Water Well Journal When all the welding has been com pleted threaded tungsten carbide hy draulic bit jets can be screwed into the a inch pipe collars These jets never wear out so we recommend welding them to the pipe collar so there is no danger of the jet backing out while in use The weld should be ground smooth so there is nothing rough on the outside diameter of the jetting tool that could damage the wire wound screen The jetting tool should be run into the casing to the bottom of the bottom screen The volume of f
12. R OF TECHNOLOGY continues on page 48 Water Well Journal September 2010 47 Table 3 TRANSFER OF TECHNOLOGY from page 47 Basic Differences Between Mud Rotary and Air Rotary Rigs turn the foam into a gel type material that improves borehole stability Keep in Component mind that the bentonite will have to be Mast hookload capacity High Low washed out of your water well Foam is not recycled Coming out of the borehole use a blooey line to divert the flow away from the rig Once again foaming agents are highly corrosive to Rotary drive Table Topdrive Bore through swivel Large Small Swivel capacity High Low Depth in feet 1500 2000 500 750 your drill In a very short time the foam Horsepower of truck 200 250 400 500 will break down and disappear while Pump Duplex 52 X 8 Compr 750 300 your cuttings will be on the ground Rotary speeds 50 160 0 60 Well Development with Air After completing a well having set the screen and casing and having filled Figure 17 The oil pump the annular space properly with gravel pack hole fill material and the top sani tary seal the mud must be cleaned out of the formation to provide clear clean groundwater A common method is to lower a pipe into the casing and turn the compressor on It will build pressure overcome the hydrostatic water column pressure and blow the water out surging fresh water through the screen After losing its air pressure the flow will stop water col u
13. TRANSFER OF TECHNOLOGY EXPANDED SERIES By John L Espoir No 20 of 30 Drilling with Air Airspeed of 35 mph is required while foam can just have its own pace What makes a screw compressor and piston machine work What is DIHH drilling elocity is the most critical part of drilling with air in the direct circulation method Air is compressed and forced to the bottom of the hole through the drill pipe and expands at the bit to near atmospheric pressure blowing upward in the annulus to get out Along the way it will blow forma tion chips water and other hole occu pants out of this hole Please note that I did not use the word carry Air does not carry chips Chips will fall because of gravity An upward air velocity that is equal to the fall speed will balance that chip A higher velocity will blow it out of the hole at 34 to 58 mph This equates to 3000 to 5000 fpm annular up hole velocity for air drilling The formula is easy D d x 16 5 cfm D bit size in inches d O D of flush joint pipe in inches cfm required cfm to get 3000 fpm velocity For example what compressor 1s needed to drill an 8 inch air hole with 42 inch O D pipe e D 8 e d 4 5 e 82 4 52 x 16 5 721 cfm If no air escapes into the formation John L Espoir has enjoyed a 40 year career in portable drilling equipment design He holds a bachelor of science degree in mechanical engineering and was formerly
14. cfm like they do at 50 psi At 1000 rpm the delivery increases from 510 to 610 cfm when switching to 50 psi The Screw Type Compressor Units are available as a complete trailer mounted unit a skid package with engine to mount on a rig a skid mounted air module to be powered by the rig or individual components to allow the engineer to put various com ponents like airend receiver tank and cooler in available space While the input speed on a screw compressor 1s typically 2100 rpm the actual screws may operate at a much higher speed The tip speed of the lobes governs the pressure Single compression can reach 220 psi The Sullair unit shown in Fig ure 14 actually has two sets of screws the larger set pumps into the smaller set In about 1986 the author designed an air transportable 1500 foot water well machine for the U S Army The com pressor was 350 cfm 220 psi The pres sure was by single stage compression so that only one airend with one set of screws was needed to save weight Because of the low profile of 8 feet maximum height over mast and the mounting on a 6x6 International truck the compressor was mounted in pieces The cooler was sideways with hydraulic drive The GHH airend model CF 128 Figures 15 and 16 had an overdrive of 1 212 to 1 meaning that these screws rotate at 2545 rpm when the truck NGWA org Figure 12 Rotary screw compression Courtesy of Sullair Simplicity is the key to the Sullair
15. e compressors have jumped from 250 to 300 to 350 to 450 to 500 psi How high will this go In 2001 I worked on a well rehabilitation project requiring 4200 psi The air compressor was rated at 5000 psi The psi in a ham mer determines the energy of the blow to the bit chisel A 5 pound hammer could be seen as 125 psi making 350 psi like a sledgehammer Downhole hammer suppliers came lt TWO STAGE OPERATION right along with better steels better tol l lt SINGLE STAGE OPERATION erances and better lubrication to use 0028P8 these higher pressures Rig manufactur Figure 7 Schematic diagram of the air flow through compressor Courtesy of Comp Air 42 September 2010 Water Well Journal NGWA org Figure 8 Typical piping diagram rig application Courtesy of Comp Air 250P 5 1 UNLOADER PILOT CHECK VALVE SAFETY VALVE AIR RECEIVER DRAIN COCK 0027PE UNLOADER PILOT SHUTOFF VALVE TO SUCTION VALVE UNLOADERS INTERCOOLER DRAIN FROM INTERCOOLER DRAIN COCK Figure 9 Model 256 S2C installed on a Ewbank M 100 C operating in the Sahara Desert Egypt ers promptly modified designs to get more horsepower bigger trucks bigger PTOs and drives to get these larger compressors on board As a side effect the rigs became much larger and much more expensive Coupling a high pressure mobile compressor to your old rig will have the same hammer performance The DTH Hammer T
16. e no longer manufactured increasing the value of out of service compressors My thanks to Duane Cook and Calvin Cook from Grand Junction Col orado and Stanley Martin from Austin Texas who had a great deal of input in this addendum Dedication This series is dedicated to the educa tion of John L Espoir s two grandsons Ethan Daniel Atwood and Elliott John Atwood right who are each destined to become a drilling rig engineer Opposing points of view or questions Contact us at Enid Drill Systems 580 234 5971 fax 580 234 5980 john eniddrill com Inspect and service your compressor today WWJ Waiver The views expressed in this article are the author s opinion and are based on the engineering education skills and experience gained in a life long industry commitment No part of this article is intended to replace or supersede any information supplied by others The contents of this article may not be used in any type of legal action NGWA org
17. e spikes unlike the reciprocating piston compressors with on off valves every revolution Rotary Speed As mentioned before the air drill ro tary speeds have changed with the de signs of more powerful higher pressure hammers Gone are the mechanical 10 speeds with four speed auxiliaries to the rotaries to get down to below 10 rpm Let s take a look at some basic differ ences between a mud rotary and an air rotary drill Table 3 A combination rig becomes very heavy and usually the secondary func tion is very limited Many mud rigs have air compressors on board used for well development and such Bits and hammers are very sensitive to weight control and rotary speed Review with the product OEM to get the recommended rpm weight and compressor volume for maximum per formance and life out of these compo nents How does the driller know if the hammer is doing its job With his ears The hammer will have a rhythm that is music to the driller s ears No it is not called hard rock or rap The Injection Pumps These include oil water foam and mixed water and foam concentrate e The Oil Pump Our injection pumps side by side are driven by air motors fed by the large compressor Flow is controlled by a nee dle valve and a pressure regulator limits the pressure The large pump delivers water and foam As stated previously use special oils to inject into your air stream when drilling Conoco EP Rock Drill 100
18. foot of water 2 31 psi This is for clean fresh water without any kinds of solids If the hole fills up with formation water while making a 40 September 2010 Water Well Journal Figure 2 Conventional three cone bits Courtesy of GT Engineering Shawnee Oklahoma Figure 3 The down the hole hammer a downstroke drill position 4 eth a poe b upstroke exhaust position Courtesy of Numa Threaded Connection UZ Backhead Case y Feed Tube Piston Blow Tube Bit Bearing Chuck connection the compressed air must e Hole fills up with 460 feet of water have enough pressure to overcome this e Compressor is rated at 125 psi hydrostatic water column Example circulation is noticed e Rig shuts down for lunch e When putting the air to the pipe no NGWA org Figure 4 a 350 cfm 220 psi deformed the kelly when using a DTHH Both sub and kelly required remachining This was a tight connection b The spindle on the Dresser T7OW is being ground down before the seal retainer can be removed Swelling was caused by 750 250 DTHH without a shock sub 6 00 al ANY CONWNECTIO a ap 3 1 2 IF PIN OR ANY CONNECTION tt 477 TRS mO Cd E OOR ne pe ANON a WLS Lf NLA 2 FLATS 180 FROM GREASE FITTING yay A er Se fg NOTE TLE LU TL W L Jer IT MAR KNA N fi li VA 17 500 OPEN 15 500
19. has a new name Conoco Hydroclear Rock Drill Oil 100 It is designed for jack hammers It is formulated with high viscosity index base oils and selected additives to reduce oxidation in the presence of compressed air And it is approved for downhole drilling equipment Most rock drill oils are made from petroleum products and as such are not TRANSFER OF TECHNOLOGY continues on page 46 Water WellJournal September 2010 45 Figure 13 Schematic of screw compressor system Courtesy of Sullair ks a NOTES YER Ba Itea morawa GUNEE wl CERTA dak STEM UNLESS OTHE Berg iD oF CUSTOMER BARE WATER J Ce a Re il Shes Hiiti as ee Ge Cee Ae a Te a wee Ls TU DO tate Da TURE OE p Fige Fe Pate Ge Oo TAMA are WERU Tha BUA G Maai SER ae WOME MAAT Pn VE ne Te oho E Veo 4 TeteiGe PP Mud BE PABMUCATE DO aT h TA E E e maa p Herad F 2 eM fa Rt RNR Set To UNLOAD eo ray coe ty NBT fe De Peren e Scie SE i i el Ld fo si eee be Lee Ne i Ara aoe EAH Te a TRANSFER OF TECHNOLOGY from page 45 classified as H 1 food grade lubri cants When drilling water wells for drinking water we recommend a bottled 46 September 2010 Water Well Journal Che LF Sta A bale 4 Crease Wik TO PESTO Tiwi YTM Te Cee ey CR en lubricant by Numa that is environmen tally safe biodegradable and nontoxic and contains no petroleum distillates Simply pour one 8 ounce bottle into t
20. he drill pipe when starting the hammer and A INLET Fate PESTRE Toe WECRTOT then add a bottle for every 300 feet of drilling A continuous water injection of 2 to 3 gpm is required These quantities are typical for a 6 inch hammer This lube works well for 8 inch hammers and smaller and has been in use since 1988 Another product for use in potable water wells is made in Canada and comes in 55 gallon drums and 5 gallon pails for easy storage The trade name is Matex RDO 302 and it has been in use in the United States since approximately 199 Shell Oil recommends their FM Gear Oil 220 which is H 1 approved and CITGO also has food grade gear lubes however neither one has any records of actually using these products in a DTHH water well application For non water well drilling the following oils have been used successfully with a DTHH type drilling e Shell Torcula Oil 320 e D A Rockdrill Lubricant 500 e Mobil Vactra Series e Hydrotex 207 and 208 NGWA org Figure 15 Note that the input gear is not connected to the female rotor near side Courtesy of GHH Germany Overdrive Air Out Figure 16 The CF 128 coupled to a chain drive with air clutch The valve in the top air intake line controls the volume of the compressor and is called the throttle Once again these are not rated for food grade quality and we do not want them in our water Chevron Texaco and Exxon Mobil do not make an H 1
21. he downhole hammer Figure 3 is a highly machined close tolerance ma chine tool It will perform to predeter mined cfm psi and lubrication The NGWA org piston has air grooves and channels to direct the compressed air to either push the piston up or blast it full speed down to impact on the bit shank It is this im pact shock on the buttons that fractures the rock formation When specifying a hammer please know what bit size and compressor will be used Please keep sand and dirt from getting inside your drill pipe and pumping into the hammer and do not forget the lube system A bigger hammer and more air pres sure will result in a bigger blow Pene tration rate will increase What happens to the hammer reaction force This energy hammers back into the drill stem Air rigs do not typically use more than one or two drill collars Pulldowns are used to maintain pressure on the bit The reaction force energy will hammer this pipe up and up right into the top drive or swivel bearings With bigger hammers we see more premature bear ing failures Kelly and topdrive spindles are hammered so badly that the material swells Figure 4 The Shock Sub To minimize the damage and isolate this reaction force our industry has developed a series of subs Figure 5 Design A This design is the most effective It is installed directly above the hammer and isolates the reaction en ergy Drill pipe connections do not ham mer up
22. ing probably should not be done because it will probably expose some of the screen to the borehole The basic principle of jetting is to jet water through the screen into the sand pack and disrupt it With enough pres sure and volume the formation behind the sand pack can actually be abraded or sandblasted The sand is disrupted and NGWA org z ans y ee he iar E F the fines are washed into the screen and as the jet moves up the screen the sand below it settles in around the screen very uniformly Assuming circulation can be maintained back to the surface the fines and possible wall cake will be caught up in the fluid and circulated back to the surface If circulation does not return to the surface then some sec ondary pumping system needs to be set Table 4 Borehole Diameter Versus cfm 400 600 cfm 200 300 cfm 90 130 cfm 25 30 cfm 26 Hole 15 Hole 10 Hole 6 Hole up to remove the fines from the casing and prevent them from being circulated back into a potentially productive for mation The reason jetting is one of the best ways to develop a wire wound screen is because it lets you expend the hydraulic horsepower where the work needs to be done which is the same reason the jetting of rock bits works so well Do not try this system on wire wound PVC screens Lubrication These high volume high pressure compressors are very expensive from 60 000 to 120 000 Please know what l
23. luid that is pumped through the tool is a function of the size of the jet and the volume and pressure capability of the pump being used to power the jet Pump pressure should be approximately 300 psi The jet should be rotated very slowly as it is pulled back through the length of each Figure 21 Foam injection Courtesy of Sellers Co Figure 22 Owner Thomas H Oast told me that he is one day older than his rig a Franks 1957 model KF 50 An auxiliary foam system allows him to use this system with the old WAH compressor at 40 psi Pictured in Okla homa in 2002 drilling a 6 inch well screen Making a second pass on each screen can be effective as well The top of the sand pack should be monitored throughout the jetting process and care should be taken to keep the sand above the top of the top screen The removal of fines and wall cake and the packing of the sand and the removal of voids in the sand will cause it to drop and additional sand will need to be added If it is not NGWA org Figure 23 A mass of foam slowly moves down a hill in Oregon A 900 350 compressor had no return air in this lava formation The water injection pumped pure foam concentrate downhole to get cuttings to come up The foam flies out of the blooey line in a steady flow Depth reached was approximately 500 feet Pictures courtesy of STACO Well Drilling ie E AOE ig MS E Fe possible to monitor the top of the sand pack then jett
24. m 360 rpm Other pumps include John Bean with a choice of two three or four pistons now sold as FMC Technology products CAT Pumps model 2020 has proven to be very reliable on drilling rigs for water injection It offers a very simple additional pump that injects foam chemicals e The Foam Pump With the CAT triplex pump it is very simple to add a foam system The pump is a diaphragm design that operates on the pressure in one of the three cylinders and a spring will push it back Capacity is 0 to 1 quart per minute and up to 1000 psi There is no other drive needed for this pump Calibration is by a built in needle valve Stainless steel and brass are used to contain the highly corrosive foam chemical a good reason to keep this out of your water pump Drilling with foam greatly increases the diameter of the well that can be drilled with the air compressor on board the rig Air volume requirements drop due to the lower uphole velocity of approximately 45 to 150 fpm as com pared to 3000 to 5000 fpm In a write up by Bernard Higgins of London from around 1975 to 1980 we find a guide for borehole diameter vs cfm Table 4 Caution must be taken not to pump in too much air The air would simply find a quick way out through the foam and cause many downhole problems The air foam should come out of the hole like a thick stream of shaving cream suspending and carrying the chips Adding bentonite to the foam will TRANSFE
25. mn pressure restores and so forth The cycling is automatic The water column is the on off valve Jetting An approach is used by Stewart Brotheres in New Mexico The following report on jetting is submitted by David Stewart president of the company We have done a lot of different things over the years to develop wells bailing Figure 18 Example of a water pump Courtesy of Fred s Water Service surging swabbing airlifting acidizing sand fracking and jetting In my opin Piston Stem Pump Shaft ion jetting is the most effective way Im Bearing to develop a well when it is completed Crosshead Bushing Ke with wire wound screen The triangular Connecting Link shape of the wire makes jetting a natural thing to do We build our own jetting tools They are very simple but very effective We Crosshead Pin genre 5 G take a short piece of casing no more f y than 4 to 6 inches in length that will KS Ei SYM ey just fit inside the wire wound screen we f a nN l A want to develop Three or four holes are Valve Seat i R Air Chamber Crosshead Cylinder Liner av cut in the side equally spaced around the circumference and on the center line just large enough to accommodate a Link Bushing Piston Cups 34 inch pipe collar The pipe collars are Valve Discs Spring amp Retainer TRANSFER OF TECHNOLOGY continues on page 50 48 September 2010 Water Well Journal NGWA org
26. n over time with enough heat causing se are completely covered with carbon rpm is equally as bad since the oil is not vere carbon buildup on the compressor LeRoi compressors run at 870 rpm thrown up inside the cylinders to lubri valves Figure 2 shows the outside ofa standard or about 1200 rpm maximum cate the pistons liners and rings compressor that has been too hot Inside speed causing reduced life but in are either broken valves or valves that creased volume Running below 600 TRANSFER OF TECHNOLOGY continues on page 54 NGWA org Water Well Journal September 2010 53 i TRANSFER OF TECHNOLOGY from page 53 The author believes in synthetic oils For a piston compressor I strongly rec ommend a Rarus 827 made by Mobil It is available in 30 weight and practically ends all of the carbon problems since there is no mineral based oil present in the manmade synthetic lubricant Figure 3 shows a LeRoi six cylinder dual stage 250 psi compressor In South Texas we find several contractors who are replac ing the small LeRoi lube pump with an external lube pump and oil filter The 54 September 2010 Water Well Journal Figure 3 Courtesy of Rental Supply Co of Grand Junction Colorado results have been excellent by the in creased pressure on the lube system If you have a used compressor of this type in the shed collecting dust it might be worth your time to try to sell it for spare parts Some of the parts ar
27. or swell the tool joints Shown in Figure 5 is a 9 inch O D shock sub Design B This design is installed directly below the topdrive and is cushioned only in the pulldown mode This flotation type sub is used to let the lower part move up as a pipe is un screwed It is very popular on rigs with carousels and keeps the hammer out of your topdrive bearings and hydraulics Design C This design is fully cush ioned for both pulldown or holdback applied drilling It can either be a pure shock sub as shown or two cushions can be taken out to get 2 inches flota tion It is installed below the topdrive Take note that a typical shock sub mounted below the topdrive will have a box down connection to meet a pin up drill pipe The author does not know of any advantage to pin up or pin down drill pipes Shock subs are available for pin down drill pipe as well as many differ ent sizes of threads NHM is currently fabricating a 22 inch diameter sub to be installed behind a 32 inch Numa hammer All shock sub designs must perform the following duties 1 Transmit full rotary torque 2 Transmit full mast hookload capacity 3 Seal air at maximum psi and temperature 4 Isolate the reaction energy TRANSFER OF TECHNOLOGY continues on page 44 Water Well Journal September 2010 43 Figure 10 A three cylinder 250 psi model 253 S2 installed on a Mayhew 1000 is used to develop water wells Note the tall receiver tank rated at 300
28. psi Operating in Nebraska Mud and airlines are valved together This requires special maintenance TRANSFER OF TECHNOLOGY from page 43 Compressors While there are many different types on the market we will limit ourselves to only the older design the piston ma chine and the newer design the screw type 44 September 2010 Water Well Journal The LeRoi 250 series S2 two stage and SDS single dual stage are found on many rigs for well developing three cylinder models and drilling with air six cylinder series A smaller piston compressor was reviewed in the June 2010 installment of the Transfer of Technology series At the 250 psi setting the compressor delivers the air volume based on the rpm of the compressor When running at 1000 rpm service frequency especially valve work will increase substantially Consult the fac tory for more details Do not overspeed these compressors The SDS allows the operator to switch from 250 to 50 psi For the lower pressure open up the shutoff to the second unloader with its setting at 50 psi Also switch two flow control valves on the piping on the com pressor On the six cylinder shown in the diagram this allows all six cylinders to produce air on single stage compres sion When pumping at 250 psi the out side four cylinders will pump into the two center cylinders for secondary com pression These two cylinders only in crease the psi and do not add to the
29. ubricant to put in and how often to change fluid and filters Fluids could very easily be synthetics with a high flash point Remember the oil also transfers the heat Piping Compressed air has a number of un wanted side effects These include lots of heat making the full flow line hot to the touch and formation of condensa tion water The compressor to flow line connection should be a stainless steel reinforced hose designed for high tem peratures properly guarded This hose absorbs vibrations dissipates heat and allows misalignments due to belt tightening Next is the reservoir These must be ASME coded for the relief valve pres sure setting Do not ever weld on this tank body unless you are an ASME approved welder The tank condensate should be drained frequently and automatic drain equipment is preferred Lines and valves get hot and with the presence of mois ture rust will form on the inside of lines and valves We recommend stainless valves with hi temp ball seats such as made by Inline Industries for maximum TRANSFER OF TECHNOLOGY continues on page 52 Water Well Journal September 2010 51 Figure 24 A model Jed A develops a large water well with a LeRoi 256 compressor TRANSFER OF TECHNOLOGY from page 51 efficiency Be sure to get full flow valves for minimum friction energy loss Stencil the word Hot on these components to warn hands could be burned followed by involuntary reac
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