US Patent Class 166
WELLS




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Current as of: June, 1999
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  DF  CLASS NOTES
335  DF  SUBMERGED WELL
336  DF  .~ Testing
337  DF  .~.~ For leak
338  DF  .~ Connection or disconnection of submerged members remotely controlled
339  DF  .~.~ With provision for removal or repositioning of member without removal of other well structure
340  DF  .~.~ Disconnection
341  DF  .~.~ With orienting or aligning of member for connection
342  DF  .~.~.~ Including removable, member mounted guide
343  DF  .~.~.~ Including means to pull member into position
344  DF  .~.~ Connection to provide fluid flow path
345  DF  .~.~.~ Connection of riser-and-tubing assembly to other structure
346  DF  .~.~.~ Yieldable tubing
347  DF  .~.~.~ Connection of lateral flow line
348  DF  .~.~ Connection of pipe hanging
349  DF  .~.~ Connection of guide means
350  DF  .~ Submerged, buoyant wellhead or riser
351  DF  .~ Means removably connected to permanent well structure
352  DF  .~.~ Surface vessel
353  DF  .~.~.~ Having means to move vessel to precise location
354  DF  .~.~.~ Having means to hold vessel at given location (e.g., anchor, etc.)
355  DF  .~.~.~ With means to compensate for vessel movement
356  DF  .~.~ Means to provide protective environment for operative access below surface of water
357  DF  .~.~ Separator
358  DF  .~.~ Drilling means
359  DF  .~.~ Removable riser
360  DF  .~.~ Well component assembly means
361  DF  .~.~ Pipe cutting means
363  DF  .~ With safety or emergency shutoff
364  DF  .~ Including disaster feature
365  DF  .~ With provision for disassembly
366  DF  .~ Multiple wells
367  DF  .~ Riser
368  DF  .~ Wellhead
244.1  DF  PROCESSES
245  DF  .~ Specific pattern of plural wells
246  DF  .~ Using microorganisms
247  DF  .~ Nuclear energy or radioactivity for treating
248  DF  .~ Electric current or electrical wave energy through earth for treating
249  DF  .~ Vibrating the earth or material in or being placed in the earth pores
250.01  DF  .~ With indicating, testing, measuring or locating
251.1  DF  .~.~ Including in situ combustion
252.1  DF  .~.~ Including production of earth fluid by driving fluid
252.2  DF  .~.~.~ Residual oil or oil saturation
252.3  DF  .~.~.~ Salinity or acidity
252.4  DF  .~.~.~ Flood front
252.5  DF  .~.~.~ Permeability or viscosity
252.6  DF  .~.~.~ And tracing material
253.1  DF  .~.~ Indicating the location, presence, or absence of cement
254.1  DF  .~.~ Determining position of earth zone or marker
254.2  DF  .~.~.~ Well logging
255.1  DF  .~.~ Determining position of object in well
255.2  DF  .~.~.~ Tool orienting
255.3  DF  .~.~.~.~ Using whipstock
250.02  DF  .~.~ Permeability determining
250.03  DF  .~.~ Determining fluid interface or fluid level
250.04  DF  .~.~ Plug indicating or releasing
250.05  DF  .~.~ Scale or corrosion determination
250.06  DF  .~.~ Steam quality
250.07  DF  .~.~ Bottom hole pressure
250.08  DF  .~.~ Leak testing or locating
250.09  DF  .~.~ Impression means
250.1  DF  .~.~ Fracturing characteristic
250.11  DF  .~.~ Holder for coupon or sensor
250.12  DF  .~.~ Tracer
250.13  DF  .~.~ Determining stuck point
250.14  DF  .~.~ Of cementing or plugging technique
250.15  DF  .~.~ Automatic control for production
250.16  DF  .~.~ Prospecting
250.17  DF  .~.~ Including testing or treating tool having at least one actuatable packer
256  DF  .~ In situ combustion
257  DF  .~.~ Injecting while producing by in situ combustion from same well
258  DF  .~.~ Plural distinct superimposed formations
259  DF  .~.~ Including fracturing or attacking formation
260  DF  .~.~ Injecting specific fuel or catalyst for burning into formation
261  DF  .~.~ Injecting specific material other than oxygen into formation
262  DF  .~.~ Solid fuel or particles in well
264  DF  .~ Sampling well fluid
265  DF  .~ Separating material entering well
266  DF  .~.~ Injection and producing wells
267  DF  .~.~ Separating outside of well
268  DF  .~ Distinct, separate injection and producing wells
270  DF  .~.~ Injecting a composition to adjust the permeability (e.g., selective plugging)
270.1  DF  .~.~ Injecting a composition including a surfactant or cosurfactant
270.2  DF  .~.~.~ Nonaqueous type
400  DF  .~.~ Sequentially injected separate fluids (e.g., slugs)
401  DF  .~.~.~ Injecting a gas or gas mixture
402  DF  .~.~.~.~ CO2 or carbonated gas
403  DF  .~.~.~.~.~ In combination with additional organic material (e.g., alkyls, carbon chains)
272.1  DF  .~.~ Involving the step of heating
272.2  DF  .~.~.~ In association with fracturing or crevice forming processes
272.3  DF  .~.~.~ Steam as drive fluid
272.4  DF  .~.~.~.~ In combination with alkyls or carbon chains
272.5  DF  .~.~.~.~ With override zone, diverting, or path blocking operation
272.6  DF  .~.~.~ Liquid material injected
272.7  DF  .~.~.~ Horizontal well
271  DF  .~.~ Including fracturing or attacking formation
269  DF  .~.~ Fluid injected from longitudinally spaced locations in injection well
275  DF  .~.~ Injected fluid comprises water and material other than inorganic gas
263  DF  .~ Cyclic injection then production of a single well
276  DF  .~ Providing porous mass of adhered filter material in well
277  DF  .~ Repairing object in well
278  DF  .~ Graveling or filter forming
279  DF  .~ Material placed in pores of formation to treat resident fluid flowing into well
280  DF  .~ Specific propping feature for a fracture
281  DF  .~ Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking formation
282  DF  .~ Specific low fluid loss feature for fluid attacking formation
283  DF  .~ Specific low fluid loss feature for fracturing fluid or cement causes fracture
284  DF  .~ Fluid flow causes pellet to block opening in wall of conduit
285  DF  .~ Cementing, plugging or consolidating
286  DF  .~.~ Tamping, vibrating, exploding or using receptacle
287  DF  .~.~ Removable molding or forming means
288  DF  .~.~ Including heating
289  DF  .~.~ Discharging cement from casing at different levels
290  DF  .~.~ By tubing which is subsequently lifted
291  DF  .~.~ With piston separator
292  DF  .~.~ Using specific materials
293  DF  .~.~.~ Cement or consolidating material contains inorganic water settable and organic ingredients
294  DF  .~.~.~ Cement or consolidating material is organic or has organic ingredient
295  DF  .~.~.~.~ Organic material is resin or resinous
296  DF  .~ Preventing flow into strainer while lowering by blocking openings
297  DF  .~ Perforating, weakening, bending or separating pipe at an unprepared point
298  DF  .~.~ Perforating, weakening or separating by mechanical means or abrasive fluid
299  DF  .~ With explosion or breaking container to implode
300  DF  .~ Chemical inter-reaction of two or more introduced materials (e.g., selective plugging or surfactant)
301  DF  .~ Freeing stuck object, grappling or fishing in well
302  DF  .~ Heating, cooling or insulating
303  DF  .~.~ Placing preheated fluid into formation
304  DF  .~ Dissolving or preventing formation of solid oil deposit
305.1  DF  .~ Placing fluid into the formation
306  DF  .~.~ Fluid enters and leaves well at spaced zones
307  DF  .~.~ Attacking formation
308  DF  .~.~ Fracturing
309  DF  .~ Producing foam or gas in well by foaming or gas producing material
310  DF  .~ Entraining or incorporating treating material in flowing earth fluid
311  DF  .~ Cleaning or unloading well
312  DF  .~.~ Liquid introduced from well top
313  DF  .~ Parallel string or multiple completion well
369  DF  .~ Producing the well
370  DF  .~.~ Including varying downhole pressure
371  DF  .~.~ Including non-expulsive material placed in well
372  DF  .~.~ By fluid lift
373  DF  .~ Operating valve, closure, or changeable restrictor in a well
374  DF  .~.~ Operated by fluid pressure controlled above ground
375  DF  .~.~.~ By auxilliary fluid control line
376  DF  .~ Destroying or dissolving well part
377  DF  .~ Disassembling well part
378  DF  .~ Assembling well part
379  DF  .~.~ Above ground parts
380  DF  .~.~ Conduit
381  DF  .~ Placing or shifting well part
382  DF  .~.~ Providing support for well part (e.g., hanger or anchor)
383  DF  .~.~ By fluid driven piston
384  DF  .~.~ With bending of tubing
385  DF  .~.~ Flexible cable or wire
386  DF  .~.~ Fluid flow control member (e.g., plug or valve)
387  DF  .~.~ With sealing feature (e.g., packer)
50  DF  WELLS WITH LATERAL CONDUITS
51  DF  MEANS FOR FORMING FILTER BEDS (E.G., GRAVEL PLACING)
52  DF  PLURAL WELLS
53  DF  AUTOMATIC
54  DF  .~ Float controlled valve
54.1  DF  WITH MEANS FOR SEPARATELY PUMPING FROM PLURAL SOURCES IN WELL
54.5  DF  MEANS FOR CUTTING CABLE OR ROPE BELOW GROUND
54.6  DF  .~ Cutting means actuated by contacting element suspended in well by cable or rope
55  DF  MEANS FOR PERFORATING, WEAKENING, BENDING OR SEPARATING PIPE AT AN UNPREPARED POINT
55.1  DF  .~ With disparate below ground feature
55.2  DF  .~ Perforating or splitting cutter
55.3  DF  .~.~ Wedge or cam actuated
55.6  DF  .~ Cutter rotates circumferentially of pipe
55.7  DF  .~.~ Internal
55.8  DF  .~.~.~ Tool moved radially by fluid pressure
56  DF  SCREEN AND OUTSIDE CLEANING PIPE
57  DF  WITH HEATING, REFRIGERATING OR HEAT INSULATING MEANS
58  DF  .~ Fuel supply or hot billet in well
59  DF  .~ Burner in well
60  DF  .~ Electrical heater in well
61  DF  .~ Heater surrounding production tube
62  DF  .~ With eduction pump or plunger in well
63  DF  WITH EXPLOSIVE OR GAS GENERATING MEANS IN WELL
64  DF  WITH TIME OR DISTANCE MEASURING, TEMPERATURE RESPONSIVE OR COUNTING MEANS
65.1  DF  WITH ELECTRICAL MEANS
66  DF  .~ Indicating
66.4  DF  .~ Electrical motor (e.g., solenoid actuator)
66.5  DF  .~ Magnetic
66.6  DF  .~ Valve
66.7  DF  .~.~ Longitudinally movable operator
67  DF  WITH BELOW AND ABOVE GROUND MODIFICATION
68  DF  .~ Eduction pump or plunger in well
68.5  DF  .~.~ With above ground (1) motor carried by casing or casing support or (2) well fluid pump
69  DF  .~ With receptacle for insertion into well
70  DF  .~ Head for tool, piston or cleaner (e.g., cement head)
71  DF  .~ With above ground casing sinking means
72  DF  .~ Above ground actuating means for below ground device
73  DF  .~.~ Tubing or casing actuated
74  DF  .~ With below ground screen
75.11  DF  ABOVE GROUND APPARATUS
76.1  DF  .~ Having structure for converting from one mode of operation to another; e.g., valve to packer
77.1  DF  .~ Moving tubing or cable into an existing well
77.2  DF  .~.~ Coiled tubing
77.3  DF  .~.~.~ Chain injector
77.4  DF  .~.~ Piston and cylinder
77.51  DF  .~ With means facilitating connecting or disconnecting supported tubing or rod sections
77.52  DF  .~.~ With elevator detail
77.53  DF  .~.~ Upper and lower slips
85.1  DF  .~ With assembly or disassembly means (e.g., handling, guiding, or tool feature)
85.2  DF  .~.~ Pitless well adapters
85.3  DF  .~.~ Seal or bushing insertion or removal
85.4  DF  .~.~ With blowout preventer
85.5  DF  .~.~ Guiding or aligning feature
86.1  DF  .~ Inner member anchor or seal with valve
86.2  DF  .~.~ Annular sealing type valve
86.3  DF  .~.~ Gate type (perpendicular to pipe) valve
87.1  DF  .~.~ Axially movable type valve
88.1  DF  .~ Inner member anchor or seal with lateral port
89.1  DF  .~.~ Plural inner pipes
89.2  DF  .~.~.~ Parallel pipes (as opposed to concentric)
89.3  DF  .~.~.~ Having slip type hanger
88.2  DF  .~.~ Slip type well anchor
88.3  DF  .~.~.~ Seal actuated with anchor
88.4  DF  .~.~ With hydraulic conduit or line extending through outer member
78.1  DF  .~ With tube rotating means (rotary tables)
79.1  DF  .~ Cap having transporting means or ground support
80.1  DF  .~ Having retractable pipe section to allow closing of gate type valve or flapper valve for rod or pipe
81.1  DF  .~ Fluid catcher around pipe coupling
82.1  DF  .~ Releasable seal or cleaner disengaged by projection on inner member
83.1  DF  .~.~ Latches releasable radially inward
84.1  DF  .~ With seal for reciprocating member
84.2  DF  .~.~ Cooling fluid or grease supplied to seals
84.3  DF  .~.~ Rotary blowout preventer type
84.4  DF  .~.~ Fluid pressure actuated seals
84.5  DF  .~.~ Seal fixedly mounted to rod
90.1  DF  .~ With means for inserting fluid into well
75.15  DF  .~ With means for injecting solid or particulate material into the well
91.1  DF  .~ With flow restrictions (e.g., chokes or beans)
92.1  DF  .~ Cap or head pivotably attached to tube or casing
93.1  DF  .~ Split cap or head
94.1  DF  .~ Laterally adjustable cap or head
95.1  DF  .~ Central valve or closure and lateral port
96.1  DF  .~ External anchoring or bracing means
97.1  DF  .~ With valve on cap or head
75.13  DF  .~ Well caps or casing heads
75.14  DF  .~ Suspension means
75.12  DF  .~ Treatment of produced fluids
97.5  DF  .~ Parallel pipes extending along distinct paths through wellhead
98  DF  GRAPPLE AND WELL ANCHORED LIFTING MEANS
99  DF  WITH JUNK RETRIEVING MEANS
100  DF  LATERAL PROBE OR PORT SEALED AGAINST WELL WALL
101  DF  PACKER OR PLUG AND PUMP OR PLUNGER MEANS EXERTING OUTWARD PRESSURE
102  DF  CONVERTIBLE
104  DF  WITH MOTOR FOR ROTARY OR OSCILLATING MOTION
105  DF  WITH EDUCTION PUMP OR PLUNGER
105.1  DF  .~ Having sediment trap or deflector
105.2  DF  .~.~ Carried by reciprocating plunger or plunger rod
105.3  DF  .~.~ Sediment trap formed in pumping chamber
105.4  DF  .~.~ In pump discharge flow path
105.5  DF  .~ Having liquid-gas separator
105.6  DF  .~.~ Gas fed to entrainment type pump
106  DF  .~ With packer or plug
107  DF  .~ Receptacles
108  DF  .~.~ Piston actuates foot valve
109  DF  .~.~ Telescoping
110  DF  .~.~ Lateral port always below piston and used in well
111  DF  .~.~ Bail engaging piston rod
112  DF  .~ With leak means
113  DF  COMBINED (E.G., WITH NON-ELECTRICAL INDICATING)
114  DF  CENTRAL MEMBER WITH PRE-SET PACKER OR PLUG IN SAME CONDUIT
115  DF  CENTRAL CHAMBER SEALED WITH RESPECT TO PREPOSITIONED MODIFIED SURROUNDING CONDUIT
116  DF  .~ Surrounding conduit carries packer or plug
117  DF  RECEPTACLE OR PART THEREOF LEFT IN WELL
117.5  DF  MEANS FOR GUIDING INSERTABLE ELEMENT LATERALLY OF WELL AXIS (E.G., WHIPSTOCK)
117.6  DF  .~ Secured in operative position by movable means engaging well conduit (e.g., anchor)
117.7  DF  MEANS ANCHORED AGAINST ROTATION IN ONE CONDUIT SECTION FOR RELATIVELY ROTATING ANOTHER SECTION
179  DF  PACKERS OR PLUGS
118  DF  .~ With expanding anchor
119  DF  .~.~ Relatively movable packers or plugs
120  DF  .~.~ Anchor actuated by fluid pressure
121  DF  .~.~.~ Pressure transmitted by cup type packer or plug seal
122  DF  .~.~.~ Pressure transmitted by packer or plug expanded by confined fluid from central chamber, pump, or plunger
123  DF  .~.~ With detachable setting means
124  DF  .~.~.~ Screw threaded
125  DF  .~.~.~ Radially movable latch
126  DF  .~.~ With controllable passage between central chamber and space below packer
127  DF  .~.~.~ Spaced packer or plug seals
128  DF  .~.~.~ Passage controllable by movement of central chamber
129  DF  .~.~ With controllable bypass outside central conduit
130  DF  .~.~.~ Packer expanded by upper valve
131  DF  .~.~ With controllable passage between central conduit and space above packer or plug
132  DF  .~.~ Portion extends beyond end of surrounding conduit
133  DF  .~.~ With controllable passage through packer
134  DF  .~.~ Support and holddown expanding anchors
135  DF  .~.~ Flow stopping type, e.g., plug
136  DF  .~.~ Spring set anchor
137  DF  .~.~.~ Spring moves anchor slip relative to wedge or cam
138  DF  .~.~ Wedge or cam and friction drag
139  DF  .~.~.~ Threaded element rotated
140  DF  .~.~.~ Anchor above packer or plug seal
141  DF  .~ Sealing portion closes port between central pipe and outside space when unexpanded
142  DF  .~ With controllable passage between central chamber and space below packer
143  DF  .~.~ Central conduit detachable
144  DF  .~.~.~ Bottom supported casing or screen section
145  DF  .~.~ Bypass closing and passage opening to upward flow constrained to occur simultaneously
146  DF  .~.~ Passage connects with space below packers and continuously open passageway connects with space between packers
147  DF  .~.~ Passage connects with space between packer or plug seals
148  DF  .~.~ Upwardly biased check valve and means for opening or bypassing it
149  DF  .~.~ With passageway between central chamber and space above packer
150  DF  .~.~.~ Passageway controllable by movement of central chamber
151  DF  .~.~.~ Passageway valve directly responsive to fluid pressure
152  DF  .~.~ Passage controllable by movement of central chamber
180  DF  .~ Adjustable over pipe or set over prepositioned pipe
181  DF  .~ With detachable setting means
182  DF  .~.~ Packer or plug locked expanded
183  DF  .~ With controllable bypass outside central conduit
184  DF  .~ With controllable passage between central conduit and space above packer or plug
185  DF  .~ With central conduit and fluid port to space outside
186  DF  .~.~ Port between sealing portions and bypass around
187  DF  .~ Expanded by confined fluid from central chamber, pump or plunger
188  DF  .~ Controllable passage through packer
189  DF  .~ For non-concentric members
191  DF  .~ Spaced sealing portions
192  DF  .~ Flow stopping type; e.g., plug
193  DF  .~.~ Free falling type (e.g., dropped ball)
194  DF  .~.~.~ With sleeve valve
195  DF  .~ Deformable portion engages conduit restriction
196  DF  .~ Central support has shoulders expanding sealing portion, or telescopes
202  DF  .~ Cup type
203  DF  .~ Non-deformable type
153  DF  PISTONS, FLUID DRIVEN INTO WELL (E.G., CEMENTING PLUGS)
154  DF  .~ Surrounding conduit valve or closure opened by piston
155  DF  .~ With downflow past piston
156  DF  .~ With stop
157  DF  SCREEN WITH WASHING POINT OR SHOE
158  DF  .~ Detachable wash pipe
162  DF  RECEPTACLES
163  DF  .~ With separate air chamber having openable passage
164  DF  .~ With destroyable closure and valve
165  DF  .~ With valved or closed top
166  DF  .~ Valve control means contacting well conduit wall
167  DF  .~ Bottom receiving and side discharge valves
168  DF  .~ Readily releasable bottom valve
169  DF  .~ Lateral ports used in well
170  DF  BRUSHING, SCRAPING, CUTTING OR PUNCHING-TYPE CLEANERS
171  DF  .~ Perforation cleaners
172  DF  .~ Bow spring type
173  DF  .~ On tubing or casing
174  DF  .~ Retractable on support while lowering
175  DF  .~ Reciprocable relative to central member extending from well top
176  DF  .~ On sucker rod
177.1  DF  SONIC DEVICE
177.2  DF  .~ With specific downhole feature
177.3  DF  WIPER
177.4  DF  CEMENTING DEVICE
177.5  DF  HYDRAULIC FRACTURING DEVICE
177.6  DF  VIBRATOR
177.7  DF  AGITATOR
178  DF  WITH JAR MEANS FOR RELEASING STUCK PART
205  DF  SCREEN WITH VALVE, CLOSURE, CHANGEABLE RESTRICTOR OR PORTION REMOVABLE IN WELL
206  DF  EXPANSIBLE ANCHOR OR CASING
207  DF  .~ Expansible casing
208  DF  .~ Liner hanger
209  DF  .~ Set by wedge or cam at any point by drop only (e.g., tubing catcher)
210  DF  .~.~ With friction drag for setting by turning movement also
211  DF  .~.~ With spring
212  DF  .~ Fluid pressure actuated
213  DF  .~ Bowed anchor means
214  DF  .~ Spring set
215  DF  .~.~ Spring moves anchor slip relative to wedge or cam
216  DF  .~ With wedge or cam and friction drag
217  DF  .~ Expansible means translated by wedge or cam
222  DF  WHIRLING OR LATERAL DISCHARGE OR PROJECTABLE NOZZLES
223  DF  .~ Rotary or projectable
316  DF  VALVES, CLOSURES OR CHANGEABLE RESTRICTORS
317  DF  .~ Destructible element
318  DF  .~ Operated by dropped element
319  DF  .~ Fluid operated
320  DF  .~.~ Variably opened
321  DF  .~.~ Fluid pressure biased to open position position
322  DF  .~.~.~ Retrievable
323  DF  .~.~.~ Locked open or closed
324  DF  .~.~.~ With fluid pressure equalizing means
325  DF  .~.~ One way, e.g., check valve type
326  DF  .~.~.~ Flexible valve element
327  DF  .~.~.~ Shoes with check valve
328  DF  .~.~.~.~ Loose ball closure
329  DF  .~.~ Loose ball closure with limited reverse flow
330  DF  .~ Rotated operator
331  DF  .~.~ Lug in branched slot, e.g., "J" slot
332.1  DF  .~ Longitudinally movable operator
332.2  DF  .~.~ Having rotational movement
332.3  DF  .~.~.~ Ball valve type
332.4  DF  .~.~ Operated by means inserted from the surface
332.5  DF  .~.~ Valving means inserted or retrieved to operate
332.6  DF  .~.~ Having a dump or discharge type means
332.7  DF  .~.~ Having equalizing valve
332.8  DF  .~.~ Flapper type
333.1  DF  .~.~ Contact with bore bottom
334.1  DF  .~.~ Vertical movement of conduit
334.2  DF  .~.~.~ And rotational movement; e.g., ball valve-type
334.3  DF  .~.~.~ Drain-type
334.4  DF  .~.~.~ Fluid flow through lateral port to exterior
227  DF  SCREENS
228  DF  .~ Porous material
229  DF  .~ Inserted screen plug
230  DF  .~ Woven mesh
231  DF  .~ Spiral
232  DF  .~.~ With spacing lug for adjacent turns
233  DF  .~.~ With perforated pipe
234  DF  .~ Strip or rod
235  DF  .~ Stacked annular sections
236  DF  .~ Concentric pipes
237  DF  DETENTS OR CLUTCHES
238  DF  .~ Flow permitting means bridging fluid conduit
239  DF  .~ Operated by dropped weight
240  DF  .~ Lug in closed branched slot
241.1  DF  GUIDE FOR DEVICE OR CONDUIT
241.2  DF  .~ On sucker or pump rod
241.3  DF  .~.~ Rotatable or having a rotatable element
241.4  DF  .~.~ Surrounding existing rod
241.5  DF  .~ For a wireline operation
241.6  DF  .~ Surrounding existing device or tubing
241.7  DF  .~.~ Removably secured by a fastener (e.g., pin) parallel to tubing
242.1  DF  CONDUIT WALL OR SPECIFIC CONDUIT END STRUCTURE
242.2  DF  .~ Flexible tube or cable
242.3  DF  .~ Plural, parallel, nonconcentric conduits
242.4  DF  .~ Corrosion prevention or deterring
242.5  DF  .~ Side entry
242.6  DF  .~ Downhole coupling or connector
242.7  DF  .~.~ Telescopic
242.8  DF  .~ Shoe detail
242.9  DF  .~ Brick or cement casing liner
243  DF  MISCELLANEOUS (E.G., ANCHOR PIPES)
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CROSS-REFERENCE ART COLLECTIONS
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901  DF  WELLS IN FROZEN TERRAIN
902  DF  FOR INHIBITING CORROSION OR COATING