US3049490A - Fresh water drilling fluids - Google Patents

Description

United States Patent 3, ifl,i% Federated Aug. 14-, 1%62 fltice 3,049,490 FRESH WATER DRILLING FLUIDS James E. Donham, Crossett, Aria, assignor to Crossett Chemical Company, a Division of The Crossett Company, Crossett, Arie, a corporation of Arkansas No Drawing. Filed Aug. 27, E59, Ser. No. 836,322 4 Claims. (Cl. 252-85) This invention relates to drilling fluids useful in the rotary drilling of oil and gas wells. More particularly, .the invention relates to novel drilling fluids which are effective extreme pressure lubricants for the drill bit bearings.

The rotary drilling of oil and gas wells conventionally entails utilization of a drilling fluid circulated through the well bore and about the drilling bit. It is customary continuously to pump the drilling fluid down the drill stem to the drill bit at the bottom of the bore hole. The stream of drilling fluid circulates about the drill bit and moves upwardly through the annular space between the drill stem and the Well bore hole to carry the cuttings out of the well.

A substantial portion of the total time consumed during well drilling operations is taken up in the replacement of drill bits. Inasmuch as changing a bit necessitates pulling the entire string of drill stem, substituting a new bit, and rerunning the entire string of drill stem back into the bore hole, it is evident that the time consumed in making bit changes increases roughly in proportion to the depth being drilled. As wells are being drilled to ever increasing depths, the economic losses attendant upon the increasing amount of time lost in making bit changes cannot be ignored. In addition to the loss of time involved in making bit changes, the necessity for making frequent bit changes, particularly when drilling at substantial depths, may create hazards, such as increasing the likelihood of cave-ins, which may arise as a result of stopping the circulation of the drilling fluid during the change of bits.

Obviously, the necessity for making a bit change is dictated by the exhaustion of the useful life of the bit. Although much has been done toward improving drill bits and drilling techniques in order to prolong useful life, in the present state of rotary bit development, the most frequent limiting factor of bit life is failure of the bearings, rather than the cutting teeth.

Thus, perhaps the most important factor tending to shorten the useful life of a drill bit is the lack of adequate lubrication of the hearings. in the past, efforts have been made to afford lubrication for the bearings by incorporating self-contained lubricating units in the bits. That such efforts have not been entirely successful is borne out by the fact that conventional bits currently in use are not provided with such self-lubricating units. Consequently, conventional bits receive only such lubrication as may be obtained from the drilling fluid being circulated thereth-rough. Since the bearings of the bit are subjected to high loads, the value of conventional drilling fluids as bit lubricants leaves much to be desired.

Conventional categories or types of drilling fluids include fresh water; fresh water base muds which comprise a combination of hydratable clay with water; oil-in-water emulsions free of clay which are known as milk emulsions; oil-in-water emulsion muds which comprise a combination of hydratable clay with oil-in-water emulsions; salt water; and salt water muds comprising salt water clay with salt water or with oil-in-salt Water emul- This invention is concerned with substantially solidsfree fresh water drilling fluids and, more particularly, with novel drilling fluids which consist essentially of substantially solids-free fresh water containing as an extreme pressure bit lubricant, a small amount of floating soap.

Extreme pressure lubricant additives heretofore utilized do not effectively disperse in water drilling fluid compositions, and hence require concomitant utilization of an emulsifying agent eflective to maintain a substantial homogeneity of the fluid composition. It is, accordingly, a primary object of this invention to provide novel fresh water drilling fluids effective to provide extreme pressure lubrication for the drill bit bearings.

It is a more specific object of the invention to provide fresh Water drilling fluids containing a single additive which is effective both as an emulsifier and as an extreme pressure lubricant.

It is a more specific object of the invention to provide fresh water drilling fluids which afford comparatively greater bit life than compositions known to the prior art.

It is yet another object of the invention to provide fresh water drilling fluids which occasion less wear of accessory equipment such as pumps, liners, and drill strings, than analogous compositions known to the prior art.

It is yet another object of the invention to provide fresh water drilling fluids which afford eflective extreme pressure lubrication to the drill bit bearings and which minimize Water loss.

It is an additional object of the invention to provide fresh water drilling fluids which effectively increase the bit penetration rate.

It is a further object of this invention to provide fresh water drilling fluids which effectively aid in the removal of cuttings from the area being drilled.

In accordance with this invention, there is provided a method of drilling wells which comprises circulating into the Well substantially solids-free fresh water containing floating soap, said floating soap being present on a dry basis in a small amount, effective to impart extreme pressure lubricating properties to the drilling fluid.

Tall oil soaps and similar materials have been suggested as additives for fresh water base muds containing clay to modify the properties of the clay, as disclosed, inter alia, in US. Patents 2,468,657 and 2,468,658. Again, tall oil soaps and the like have been said to fall within the broad class of emulsifying agents which may be added to oil-in-fresh-water emulsions. The ability of tall oil soaps, however, to impart extreme pressure properties to fresh water drilling fluids has not been recognized by the art.

In addition to imparting extreme pressure lubricating qualities to the fresh Water drilling fluids, the floating soap has been found to aid in removing cuttings from the area being drilled by reducing the surface tension at the cutting face of the drill bit. Since the cuttings readily are removed from the area being drilled, the phenomenon known as balling, wherein the cuttings stick to the teeth of the drill bit, is substantially absent when employing the drilling fluids of this invention. The rapid removal of the cuttings from the drilling area also prevents the cuttings from being ground into extremely fine form and thereby further aids in the removal of these cuttings from the drilling fluids in the mud pits. Since the cuttings are larger in size, they readily will separate in the mud pits.

The term floating soap as employed in this specification refers to the saponaceous byproduct of a neutral or alkaline pulping of cellulosic materials. Upon concentration of the used pulping liquors from such pulping operation, floating soap separates on the surface of the liquor and may be recovered. Such a product may be freed of entrained liquors by salting out, centrifuging, or the like. In general, floating soap is synonymous with or equivalent to tall oil soaps. Accordingly, comparable 3 materials contemplated for use in the invention embrace water-soluble soaps produced from tall oil.

Floating soap is preferably utilized in commercial granulated or free-flowing form as described, inter alia, in US. Patents 2,854,419 and 2,854,442. Such material is conventionally prepared by the vacuum-drying, drumdrying, or spray-drying of floating soap. Such commercially available floating soap products may be expected to contain from about 1 to about 35 percent and more frequently from about 3 to about 10 percent by weight of water. The proportions of floating soap specified herein relate to a moisture-free basis.

The floating soap is utilized in the drilling fluids contemplated by this invention in a small amount effective to impart extreme pressure lubricating properties thereto. As is apparent from the ensuing examples, the floating soap additive imparts extreme pressure lubricating characteristics to fresh water drilling fluids when present in exceedingly small amounts. Normally the floating soap is employed in an amount of at least about 0.04% by weight based on the total weight of the drilling fluid and generally from about 0.04% to about 0.5%. Proportions of from about 0.07 to about 0.28% are particularly preferred proportions. While drilling fluids containing small proportions of floating soap tend to be more economically attractive, it will be apparent that larger proportions may be employed. Accordingly, the present invention contemplates the addition of any amount of floating soap effective to impart extreme pressure properties to the drilling fluid. Excessive amounts of floating soap, such as amounts of 5% and over, do impart extreme pressure lubricating properties to the fluid but generally these proportions are not economically attractive. Amounts less than 0.04% may also be employed to increase the extreme pressure lubricating properties of fresh water.

The utilization of water per so as a drilling fluid as contemplated by this invention is well known. The water normally is circulated through the well and then passed to mud pits wherein the entrained solids settle out of the water. In an eflort to maintain the water in a substantially solids-free condition, flocculating agents such as organic polymers and vegetable gums and the like may be added in conformance with conventional practice. Water is often employed at the outset of the well drilling. The use of water permits high velocities to be obtained in the circulation of the drilling fluid and, accordingly, water is advantageously employed at least for surface drilling. As the drilling of the well progresses, it becomes increasingly diflicult to maintain sufficient velocities to lift the cuttings from the drilled area, and, consequently, at greater depths the drilling fluid may be converted to clay muds or the oil-in-water milk emulsions. Such practice also is conventional in the art.

The present invention contemplates all conventional rotary drilling operations known to the art. Since these are well known, they will not further be described here.

It will be appreciated that the invention contemplates fresh water drilling fluids containing in addition to the floating soap extreme pressure additive, conventional ingredients known to be useful in drilling mud formulations. Such additives include antifoaming agents, viscosity modifiers, agents for reducing fluid loss, water softeners, flocculants, and the like. Such materials are Well known to the art and are contemplated for use in a conventional manner in the drilling fluids with which this invention is concerned.

The extreme pressure lubricating qualities of the drilling fluid compositions of the invention are eflectively demonstrated by the experiments reported in the ensuing examples.

EXAMPLE I Floating soap was added to fresh Water in the amounts indicated in Table I below, to provide fresh water drilling fluids which exhibit extreme pressure lubricating properties.

The lubricity or extreme lubricating properties of the resulting fluid were determined by a conventional Baroid extreme pressure drilling fluid tester. Essentially, the apparatus consists of a smoothly ground steel collar arranged to rotate in contact with a ground steel block while submerged in the fluid under test. The steel block is mounted on a pivoted lever by means of which the pressure against the rotating collar can be adjusted through a crank and screw arrangement. The torque on the pivoted lever which is proportional to the pressure under which the block and collar are in contact is read from a dial on the lever arm. An ammeter is provided to measure the power input to the motor which drives the collar. Two determinations may be made with the apparatus, i.e., the breakdown point and the pass point.

To determine the breakdown point, the apparatus is run for thirty seconds with the block out of contact with the collar, after which the block is brought to bear against the collar and the torque is increased uniformly at the rate of 50 inch pounds per ten seconds until a seizure occurs. Seizure can be detected by a change in the sound and by a sudden increase in the power input to the driving motor. When a seizure has occurred, examination of the block and collar reveals rough, scored surfaces. The book and collar are replaced for each test.

The pass point is determined by repeating the test at successively lower 50 inch pound increments of torque from the breakdown point until a value is found at which the machine can be run for five minutes without occurrence of a seizure.

The data reported under the heading of Timken pounds in Table I expresses the results in terms of the corresponding load on a Timken extreme pressure apparatus using the conversion table supplied with the Baroi-d equipment. Corresponding Timken loads are reported up to 450 inch pounds, the upper limit of the conversion table. As reflected, inter alia, by Tailleur Patent 2,773,030, the load-carrying capacities of muds as reflected by the Timken machine also correlate well with actual field tests. It is thus possible to test the field eflicacy of drilling muds in the laboratory. In general, drilling muds which demonstrate a load-carrying capacity on the Timken machine of not less than about 30 pounds demonstrate excellent extreme pressure lubrication in actual field use. It will be appreciated that the invention is not restricted to floating soap concentrations which afford a load-carrying capacity of at least 30 pounds on the Timken machine, but includes muds containing floating soap in all concentrations which demonstrate extreme pressure lubrication properties.

The significance of the data reported above can be appreciated more fully when it is recognized that fresh water has no extreme pressure lubricating qualities. Even the lowest pressures applied in the testing machine cause seizure.

EXAMPLE II In order to demonstrate the effectiveness of the additive of this invention, the data shown in Table II was obtained with respect to the drilling of three closely located wells in Andrews County, West Texas. All wells employed fresh water as the drilling fluid for the stated interval. Well A employed fresh water contain-ing about 0.25 lb./bbl. or 0.07% floating soap, Whereas wells B and C employed fresh water, per se.

It is apparent from the above data that the floating soap significantly increased the bit life of well A.

Since modifications of this invention will be apparent to those skilled in the art, the present invention is intended to be limited only by the scope of the appended claims.

The incorporation of floating soaps as extreme pressure bit lubricants in other types of drilling mud compositions is shown in my copending applications Serial Nos. 836,323, 836,324, and 836,325, filed of even date.

I claim:

1. The method of drilling wells which comprises circulating into the well, while drilling, a substantially solidsfree fresh water containing from about 0.04 to about 0.5% by weight based on the total Weight of the drilling fluid of floating soap, said floating soap being present on a dry basis in a small amount effective to impart extreme pressure lubricating properties to the drilling fluid.

2. The method of claim 1 wherein the drilling fluid contains floating soap in an amount of from about 0.07 to about 0.28% by weight based on the total weight of the drilling fluid.

3. A drilling fluid consisting essentially of fresh water and from about 0.04 to about 0.5% by weight of floating soap based on the total weight of the drilling fluid.

4. A drilling fluid consisting essentially of fresh water and from about 0.07 to about 0.2 8% by Weight of floating soap based on the total weight of the drilling fluid.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,657 Dyke et al Apr. 26, 1949 2,468,658 Dyke et a1 Apr. 216, .1949 2,773,030 Tailleur Dec. 4, 19 56 OTHER REFERENCES McGhee: New Oil Emulsion Speeds West Texas Drilling, article in the Oil and Gas Journal, August 13, 1956, pages -111 and 112.

Mallory: How Low Solids Muds Can Cut Drilling Costs, article in the Petroleum Engineer, April 1957, pp. B21, B22, B23, and B24.

Ellis: Lubricant Testing, publ. 1953 by Sci. Publications (Great Britain) Ltd., pp. .147 to 150.