NL8006888A - Abrasive weightings containing drilling fluids, - Google Patents

Description

N.0. 29,673 * -1- '*'

Abrasive weighting agents containing drilling fluids.

The present invention relates to improved compositions and methods for drilling boreholes such as oil wells, gas wells or the like. More particularly, the invention relates to high density drilling fluids prepared from abrasive weighting agents.

Drilling muds "used in drilling oil wells, gas wells and similar wells in the earth are usually water-based mixtures" containing clays or other colloidal products "as well as certain additives" which are used depending on the well conditions. The drilling mud or drilling mud primarily functions as a means to transport debris generated by the drill bit to the surface. Also, the drilling mud serves as a lubricant for the drill bit and drill string and prevents formation fluids such as oil »gas 15 and salt water from entering the borehole» while drilling progresses. The drilling mud serves other purposes and has other features which need not be discussed in detail here as they are known and described in numerous publications such as in Walter.

F, Rogers * Composition and Properties of Oil Well Drilling Fluids »20 3® edition, Houston, Texas, 1963» Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd edition, New York, 1965 »part 7, p. 287-307.

As mentioned, one of the functions of a drilling mud is to maintain a sufficient hydrostatic pressure in the borehole fluid column to prevent formation fluids from entering the borehole and, under extreme conditions, to prevent the well from blowing out. Depending on the drilling conditions encountered, a sufficient hydrostatic pressure can be achieved practically with plain water. However, under normal circumstances and usually as a safety precaution, it is necessary to achieve the desired hydrostatic pressure to provide the suspension with a suitable weighting agent to increase its density. These weighting agents are generally in the form of finely divided solids of a material having a high intrinsic density. The most common weighting agent is finely ground barite, although Iron oxides, celestite, lead luster and other materials have been used at different times. Barite, due to its relatively high density, insolubility, chemical inertness and hitherto easy availability, is the weighting agent of 800688 8 m m -2 choice. However, with the decreasing availability of barite, other weighting agents are being sought.

Apart from the fact that »barite wells are dwindling and in some areas of the world, where drilling activity is high, practically nonexistent, barite is relatively soft with a hardness on the Mhos scale of 2.5 - 3.5 *. relatively soft property of barite affects the rheological properties of the drilling mud after the barite has circulated in the borehole during the drilling treatment. In the drilling operation, the entire circulation system behaves somewhat in the manner of a fluid mill, such that the softer mineral particles are sheared and reduced in particle size. This reduction in particle size results in a direct increase in the viscosity of the drilling mud resulting from a much smaller particle size and an increase in the total number of particles.

It has been proposed to use weighting materials other than barite to overcome the aforementioned difficulties associated with relatively soft weighting agents such as barite, which are subject to progressive crushing. British patent specification 1.4-95.87, describes the use of ilmenite and / or hematite described as an aggravating agent for drilling fluids. In addition, Colombian Patent 9396 describes the use of hematite glimmer for use as a weighting agent in drilling fluids.

Hematite is a naturally occurring mineral, which is widely distributed around the world in various forms and different purities. For example, the hematite glimmer, described as a drilling mud aggravating agent in Colombian Patent 9396, is a relatively soft, flaky, mica-like mineral with a distinct laminar structure. This form of hematite shimmer tends to form very thin flat plates after reaming, and after use in a drilling fluid, these plates are easily comminuted into very small particles, which tend to increase the viscosity of the drilling fluid. The hematite glimmer is substantially non-abrasive under borehole conditions.

The hematite shimmer to which the present invention is directed is a non-hydrated mineral which, although of generally laminar structure, is hard and after milling forms particles with irregular, abrasive edges. Such a hematite glimmer has a 4Ό relatively large intrinsic density, i.e. 800688 8 density

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-3- greater than about * f, 3 and has a hardness on the Mhos scale of about 5 - 6. After use as a weighting agent in a drilling mud, the hematite shimmer of the present invention does not tend to be comminuted into smaller particles. would significantly alter the rheological properties of the drilling mud * Due to its intrinsic hardness, however, the hematite shimmer of the present invention is quite abrasive and can result in excessive wear of the drilling equipment, in particular the drill string and drill bit. As the search for oil and gas results in the drilling of ever deeper wells, the excessive wear or erosion of the drill string and drill bit becomes an increasingly serious problem.

It is therefore an object of the present invention to provide a new and improved drilling mud.

Another object of the present invention is to provide a new and improved drilling mud in which relatively hard abrasive weighting agents can be used.

A further object of the present invention is to provide a new and improved method of drilling a borehole using a drilling mud containing a relatively hard weighting agent.

The above and other objects of the present invention will become apparent from the description, the figures and the claims.

In one embodiment, the present invention provides an improved water-based drilling mud containing a weighting agent of a non-hydrated hematite shimmer and a water-dispersible anti-wear agent present in the drilling mud in an amount sufficient to substantially reduce the abrasive action of the 50 to reduce drilling mud. The particle size of the weighting agent used in the drilling mud should be such that at least 85% by weight passes a sieve with a mesh size of 0.0kh mm.

The amount of weighting agent present in the drilling mud will vary depending on the drilling conditions encountered, but the weighting agent will generally be present in sufficient amounts to significantly increase the density of the drilling mud.

In another embodiment, the present invention provides an improved drilling method for earth boreholes, characterized in that the new drilling mud described above is circulated 800 68 8 8 ƒ -F in the borehole during the drilling operation.

Fig. 1 is a graphic representation showing the abrasion weight loss caused by various drilling fluid formulations. 5 FIG. 2 is a graphic representation »showing the abrasive wear properties of various drilling fluid formulations ·

The weighting agents useful in the drilling fluids of the present invention are hard, non-hydrated minerals with a density of about 4.3 or greater, such as, for example, hematite shimmer. Hematite shimmer is a common mineral, which is chemical iron (III) oxide (FegO ^). It is described, for example, in Ivan Rostov Mineralogy, (Oliver & Boyd, Edinburgh and London) 1st Eng. Ed. (1968). Usually hematite shimmer contains 69.94,9 Fe and 30.06¾ 0. Some Ti may be present. Hematite glimmer 15 is often found mixed with hydrated iron oxides, iron carbonate and magnetite as well as iron silicates. However, deposits of non-hydrated hematite shimmer are available where hydrate water removal is not required.

The weighting agents suitable for the present invention should have a density of at least 4.3 and preferably at least 4.5. If necessary, the weighting agent can be improved in quality by known metallurgical methods such as flotation, to achieve the desired minimum density. The weighting agent must have a hardness scale on the Mhos hardness scale of at least 4.3. Indeed, many hematite glimmers have a hardness of 5-6. For use in the present invention, the weighting agents must have a particle size such that at least 85% by weight of a sieve having a mesh size of 0.044 mm and at least about 98% passes a sieve with a mesh size of 0.074 mm. More preferably, the particle size should be such that 90-92¾ passes through a 0.044 mm mesh sieve. The desired particle size of the weighting agent can be achieved by grinding methods known in the art.

The amount of weighting agent present in the drilling mud will vary widely depending on the desired density of the drilling mud. The latter is of course dependent on the encountered or expected drilling conditions. In any event, the amount of barite necessary to achieve a desired slurry density is known, and tables showing this relationship are readily available. From a comparison of the intrinsic density of the present weighting agents with that of barite, such tables can be used to determine the amount of weighting agent necessary to provide drilling muds or muds of the desired density.

As indicated above, the weighting agents of the present invention are products which are relatively hard and consequently less sensitive to progressive crushing. In addition, the weighting means exhibit relatively high abrasion properties, which can result in excessive erosion of drilling equipment such as pumps, drill lines and drill bits during drilling operation. It has now been found that when suitable water-dispersible anti-wear agents are added to the drilling muds prepared with the relatively hard weighting agents of the present invention, the abrasive action of the drilling mud can be reduced to the point where virtually no more wear is observed. than the wear that will occur with drilling muds of similar density using the much softer barite as weighting agent. The anti-wear agent used in the drilling fluid of the present invention should be dispersible in water to such an extent that it forms a colloid, emulsion or other such heterogeneous system in which the anti-wear agent is it is generally evenly dispersed or distributed in the water phase. The anti-wear agent should be of a type that will allow the achievement of the desired rheological properties of the drilling mud. Preferably, the anti-wear agent will be a product which will produce in sufficient amounts a suitable drilling mud using the hard weighting agents of the present invention which will exhibit wear and / or abrasion properties which are generally similar or substantially the same as those obtained with a drilling fluid of substantially the same density or weight using barite as a weighting agent. One group of anti-wear agents, which have been found to be particularly effective in fresh water-based drilling muds of the present invention, are those containing fatty acids such as oleic, stearic, linoleic, palmitic and the like. Such fatty acids are commonly found in vegetable oils such as cottonseed oil, soybean oil, corn oil, castor oil, linseed oil, etc.

The fatty acids, either in pure form or in the form of the vegetable oils, as mentioned above, are mixed with small amounts of surfactants or other agents to be dispersible in water. Such surfactants include, for example, long chain alcohols, long chain alkanolamines, sulfonated vegetable oil derivatives such as sulfonated castor oil, etc. A particularly effective anti-wear agent is a mixture of soybean oil, long chain alcohols and sulfonated castor oil. This preparation and similar products are ideal anti-wear agents since they need only be added to the drilling fluid in relatively small amounts to reduce the abrasive properties to an acceptable level. Moreover, since only relatively small amounts are required, only a minor to negligible deterioration in rheological properties occurs.

The amount of anti-wear agent in the drilling fluid may vary widely, but will generally range from about 0.1 to about 5 weight percent. In general, however, the anti-wear agent need only be present in an amount which will effect a significant reduction in the abrasive action of the drilling fluid.

Preferably, the drilling fluid will contain thickeners.

Such thickeners may consist of clay-bearing formations, such as clay shale or clay-containing sands, which are encountered in the drilling operation and which are taken up by the drilling mud or drilling mud and become part thereof. Alternatively or additionally, clays can be added to the suspension. Non-limiting common examples of highly colloidal clays include smectites, especially bentonite, attapulgite and sepiolite, with bentonite being the preferred clay. A wide variety of other water-dispersible products, especially organic colloids, can serve as thickeners, such as starch derivatives, cellulose derivatives, synthetic polymers such as sodium polyacrylate, natural gums such as guar gum, bacterial gums such as those gums processed by certain Xanthomonas species and the like. If desired, mixtures of such suitable thickeners can be used. The technology of using such thickeners in drilling muds is well developed and known to those skilled in the art. The various thickeners have a wide variety of weighting efficiency expressed in KQ in the number of kg thereof to be included in a 800688 8 '. "-7-liter drilling fluid or drilling mud of a given type in order to achieve the desired quality.

In addition to the thickeners, the drilling mud may optionally contain flow control agents, viscosity control agents, anti-foaming additives, freezing point depressants and the like.

It will be appreciated that in the method of the present invention using the subject drilling muds and while the borehole is being drilled during the drilling operation, additional amounts of weighting agents and / or antiwear agents may be added to maintain density and abrasion resistance if desired. or change.

In order to more fully illustrate the present invention, the following non-limiting examples are given.

The hematite shimmers used were obtained from D.S. Steel

Corporation, were not hydrated and had a density range of 4.9-5.1.

Example I.

A basic drilling mud or drilling mud was prepared by mixing 25 g of 20 AQIAGEL (bedding name of a bentonite clay marketed by NL Baroid, Houston, Texas) and 50 g of Glen Kose clay scalife for 20 minutes using a high speed disperser in 550 ml of water. stir. To the suspension were then 5 g of Q-BROXIN (trade name of a lignosulfonate marketed by NL Baroid, Houston, Texas), 5 g of CARBONOX (trade name of an organic humic acid product marketed by NL Baroid, Houston, Texas) 1.5 g of sodium hydroxide and 4 g of AKTOFLO S (trade name of a drilling fluid surfactant marketed by NL Baroid, Houston, Texas) under stirring on the disperser-50 generator, for 10 minutes, The thus prepared suspension was kept overnight.

Example II.

Using the base slurry prepared in Example I, various weighted drilling muds were prepared using BAROID (trade name of a barite marketed by NL Baroid, Houston, Texas) and hematite shimmer. Ratings of the weighted drilling muds thus prepared were obtained for a slurry of 1.56 kg / l (Table A), a slurry of 1.92 kg / l (Table B) and a slurry of 2.16 kg / l (Table C). ).

40 C see Tables A, B and C).

800688 8 -ö-

As can be seen in comparing the results of Tables A, B and C, drilling muds prepared with hematite shimmer compare favorably with a conventional drilling mud prepared using barite as a weighting agent.

Example III.

To investigate the comparative shear rates under high shear of different weighting agents in rinse suspensions, the 1.92 kg / l rinse suspensions prepared according to Examples I and II were used. As shown in the data in Table 10D, the shear rate of hematite shimmer is significantly slower than that of barite in comparable coil suspensions. This shear resistance is advantageous in ensuring that the rheological properties of the drilling mud are not as sensitive to change during drilling operations as the slurry is constantly circulated in the wellbore.

(see table D).

Example IV.

A water based drilling mud was prepared using 15 g of AQUAGEL and 60 g of Glen Rose clay scale hydrated in 350 ml of water followed by the addition of 300 g of the especially appreciated weighting agent. Suspensions prepared with hematite shimmer were diluted with 0.1 part per billion BARAFOS (trade name of a polyphosphate compound marketed by NL Baroid »Houston, Texas). To test the abrasive or wear properties of the obtained suspensions, the effect of addition of anti-wear agents, two methods were used. One method, Method A, took into account the phenomenon of wear caused by the movement of particles in a fluid against a metal surface.

In this method, the total weight loss of the entire surface was measured.

Method A.

A Hamilton Beach mixer, model 956 »operating at 15,000 rpm was used to produce simulated abrasive effects and particle breakdown in the laboratory. For each rinse slurry, a new weighted mixing blade was used as a reference site for the scouring activity. Periodically, the leaf was examined for weight loss after different stirring periods. The suspensions were immersed in a cooling bath during mixing to avoid overheating and evaporation. The thickening of the weighted sus-4-0 suspensions while stirring was minimized by the 800688-8-9.

addition of BAEAFOS. The results of the wear rate tests are given in Table E.

(see table E).

A second wear or abrasion test method, Method B, was used, taking into account the movement of metal surfaces against each other when exposed to a flowing fluid. In Method B, the object was to measure the weight loss of the surface exposed to the loads.

Method B.

The test block used to measure extreme pressure (EP) properties was modified by processing so that a constant wear surface will be exposed to the test column during the tests. A ring speed of 432 revolutions per minute was chosen, as it is approximately equivalent to the drill pipe rotation at 130 revolutions per minute and is quite typical of well drilling methods. Different torque loads were applied to the ring and block at this speed at 15 minute intervals. The starting weight and the final weight of the test block were measured and a weight loss of the block was determined in each suspension. The wear rate was then determined and calculated for one hour. The results are shown in Tables F - H (see Table F H).

As can be seen from the data in Tables E-H, the resume does not exhibit much smoother resistance to abrasion compared to barite. With reference to Table E, it appears that the addition of an anti-wear agent largely reduces the abrasion wear of a coil slurry weighted with hematite glimmer. The results are graphically depicted in Fig. 1, comparing a coil slurry weighted with hematite shimmer, which does not contain an anti-wear agent (curve A), to a similar weighted suspension, containing about 4 parts per billion of an anti-wear agent (curve B) and a conventional barite weighted coil slurry (Curve C).

Referring to Tables F-H and Fig. 2, it also appears that the wear rate of suspensions prepared with hematite shimmer is much greater than that of a conventional slurry weighted with barite. However, as the data plotted in Fig. 2 show, the addition of relatively small amounts of anti-wear agent significantly reduces wear rates. For example, it should be noted that the abrasion rate of a hematite shimmer 8006888 * '*' * - 10 heavy suspension (curve A), which is fairly abrasive without the addition of anti-abrasive, exhibits abrasion when combined with about parts per billion anti-wear agent (curve D), is similar or substantially the same as that of a conventional coil slurry weighted with barite (curve C). Even at relatively low levels of anti-wear agent, i.e. parts per billion (curve B), the wear force is significantly reduced.

Thus, it has been found that particularly improved coil suspensions, which exhibit excellent rheological properties, can be prepared with hard or relatively hard weightings without excessive wear and abrasion, when the coil suspension additionally contains an anti-wear agent, as described above.

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Tab el E.

Sample designation A B C D E E

base suspension 1.0 1 * 0 1 * 0 1 * 0 1.0 1.0 BAROID * kg '555 555 270 hematite shimmer, kg A-310, 92.6 # 0 * 044 mm 512 270 A-314, 93.1 # 0.044 ram 512 397 BARAFOS, kg / 1 0.017 0.017 0.06 0.03 anti-wear additive, kg / 1 0.48 properties: e.g.

plasticity viscosity, cP 18 20 16 12 23 22 elastic limit, kg / m2 0.15 0 0 0.68 0.10 0.98 10 sec. gel, kg / m2 0.15 0.05 0 0.83 0.05 0.44 10 min.gel, kg / m2 0.59 0.54 0.20 2.49 0.59 i ', 17 PH 8 , 2 8.2 9.0 9.8 9.6 9.1 properties: 4 h plasticity viscosity, cP 30 29 24 19 28 49 elasticity limit, kg / m2 2.54 1.76 0.34 0.10 7Λ7 1, 32 10 sec. gel, kg / m2 2.78 2.15 0.15 0.10 6.69 0.64 10 min.gel, kg / m2 6.34 5.71 1.07 0.59 12.54 2.15 PH 8.4 8.3 9.0 9.6 9.5 8.9 properties: 8 h plasticity viscosity, cP 36 31 15 elastic limit, kg / m2 2.34 1.92 3.95 10 sec. gel, kg / m2 2.68 2.39 3.03 10 min.gel, kg / m2 5.12 5.32 9.32 pi 8.2 8.2 9.6 abrasive, abrasion, g 5 , 17 5.15 5.21 5.18 5.21 5.19 weight loss, # mixing blade after h 1 0.24 0.50 3.92 2.85 1.47 2.64 2 0.47 0, 98 8.00 5.42 2.50 4.86 4 0.94 1.93 14.10 10.20 4.67 8.56 8 1.52 3.23 14.33 8006 888 -15-

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Table Η,

Heating medium HEMATITE GLIMMER

anti-wear agent, kg / 1 0.48 0.48 0.96 0.96 load, cm.kg 345 230 345 230 ring speed, note 432 432 432 432 'ring speed, cm / sec. 79 79 79 79 abrasion test, min 15 15 15 15 initial block weight, g 8.4698 8.4483 8.4318 8.4170 final block weight, g 8.4483 8.4318 8.4178 8.4087 weight loss, g 0 .0215 0.0165 0.0140 0.0091 wear rate, g / h 0.0860 0.0660 0.0560 0.0364 1 8006888

Claims (5)

Waterborne drilling mud with a weighting agent selected from the group consisting of non-hydrated minerals having a hardness of at least about 4.5 vMhos scale and a density of at least 4.4 * which weighting agent has such a particle size that at least 85% by weight passes through a sieve having a mesh size of 0.0¼mm and about 98% by weight passes through a sieve with a mesh size of 0.074mm, which weighting agent is present in an amount sufficient to significantly increase the density of the drilling fluid and with a water-dispersible anti-wear agent present in the drilling fluid in an amount sufficient to significantly reduce the wear force of the drilling fluid. Drilling mud according to claim 1, characterized in that the water-dispersible anti-wear agent is present in an amount from about 0.1 to about 5% by weight. Drilling mud according to claim 1 or 2, characterized in that the weighting agent is a hematite shimmer, Drilling mud according to claims 1-3 », characterized in that an additional weighting agent is present, such as barite, celestite, galena and mixtures thereof. Drilling mud according to claims 1-4, characterized in that additives are present such as thickeners, agents for combating the loss of flowability, additional weighting agents, diluents and mixtures thereof. ****** 800688 8