Patent Application
20190242208
Although little is known by the public in general about magnetorheological fluids (MRFs), MRFs have been adopted at an industrial scale over the last decade. MRFs can have a suspension of magnetic particles in a liquid. Under the influence of a magnetic field, the suspended magnetic particles interact to form a new structure that resists shear deformation or flow. The interaction of these particles and the magnetic field restricts motion of the fluid, therefore, increasing its rheological properties. This feature has attracted scientists and technology companies to use these fluids to overcome old engineering limitations. The relevance of these fluids is such that several applications using MRF are found in dampers, bridges, body armors, and shock absorbers systems, among others.
The properties of MRF depend in part on the magnetizable particles volume fraction (dispersed phase), the carrier fluid (continuous phase), and the strength of the magnetic field. The fluid structure once a magnetic field is applied is accountable for the formation and reversibility from a free-flowing liquid to a semi-solid. The reversibility is of importance and may be tuned for certain applications. On the one hand, soft magnetic materials can be easily magnetized and demagnetized, which provides a better control over the MRF. On the other hand, hard magnetic materials can maintain the magnetized fluid structure in the absence of the presence of the magnetic field. This fact is of importance because depending on the application, an independent design needs to be considered.
Although conventional drilling fluids in the oil and gas industry have been used extensively for several decades, these fluids remain limited to crucial application where MRF can be proven more beneficial. The drilling fluids in the industry are a mixture of a carrier phase, either water or oil, and chemical additives designed to set the properties of this fluid. Two of these properties are viscosity and yield stress, known in fluid mechanics as rheological properties. Setting the rheological properties of a drilling fluid is important because they determine flow behavior in the downhole, the debris removal capacity while drilling, and the expected operational pressures to maintain wellbore stability. A drilling fluid can be a drilling mud, a cementing slurry, a completions fluid, or any other type of fluid used while drilling a well. Although conventional drilling fluids in the oil industry have been used extensively for several decades, the rheological properties of those fluids can in many cases only be set at surface by adding chemical additives and cannot be tuned once these fluids are pumped downhole. This is a natural limitation for these fluids, making any rheological change time consuming, non-immediately reactive, and frequently expensive because of the high amount of volume to be treated with chemicals.
The rheology in MRF drilling fluids, which can be formed by the addition of magnetic particles to conventional drilling fluid, are not chemically dependent. The change of the rheological properties of an MRF can be tuned according the intensity and direction of a magnetic field applied to the fluid. This feature allows any rheological change to be achieved even downhole or at surface when a magnetic field of a certain intensity is applied to the MRF with fixed magnets or electromagnets. Thus, MRFs can be used to develop a rapid and localized rheology modification, which makes the use of magnetorheological drilling fluid less expensive and more efficient than using conventional drilling fluids.
For a more complete understanding of the embodiments described herein and the advantages thereof, reference is now made to the following description, in conjunction with the accompanying figures briefly described as follows:
The drawings illustrate only examples and are therefore not to be considered limiting of the scope described herein, as other equally effective examples are within the scope and spirit of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the examples. For example, a very smooth transition with smoothly bent pipe may, for the purpose of better understanding the phenomenon, may be shown in the drawings as a sharp bend right after a vertical section. Additionally, certain dimensions may be exaggerated to help visually convey certain principles. In the drawings, similar reference numerals between figures designate like or corresponding, but not necessarily the same, elements.
Stuck pipe refers in the oil & gas industry to any tool, such as drill pipes, drill collars, stabilizers, motors, reamers, or logging tools, that is stuck in the borehole and make the drill string immobile. Stuck pipe can occur while drilling, tripping, logging, or running casing. There are generally two types of stuck pipe mechanisms, including (1) Differential Sticking and (2) Mechanical Sticking. Differential sticking occurs when there is an overbalance of pressure between the fluid in the wellbore and the formation fluid. When a tool touches the borehole wall of a depleted formation (e.g., a low pressure zone), the pressure exerted by the hydrostatic column above it pushes the pipe against the borehole wall. The differential pressure over the tool creates the differential sticking. A mud cake generated by the drilling mud to provide wellbore stability is squeezed by the stuck pipe, exacerbating the problem. In consequence, the tool remains immobile and rotation or reciprocation is impaired.
When the tool remains at the center of the borehole, the hydrostatic pressure of the mud over the tool is distributed radially and no differential sticking takes place. Some factors affect the probability of differential sticking, such as:
a. The differential pressure between the wellbore exerted by the mud hydrostatic column and the pressure of the formation fluids. The greater the differential pressure, the higher the probability of occurrence.
b. The drilling mud dehydrates against the permeable formations creating a mud cake that provides wellbore stability. If the mud cake is too thick, there is more contact area with the cylindrical tool, increasing the probability of occurrence.
c. If the contact area of the tool is too large, there is an increasing probability of occurrence.
Mechanical sticking on the other hand refers to a tool stuck in a collapsed well, based on the accumulation of solids or debris around the tool. During differential sticking, the well can be circulated. That is, the mud or any treatment can be pumped downhole and recovered at the surface. That provides an advantage compared to mechanical sticking when well circulation can be impaired. In general, the release mechanism during a differential sticking includes:
d. Reduce the mud weight (mud density) to decrease the fluid hydrostatic in the wellbore and hence the pressure differential. This mechanism can be limited when the formation integrity is at risk.
e. Use spotting fluids intended to degrade the mud cake, reducing the contact areas of the formation and the stuck tool.
f. A combination of the previous two mechanisms.
Some problems can be encountered while applying these mechanisms. Reducing the mud weight can make the wellbore susceptible to wellbore instability, leading to wall collapse or formation fluid migration to the wellbore due to an underbalance condition. Additionally, to reduce significantly the hydrostatic over the problematic zone, a long column of light fluid needs to be in the wellbore, changing the pressure profile of the well. Experience has shown that the spotting fluids need a soaking time to effectively degrade the mud cake. This waiting time is non-productive time, and it delays the drilling operations and increases the operational costs.
The MRF can provide a competitive solution to overcome this problematic. When MRF is activated in the annulus, it can form an open-hole packer that withstands the hydrostatic pressure above it. The pressure below the packer can be modified (e.g., reduced) locally to decrease the differential pressure over the stuck pipe to a point that the formation fluids pressure can help to release the pipe.
In view of the stuck pipe problem and limitations on the conventional techniques used to address it, one example described herein uses a tool with permanent magnets with a coil tubing set or wireline to set a packer to release a differential sticking. Another example is to use a bottom hole assembly (BHA) with permanent magnets preinstalled to set a packer to release a differential sticking.
To illustrate the concept,
According to the methods described herein,
In this way,
The current technology for releasing a stuck pipe, called BLACK MAGIC™ spotting fluid, needs a soaking time. Sometimes several cycles of BLACK MAGIC™ spotting fluid are pumped to release the stuck pipe. If there is a differential sticking where circulation is allowed, an MRF spotting fluid can be pumped and located downhole in proximity to permanent magnets as described above. This can create a packing effect that would reduce the hydrostatic over the pipe, generating a potential reduction of the hydrostatic. If that occurs in effect, there is a potential to release the stuck pipe.
A fluid loss occurs when the drilling fluid migrates to subsurface thief formations. Frequently, these formations are characterized for being highly permeable or naturally fractured. In consequence, the drilling fluid that is supposed to be circulating from surface to downhole, and from downhole to surface, is lost in these formations and cannot be recovered, as shown between FIGS. 3A and 3B. The lost volume needs to be compensated by mixing more fluid, but drilling fluids are expensive. Therefore, fluid loss is undesirable and should be prevented or mitigated.
By using conventional drilling fluids, one mitigation alternative is adding high size solids, also known as bridging agents or lost-circulation materials (LCMs). Although LCMs have been extensively used, using high size solids can damage the producing formation and reduce the oil or gas productivity in the long run. Additionally, the concentration and particle size should be limited to avoid damaging the expensive BHA, particularly the motor and measurement-while-drilling (MWD) components.
MRF can be used to thicken the drilling fluid and avoid fluid loss because they are capable of building a pressure and flow-prevention seal. Doing that, fluid loss mitigation can be immediate, localized, and may not affect the well productivity. Once the treatment fluid is located at the thief zone, a magnetic field can be applied to the fluid by using fixed magnets attached to the pipe. The increased viscosity and yield stress of the fluid will avoid the treating fluid to flow towards the thief zones. The treating fluid can be mixed with some cementitious material to set with time and seal the thief zones even when no magnetic field is applied.
More research may determine whether strong magnetizable particles (e.g., CIP) can maintain their structure even when no magnetic field is applied. Although the principle works theoretically, current experimentation is being performed to determine how the magnets need to be placed in the pipe to generate the intensity and direction of the magnetic waves desired. This aspect is relevant because the treating fluid is pumped downhole and, once located at the thief zone, the pipe is retrieved to allow the fluid to set, avoid the consequence of any stuck pipe. In some cases, the magnetorheological effect can be lost if the pipe is retrieved with the magnets. One feasible workaround would be to look for magnetic particles that sustain a magnetorheological effect even when no magnetic field is applied to them. Thus, the use of MRF can be proven to be beneficial to solve fluid loss, a very common problematic while drilling a well.
To illustrate the concept,
The process includes adding hard grade CIP to the circulating mud. The mixture travels through the BHA as a fluid phase. Once the mixture enters the annulus at a slow flow rate, its rheological properties are modified by the presence of the permanent magnets on the BHA. It is expected that the rheology development creates a semi-solid that blocks the thief zones. The activated MRF blocks the thief zones near the wellbore and beyond. The annulus can be momentarily blocked by the activated MRF. When the circulation of drill fluid is re-established, the increase in the flow rate can create enough shear to brake the MRF chain in the annulus while the thief zone is still isolated. The drilling process can be resumed and more CIP particles added, to the extent necessary, in some examples.
The MRF can be used to thicken the drilling fluid and avoid fluid loss because it is capable of building a pressure and flow-prevention seal. Doing that, the fluid loss mitigation can be immediate, and localization can be done in a way that will not affect well productivity. Once the treatment fluid is located at the thief zone, a magnetic field can be applied to the fluid by using fixed magnets attached to the pipe or the BHA. The increased viscosity and yield stress of the fluid will avoid the treating fluid to flow towards the thief zones. In some cases, the treating fluid can be mixed with some cementitious material to set with time and seal the thief zones even when no magnetic field is applied.
When fluid losses are severe and the BHA needs to be pulled out of the hole, MRF can provide an advantageous alternative to overcome problem. In severe cases, the cement slurry itself is not capable to cure fluid losses because of its fluid nature. The cement slurry, in that sense, will continue flowing through the thief zone until the setting time is reached, generally 2-3 hours, leaving the near wellbore zone exposed to additional thief zones and more fluid losses. When MR cement slurry is used, the gelling or semisolid effect can be created immediately near the wellbore. A balanced plug technique for placing the MR cement slurry can be useful so that a longer stinger with a magnet arrangement can be used to activate the fluid. After the fluid is balanced and the stinger pulled out, the magnets are left in contact with the fluid and activate it near the wellbore. A polycrystalline diamond compact (PDC) bit can be used to drill-out the cement and the tool that has the magnets.
In the example shown in
Once a well is drilled to the target formation and a formation evaluation has taken place, the well can become a producer or can be abandoned. Well completions refer to the series of steps followed to convert a drilled hole into a producer. Therefore, some decisions must be considered to optimize the productivity and the costs of the well. Principally, there are three types of completions, including (1) Barefoot, (2) Open Hole, and (3) Cased Hole. In a barefoot completion, no tubulars are run into the well. This type requires a very strong and competent formation.
In open hole completions, a steel pipe (casing) is run into the drilled well to protect the interest zones. However, the casing or liner is not cemented. The cased hole can be cemented when a better formation stability and formation selectivity is desired. Horizontal open hole completions have become common today because that extends the contact of the interest zone with the wellbore, maximizing the well productivity. Open hole completions are accompanied by open-hole packers, such as mechanical packers or swelling elastomers to provide zonal isolation.
In extended horizontal wells, interval segmentation takes place to control the heterogeneities of the formations. Some reservoirs can exhibit different permeability contrasts. In such cases, open hole packers are used to provide segmentation along the producing zone. Experience has shown uncertainty with sealing washout and low-compressive-strength holes. Because of this, operators typically cement the well, therefore, affecting the productivity of the well by reducing the exposed formation area.
The horizontal well fracturing has been of vital importance for the economic exploitation of oil and gas reservoirs with low and ultra low permeability. The process includes injecting a fluid at high pressure in a predetermined interval to generate as many possible fractures and of greatest extension in the producing formation. Preferably, horizontal wells are oriented in the direction parallel to the least in-situ principal stress. Thus, the fractures generated in this type of well will be perpendicular to the borehole axis. The fluid to create the fracture is generally mixed with a proppant material to maintain the fracture open for a longer period. Over the last decade, the advance of downhole fracturing has allowed to create larger number of fractures in longer horizontal wells. The fractures can be created in open-hole or cased hole completions.
Experience has shown that in open-hole completions the fractures tends to propagate initially longitudinally, sometimes causing a fracture extension across the open-hole packers. Additionally, there is a strong evidence that the sealing balls used for separating the fracture stages tend to break, impairing the fracturing process for some segments, and therefore, hindering the production potential of the well. Two basic type of completions are frequently used in horizontal wells are open-hole with liner, or cemented casing or liner.
Continuous Fracturing Systems: This is a frequent method used for extended reach wells in deeper formations. The objective is to create multiple hydraulic fractures in single and continuous pumping operations. The most common setup uses multiple frac ports opened individually by sliding sleeves that are activated hydraulically when a spherical ball of a diameter falls in the corresponding ball seat. Daneshy (Daneshy, 2011) shows a schematic of open-hole liner completion activated by ball drop. According to Daneshy, this type of completion has some benefits and disadvantages.
Benefits:
Disadvantages:
For continuous fracturing systems (fracturing ports with sliding sleeves), the disadvantages 2, 3 and 5 previously described could be surpassed with the use of MRF valves. In that context, instead of using balls to fall into a ball seat, among other activation mechanisms, and create the seal to increase pressure and activate the sliding sleeve, an MRF could travel through a magnetic field and create a full seal inside the casing or in the annulus of workstring-casing. There can be various ways to activate or deactivate the valve, including:
In one example operation,
In this example, performing a multistage fracturing operation can allow for production or various other drilling operations.
It is common that during the production of a well, unwanted water or gas production can occur. The reservoir thermodynamics and the drive type mechanisms are factors to determine if that problem will be encountered. Conformance is known as the technology offered to reduce the amount of water (or gas) produced be the well. The state of the art of conformance relies on crosslinked polymers that in contact with water produce a seal of the problematic zone. This technology exhibits environmental limitations that is limiting their use. Other problems include thermal instability.
MRF Packers are proposed as a mechanical barrier to isolate the zones were unwanted gas and water is being produced.
When a well is not currently profitable, the operators can decide to abandon the well temporarily or permanently. Nowadays, the oil industry is facing its busiest times on plug and abandonment of their wells. Under US Law, 30 CFR 250 establishes guidelines for decommissioning activities. The state of the art relies on cement slurries placed in the well in order to:
30 CFR 250.1715 describes how a well can be abandoned according to the specification. Technology opportunities appear in multiple annuli to properly abandon. The fact that individual sections may have been drilled with different mud weight makes the fluid segregation a severe problem to properly set a cement plug. MRF is proposed as an alternative to accurately place the cement at the right depth.
External casing packers are permanent; however, the nature of the reservoir makes the contacts (Oil/Gas/Water) to move along the well. Additionally, the wells need to be refractured when the productivity decreases. These needs make convenient to be capable to re-set external casing packers. With the current technology this is not possible, especially when swellable rubber packers are used. With MRF resettable packers this could be possible. The MRF packer is activated when the magnetic field is applied to the fluid. A tool with permanent magnets is placed with a coil tubing set or wireline to activate a MRF in the annulus. Later, after production, the tool with the magnets can be retrieved. When no magnetic field is applied, the MRF packer becomes fluid. To achieve another selective production configuration, the MRF can be squeezed to the annulus and another permanent magnet assortment placed in the new location.
In the context outlined above,
In another example,
Placing a magnetic assembly tool to apply a magnetic field to a flow of magnetorheological fluid can allow for the yield stress of the fluid to be varied downhole. Often in the oil and gas industry, a term called “gel strength” is reported in addition to yield strength for a fluid's rheology. These terms are [usually] correlated strongly and directly. In this context, the magneto-rheological effect refers to a change in either one of these properties or both. These downhole yield stress (and/or gel strength) variations, which can be up to several orders of magnitude, allow for the creation of pressure drops within the annulus that act like “pseudo downhole chokes.” The creation of this effect is not limited to a variation in yield stress (and/or gel strength) of the fluid; a similar effect can be obtained by a change in the “plastic viscosity” of the fluid or by a combination of the two effects. The property “plastic viscosity” refers to the rheology that fluid displays at higher shear rates. These increases in yield stress, and/or gel strength, and/or plastic viscosity can occur over a desired interval, and correspond with a length of a magnetic assembly tool (or an arrangement of magnets on the magnetic assembly tool). A magnetorheological drilling fluid can be created through the replacement of traditional weighting materials with ferromagnetic weighting materials. Using the aforementioned pseudo downhole chokes, the operator can control the influx from a shallow gas well without exceeding downhole pressure limits, at multiple points, predetermined by shallower formation integrity.
A system that includes a magnetic assembly tool and a magnetorheological drilling fluid can enable to safely drill these formations when influx and pressure control methods such as closing a blowout preventer (BOP) would be unfeasible due to the characteristics of the weaker formations in the open hole which could result in underground blowouts or loss of hole. Another proposed use for this system is to navigate tighter mud weight windows typically seen at greater depths in ways that cannot be accomplished with current managed pressure drilling technology in order to extend casing setting points. This can allow for the drilling to hydrocarbon bearing formations that were previously unobtainable due to the complicated mud windows involved. Magnetorheological fluids can be applied in drilling systems for annular pressure control in challenging situations.
A system that includes a magnetic assembly tool and a magnetorheological drilling fluid can allow for a yield stress, or other rheological properties of the fluid as described in [0092], of the fluid to be varied downhole to result in one or more pressure drop(s) of determined length and magnitude. In one example, the system described herein can include a magnetic assembly tool and a magnetorheological fluid. When placed, the magnetic assembly tool can apply a magnetic field to a flow of the magnetorheological fluid. Applying a magnetic field can then create a semi-solid packing element that is based on a build-up of the magnetorheological particles of the magnetorheological fluid that are near the magnetic field. Applying a magnetic field can also create a magneto-rheological effect based on an alignment of magnetorheological particles with the magnetic field. Thus, applying the magnetic field can result in a partial seal or a full seal.
Placing the magnetic assembly tool can achieve a purpose including to release a differential sticking, to form a seal in a sub-pressurized formation, to allow several stages of hydraulic fracturing, to create a selective-resettable zonal packer, to isolate gas or water, or to set at a designated depth in a plug and abandonment operation. The system can include placing the magnetic assembly tool in a drill pipe or a hole. The system can also include placing (and/or) embedding an arrangement of the magnetic assembly tool outside a drill pipe. In some examples, the magnetic assembly tool comprises an arrangement of a plurality of magnets, and the placing the magnetic assembly tool comprises embedding the arrangement inside a casing.
Various examples of the system(s) described herein can create a partial seal or a full seal, and can include a partial seal or a full seal between a pipe and an annulus. Additionally, placing the magnetic assembly tool to create a full seal can include creating a full seal in a plurality of annuli.
Examples of the present disclosure include a magnetic assembly tool. In one example, a magnetic assembly tool can include an arrangement of at least one of a plurality of magnets configured to alter at least one of a plurality of rheological properties of a region of a flow of a magnetorheological fluid. The at least one of the plurality of magnets can for example include a permanent magnet, an electromagnet, or a magneto-elastic magnet.
The arrangement can include a ring, a segmented ring, a multi-segmented ring, or a spiral. The magnetic assembly tool can further include an orientation of the at least one of the plurality of magnets configured to create a magnitude and orientation of a magnetic field to alter the at least one of the plurality of rheological properties. The magnetic assembly tool can also be configured to generate a packing mechanism that can include a radial packing or a lateral packing.
In some examples, the arrangement of the magnetic assembly tool is configured to be placed in a drill pipe, a casing, or a hole. The arrangement can be a ring, and the orientation can include a dipole of each one of the at least one of the plurality of magnets oriented in a same radial direction. The arrangement can also be located on a tubing, a wireline, or a bottom-hole assembly (BHA). In other examples, the magnetic assembly tool can include an attachment configured to locate the at least one of the plurality of magnets on a downhole tool. The downhole tool can include a tubing, a wireline, or a bottom-hole assembly (BHA).
Examples of the present disclosure include a magnetorheological fluid. A magnetorheological fluid (MRF), also described as a magnetic field responsive fluid, is a combination of magnetically polarizable particles in a carrier fluid. A MRF is a fluid whose rheological properties, specifically its yield stress, can be altered when under the influence of a magnetic field. This type of fluid has the ability to modify its rheological properties under the influence of a magnetic field. The generation of a tunable pressure drop can control fluid losses while drilling and cementing in narrow operating windows and to provide a tunable fluid barrier that works as a packer. Using the reduced form of the Navier-Stokes equation and a model to estimate the yield stress of the fluid based on the magnetic field strength, it is possible to determine the pressure drop caused by the fluid behavior. A magnetorheological drilling fluid can be created by changing all, or just a portion, of a weighting material of a drilling fluid from barite to iron particles.
A magnetorheological fluid can include a suspension of magnetizable particles in a liquid. The liquid can include a drilling fluid, and the magnetizable particles can include an iron powder. The magnetorheological fluid can thus be a mixture of a carrier fluid, magnetic (or magnetizable) particles and a viscocifier (or stabilizer) to avoid the sedimentation of the particles.
The iron powder can be a soft grade Carbonyl Iron Powder (CIP) or a hard grade CIP. The CIP can be an iron powder manufactured through thermal decomposition. A factor for the design and stability of MRF is the magnetizable particle size. The range of between about 0.1-10 μm may be an optimum size to prevent particle sedimentation due to the unusually high density (7.5 g/cm3) of the particles. Carbonyl Iron Powder (CIP) can be used as a magnetizable particle to prepare MRF.
The magnetorheological fluid can also include a viscocifier agent and/or a carrier fluid. A viscocifier agent (or stabilizer) can be an additive that is aggregated to the MRF to prevent the magnetizable particle settling and to modify the initial viscosity of the MRF. Examples of the viscocifier agent include a clay, a polymer, or a biopolymer. For example, Bentonite is a natural and industrially available clay. Other stabilizers include synthetic colloidal clay Laponite RD, non-polar Polyalphaolefin (PAO), Dioctyl Sebacate (DOS), Carbonyl Methyl Cellulose (CMC), or Xanthan Gum Kelzan.
The carrier fluid can be a continuous phase in which the magnetizable particles are suspended. One aspect in selecting a carrier fluid is that it be thermally stable, non-corrosive, non-reactive to the magnetizable particles, cost-effective and environmentally friendly. Examples of a carrier fluid include a petroleum-based oil, a mineral oil, water, a paraffin oil, a silicon oil, a polyether, a glycol, a drilling fluid, or a cement slurry.
Any of the examples of magnet arrangements shown in
In one example, the magnet arrangement 1003 was embedded or attached to an inner drill pipe (workstring). The magnet arrangement 1003 was used in an experimental setup (
As described, a magnet arrangement 1003 (or magnet ring) can include a plurality of magnets 1006 making up a segment of the magnet arrangement 1003. The segments can be arranged so that all the magnets 1006 on a ring have their dipoles oriented in the same radial direction to prevent magnetic fields from different dipoles meeting and canceling out. The same logic can be applied for rings which have dipoles pointed into the annular flow area.
The strength of magnetic rings in some examples ranged from around 3000 Gauss on the outside of the epoxy coating to near 450 Gauss at ½ an inch radially outwards for the larger magnets. The strength near the epoxy was similar for the smaller magnets, but their strength at ½ an inch radially outward was closer to 50-60 Gauss.
Referring now to
A magnetic assembly tool such as the magnetic assembly tool 1103, 1106, or 1109 shown by
The ability of a magnetic assembly tool 1103, 1106, or 1109 to create a tunable pressure drop has been validated. The magnetic assembly tool 1103, 1106, or 1109 allows for modification of viscosity downhole. Magnetorheological fluid can be created through the replacement of API barite with iron microspheres that are round and smooth. The iron particles can be synthetically created iron microspheres. The diameters of these particles can range for example from 1 to 10 micrometers. The particles can be uncoated and almost entirely pure iron.
When a magnetic field is applied, the iron particles align themselves with the magnetic field and create a barrier to flow. The particles are attracted to each other due to the magnetic dipoles they obtain while under the influence of the magnetic field, resembling a chain of particles. The strength of this effect can be dependent on the strength of the magnetic field, as well as the volume percent of ferromagnetic materials, as described in “Magnetorheological Fluids. Journal of Magnetism and Magnetic Materials” Volume 252. (2002) by Bossis, G., Lacis, S., Meunier, A., Volkova, O.
In tests in a flow loop (shown in
350 mL of soft water was mixed with different amounts of bentonite for 10 minutes. These mixtures were then allowed to sit and hydrate for 24 hours before being mixed with their respective weighting materials. Weighting materials of either barite, or iron microspheres were then added to the hydrated bentonite samples and allowed to mix for an additional 10 minutes. All mixing took place in a drink mixer at the mixer's 17,000 rpm setting.
Sample 0.2 was designed to have a base reading to compare the magnetorheological fluid against.
A larger 55 gallon sample was mixed for use in the flow loop using 23 lbs./bbl. bentonite and 48 lbs. (pounds)/bbl. (barrel) barite. The reason for using a different amount of bentonite for the flow loop sample was so that the amount of bentonite would be the same in both the “normal” and the magnetorheological fluids in order to simulate replacing the barite with iron.
Multiple samples of iron microspheres and bentonite were created using 23 grams of bentonite and 41 grams of iron particles per sample.
Electron Dispersive Spectrometer (EDS) quantitatively examined the elements present and confirmed that the iron particles were indeed embedded in the bentonite, and did not show significant chemical changes otherwise.
Data for EDS Spot 3:
The magnetorheological fluid was tested in an actual flow loop (
Pressure transducers were set up, equidistant, both upstream and downstream of the magnets. The pressure difference between these pressure transducers allowed for a qualitative analysis of the difference between the bentonite/barite and magnetorheological fluid as the fluids weights were increased.
A mud tank was filled to pre-determined levels and then bentonite was added and allowed to mix for 24 hours. The mixer for the mud tank was turned on to its 1750 rpm rating. As previously mentioned the amount of bentonite was approximately the same for each mixture, meaning that the only variable being changed was the type of weighting material being used. The amount of bentonite was approximately 23 lbs./bbl.
The barite was added in separate batches of 0.575 kg per batch, whereas the iron microspheres were added in batches of 0.5 kg per batch. These amounts were chosen so that the same number of batches were added in total during the experiments to reach the predetermined amount of weighting material to be added. All batches were pumped through the system at 20 gallons per minute. This gives an average annular velocity of 0.62 ft./s
Referring now to
The drop in pressure seen from 8 to 10 batches for the magnetorheological fluid is likely tied to the fact that those test took place on different days. It is therefore likely that some change in the fluid had occurred. The drop seen from batches 11 to 13 for the barite based fluid occurred across all pressure transducers, and not just across the magnet area. This is also a potential explanation for the magnetorheological pressure change from 8 to 10 batches.
There is also a noticeable change in the pressure differential starting at 22 batches of iron microspheres. At this point the pressure becomes more dynamic. It is believed that this is the point where a saturation of iron particles has been reached for this particular setup. The results of this saturation would be a bridging of particles and start/stop phenomenon for the flow, where flow stops until a pressure builds up to break the particles apart and start the process over.
A 55 gallon flow loop sample had weighting material added until it reached 23 lbs./bbl. of bentonite and 41 lbs./bbl. of iron microspheres. This flow loop sample was created over the course of 6 days. On the 7th day, a small 350 mL sample was taken from this to be tested in the lab. All of the rheological and density values were consistent with the previously created lab samples, except for the higher 13 cp plastic viscosity.
It has been shown that a magnetorheological drilling fluid with stable properties can be created. It has also been shown that a drill pipe can provide enough magnetic shielding to allow for a magnetic field to be created in the annulus without affecting the fluid inside the drill pipe.
In operation, the magnet arrangement 1012 can include a plurality of magnets inside the casing 1063. Magnets 1015 and magnets 1066 are opposite each other and in a first region of the casing 1063. Magnets 1069 and magnets 1072 are opposite each other and in a second region of the casing 1063. A system that includes a magnetic assembly tool 1103, 1106, or 1109 can place the magnet arrangement 1012 inside the casing 1063 as depicted in
Next,
For example, a magnetic assembly tool 1103, 1106, or 1109 can apply a magnetic field to a flow of magnetorheological fluid to create a seal that partially packs a region with a packing medium 1078. The packing medium 1078 can be outside of the drill pipe 1060. MRF can flow between the drill pipe 1060 and the annulus 1075. While
The packing medium 1078 also refers to the blockage, partial or total, of the subterranean formation 1087 wall, also known as wellbore. The blockage can extend a few feet beyond the wellbore and/or protrude from the wellbore inside the hole.
In operation, a magnetic assembly tool 1103, 1106, or 1109 can be placed in a hole to properly abandon a well. Placing the magnetic assembly tool 1103, 1106, or 1109 in a drill pipe 1060 can form one or more partial and/or full seals in a plurality of annuli. The multiple annuli can be perforated to communicate among the multiple annuli. The approach depicted in
The magnetorheological fluids (MRF) are well known by some other industries; their discovery is attributed to Jacob Rabinow in 1949; however, just in the recent decade this type of fluid has been used at an industrial scale.
Nowadays, they are providing a turning point in how fluid mechanics works. These “smart-fluids”, also known as magnetorheological fluids (MRF), include a suspension of magnetic particles in a liquid. Under the influence of a magnetic field, the suspended magnetic particles interact to form a new structure that resist shear deformation or flow. The interaction of these particles and the magnetic field creates a form of columnar structure that restricts the motion of the fluid, thus, increasing its rheological properties (as described in a paper by Kolekar, S. (2014). Preparation of Magnetorheological Fluid and Study on Its Rheological Properties. International Journal of Nanoscience, 13(2), 1450009 (1-6). https://doi.org/10.1142/S0219581X14500094). This feature has attracted some industries to use these fluids to overcome old engineering limitations. Some examples of the MRF applications are found in dampers, bridges, body armors and shock absorbers systems. Thus, as the MRF have revolutionized different industries and how the fluid mechanic works, the Oil and Gas Industry can benefit from using this type of fluid to provide solutions for drilling and completions operations.
The properties of the MRF are susceptible depending on 3 factors:
The fluid structure, once a magnetic field is applied, is accountable for the formation and reversibility from a free-flowing liquid to a semi-solid. The reversibility can be tuned for each application presented in this disclosure, some applications benefit from fast reversibility while others benefit from delayed reversibility. The reversibility can depend on the grade of the magnetizable particles available on the market, being Carbonyl Iron Powder (CIP) the one used for this research. The CIP is an iron powder manufactured through thermal decomposition and is one of the most common magnetic particle used for MR applications. Because of its high magnetic susceptibility, these particles align easily in the direction of the magnetic field. The commercialized CIP can be hard grade or soft grade. On the one hand, soft grade magnetic materials can be easily magnetized and demagnetized, which provides a better control over the MRF. On the other hand, hard grade magnetic materials can maintain the magnetized fluid structure without the presence of the magnetic field (as described in a paper by Hajalilou, A., Amri Mazlan, S., Lavvafi, H., & Shameli, K. (2016). Field Responsive Fluids as Smart Materials. https://doi.org/10.1007/978-981-10-2495-5). This characteristic is of vital importance because depending on the intended application, an appropriate magnetic material needs to be considered to create an immediate or delayed stiffening.
Another important factor for the design and stability of MRF is the magnetizable particle size. The range of between about 0.1-10 μm may be an optimum size to prevent particle sedimentation due to the unusually high density (7.5 g/cm3) of the particles. Carbonyl Iron Powder (CIP) can be used as a magnetizable particle to prepare MRF. Additionally, the particle size determines the chain-like formation on the SEM micrograms (Hajalilou et al., 2016). The chains are less stable in the micron size particles but well defined and structured in the nano size domain. The more regular the chain formation, the better the rheological response of the MRF.
Although the conventional drilling fluids in the oil industry have been used extensively for several decades, their rheological properties can only be set at surface by adding chemical additives and cannot be tuned once these fluids are pumped downhole. This imposes a limitation for these fluids, making any rheological change time consuming, non-immediately reactive and frequently expensive because of the high amount of volume to be treated with chemicals. Particularly, the rheology in Magnetorheological Drilling Fluids, which is the addition of magnetic particles to the conventional drilling fluid, are not chemically dependent. Furthermore, the change of the rheological properties of a MRF is tuned according to the intensity and direction of a magnetic field applied to the fluid (as described in a paper by Vryzas, Z., Kelessidis, V. C., Bowman, M. B. J., Texas, A., & Nalbantian, L. (2017). SPE-183906-MS Smart Magnetic Drilling Fluid With In-Situ Rheological Controllability Using. https://doi.org/10.2118/183906-MS). This feature allows that any rheological change can be achieved even downhole or at surface when a magnetic field of a certain intensity is applied to the MRF with fixed magnets or electromagnets (as described in a paper by Zitha, P. L. J., & Wessel, F. (2002). Fluid Flow Control Using Magnetorheological Fluids. Proceedings of SPE/DOE Improved Oil Recovery Symposium, 1-10. https://doi.org/10.2523/75144-MS). In addition, the possibility of a fluid creating a fluid barrier when a magnetic field is applied provides an advantage where potential application in the industry can be evaluated.
An experimental apparatus and experimental setup was used to evaluate the MRF behavior in a flow loop. The objective of the setup is to flow the MRF through two concentric pipes that simulate the workstring and the annulus of a well and determine how the pressure drop in the annulus is affected as a function of the magnetic field generated. Therefore, a modifiable magnet arrangement of Neodymium permanent magnets was placed in the workstring and fixed with a layer of epoxy. The magnet arrangement of the Neodymium magnets create a magnitude and orientation of the magnetic field and in consequence, an alteration of the rheology of the MRF.
Referring still to
The pump selected to run the experiments is peristaltic Watson Marlow Bredel 40. In this type of pumps, the fluid is pushed from the inlet to the outlet through a hose squeezed by some rollers. This positive displacement pump can prevent the MRF to be in contact with moving parts to avoid any contamination. Also, this pump can allow a constant flow rate whilst the back pressure is altered. The later feature can help with establishing the relationship between the rheology and pressure drop developed by the MRF when flowing next to the magnets. The MRF was mixed in an 85 gal drum with 45 grades pitched blade turbine impellers. The electric motor for the mixer is located far enough from the MRF to avoid any premature activation. The MRF is pumped by the peristaltic pump and a pulsation dampener Blacoh C905ND is used to reduce the pressure pulsation. The MRF enters the drillpipe and is pumped through the annulus where the pressure transducers read the pressure drop. The MRF fluid reaches the outlet (flowline) and dumped to the mud tank to be circulated again to the system.
The MRF was prepared with Carbonyl Iron Powder. These particles have a purity of 99.5% (metal basis) and a specific gravity of 7.86 g/mL at 77° F. The CIP is also the weighing material for the sample fluid. Additionally, bentonite with a specific gravity of 2.5 g/mL was added as the viscocifier agent. The carrier fluid was fresh water. A general information of the sample fluid is presented on the following table:
Referring now to
As the Yield Stress of the MR fluid can be modified according to the intensity and direction of the magnetic field, two different approaches are evaluated to estimate the pressure drop in concentric annuli for laminar flow as a function of the Yield Stress (as described in Ermila, M., Eustes, A. W., & Mokhtari, M. (2012). Using magneto-rheological fluids to improve mud displacement efficiency in eccentric annuli. SPE Eastern Regional Meeting, 17-29. Retrieved from http://www.scopus.com/inward/record.url?eid=2-s2.0-84873803403&partnerID=tZOtx3y1 and Kelessidis, V. C., Dalamarinis, P., & Maglione, R. (2011). Experimental study and predictions of pressure losses of fluids modeled as Herschel-Bulkley in concentric and eccentric annuli in laminar, transitional and turbulent flows. Journal of Petroleum Science and Engineering, 77(3-4), 305-312. https://doi.org/10.1016/j.petrol.2011.04.004). These approaches are derived from the Navier-Stokes equations for incompressible fluids. Also, an empirical equation is used to determine the yield stress as a function of the magnetic field applied to the MR fluid. For the pressure drop calculations, the following approaches are presented and are compared to the results obtained experimentally:
The Ermila et al model was obtained to estimate the frictional losses for laminar regimes for Herschel-Bulkley fluids in concentric annuli:
Where, r2 is the outer radius and r1 is the inner radius [m], q is the flow rate [m3/s], δp/δL is the pressure drop gradient [Pa/m], τy is the field dependent yield stress [Pa] and n is the flow behavior index.
The Kelessidis et al model is applicable for laminar, transitional and turbulent regimes and uses the same correlations for laminar flow as per API Recommended Practice 13D. Also, estimates the pressure losses for a Herschel-Bulkey in 100% concentric annulus, other expressions for eccentric annuli are presented in the publication. The model is simplified to the following expression for transition and turbulent regimes:
Where, Δp/ΔL is the pressure drop gradient [Pa/m], f is the Fanning friction factor, ρ is the fluid density [kg/m3], V is the mean velocity [m/s], do is the diameter of the outer tube of annulus, and di the diameter of inner tube of annulus [m].
Where, q is the flow rate.
The flow regime is a function of the channel shape and size, fluid viscosity and fluid density. For the maximum flow rate and the type of fluid used during the experimental phase, the flow regime experienced is laminar. For the laminar flow portion, the Fanning friction factor (f) is well represented by the following expression:
Where, Re represents the Reynolds number.
Where, n′ is the flow behavior index for local power-law parameters and K′ is the flow consistency index for local power-law parameters.
Where, n is the flow behavior index from equation (10) and ε is the dimensionless shear stress for annulus from equation (12).
Where, τy is the field dependent yield stress [Pa], γNw is the Newtonian shear rate on the wall [s−1] and K is the flow consistency index.
Where θx00 is the the cylindrical viscosimeter reading at the corresponding shear rate.
V is the mean velocity [m/s] from equation (4).
Where, τw is the shear stress at the wall [Pa].
The yield stress can be modeled as well. The model proposed by Carlson and presented by Goncalves (in Goncalves, F., Guth, D., & Maas, J. (2015). Characterization and modeling of the behavior of magnetorheological fluids at high shear rates in rotational systems. Journal of Intelligent Material Systems and Structures, (January), 114. https://doi.org/10.1177/1045389X15577646) relates the yield stress τy and the magnetic field strength H:
τy=C·271700·Ø1.5239·tan h(6.33·H) (14)
Where, τy is the field dependent yield stress [Pa], H is the magnetic field strength in [A/m], Ø is the magnetizable particle concentration as a fraction and C is a constant that depends on the carrier fluid given as:
Various results were obtained from the experimental setup. The fluid was circulated in the experimental setup at the minimum concentration of CIP (0.447 wt %), the pressure drop was measured and recorded. The CIP concentration was increased incrementally until reaching the maximum concentration (10.5% wt). The annulus pressure drop between transducers P4-P5, where the magnet arrangement is located, was recorded and compared to the models. In these models, Ermila and Kelessidis, the field dependent yield stress was calculated using the Equation (14) from the magnetic fields presented in Table 1—Magnetic Field [mTesla]. Table 3 (below) and
The calculations determined that an additional pressure drop can be generated across the magnets as a function of the magnetic field strength and the concentration of the CIP. Additionally, the pressure drop measurements show a steady increase until a CIP concentration of 7.599% wt. This is interpreted as a maximum saturation where the magnetizable particles are affected by the magnetic field strength. The simulated pressure drop values are higher in Ermila et al model because it gives a higher pressure drop effect to the value of the field dependent yield stress in comparison to Kelessidis et al.
The MRF with a CIP concentration of wt % 10.5 was held static for a period of 60 hours inside the experimental setup to evaluate its behavior. When the fluid was circulated after this period, the pressure drop across the magnets showed an increased in comparison to the measurements previously presented i.e. at 21.1 gpm the pressure drop across the magnets was 1.33 psi whereas the new measurement rounded 3.11 psi, as shown in
The preliminary interpretation of the results is that the rheology of the MRF can be modified accordingly to the magnetic field strength and magnetizable concentration. However, for the parameters of this particular experimental set-up, it does not play the dominant role in the packing and/or pressure drop. Instead, the built-up iron particles create a mechanical restriction as shown in
Although the benefits of applying the MRF are clear and known for scientists and industries that have used this type of fluids, this technology needs more research to overcome its inherent challenges. As an example, one of the most relevant problems is the MRF instability against sedimentation and low MR effect (as described in Ashtiani, M., Hashemabadi, S. H., & Ghaffari, A. (2015). A review on the magnetorheological fluid preparation and stabilization. Journal of Magnetism and Magnetic Materials, 374, 711-715. https://doi.org/10. 1016/j.jmmm.2014.09.020). The magnetic particles have a high specific gravity, or weight, making it difficult for the carrier fluid to keep them dispersed homogeneously in the fluid. Several stabilization methods have been studied such as: Particle coating, Nano spherical Particles, various carrier fluids, other additives as surfactant and thixotropic agents, and Nano Wire Particles (Ashtiani, Hashemabadi, & Ghaffari, 2015). The MRF can find application in high temperature and high-pressure environments, proper for the Oil and Gas Industry.
The Oil and Gas Industry has relied its drilling operation to conventional (conventional, in the sense of being not active in the presence of a magnetic field) drilling fluids that have some limitations. However, potential application of using Magnetorheological Fluids to create fluid barriers downhole could be explored. Therefore, if a magnetic field strength is generated downhole, the pressure drop of the MRF could be high enough to block the flow. This property has the potential to reduce fluid losses and gas migration.
A magnetic field responsive fluid was developed with the incorporation of Carbonyl Iron Powder (CIP), a magnetizable particle, on a water-bentonite dispersion. It has been shown that increasing the concentration of the CIP in the presence of a magnetic field is responsible for the modification of the rheological properties of the fluid. In that sense, a non-chemical rheology modification was presented experimentally. Particularly, the rheology effect can be predicted by determining the magnetic field dependent yield stress and the concentration of the magnetizable particles. The pressure drop on a laminar flow regime in a concentric annulus could be modeled considering the Herschel-Bulkley Model.
Additionally, a packing effect could be observed after the MRF sample remained static for a period of 60 hours. The preliminary interpretation is that this effect could be created through the built-up of the magnetizable particles in front of a magnetic field. We expect that, depending on the magnetic geometry and strength and also the recipe design of the MR fluid, the magneto-rheological effect versus the physical blockage as a result of magnetic particles built-up around the magnet will compare differently.
In the case of these experiments, the pressure drop effect can be increased as a function of the time exposure to the magnetic field and to a less extent, to the instantaneous rheology modification when the MRF crosses in front of the magnetic field. The ability of the MRF to create a pressure drop and potentially a fluid barrier, can be used in the future for potential applications such as controlling fluid losses or temporarily zonal isolation.
Any of the examples described herein may include MRF that includes “proppants” that are widely used in hydraulic fracturing operations. Additionally, any of the examples described herein may be implemented and a conductivity log run to determine the fracture (or injection) shape, distribution, etc. from the spikes in the measured conductivity and using the values of MRF resistivity as weight averaged from their recipe.
Any of the examples described here may include a work-string, or a plurality of work strings, with a magnetic assembly installed on the work-string(s). The work-string can for example be pulled out of the hole with a speed slow enough allowing several stages of hydraulic fracturing.
Also, any of the described examples can include an application of a magnetic field to the MRF over a period of time. Experimental results have shown that if a magnetic field is applied to MRF that remains static for 60 hours, there is a build-up of magnetorheological particles near the magnetic field that is capable to create a mechanical barrier. In other words, in some examples a restriction caused by the built-up iron particles creates a mechanical restriction that plays a dominant role in the packing and/or pressure drop. The fluid rheology could still be modified in these examples.
The term “substantially” is meant to permit deviations from the descriptive term that don't negatively impact the intended purpose. Descriptive terms are implicitly understood to be modified by the word substantially, even if the term is not explicitly modified by the word substantially.
It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt % to about 5 wt %, but also include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated range. The term “about” can include traditional rounding according to significant figures of numerical values. In addition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ to about ‘y’”.
A related description of certain magnetic gradient drilling concepts that may be relevant to the disclosure provided herein, including descriptions of a magnetic assembly tool that includes a magnetic shielding material to shield at least part of the magnetic field, is provided in PCT Publication No. WO 2017173305, titled “MAGNETIC GRADIENT DRILLING,” filed on Mar. 31, 2017, and which is herein incorporated by reference in its entirety.
It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.
This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/626,797 entitled “MAGNETORHEOLOGICAL DOWN-HOLE PACKING ELEMENTS,” filed Feb. 6, 2018, the contents of which being incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62626797 | Feb 2018 | US |
