Patent Grant
9297251
1. Field
This case relates to drill bit systems for drilling geological formations, and more particularly to drill bit systems incorporating temperature sensors. This case also relates to the use of temperature sensor measurements obtained from drill bits having temperature sensors, including, but not limited to the use of the measurements to improve drill bit reliability, to predict wear, and to increase drilling efficiency.
2. Background
Geological formations are drilled for exploration and exploitation purposes. In commercial environments, the drilling may include a drilling rig and a drill string with a drill bit located at the distal end of the drill string. Different types of drill bits are known, including roller cone bits and polycrystalline diamond compact (PDC) bits. Roller cone bits include a plurality of cutting elements arranged on two or three cones that rotate on bearings about their own axis as the drill string turns the body of the bit. PDC bits include a plurality of fixed (also called “stationary”) lands or blades separated by flutes with the blades including a plurality of synthetic diamond discs (teeth) that provide a scraping cutting surface as the drill string turns the body of the bit. While PDC bits rotate about the longitudinal axis of the drill string, they are often called “stationary” bits because they do not also rotate separately as do roller cone bits.
PDC bits drill primarily due to a wedging mechanism that involves scraping and grinding. More particularly, a vertical force is applied to the teeth as a result of applying drill collar weight to the bit, and a horizontal force is applied to the teeth as a result of applying torque that turns the bit. The result of these forces defines the plane of thrust of the teeth. As the forces are applied, the teeth shear off cuttings from the formation. As the PDC bit encounters the formation, the PDC bit heats up due to friction. In order to reduce the heat build-up, it is common to inject a drilling “mud” through the drill string and down to the bit to cool the bit. Thus, in drilling into the formation, the drill operator may control the drill string RPM, the mud flow-rate, and the weight-on-bit (WOB), each of which will impact the build-up of heat at the drill bit.
Drill bit failure requires a tripping of the drill string out of the borehole, and tripping is costly because of the time and effort involved. Drill bit failure can occur for various reasons including gradual bit wear, bit damage (e.g., loss of one or more cutter elements), and bit balling (i.e., accumulation of clay or other materials coating the bit face and preventing the cutter elements from gaining purchase into the formation).
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
According to one aspect, a drill bit system is provided and includes a shaft (also called a “shank”) and a head having a plurality of blades (also called “wings,” “lands” or “ribs”) at the distal end of the shaft. The blades are separated by a plurality of flutes. Each blade has a distal end that is provided with a plurality of cutting elements or teeth that are arranged on a leading face of the blade. A temperature sensing element is provided adjacent to at least one of the teeth of at least one blade. According to one aspect, the temperature sensing element senses a local temperature of the blade adjacent the tooth. In one embodiment, multiple temperature sensing elements are provided adjacent different teeth of at least one blade. In another embodiment, a temperature sensing element is provided adjacent at least one of the teeth of at least two blades. In another embodiment, multiple temperature sensing elements are provided adjacent different teeth of at least two blades.
In one embodiment, in addition to providing a temperature sensing element adjacent a cutting tooth of a blade of the drill bit, another temperature sensing element is provided either on a proximal portion of the blade distant from the cutting elements or on the shank of the bit. This additional temperature sensing element may serve to provide a reference temperature for the drill bit or for the blade.
In one aspect, the one or more temperature sensing elements on the drilling bit are coupled to circuitry or a processor that can analyze the information provided by the temperature sensing element(s). In one embodiment, a coupling of the temperature sensing elements and the circuitry or processor is accomplished by one or more electrical conductors (e.g., wire(s)). In another embodiment, coupling is accomplished by fiber optics. In another embodiment, coupling is accomplished by wireless transmission (e.g., short-hop electromagnetic or acoustic transmission).
In one aspect, the temperature information obtained by the temperature sensing element is used to provide information regarding at least one of the drill bit, the drilling environment and the formation.
A drilling operation is shown in
A prior art stationary drill bit 50 is seen in
In
As seen best in
In one embodiment, only one temperature sensor element 151 is provided adjacent a tooth of one of the blades.
In other embodiments, at least one temperature sensor element 151 is provided adjacent one tooth of at least two blades or of at least three blades, or at least four blades, or on every blade.
In another embodiment, at least two temperature sensor elements 151 are provided adjacent two different teeth of one of the blades.
In one embodiment, at least two temperature sensors elements 151 are provided at different radial positions on two different blades.
In one embodiment, temperature sensor element 151e is located on a proximal portion of a blade distant the closely spaced teeth 180.
In one embodiment, a temperature sensor element 151 is located in a blade of the drill bit 150 by drilling a pathway 193 inside the shank 155 and the blade (as seen in
In another embodiment, a temperature sensor 151 is located in a blade of the drill bit 150 by drilling or forming a cavity in the blade adjacent a tooth from the outside of the blade. The temperature sensor element 151 may be secured in place with a heat conductive epoxy or by other suitable means and the cavity may be plugged with a plug (not shown) to protect the temperature sensor element 151 from the formation or from the drilling mud or other substances.
In another embodiment, a temperature sensor 151 is located in the opening 170 provided for a tooth prior to the tooth being inserted such that the temperature sensor 151 is in direct contact with the tooth. The temperature sensor element 151 may be secured in place in the opening with a heat conductive epoxy or by the fit or securement of the tooth itself, or by other suitable means.
In one embodiment, a coupling of the temperature sensing elements 151 and the circuitry or processor is accomplished by one or more electrical conductors (e.g., wire(s)). In another embodiment, coupling is accomplished by fiber optics. In another embodiment, coupling is accomplished by wireless transmission (e.g., short-hop electromagnetic or acoustic transmission).
Also shown in
It will be appreciated that while
The temperature sensors 151 may be of any type consistent with downhole temperature values and environmental conditions; e.g., thermocouples, platinum sensors, resistance temperature detectors (RTDs), semiconductor sensors, or others. In addition, sensors based on optical interrogation may be utilized such as DTS whereby the Raman-scattered light from the bulk of an optical fiber gives a time-domain-reflectometric reading of the fiber's distributed temperature(s). Such a fiber arrangement could give a distributed temperature profile across or along a drill bit. For example, a helical fiber winding its way from the bit face to the shank could give a profile of temperature readings along the length and circumference of the drill bit.
It should be appreciated that a temperature sensing element adjacent a tooth of a drill bit will provide a local temperature measurement at that point. A temperature sensing element located on a blade far from the teeth may provide an “average” temperature for the blade, and a temperature sensing element located on a shank may provide an average temperature for the tool bit or a reference temperature for the environment.
A particular temperature at a specific point (local temperature) such as at a particular tooth may be denoted by Ti, with the subscript i labeling the measurement point. An average temperature <T> of a plurality of specific points can be computed from any array of N different temperature measurements at various points in the drill bit according to
<T>=ΣTi/N (1)
Various temperature points can be compared to this average bit temperature by subtraction {Ti−<T>}. Likewise, various temperature points can be compared to a reference temperature by subtraction {Ti−Tref}, where Tref is some reference temperature measurement point, such as on the bit shank, well back from the contact points and cutter elements.
Differential schemes such as a Wheatstone bridge arrangement (with different temperature sensors as bridge elements, e.g.) may be used to make more accurate or precise measurements of small differences in temperature from point to point directly.
With the use of one or more of temperature sensing elements 151a-151d adjacent the teeth 180 of the drill bit, with or without temperature sensing element 151e located on the shank, information can be obtained regarding at least one of the drill bit, the drilling environment, and the formation. More particularly, changes in various local drill bit temperatures may be used to infer changes in the condition or environment of the drill bit.
As previously suggested, three operational factors that the driller actually controls—drill-string rotational velocity (rpm), mud flow-rate, and weight-on-bit (WOB)—are very significant determinants of drill bit temperature, as they control the amount of friction at the cutting surfaces of the drill bit and also the amount of convective cooling that is applied to the bit by the flowing mud. In addition, the driller is able to measure the average rate of penetration (ROP) of the drilling assembly and also the torque at the surface (and possibly close to the bit, as well). All the temperature interpretations that are performed (below) desirably take these factors into account. For example, if rpm, flow-rate, and WOB are held constant, and ROP drops along with an increase in average drill bit temperature, then that may be consistent with either an increase in formation hardness or mechanical damage to the bit, such as cutter dulling or damage or loss of a cutter. Moreover, the formation temperature does increase gradually with depth and is typically characterized by a “geothermal gradient” of about +2° C. per 100 m of increased depth.
According to one aspect, average bit temperature <T> rise over time d<T>/dt, to the extent that this temperature increase is not attributable to WOB or rpm or mud flow-rate changes or geothermal gradient, could indicate bit wear, bit damage (e.g., lost tooth), or bit balling (accumulation of clay or other materials coating the bit face and preventing the cutters from gaining purchase into the formation). Gradual wear or dulling or bit balling would be expected to lead to a gradual temperature increase (small d<T>/dt). A relative abrupt change in the rate of temperature rise (large d<T>/dt) could indicate the loss of one or more teeth from one or more blades of the bit. The average bit temperature may be the average temperature calculated from a plurality of temperatures indications provided by a plurality of sensors located adjacent the teeth as in equation (1), or the temperature sensed by a sensing element located on a blade or on the shaft far from the teeth. Thus, in one embodiment, the rate of temperature rise is measured and compared to either previous rate of temperature rise or to a threshold value, and if the rate of temperature rise is increasing or a threshold is exceeded, action is taken accordingly. The action could include, inter alia one or more of reducing WOB or rpm, increasing the mud flow-rate changes or tripping the bit out of the borehole.
According to one aspect, the local bit temperatures measured by temperature sensors 151 at a plurality of locations adjacent teeth of the bit are utilized to detect bit damage and the site thereof. More particularly, the temperatures at the plurality of measurement locations adjacent the teeth are compared to the average bit temperature <T> or to a reference temperature Tref. Over time, typical excursions from the average can be noted. A sudden temperature decrease or increase at one particular point relative to the average bit temperature or reference temperature could indicate where a tooth had been lost or damaged. By way of example only, if a tooth is lost but there are other cutters nearby functioning properly, the temperature might drop, whereas if the lost tooth is on an exposed promontory, the temperature might increase due to inefficient rubbing. Likewise, a sudden temperature increase at a particular point could indicate diminished hydraulic cleaning of cutting due to a plugged bit jet adjacent the tooth or teeth monitored by that sensor. Thus, in one embodiment, the temperature at a plurality of teeth are measured and compared to either an average bit temperature or to a reference temperature, and if a sudden temperature decrease or increase for one of the sensors is noted, action is taken accordingly. The action could include, inter alia one or more of increasing, pulsing or cycling the flow pressure of the drilling mud in an attempt to unplug the bit jet, or tripping the bit out of the borehole.
According to one aspect, geological information can be obtained by monitoring the average bit temperature obtained by one or more sensors 151 in conjunction with the rate of penetration (ROP) of the drill bit. More particularly, it is appreciated that wear and bit damage can cause a monotonically increasing temperature of the drill bit with time, and the geothermal gradient causes a very slowly increasing temperature with depth. On the other hand, average temperature of the drill bit may also increase due to increasing formation hardness and/or density, or may decrease due to decreasing formation hardness and/or density. Such variable and potentially reversible temperature changes, if correlated with ROP at a constant WOB and with torque at constant rpm can be interpreted to provide geological information. The geological information can be used for well placement and for correlation purposes. More particularly, if the average temperature of the drill bit rises while the ROP decreases and the torque increases, it can be assumed that the formation hardness has increased. Similarly, if the average temperature of the drill bit decreases while the ROP increases and the torque decreases, it can be assumed that the formation hardness has decreased. Thus, in one embodiment, the average temperature taken from a plurality of teeth is measured and correlated with one or both of the ROP of and torque on the bit. Based on the measurements and correlations determinations are made as to the relative formation hardness at different depths of the formation, and a log of the same can be made.
If the average bit temperature drops without a change in the ROP, this may indicate a gas influx at the bit, or in general, an overpressured zone. Thus, in one embodiment, the average bit temperature obtained through the use of one or more temperature sensors 151 is correlated with the ROP, and if the ratio of average bit temperature to ROP drops, appropriate action is taken. For example, the drilling forward progress may be halted abruptly, the mud weight may be increased appropriately or surface pressure-containing facilities (blow-out preventers) may be actuated and closed.
It should be appreciated that the temperature sensed at any location by the temperature sensor elements may be displayed (via the processor) as a log or in another manner either on paper, on a computer screen, or otherwise. In addition, average bit temperature <T>, rate of change of the average bit temperature, and any desired correlations calculated by the processor may likewise be displayed as a log or in another manner either on paper, on a computer screen, or otherwise. In addition, drill-string rotational velocity (rpm), mud flow-rate, weight-on-bit (WOB) may likewise be displayed. Thus, the processor is programmed or hard-wired or otherwise arranged to provide an output that may be displayed accordingly. Further, the processor in conjunction with associated circuitry or equipment may generate an alarm (audible or visual) when desirable.
Temperature sensor elements 251 are provided adjacent respective teeth 280 of the tool bit 250. In
With the use of one or more of temperature sensing elements 251a-251g adjacent the teeth 280 of the drill bit, with or without temperature sensing element 251g located on the shank, information can be obtained regarding at least one of the drill bit, the drilling environment, and the formation. More particularly, in one aspect, changes in various local drill bit temperatures may be used to infer changes in the condition or environment of the drill bit. For example, as previously discussed, average bit temperature <T> rise over time d<T>/dt, to the extent that this temperature increase is not attributable to WOB or rpm or mud flow-rate changes or geothermal gradient, could indicate bit wear, bit damage (e.g., lost tooth), or bit balling (accumulation of clay or other materials coating the bit face and preventing the cutters from gaining purchase into the formation). According to another aspect, as discussed above with reference to
Temperature sensor elements 351 are provided adjacent the diamond pads of the tool bit 350. In
With the use of one or more of temperature sensing elements 351a adjacent the pads 365 of the drill bit, with or without a temperature sensing element located on the shank, information can be obtained regarding at least one of the drill bit, the drilling environment, and the formation. More particularly, in one aspect, changes in various local drill bit temperatures may be used to infer changes in the condition or environment of the drill bit. For example, as previously discussed, average bit temperature <T> rise over time d<T>/dt, to the extent that this temperature increase is not attributable to WOB or rpm or mud flow-rate changes or geothermal gradient, could indicate bit wear, bit damage (e.g., lost pad), or bit balling (accumulation of clay or other materials coating the bit face and preventing the cutters from gaining purchase into the formation). According to another aspect, as discussed above with reference to
Turning now to
In one embodiment, at least one temperature sensor element 451 is located adjacent a tooth 470 on one of the distal blades 465, and at least one temperature sensor element is located adjacent a tooth on one of the proximal blades 466 of the reaming side lobe 460b. Data from the temperature sensor elements 451 are passed farther back up the drill string through a physical connector (e.g., electrical or fiber-optical) between the drill bit and the sub above it, or by short-hop wireless means to a receiver located higher up in the drill string. In one embodiment, a bored channel 493 (shown in phantom) carries cabling 496 (shown in phantom) from the temperature sensor(s) back to a dedicated or possibly, shared electronics sub-module 497 (shown in phantom) located back in the protected shank portion 455 of the bit 450.
According to one aspect, local temperature changes measured at various key locations in a bi-centered bit 450 could indicate changing bit motion conditions (bouncing, whirling motion vs. smooth rotation) and/or hole size being drilled. For example, changes in the relative temperatures of a tooth on the outside of the reaming side-lobe and a tooth on the side of the smaller round cutting head may indicate a change in the respective intensities of engagement of these teeth with the formation (cutting duty-cycle). Taking the bi-centered bit's geometry into account, this information may allow the drilling engineer to infer the effective size of the hole being drilled at that moment. Likewise, an increased temperature at a tooth that suggests increased intensity of engagement at a certain point on the bit may correspond to an undesirable bouncing or whirling motion that periodically strikes that point on the bit preferentially against the formation. If the bi-centered drilling bit's motion condition detected is unsatisfactory to the driller in terms of safety, drilling efficiency or wear and tear on the bit, the driller may attempt to modify the bit motion by varying the WOB and/or the rpm conditions while monitoring any changes in the temperature measurement points.
A schematic diagram of a reamer 550 located on the drill string proximal of a drilling bit is seen in
According to one aspect, a reamer 550 is provided with one or more local temperature sensor elements 551. More particularly, reamer 550 includes a central hollow body 552 with an outer circumference to which a plurality of elongate blades 565a, 565b, 565c . . . (generally referred to as 565) are circumferentially spaced, thereby defining therebetween a plurality of flutes 567a, 567b . . . . The reamer 550 may include two, three, four or more blades 565. The blades 565 have a proximal portion 566 that extends radially outwardly and is provided with a plurality of openings or cavities 570 formed or drilled into their leading faces 573, and a distal portion 568 which tapers back toward the central hollow body 552. The blades may have different or the same numbers of openings 570 provided. The openings 570 are generally situated perpendicular to the longitudinal axis of the reamer 550 and in the direction of rotation of the drill string. The openings 570 receive cutting elements or teeth 580 (e.g., PDC teeth) that project from the leading faces 573 and are adapted to scrape and cut. The teeth 580 assume different axially positions relative to the longitudinal axis of the reamer 550. The teeth may also be at different radial distances from the longitudinal axis. The hollow body 552 has a central passageway (not shown) for receiving drilling fluid (mud). One or more openings (not shown) may be formed in the flutes to deliver drilling mud to the blades 565 of the reamer.
In
In one embodiment, only one temperature sensor element 551 is provided adjacent a tooth of one of the blades. In other embodiments, at least one temperature sensor element 551 is provided adjacent one tooth of at least two, three, four or all of the blades. In another embodiment, at least two temperature sensor elements 551 are provided adjacent two different teeth of one of the blades. In another embodiment, at least two temperature sensors elements 551 are provided at different radial positions on two different blades. In one embodiment, temperature sensor element 551 is located on a portion of a blade distant the closely spaced teeth 570 or on a portion of the reamer relatively distant from the teeth 570. The temperature sensors elements 551 can be of any desirable type as previously discussed with reference to
In one aspect, the temperature sensor elements 551 are used to monitor the health and effectiveness of the reamer 550. Increasing temperatures could indicate reamer cutter wear or damage, or overly aggressive reaming, possibly with excessive vibration or chattering motion in the hole. As with the drill bit examples above, differentiating between localized, blade-specific or tooth-specific temperature measurements and averaged temperatures can lead to insightful interpretations of the damage conditions, possibly at specific location(s) on the reamer 550.
According to one aspect, one or more temperature sensors may be provided in a mud turbine or positive-displacement motor (PDM) of a drilling bottom-hole assembly. The temperature sensors in the mud turbine or PDM may be in addition to providing temperature sensors adjacent teeth or pads of a drill or teeth of a reamer of a drill string.
A common failure of a drilling motor occurs when rotating shaft bearings (which are either mud-lubricated or sealed and oil-lubricated) become contaminated and/or worn.
The temperature sensor 613 of
In one aspect, the temperature sensing element(s) 613 can be used to provide an indication of wear of the mud motor bearings and help to predict end-of-life of the mud motor. Having to trip out to change a failed mud motor (or a failed drill bit) is an extremely costly event, and it is also very beneficial to obtain maximum operating hours of reliable use from both motors and bits when in the well and drilling on an expensive job, particularly in the offshore drilling market.
As discussed above, all of the drilling equipment of
There have been described and illustrated herein several embodiments of formation drilling systems incorporating temperature sensing elements. While particular embodiments and aspects have been described, it is not intended that the disclosure be limited thereto, and it is intended that the claims be as broad in scope as the art will allow and that the specification be read likewise. Thus, while particular types of stationary drill bits have been described, other types of may be utilized with the temperature sensor elements adjacent the teeth, pads or scraping elements of the bits. Likewise, while particular data transmission mechanisms have been described for transmitting data from the temperature sensor elements to a processor, it will be appreciated that other transmission mechanisms can be utilized. Further, while average temperature determinations have been described as being based on averaging the readings from all of the temperature sensors located adjacent teeth (or pads) of a bit, or from a sensor located distant the teeth, it will be appreciated that fewer than all of the sensors could be utilized to generate an “average.” It will therefore be appreciated by those skilled in the art that yet other modifications could be made. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses, if any, are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.
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