Patent Application
20090032304
The present invention relates to determining the level of drilling mud in the return line from an oil drilling apparatus.
An oil drilling apparatus typically uses a drill bit at the end of a long pipe. This pipe supplies fluid to the bit to keep it cool and to flush away the cuttings and bring them to the surface. The slurry-like liquid passed to the bit is referred to as mud. The mud is prepared on the surface and pumped down the center of the pipe and out the drill bit where it travels back to the surface while being in contact with the sides of the drilled hole. The liquid carries with it the cuttings from the bottom of the hole, and any material in the surrounding earth that may flow into and join the mud. The liquid can also be lost into fissures in the surrounding earth. The rate of the flow of liquid can be suddenly increased by contact with a pressure pocket in the earth. Operators of oil-drilling apparatus frequently perform quantitative and qualitative analysis of the quantity of mud and other materials returning to the surface to obtain information of what is happening in the hole. The quantity of returning mud is most immediately measured in the return line from the drilling apparatus back to the storage pit. This has advantages over simply measuring the height of the mud in the storage pit that contains both newly added mud and mud returning from the hole. The method used to measure the quantity traveling in the return line has usually required a device such as a paddle or a wheel that contacts and extends into the flow. By nature, such contact devices have been susceptible to clogging, sticking, and wear. Clogging is especially a problem when the materials suspended in the returning mud are of a type that clump together, eventually forming large pieces that are unable to flow past the contact devices placed in the mud return pipe.
Non-contact methods avoid the problems with clogging, sticking, and wear just described. One example, U.S. Pat. No. 4,228,530 to Bergey, is an example of a non-contact gauge that makes use of sound waves. However sound waves are affected by off-gasses, condensation, steam, and other process parameters that influence the propagation of an ultrasonic signal. Microwaves, as used in an embodiment of the present invention, are not affected by these conditions. Also, the method of mounting and directing the beam of a non-contact device is important in its overall long-term success in accomplishing the task for which it was designed, while avoiding the rigors of being in an oil drilling environment. The microwave device of the present method has been mounted and protected in ways that contribute to its long term success when compared to the prior art.
In a first aspect, the invention features a non-contact level sensing system for measuring an attribute of mud and cutting flow returning from an oil-drilling hole including a mounting connectable to a conduit, such as a pipe, that is connected to the oil-drilling hole and contains the flowing mud and cuttings. The system includes an electromagnetic signal emitter and an electromagnetic signal receiver, and a housing adapted to hold them and mount them on a mounting. Circuitry is included within the housing for processing signals from the receiver to generate a measure of the height of the mud and cutting flow inside the pipe or conduit. In a second aspect, the invention features a non-contact system for measuring an attribute of mud and cutting flow returning from an oil-drilling hole, wherein the system includes a signal emitter and a signal receiver and a housing adapted to hold them and mount on a mounting, and the mounting includes a signal reflector in the path of the signal emitted by the signal emitter for reflecting signals from the signal emitter toward the mud and cuttings.
Knowledge of the measure of height and the cross sectional size of the conduit and the way in which the mud pumping and reclamation system work, allows the calculation of the flow of the returning mud and cuttings, including any liquids that they may carry with them from the surrounding earth.
The above and other objects and advantages of the present invention will be made apparent from the accompanying drawings and the description thereof.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.
The mud 14, carrying with it cuttings and any other liquids, gases, or solids that have mixed in, exits the side of the drilling apparatus 22 to flow in a mud return pipe or conduit 38, which is usually angled downward to assist the flow. The return pipe 38 is open to atmospheric pressure and sized so that the flow does not fill the entire cross-section of the pipe 38. Instead, the pipe 38 contains the mud 14 and cuttings in its lower portion, and air in its upper portion. Sitting on the exterior of a generally top surface of the pipe 38 is the non-contact measuring system 12. This system, and the area of pipe local to it, will be explained in much greater detail with reference to later figures. The mud return pipe 38 terminates at a particle and mud processing area 40 that is well known in the art. At this area the cuttings and debris are removed to the degree that is practical and disposed of in a reserve pit 42 so they may be later buried or disposed of elsewhere. The mud 14 is reconditioned and supplemented as needed and returned to the mud pit 16 for another trip through the process just described.
The pipe 38 has a mud and cutting flow 44 that contains debris and clumps 44a traveling in the direction shown by the arrows. An air gap 46 is above the mud and cuttings. The upper surface of the pipe has an aperture 48, and bolted or otherwise attached in line with this aperture is the flange or saddle 50 of the mounting 52 specifically engineered to fit on the pipe 38 and hold a gauge 54 in the correct orientation. The attachment between the mounting 52 and the pipe 38 may be airtight, such as by including a gasket (not shown) or by welding, or it may be loosely fitting since the system normally has only air in the upper portion of the pipe 38.
The mounting 52 is made of heavy gauge sheet metal or other suitable materials, and its shape is engineered to accommodate certain difficult operational conditions found in the oil industry. For example, the costly portion, the gauge 54, is kept in a low profile to the pipe 38 by positioning it at an end 56 rather than a top 58 of the mounting 52. This is to avoid it being bumped and damaged. Protection from damage is necessary in the oil industry because heavy equipment and pipes are often being moved about in close proximity to where the gauge 54 is used. In addition, when the drilling apparatus is disassembled and moved to another site, the lower profile will serve to minimize contact and damage if the mounting 52 and gauge 54 are left installed on the pipe 38. If the pipe 38 were to be placed on the ground and allowed to roll, the mounting 52 will make contact with the ground or another section of pipe 38 before the gauge 54 does. The gauge 54 is located on the upstream side of the flow direction, rather than the downstream side, so that if a malfunction should occur that temporarily fills the interior space 60 of the mounting 52 with mud and cuttings, the gauge 54 would be the last object to be reached by the mud. Ideally, the gauge 54 would not be reached, so long as the drill operators quickly correct the condition. For the same reason, the upstream angled surface 62 is on a negative slope from the gauge 54 so that any mud and cuttings that splash on the angled surface drain back into the pipe. The other angled interior surface is a reflective surface 64 that is angled for at least two reasons. One reason again has to do with drainage of unwanted mud and cuttings. The negative slope will cause any cuttings 44b reaching it, to glance off and stay low, rather than to be piled high into the interior space 60. The second reason is that the approximately 45-degree angle of surface 64 relative to the gauge 54 and the mud and cuttings surface 66 allows the surface 64 to function as a reflector of the signal from gauge 54 when it is mounted as shown. This will be explained further when describing the operation of gauge 54. Other aspects of the mounting include a second flange 68, for the purpose of mounting the gauge 54. This flange 68 has holes to accept the fasteners 70 passing through the mating flange 72 of the gauge. Welded to or otherwise solidly a part of the flange 68 is a protective cap 74, to further protect the gauge 54. There is a cutout 76 in the cap 74 to allow the necessary connections 77 to be made. Examples of likely connections are power and signal output. The cap 74 has cutouts 75 to allow wrench access to the installation fasteners 70.
In this embodiment, the gauge 54 is a microwave emitting gauge part number VEGAPULS 62 sold by the assignee of the present application, although other similar non-contact gauges could be used. Gauges using pulsed or continuous radar (e.g., frequency modulated continuous wave (FMCW)) or other electromagnetic, ultrasonic or other non-contact methodologies are suitable for use in connection with embodiments of the invention. Within the gauge's housing 78 is an emitter 80 and a receiver 82 (both represented conceptually with hidden lines) and circuitry to interpret the reflective signal captured by the receiver 82. Both emitter 80 and receiver 82 are behind a protective plug of material, such as PTFE, that is transparent with respect to the signal sent and received by the gauge 54.
In operation, the microwave signal pulse 84 is generated and emitted from the emitter 80. The signal is directed toward reflective surface 64. The reflective surface 64 is made of a material, such as steel, chosen to efficiently reflect the microwaves. The reflective surface 64 can be a structural member of the mounting 52, as is shown, or it can be an added surface or reflective coating. The surface or reflective coating can be further coated (such as for corrosion protection, or to repel dirt) as long as the protective coatings do not interfere with the signal. PTFE or epoxy paints are both examples of protective coatings. The reflective surface 64 directs the signal to the mud and cuttings flow surface 66 in a generally perpendicular orientation. When the signal reaches the surface 66, it is reflected back as reflected signal 86 to the reflective surface 64 and back to the gauge 54. The receiver 82 in the gauge 54 receives the reflected signal 86. Circuitry (not shown) in the gauge processes the time lapse from when the signal was emitted to when it was received. The time lapse determined by the circuitry is a function of the height of the mud in the pipe, which is an attribute of the flow of mud and cuttings traveling through the pipe. Thus, the gauge output provides an attribute of the flow rate of the mud and cuttings. This attribute of the flow is displayed for operators of the oil drilling system 10. This information may then be used while controlling the drilling process.
In use, the procedures and equipment take into consideration several circumstances. Since a condition of zero flow and high flow can both have the same mud and cutting flow height within the pipe, the oil-drilling system is designed so that the operator knows the difference between the two. One way that this is may be done is by sloping the pipe sufficiently so that the substantial portion of the mud and cuttings cannot remain stationary in the pipe. During a time of zero flow, the pipe 38 would automatically empty. Another way is by interlocking or coordinating the interpretation of the gauge signal with other known parameters, such as pressure.
Another operational fault condition is the unintended shrinking of the available pipe cross section that would be caused by surfaces of the pipe accumulating caked on mud and cuttings. If the pipe's surfaces are caked with material, the air/mud interface in the pipe will rise closer to the reflective surface 64 than would be the case in a clean pipe for the same amount of flow. The higher air/mud interface in turn would decrease the travel time of the signal, and a higher than actual flow rate would be reported. A sharply sloped pipe and scheduled maintenance are some of the practices to limit accumulated caked on mud and cuttings.
While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.
