Patent Application
20170089137
Directional drilling involves the practice of drilling non-vertical wells and is typically employed in oilfield directional drilling, utility installation directional drilling (horizontal directional drilling or directional boring), and surface-in-seam drilling, which horizontally intersects a vertical well target to extract coal bed methane.
Known directional drilling systems generally include a mud motor placed in the drill string to power a bit while drilling. A mud motor is a progressive cavity positive displacement pump that uses drilling fluid from the drill string to create eccentric motion in the power section of the motor (e.g., via turning a helical rotor). This motion is transferred as concentric power through a stator to the drill bit. As a result, the flow of fluid transmits power, allowing the assembly to rotate and turn the bit.
Mud motors can be configured to have a bend in them using different settings on the motor itself. Typical mud motors can be modified from 0 degrees to 4 degrees with several increments in deviation per degree of bend. The amount of bend is determined by a rate of climb or radius of curve needed to reach the target zone. By using a downhole measurement tool such as a measurement-while-drilling (MWD) tool or a logging-while-drilling (LWD) tool, a directional driller can receive and monitor guidance information and/or information regarding rock or sediment characterization in the borehole (e.g., borehole inclination, pressure, and/or gamma radiation counts) and steer the bit to the desired target zone.
Downhole measurement tools such as MWD/LWD tools (hereinafter “information subs”) are ordinarily located a considerable distance away from the bit/bore end when the mud motor is in use. Because downhole mud motors are generally not designed or equipped to incorporate information subs at the bit box where the bit attaches to the motor, the sub is often located at a trailing point on the mud motor or along the drill string, placing the information sub anywhere from ten to eighty-five feet above the bit/wellbore end. As a result, guidance and rock characterization information transmitted from the information sub is instructive regarding the location and rock conditions where the bit has previously travelled, not where it currently is. This lack of real-time information has been described as driving a car forward, while looking through the rear window. This information delay becomes problematic in instances where the bit veers of course. Before the driller detects a potential problem, the boring device has veered many feet off of an acceptable trajectory, risking costly and even dangerous mistakes should the bit encounter cable lines, gas lines, unfriendly rock characteristics, or the like.
Even in instances in which it is or could be possible to attach an information sub to the bit box of a downhole mud motor, current bit-to-bend lengths, or the distance between the bit attached to the mud motor and the bend in the mud motor, prevent proper steering. That is, the bit-to-bend lengths of existing downhole mud motors do not allow for modern planned drill trajectories or trajectories that take into account real-time borehole information to be achieved in the vertical, curved, and horizontal sections of the well bore.
As a result of the distant placement of information subs and extended “bit to bends,” drillers operate on delayed wellbore location and characterization knowledge and are unable to achieve desired wellbore trajectories or make informed, real-time decisions regarding maintaining and/or correcting wellbore paths.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter.
One embodiment provides a downhole assembly for drilling a planned wellbore trajectory. The assembly includes (1) a power assembly having a rotor activated by fluid transferred from a drill string; (2) a transmission configured to transfer power from the rotor to an output shaft, the output shaft terminating in a bit box having a forward end; (3) a bearing assembly radially and axially supporting the output shaft, where the output shaft is configured to drive a drill bit coupled to the output shaft via the bit box and an information sub, and where the drill bit and the information sub each have forward and rearward ends, the rearward end of the drill bit attaching to the forward end of the information sub and the rearward end of the information sub attaching to the bit box; and (4) a housing structure encompassing the power assembly, the transmission, and the bearing assembly, where the housing structure has a fixed bend located a distance from the forward end of the bit box that is less than or equal to forty inches.
Another embodiment provides a bottom-hole assembly for drilling a planned wellbore trajectory. The assembly includes a downhole mud motor having a housing with a fixed bend encompassing a bearing assembly, a transmission, and a power assembly. The power assembly includes a rotor activated by fluid transferred from a drill string, and the transmission transfers power from the rotor to a bearing mandrel supported by the bearing assembly. The bottom-hole assembly also includes an information sub located below the downhole mud motor, where the information sub is mounted at a forward end of the bearing mandrel. The bottom-hole assembly further includes a bit mounted at a forward end of the information sub. The bit is indirectly driven by the bearing mandrel, where a distance between the forward end of the bearing mandrel and the fixed bend of the housing is less than or equal to forty inches.
Yet another embodiment provides a process for drilling a subterranean wellbore using a bottom-hole assembly for a mud motor. The assembly includes an information sub having forward and rearward ends and a drill bit having a forward end in contact with an end of the wellbore and a rearward end, where the information sub is attached between the rearward end of the bit and a forward end of a bit box of a bearing mandrel driven by the mud motor. The mud motor is encased within a housing having a fixed bend at a distance less than or equal to forty inches from a forward end of the bit box. The process using the bottom-hole assembly includes the steps of (1) receiving, from the information sub, real-time drill data defining wellbore conditions adjacent to the bit; and (2) in response to the real-time drill data, steering the bit along a planned trajectory.
Additional objects, advantages and novel features of the technology will be set forth in part in the description which follows, and in part will become more apparent to those skilled in the art upon examination of the following, or may be learned from practice of the technology.
Non-limiting and non-exhaustive embodiments of the present invention, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Illustrative embodiments of the invention are illustrated in the drawings, in which:
Embodiments are described more fully below in sufficient detail to enable those skilled in the art to practice the system and method. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense.
Various embodiments of the systems and processes described herein relate to drilling subterranean wellbores. More specifically, this description discusses an improved bottom-hole assembly for a downhole mud motor and a corresponding process for drilling a planned subterranean trajectory in which a driller may rely on real-time data relating to conditions at the drill bit/bottom of the wellbore and take that real-time drilling data into account in steering the bit along a planned wellbore trajectory.
With reference to
As discussed above in the Background section, information subs may take a variety of forms and provide numerous types of drill data to the driller. Oftentimes, information subs take the form of measurement-while-drilling or logging-while-drilling tools and include a variety of sensors, a battery, and an antennae having a transmit/receive module (a “TR module”) that communicates with above-ground equipment/personnel. Information subs generally provide wellbore location information and/or rock or sediment characterization information. In this regard, drill data may include, by way of a limited sampling, information relating to wellbore inclination, direction, pressure, gamma count, and/or tool face. Transmitting drill data from information sub 52, located below bearing assembly 16 and between bit box 54 and drill bit 24, provides a number of advantages to the driller. Namely, because information sub 52 is located adjacent to drill bit 24, rather than at a rearward location in the bearing assembly or even at a farther rearward location along the mud motor or drill string, drill data is provided to the driller in real time, from a relevant location. The driller receives drill data pertaining to where the bit is currently located, rather than where the bit was located up to eighty-five feet up-hole.
Returning to
The combination of a forward-located information sub 52 and a micronized bit-to-bend length, L, results in numerous practical benefits over existing bottom-hole assemblies for downhole mud motors. First, the driller receives real-time information from a location as close as possible to the wellbore end and can use that information to properly steer drill bit 24, either to maintain a planned subterranean trajectory or to correct the trajectory in response to the real-time drill data. Without the micronized bit-to-bend length, L, existing bottom-hole assemblies have high-angled builds and turn rates that cannot achieve modern trajectories. Even if a driller were to receive real-time, bottom-hole information, the lengthy bit-to-bend length of existing assemblies would not provide for the desired steering capabilities. With the micronized bit-to-bend, the driller can take advantage of real-time drill data to achieve a planned wellbore trajectory in the vertical, curved, and horizontal sections of the wellbore. Because the driller (or engineer or geologist) may operate on real-time drill data that reflects where the bit is, rather than where it has already traveled, subterranean wellbore adjustments made be made as rock/sediment formation and dip changes occur. This limits sidetracks, plug backs, and missed targets. As a result, the improved wellbore knowledge and steering abilities of the micro bit-to-bend reduce the cost and improve the economy of wellbore construction because decisions regarding correcting or maintaining the wellbore path may be more clearly and rapidly made.
The improved bottom-hole assembly 50 is also easier to use and more friendly toward less skilled or less seasoned personnel, and may eliminate the need for specialty services that are currently required to assist in drilling a horizontal/directional wellbore. In this same vein, the more sophisticated and accurate bottom-hole assembly opens opportunities for automation using existing drilling rig equipment, allowing for further cost savings and increased safety resulting from maintaining fewer personnel at the drilling site. Improved bottom-hole assembly 50 also allows for easy assembly on site at the drilling rig and/or in the shop. This time savings translates to lower costs and added safety benefits. Additional savings are achieved because the micronized parts of bearing assembly 16 are smaller and incur lower manufacturing costs due to decreased material usage and manufacturing time.
Overall, bottom-hole assembly 50 allows the drilling system to work and communicate synergistically, from the personnel (e.g., operators, engineers, geologists, rig personnel) to the rig to the assembly itself. Specialty service providers are no longer required to analyze and interpret projected data because the drill data coming from assembly 50 reflects real-time conditions, allowing decisions to be made accurately and in harmonious agreement, without the risks and hassles of predicting, estimating, and guessing that oftentimes invites differing and even fraudulent opinions that skew the drilling process. As a result, the improved bottom-hole assembly 50 with its forward-located information sub and micronized bit-to-bend length adds integrity and accuracy to the whole operation surrounding wellbore drilling.
Although the above embodiments have been described in language that is specific to certain structures, elements, compositions, and methodological steps, it is to be understood that the technology defined in the appended claims is not necessarily limited to the specific structures, elements, compositions and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed technology. Since many embodiments of the technology can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.
