Abstract: Apparatus and methods include a well-center drilling opening in a drilling rig floor of a mobile drilling rig and a v-door to the drilling rig. A mast is disposed about the well-center drilling opening and carrying drilling components of a drilling system. The mast supports a fingerboard that includes a plurality of parallel longitudinally extending fingers having openings between ends thereof and being arranged to receive tubulars therebetween. The plurality of fingers extending in the same direction as a line between the well-center drilling opening and the v-door. A racker device is moveable in a lateral direction relative to the direction of the line between the well-center drilling opening and the v-door.

Abstract: A device for handling oil pipes and a method for workover includes a base, which includes an oil pipe bearing area extending in a longitudinal direction, the oil pipe bearing area being provided therein with at least one positioning member arranged in a transverse direction perpendicular to the longitudinal direction of the base, for positioning an oil pipe; and a movable oil pipe grasping assembly, which is located above the base and configured to grasp the oil pipe and place the oil pipe in the oil pipe bearing area, or grasp the oil pipe from the oil pipe bearing area and place the oil pipe in an area outside the oil pipe bearing area. The device for handling oil pipes provided by the present disclosure is able to achieve automatic handling of oil pipes, thereby decreasing labor intensity of operators, and improving working efficiency and safety factors of the work.

Abstract: Methods and apparatus for running a tubular into a wellbore. The method includes attaching a first member of a lifting coupling to a first tubular, and attaching a second member of the lifting coupling to a second tubular. The second tubular extends downward through an opening of a rotary station. The method also includes connecting together the first and second members of the lifting coupling, such that a weight of the second tubular is transmitted via the lifting coupling to the first tubular. The method further includes lowering the lifting coupling, the second tubular, and at least a portion of the first tubular through the opening, and disconnecting the second member from the first member. The method additionally includes moving the second member of the lifting coupling and the second tubular laterally, away from the opening.

Abstract: The exemplary embodiments relate to misalignment correction devices and methods for mitigating misalignment of a piece of oilfield equipment in or proximate an RCD. A rounded shoulder appears on a first surface within or proximate the RCD, and a socket profile appears on a second surface within or proximate the RCD. The second surface is configured to abut the rounded shoulder. The rounded shoulder is configured to rotate within the socket profile. Further, a floating joint may be implemented into or proximate the RCD and combined with the foregoing rotation mitigation features.

Abstract: Stable back pressure control devices are used to control fluid pressure in a wellbore to provide constant downhole pressure. Back pressure may be estimated from a correlation between the speed of a mud pump and the pressure exerted from the pump. Drilling plans disclosed herein provide for the continued operation of one or more back pressure control devices for providing constant bottomhole pressure when casing connections are being made.

Abstract: An off bottom flow diverter subassembly. A fronthead and shank each includes a central bore. One of the shank and the fronthead has an outer diameter configured to fit within the central bore of another of the fronthead and shank. The shank and fronthead are arranged to slide longitudinally with respect to each other and are limited from sliding out of contact with each other. At least one diverting flow passage is between adjacent sliding surfaces of the shank and fronthead. Sliding the fronthead and shank with respect to each other opens and closes the diverting flow passage. Application of a force, sufficient to open the diverting flow passage, to a drill string to which the subassembly is attached in a direction toward an opening of a hole being drilled causes the diverting flow passage to open and drilling fluid to flow out of the subassembly away from the bit.

Abstract: A feeding device is for a rotatable downhole tool. The feeding device is provided with several feeding wheels lying in a plane which is slanted relative to a plane which is perpendicular to the center axis of the downhole tool. A method is for feeding a downhole tool axially by the use of the feeding device, when working a portion of a surrounding pipe body.

Abstract: A casing cutting tool, to be disposed downhole in a casing string on a drillstring, for the cutting and/or milling of casing strings. The tool has a main body with a plurality of rotatable blades which can rotate between a first retracted position to a second position substantially at right angles to the main body. In this second position, cutting surfaces on the blades engage the casing wall, and rotation of the tool results in cutting of the casing. A plurality of stabilizing arms are rotatably attached to the main body. A link between the blades and the stabilizing arms forces the stabilizing arms to rotate outward when the blades rotate outward. The stabilizing arms are dimensioned to span the inner diameter of the casing string, while leaving clearance to rotate the tool. The outermost ends of the stabilizing arms are rounded to avoid cutting the casing and reduce drag.

Abstract: Methods of removing two or more isolation devices is provided. An example method includes introducing two or more isolation devices into a wellbore comprising at least two wellbore intervals. Each isolation device comprises a substance and each of the substances degrades within the wellbore. The degradation rate of each of the substances causes fluid communication to be restored between the wellbore intervals in a desired amount of time. The method further includes causing or allowing each of the substances to degrade.

Abstract: A severance tool for severing a target is described. The severance tool comprises a housing, a plurality of focused energetics, each focused energetic adapted to release energy in a preferred direction and a trigger mechanism adapted to detonate the focused energetics. The focused energetics are aligned such that, on impact with a target comprising a material, the energy released by one of said focused energetics cooperates with the energy released by another of said focused energetics to establish a separating force within the target material.

Abstract: An example whipstock assembly includes a whipstock providing a ramped surface and a longitudinal groove defined in the ramped surface. A lead mill is coupled to the whipstock with a shear bolt and providing one or more blades, and a bearing support is arranged within the longitudinal groove and provides opposing sidewalls that define a slot configured to receive one of the one or more blades and thereby prevent the lead mill from rotating with respect to the whipstock.

Abstract: A rotating locking device includes a locking arm, including a throughbore, coupled to a housing and axially rotatable relative to the housing. The rotating locking device also includes a plunger including a biasing profile disposed within the throughbore and a locking head coupled to a distal end of the locking arm, the locking head including a recess to at least partially receive the distal end of the locking arm. The rotating locking device further comprises a load pin that couples the locking head to the distal end of the locking arm and is configured to resist separation of the locking head and the locking arm when in a securing position. Axial translation of the plunger causes the biasing profile to engage the load pin and cause the load pin to transition to a breakaway position.

Abstract: Present embodiments of the disclosure are directed to a seal assembly for generating a seal between two opposing shear blades of a ram unit after shearing a tubular. The seal assembly may include at least a wiper, a sealing element, and an energizer. The wiper may clean a surface of a shear blade as the blade moves relative to the seal assembly. The sealing element may include an elastomeric material that can be deformed into engagement with the shear blade to generate the seal. The energizer may be a hard component that energizes the sealing element against the cleaned surface of the shear blade as the blade moves further relative to the seal assembly. The wiper may clean the sealing surface of the blade by removing debris from the surface prior to the energizer activating the seal.

Abstract: A method of performing an operation in a wellbore is provided. The method includes introducing a tool into the wellbore. The tool comprises a mandrel comprising a port; and a plug located within the port. The plug comprises at least a first material that partially or wholly dissolves via corrosion. The method further includes introducing a cement composition into an annulus located between the outside of the tool at least at the location of the port and the inside of the wellbore, and causing or allowing at least a portion of the first material to dissolve. The step of causing or allowing is performed after the step of introducing the cement composition.

Abstract: A method for fluid treatment of a borehole including a main wellbore, a first wellbore leg extending from the main wellbore and a second wellbore leg extending from the main wellbore, the method includes: running a wellbore tubing string apparatus into the first wellbore leg; conveying a plug into the wellbore tubing string apparatus to actuate a plug-actuated sleeve in the wellbore tubing string apparatus to open a port through the wall of the wellbore tubing string apparatus covered by the sleeve; employing a plug retainer to retain the plug in the tubing string against passing outwardly from the tubing string apparatus; allowing fluids to flow toward surface outwardly from the tubing string apparatus; and performing operations in the second wellbore leg.

Abstract: A helix nozzle oscillating tool that creates a fluid pattern with both spinning and acoustic/oscillating methods. The tool has no moving parts and its function is not limited by pressures, temperatures, volumes of fluid or fluid type. The tool more efficiently cleans out scale and debris build-up from a productive or formerly productive well, perforations and near region surrounding the well. The tool can be used in a variety of wells, including, but not limited to oil, gas, and wastewater wells.

Abstract: A system using a semi-tractor and the engine of the semi-tractor to heat a fluid from a cryogenic temperature to approximately room temperature while pressurizing the fluid is disclosed. The system is mounted on the frame of the semi-tractor and preserves the ability of the semi-tractor to haul a standard semi-trailer tanker. The system uses a semi-tractor having an internal combustion engine cooled by a liquid coolant, a cab with a sleeper section. The sleeper section is used as a control cabin for allowing an operator to monitor the operation of the system in the field. The frame includes a fifth wheel type coupler that is mounted forward of the rearmost wheel axle of the semi-tractor.

Abstract: A fracturing system is provided. In one embodiment, the fracturing system includes a fracturing manifold for routing fracturing fluid to multiple wells. The fracturing manifold can be coupled via fluid conduits to fracturing trees installed at the wells. In some cases, each fracturing tree that is coupled to the fracturing manifold is coupled by at least one rigid fluid conduit. The fracturing manifold can include a trunk line that provides fracturing fluid to multiple outlet branches, which can include valves for controlling flow of fracturing fluid to wells downstream of the valves. Additional systems, devices, and methods are also disclosed.

Abstract: A method for stabilizing a cavity at a production or injection zone in an underground well includes providing a filtering element in the well at the cavity that is to be stabilized. The filtering element is formed with openings. The method further includes injecting a first fluid including expandable particles through the filtering element into the cavity. The expandable particles have a non-expanded state with a diameter smaller than the diameter of the openings of the filtering element. The method further includes injecting a second fluid through the filtering element. The second fluid is configured to react with the expandable particles such that the expandable particles expand to a diameter larger than the diameter of the openings in the filtering element, whereby the expanded particles and the filtering element form a filter at the production or injection zone in the well.

Abstract: Embodiments of the present disclosure are directed towards a downhole slot cutter. The downhole slot cutter a housing of the downhole slot cutter configured to be inserted into a tubular positioned within a wellbore, and a plurality of dies supported by the housing, wherein the plurality of dies is configured to extend radially outward from the housing.

Abstract: A laser-jet apparatus for creating a penetration through a stress region adjacent to a wellbore includes an outer tool housing, the outer tool housing having a housing central bore. A laser assembly includes a lens case with an outer diameter that is smaller than an inner diameter of the housing central bore, defining an annular passage between the outer tool housing and the lens case. A focusing lens and a collimating lens are located within the lens case. The focusing lens is shaped to control the divergence of a laser beam and the collimating lens is shaped to fix the diameter of the laser beam. A jet fluid path is located in the annular passage, the jet fluid path shaped to merge jet fluid with the laser beam. The outer tool housing has a frusto-conical tip for directing the combined jet fluid and laser beam to the stress region.

Abstract: A repeatedly usable downhole pumping assembly including; a conduit comprising a plurality of pipes, wherein the pipes are uniformly entwined together along their length to provide multiple fluid passageways, wherein the conduit is to be wound onto a reel and off the reel repeatedly; a rotatably mounted reel, upon which the conduit is adapted to be wound without collapsing; a pump for pumping fluid through the conduit; and a driving means to lower and raise the conduit relative to the bore.

Abstract: A downhole tool, e.g., a plunger, and a method for manufacturing a plunger. The downhole tool includes a mandrel including a flow-restriction recess, and a plurality of sealing pads configured to be disposed around the mandrel, biased radially-outward therefrom, and interlocked with one another. Each of the plurality of sealing pads includes a flow-restriction tab having an axial thickness that varies as proceeding circumferentially around the mandrel. The flow-restriction tab of each of the plurality of sealing pads is configured to be disposed in the flow-restriction recess when the plurality of sealing pads are disposed on the mandrel.

Abstract: An apparatus, system and method for reducing gas to liquid ratios in submersible pump applications are described. A method for reducing a gas to liquid ratio (GLR) in a pumped fluid includes pumping a gas laden fluid to a surface of a subsurface formation using a downhole electric submersible pump (ESP) assembly including an ESP pump and an ESP motor, monitoring one of a load of the ESP motor, intake pressure of the ESP pump, temperature of the gas laden fluid, or a combination thereof to obtain ESP assembly condition data, determining whether a GLR of the gas laden fluid exceeds a predetermined allowable maximum based on the ESP assembly condition data, injecting liquid from an external source into the gas laden fluid, and varying a rate that the external liquid is injected based on the GLR so determined.

Abstract: A system and method for creating a controlled geyser well with sustained periodical production includes a cap (16) which prevents gas from entering a well tubing (14) while allowing liquid to enter and accumulate in the tubing, means for compressing the gas, and means for injecting the gas in the annulus so that the gas enters the bottom end of the well tubing (14), thereby creating a controlled geyser effect which blows out most of the liquid residing in the well tubing (14). The gas being compressed can be a produced gas or a supplied gas.

Abstract: A process of producing liquid oil from shale gas condensate reservoirs and, more particularly, to increase liquid oil production by huff-n-puff in shale gas condensate reservoirs. The process includes performing a huff-n-puff gas injection mode and flowing the bottom-hole pressure lower than the dew point pressure.

Abstract: A method of hydraulic fracturing geometry evaluation, comprising injecting a fracturing fluid comprising a magnetic material into a fracture, measuring a field affected by the fracturing fluid in the fracture, and modeling, based on the measuring, a geometry of the fracture.

Abstract: An oil recovery process is provided where an oil-water mixture is recovered from an oil-bearing formation. Oil is separated from the oil-water mixture to yield produced water. The produced water is typically subjected to a pre-treatment process. After pre-treatment, the produced water is directed to an evaporator that evaporates at least some of the produced water and produces steam and an evaporator blowdown. The evaporator blowdown is directed to a dual stage crystallizer that concentrates the evaporator blowdown.

Abstract: The invention provides a control system and method for limiting vibrations in a tool string system. The system comprises a pump connected to a rotatable tool string driven by a drive system. The control system comprises feedback of both torque and rotational speed signals into a controller. An objective of said controller is to maintain the drive speed over torque ratio equal to the connected tool string impedance (Z). A secondary objective, for lower frequencies, is to approach and maintain a setpoint speed as drive rotation speed. The system includes a rotational speed sensor and a torque sensor, with the latter optionally replaced by a motor torque signal already available from a variable frequency drive (VFD) for an AC motor and the current safeguarding signal for a DC motor.

Abstract: An excavation status monitoring system for a tunneling machine that includes a detecting portion mounted on a cutter head of the tunneling machine, including an accelerometer that detects a vibration or an acoustic sensor that detects a sound wave and a sound output portion that outputs a signal detected by the detecting portion as sound.

Abstract: Calibrating Friction Factors. At least some of the illustrative embodiments are methods including: calibrating friction factor for a drilling operation by: plotting on a display device the expected hook load versus depth for the drilling operation; displaying plot points on the display device, each plot point indicative of a measured hook load versus depth for the drilling operation; selecting a plot point associated with a depth, the selecting responsive to a cursor hovering over the plot point on the display device; displaying a friction factor values which correlates the expected hook load versus depth for the particular depth to the measured hook load versus depth for the plot point, selecting the value responsive to the cursor hovering over the value; and then shifting on the display device at least a portion of the indication of expected hook load versus depth based on the value of friction factor.

Abstract: A validation tool (100) has a central body member (10) with threaded connections at each end (12, 13), as well as a central bore (11) extending there through. At least one battery powered video camera (20) or other optical data sensor is disposed along an outer surface of the body member and can be selective activated and de-activated. Optional mirror(s) (50) are provided to permit optimum viewing of the surrounding environment, while visual images and/or other sensed data is recorded and stored on at least one data storage media. The validation tool can be used for various purposes including wellbore integrity and verification that drilling mud has been fully displaced with completion fluid in a wellbore.

Abstract: A technique facilitates monitoring of strain related effects along a tubing string, such as a tubing string extending from surface equipment toward a sea floor in a subsea well application. A monitoring module is employed to monitor the strain related effects and may have a tubular structure. The monitoring module also has a reduced wall thickness region constructed to concentrate strain in this reduced wall thickness region. Additionally, the monitoring module comprises at least one sensor mounted to the tubular structure in the reduced wall thickness region for monitoring of strains.

Abstract: The subject matter of this specification can be embodied in, among other things, a system for mounting a strain sensor on a tubular pipe, which includes a mechanical clamp. The clamp has a bottom flexing section having an arcuate portion terminating at a first terminal and at a second end, and a first and second upper flexing sections having an arcuate portions terminating at first terminal ends and at second terminal ends in a pivot pin assembly having a bore parallel to a central longitudinal axis of the clamp, the bore there through for receiving a removable connector. Sensor mounting arms are disposed outwardly on the first and second upper flexing sections, said sensor mounting arms including at least one receptacle sized to receive and retain ends of a strain gauge.

Abstract: A wellbore tool includes a cooling section positioned within the tool for the purpose of maintaining the temperature sensitive components within their rated operating temperature range. The cooling section includes an evaporator, compressor, condenser, power device, expansion device. The compressor is positioned within the condenser. The components whose temperatures are to be maintained are in thermal contact to the evaporator. The cooling process is based upon the vapor compression cycle.

Abstract: A system for drilling at least one well of interest proximate a reference well comprises at least one sensor in a drill string in the at least one well of interest to detect at least one parameter of interest related to a distance and a direction to the reference well. A controller is operatively coupled to the at least one sensor to determine the distance and the direction from the sensor to the reference well based at least in part on the at least one detected parameter of interest. A steerable assembly is operatively coupled to the controller to receive commands from the controller to adjust the path of the at least one well of interest being drilled based at least in part on the distance and direction from the sensor to the reference well.

Abstract: A method for creating a second borehole in an earth formation at a selected orientation relative to a first borehole, wherein a position parameter represents a position of the first borehole. The method comprises: a) providing a borehole element that generates a magnetic field; b) measuring the magnetic field; c) installing the borehole element in the first borehole; d) measuring the magnetic field in the second borehole; e) providing a finite element model of the magnetic field; f) calculating the magnetic field in the second borehole using the finite element model, and determining a difference between the calculated magnetic field in the second borehole and the measured magnetic field in the second borehole; g) adjusting the position parameter so as to minimize said difference; and h) determining a selected direction dependent on the adjusted position parameter and further drilling the second borehole in the selected direction.

Abstract: A method to perform a drilling operation. The method includes calibrating an axial survey sensor of a bottom hole assembly (BHA) by obtaining, from the axial survey sensor, a data log as a first function of azimuthal angle within a borehole, generating, by a computer processor of the BHA and using a pre-determined algorithm, a fitted curve as a second function of the azimuthal angle, wherein the fitted curve is generated based on the data log to represent a calibration error of the axial survey sensor, and extracting, by the computer processor of the BHA, a calibration parameter from the fitted curve. Accordingly, the drilling operation is performed using at least the axial survey sensor based on the calibration parameter.

Abstract: A bend angle sensing assembly for determining a downhole bend angle of a downhole adjustable bent housing. The bend angle sensing assembly includes a flow diverter having a plurality of diverter apertures for receiving drilling fluid, the flow diverter orientable to a plurality of diverter configurations in dependence on the bend angle of the associated downhole adjustable bent housing. Each of the plurality of diverter configurations have one or more of the plurality of diverter apertures opening or closing to form a corresponding flow path configuration, each flow path configuration having a different flow area whereby the pressure of the drilling fluid changes for each flow path configuration. Additionally, a pressure sensor is communicatively coupled to the drilling fluid.

Abstract: There is provided a thin-bottom type bore gauge having damping unit between a gauge head and a head main body part, and a long life. A head part of a bore gauge includes a head main body part, a measurement spherical face at one end face, and a gauge head slidably provided by penetrating an inside and an outside of the head main body part. The gauge head a spring holding groove carved in a circumferential direction at the other end side, and a compression coil spring is interposed between the spring holding groove and an inside end face of the head main body part.

Abstract: A selective locking apparatus for an indicating tool, the selective locking apparatus includes a mandrel having a rotational collet finger receiving area including a plurality of unlocked-position tracks alternatingly arranged with a plurality of locked-position detents. A rotational collet rotatably supported on the mandrel, the rotational collet including a j-track on an outer periphery of the rotational collet, the rotational collet further including a plurality of rotational collet fingers having heads engageable within the rotational collet finger receiving area of the mandrel.

Abstract: A method for transmitting data from a downhole tool is provided. In one embodiment, the method includes acquiring data for a formation fluid through downhole fluid analysis with a downhole tool in a well. The acquired data can include optical spectrum data measured with a spectrometer and other data. The method also includes generating time blocks of the acquired data and transmitting the time blocks from the downhole tool. More particularly, generating the time blocks may include compressing at least some of the optical spectrum data according to a first compression technique and compressing at least some of the other data according to one or more additional compression techniques. The compressed data can be packaged into the time blocks such that at least some of the time blocks include both compressed optical spectrum data and compressed other data for the formation fluid. Additional methods, systems, and devices are also disclosed.

Abstract: Wellbore tools in accordance with the present disclosure may include a gas chromatograph; and a mass spectrometer, wherein the mass spectrometer is configured to operate at a pressure greater than 10?2 Torr. Systems in accordance with the present disclosure may include a gas chromatograph; and a mass spectrometer, wherein the mass spectrometer is configured to operate at a pressure greater than 10?2 Torr. Methods in accordance with the present disclosure may include emplacing a wellbore tool in a wellbore, the wellbore tool containing a gas chromatograph and a mass spectrometer, wherein the mass spectrometer is configured to operate at a pressure greater than 10?2 Torr; drawing a sample of a fluid from the wellbore into the wellbore tool; and determining a molecular weight of one or more components of the fluid.

Abstract: The present disclosure relates to a mobile mining machine which may comprise a movable machine base frame, a rotatable tool drum and including excavating tools. The mobile mining machine may further comprise a cantilever unit including a front support arm part and a base part, and a pivotal device to pivot the cantilever unit. The mobile mining machine may further comprise a tilt device to tilt the cantilever unit and a rotary mechanism to rotate the support arm part and the tool drum. Thus, a mobile mining machine with which tunnels, galleries or shafts may be continuously driven in even in hard rock with a high mining output and low tool wear may be provided.

Abstract: A radial piston device includes a housing and a pintle fixed thereto that includes an inlet and an outlet, each aligned with a pintle axis. A rotor is rotatably disposed around the pintle and includes radially oriented cylinders. A piston is axially displaceable in each cylinder and includes a head defining a spherical contact surface. A thrust ring is rotatably disposed within the housing about the rotor and is in contact with each piston, such that a rotation of the rotor rotates the thrust ring. An inner surface of the thrust ring defines a toroidal contact surface. A contact location between the spherical contact surface and the toroidal contact surface varies as the rotor rotates about the pintle. A drive shaft is engaged with the rotor, such that a rotation of the rotor rotates the drive shaft.

Abstract: An axial piston machine (1) is shown, comprising: a shaft (2) having an axis (3) of rotation, a cylinder drum (4) connected to said shaft (2) and having at least a cylinder (5) parallel to said axis (3) of rotation, a piston (6) movable in said cylinder (5), a swash plate (13), a slide shoe (11) pivotally mounted to said piston (6), and holding means holding said slide shoe (11) against said swash plate (13), said holding means having a pressure plate (14) and a number of coil springs (15) arranged between said cylinder drum (4) and said pressure plate (14). The object is to have a reliable operation of said machine with a simple construction. To this end each coil spring (15) is at least at one end fixed by a protrusion (20) extending into said coil spring (15).

Abstract: In order to suppress the damage and the degradation in durability of a bearing of an expander, simplify the configuration of the expander, and reduce the manufacturing cost thereof, an expander of the present invention includes an expander rotor that is rotationally driven by an expanding force transmitted from vapor of a working medium introduced into an expansion chamber and a first bearing that supports a first rotation shaft of the expander rotor to a vapor inlet, a casing includes therein first bearing chambers that have a pressure lower than that of the vapor inlet and accommodate the first bearing, and a passage that leads lubricant to a low-pressure portion having a pressure lower than that of the first bearing chamber is connected to a position above the lowermost portion of the first bearing in the first bearing chamber.

Abstract: Efficient energy storage is provided by using a working fluid flowing in a closed cycle including a ganged compressor and turbine, and capable of efficient heat exchange with heat storage fluids on a hot side of the system and on a cold side of the system. This system can operate as a heat engine by transferring heat from the hot side to the cold side to mechanically drive the turbine. The system can also operate as a refrigerator by mechanically driving the compressor to transfer heat from the cold side to the hot side. Heat exchange between the working fluid of the system and the heat storage fluids occurs in counter-flow heat exchangers. In a preferred approach, molten salt is the hot side heat storage fluid and water is the cold side heat storage fluid.

Abstract: A ceramic component retention system includes a metallic component, a ceramic component, and at least one spring element arranged between the metallic component and the ceramic component. The metallic component has a first coefficient of thermal expansion, and the ceramic component has a second coefficient of thermal expansion. The at least one spring element is configured to mechanically couple the ceramic component to the metallic component.

Abstract: A method of balancing a spool of a gas turbine engine, the spool including a forward rotor assembly and an aft rotor assembly separated by a spacer, the method comprising: balancing the forward rotor assembly and the aft rotor assembly independently from one another using conventional balancing techniques; and mathematically modeling the spool; applying a modeled axial load to the modeled spool to determine a trim weight which would balance the spool when subjected to the modeled axial load; and physically placing the trim weight to one of the forward rotor assembly and the aft rotor assembly.