Patent Description:
Drilling fluid (often called drilling mud) is used by various drilling systems to aid in the drilling of boreholes into the earth. One example of a drilling system that uses drilling fluid is a HDD. In a HDD, used drilling fluid is pumped by a pit pump in a recycling system which recycles the drilling fluid for re-use. The pit pump can be disposed in either the exit pit or the entry pit (or there can be a pump in each pit) where the used drilling fluid collects. During operation the pit pump is typically submerged within the drilling fluid.

During a drilling process, a conventional pit pump often needs to be lifted from the pit for servicing of the pit pump. For example, the drilling fluid typically cakes on the exterior of the pump creating an insulating shell that can prevent dissipation of heat from the pump motor. In addition, the inlet of the pit pump can often become blocked by rocks and other particulate material that is carried by the drilling fluid from the borehole. However, servicing of the pit pump is time consuming and results in down time of the drilling operation. Document <CIT> describes a forced closed-loop cooling for a submersible pump motor. Document <CIT> describes a submergible pump. Document <CIT> describes a situ system and method for treating an oil and gas well drilling fluid. Document NO <CIT> describes a method for treating waste substances for injection into underground formations.

A pit pump is described herein that is configured to permit the pit pump to remain disposed within the pit and submerged in the drilling fluid for long periods of time, thereby reducing or eliminating the need to remove the pit pump from the pit for servicing. The pit pump can be used in any drilling fluid recycling system. A drilling fluid recycling system can be used with many types of drilling systems that use drilling fluid while drilling boreholes in the earth. For example, the drilling fluid recycling system can be used with a HDD. The pit pump according to the invention is as defined in claim <NUM>. Claim <NUM> also defines a drilling fluid recycling system. comprising the pit pump.

The pit pump is driven by a liquid cooled electric drive motor. In an embodiment, a liquid is in direct contact with the electric drive motor to cool the electric drive motor, and the cooling liquid is circulated to an external heat exchanger located outside of the pit to cool the cooling liquid before being returned back to the electric drive motor. The pit pump can stay submerged in the drilling fluid within the pit indefinitely since the pit pump does not require removal of caked-on drilling fluid to prevent overheating of the electric drive motor since the cooling liquid cools the electric drive motor. Further, the liquid cools the electric drive motor even if the pump is stalled.

The electric drive motor can be any electric drive motor that is liquid cooled. In one embodiment, the electric drive motor can be a bi-directional permanent magnet motor. Because the motor is bi-directional, the rotation direction of the pump impeller can be reversed. Reversal of the rotation direction can be useful to help clear away material that may be blocking or impeding flow through the pump inlet. In particular, the discharge hose of the pump normally holds a certain amount of head volume and pressure while pumping. If the pump impeller is reversed, the head volume and pressure is released back out of the inlet of the pump thereby dislodging any material that may be lodged in the inlet.

In another embodiment, the pit pump can be configured to permit remote, electronic monitoring of the pit pump. For example, one or more of the motor temperature, temperature of the cooling liquid, motor torque, revolutions per minute of the electric motor and/or of the impeller, horsepower, and vibrations of the electric motor and/or of the pump impeller, and other variables can be monitored. Non-pump variables such as the weight of the drilling fluid, viscosity, head pressure, and the length of the hose connected to the outlet of the pit pump can also be measured. The operation of the pit pump can also be remotely controlled, either wirelessly or via a physical connection via a tether or a wire. The pit pump can include a controller thereon that receives readings from one or more sensors.

In one embodiment, readings concerning the motor torque, the revolutions per minute of the electric drive motor, the horsepower being provided by the electric drive motor, the drilling fluid weight and the hose length can be used together to determine or calculate the volume of the drilling fluid being pumped. This permits the operator to calculate the volume without using a mechanical flow meter or ultrasonic sensor. In some embodiments, one or more sensors can be provided, for example at or near the outlet of the pump, to sense an actual volume being output which can then be used to validate the determined/calculated volume. In addition, the weight of the drilling fluid in the pump output can be calculated based on the torque on the electric drive motor.

Referring to <FIG>, a drilling system <NUM> is illustrated in which a pit pump <NUM>, forming part of a drilling fluid recycling system, described herein can be used. The drilling system <NUM> can be any type of drilling system that drills boreholes in the earth and in which a drilling fluid (or drilling mud) is used to aid in the drilling process. For sake of convenience in facilitating this description, the drilling system <NUM> will be described as being a horizontal directional drilling (HDD) system. However, the drilling system <NUM> could be a vertical drilling system or other type of drilling system.

The pit pump <NUM> is part of a drilling fluid recycling system that is used to recycle used drilling fluid for re-use during a borehole drilling operation. Used drilling fluid from the drilling operation, mixed together with solids from the borehole, can collect in a pit <NUM>, which can be an exit pit or an entry pit, with the used drilling fluid mixed with solids then being pumped by the pit pump <NUM> to a drilling fluid recycler where the used drilling fluid is processed to remove the solids and to make the drilling fluid otherwise suitable for reintroduction back into the borehole. The construction and operation of a drilling fluid recycling system is well known in the art. The pit <NUM> is illustrated as having used drilling fluid <NUM> therein, and the pit pump <NUM> is disposed in the pit <NUM> so that the pit pump <NUM> is at least partially submerged in the used drilling fluid <NUM>. Typically, the pit pump <NUM> will be completely submerged in the used drilling fluid <NUM> as is illustrated in <FIG>.

As will be discussed in further detail below, the pit pump <NUM> can be driven by an electric drive motor, and a cooling liquid is used to cool the electric drive motor. The cooling liquid is circulated between the pit pump <NUM> and an external heat exchanger <NUM> by a cooling liquid supply pipe (or hose) <NUM> and a cooling liquid return pipe (or hose) <NUM>. One or more pumps <NUM> can be provided for circulating the cooling liquid in the closed coolant loop. For example, the pump <NUM> can be provided in the supply pipe (or hose) <NUM> within or outside the drilling fluid <NUM>, in the return pipe (or hose) <NUM> within or outside the drilling fluid <NUM>, in the heat exchanger <NUM> or in the pit pump <NUM> itself. The heat exchanger <NUM> is located outside the pit <NUM>, and is configured to cool the cooling liquid before the cooling liquid is returned back to the pit pump <NUM> to cool the electric drive motor. The heat exchanger <NUM> can be configured as, for example, a liquid-to-air heat exchanger or a liquid-to-liquid heat exchanger.

In addition, electrical energy for powering the electric drive motor of the pit pump <NUM> can be provided via a power line <NUM> from a controller <NUM> that is configured to control operation of the pit pump <NUM> and the heat exchanger <NUM>. In addition, various data signals can be transmitted over a data line <NUM> between the pit pump <NUM> and the controller <NUM>. Electrical energy for powering operation of the various mechanisms described herein can be supplied from a suitable electric power supply <NUM>. Data and power lines <NUM> can also be provided between the controller <NUM> and the heat exchanger <NUM> to direct electrical power to the heat exchanger <NUM>, to control operation of the heat exchanger <NUM>, and to send data signals from the heat exchanger <NUM> to the controller <NUM>.

The electric power supply <NUM> can be any supply that is suitable for providing electrical power to the pit pump <NUM>. In one embodiment, the power supply <NUM> can be an electrical generator. In another embodiment, the power supply <NUM> can be line power obtained from an available electrical power line. In addition, two power supply sources can be provided with one power supply acting as a back-up in case of failure of the first or primary power supply.

The system <NUM> can further include a HDD rig <NUM> that is separate from the drilling fluid recycling system. The HDD rig <NUM> can have any configuration that is suitable for performing horizontal directional drilling.

One embodiment of the pit pump <NUM> is illustrated in <FIG>. In this embodiment, the pit pump <NUM> includes a pump portion <NUM> and a drive motor portion <NUM> that is suitably coupled to the pump portion <NUM> to drive the pump portion to perform a pumping operation on the used drilling fluid <NUM>. The portions <NUM>, <NUM> are detachably interconnected to one another to permit removal of any one of the portions <NUM>, <NUM> and replacement with a different portion <NUM>, <NUM> or the same portion <NUM>, <NUM>, for example after being serviced.

The pump portion <NUM> can have any configuration that is suitable for pumping the used drilling fluid <NUM> mixed with solids. The pump portion <NUM> will have an inlet, generically designated as <NUM>, through which the used drilling fluid enters the pump portion <NUM> and an outlet, generically designated as <NUM>, through which the used drilling fluid exits the pump portion <NUM>. The pump portion <NUM> also includes a pump impeller <NUM> or other motive device for pumping the used drilling fluid from the inlet <NUM> to the outlet <NUM>. One example of a suitable pump configuration includes, but is not limited to, a centrifugal pump with the inlet <NUM> being an axial inlet, the outlet <NUM> being a radial or tangential outlet, and the pump impeller <NUM> being rotatably mounted in the pump portion <NUM>. However, other pump configurations can be used.

With continued reference to <FIG> along with <FIG>, the drive motor portion <NUM> comprises an optional housing <NUM> that defines an interior space in which an electric drive motor <NUM> is disposed for driving the pump impeller <NUM>. The electric drive motor <NUM> is powered by electricity provided from the electric power supply <NUM> and the controller <NUM>. The electric drive motor <NUM> is also reversible in rotation direction in order to be able to reverse the rotation direction of the pump impeller <NUM>. Reversing the direction of rotation of the pump impeller <NUM> can help to clear away material that may be blocking or impeding flow through the pump inlet <NUM> or through the impeller <NUM>. In particular, during pumping the outlet <NUM> of the pump portion <NUM> holds a certain amount of head volume and pressure from the drilling fluid and perhaps other material entrained in the drilling fluid. If the pump impeller <NUM> is reversed, the head volume and pressure is released back out the inlet <NUM> of the pump portion <NUM> thereby dislodging any material that may be lodged in the inlet <NUM> or in the impeller <NUM>.

The electric drive motor <NUM> can be any drive motor that can be reversed in rotation direction. In one embodiment, the electric drive motor <NUM> can include a bi-directional permanent magnet drive motor which permits reversal of the rotation direction. However, other electric drive motors are possible. In addition, as discussed in further detail below, the electric drive motor <NUM> is configured to be cooled by a suitable cooling liquid, such as, but not limited to, a <NUM>/<NUM> water/ethylene glycol mix, that is circulated through the electric drive motor <NUM>. Liquid-cooled electric drive motors are known in the art.

Referring to <FIG>, the electric drive motor <NUM> includes a motor housing <NUM> that houses the motor components. The housing <NUM> includes a cooling liquid inlet <NUM> through which the cooling liquid can be input for cooling the motor components, and a cooling liquid outlet <NUM> through which the cooling liquid can be output after cooling the motor components. A coolant hose <NUM> is within the interior space of the housing <NUM> and is connected between the inlet <NUM> and the supply pipe (or hose) <NUM> (<FIG>) to direct cooling liquid from the heat exchanger <NUM> after being cooled into the motor housing <NUM>. Similarly, a coolant hose <NUM> is within the interior space of the housing <NUM> and is connected between the outlet <NUM> and the return pipe (or hose) <NUM> (<FIG>) to direct cooling liquid back to the heat exchanger <NUM> to be cooled after absorbing heat in the drive motor <NUM>. The cooling liquid cools the drive motor <NUM> during normal operations of the drive motor as well as during abnormal operations of the drive motor <NUM>, for example if the pump is stalled.

In one embodiment best seen in <FIG>, the supply pipe/hose <NUM> and the return pipe/hose <NUM> can be disposed within a common umbilical <NUM> extending from the housing <NUM> which protects the pipes/hoses <NUM>, <NUM> from damage. However, the supply pipe/hose <NUM> and the return pipe/hose <NUM> do not need to be disposed in the umbilical <NUM>. The data line <NUM> may also be disposed within the umbilical <NUM>. In addition, electrical energy for powering the drive motor <NUM> is routed to the drive motor portion <NUM> via a power umbilical <NUM> extending from the housing <NUM> and in which the power line <NUM> is disposed to protect the power line <NUM> from damage. In another embodiment, all of the data lines and the power lines can be disposed in a single umbilical.

The drive motor <NUM> includes a drive shaft <NUM> (shown in dashed lines in <FIG>) that is suitably coupled to the pump impeller <NUM> using coupling techniques known in the art.

Referring to <FIG> and <FIG>, the operation or performance of various components of the pit pump <NUM> can be electronically monitored and/or operation of the drive motor <NUM> can be controlled. Data from various sensors and/or for controlling operation of the drive motor <NUM> can be transmitted between the controller <NUM> and the pit pump <NUM> via the data line(s) <NUM> within the umbilical <NUM> (and/or within the umbilical <NUM>). Data can also be transmitted between the heat exchanger <NUM> and the controller <NUM>.

For example, one or more of the following parameters can be monitored by suitable sensors: temperature of the drive motor <NUM>, temperature of the cooling liquid used to cool the drive motor <NUM>, torque of the drive motor <NUM>, revolutions per minute of the drive motor <NUM> and/or of the impeller <NUM> (and/or the shaft <NUM>), horsepower, and vibrations of the drive motor <NUM> and/or of the pump impeller <NUM>. Non-pump variables such as the weight of the used drilling fluid <NUM>, viscosity, head pressure, and the length of the hose connected to the outlet <NUM> of the pump portion <NUM> can also be measured. Moisture in the housing <NUM> (if present) may also be monitored using one or more sensors. The types of sensors necessary to monitor these parameters are well known in the art. Data from the sensors is routed to the controller <NUM> (and/or routed to an internal controller of the pump described further below) which can monitor the parameters to determine the health of the individual components and how the pit pump <NUM> is operating. This permits the performance parameters of various elements of the pit pump <NUM> to be monitored, and if the monitoring determines that an element is not operating correctly, maintenance can be scheduled to replace or repair the element and/or the sensors. Additional sensors can also be added as needed in order to monitor other parameters.

With reference to <FIG>, in another embodiment, a controller <NUM> can be incorporated onto the pump <NUM>, for example located on or within the housing <NUM> or located on the drive motor <NUM> itself. Signals from the various sensors monitoring the pump <NUM> can be routed to the controller <NUM> which in turn can direct signals outside the pump <NUM> as well as receive signals, such as control signals for controlling operation of the pump <NUM>, from outside the pump <NUM>.

In still another embodiment, a power converter <NUM>, such as a DC to AC inverter that converts DC power to AC power or an AC to DC inverter that converts AC power to DC power, can be incorporated onto the pump <NUM>. For example, the power converter <NUM> can be located on or within the housing <NUM> or located on the drive motor <NUM> itself. If present, the power converter <NUM> can be connected to the power line <NUM> to convert incoming electrical power into the appropriate form for use by the pump <NUM>.

<FIG> illustrates an example of the drilling system that includes a drilling fluid recycling system <NUM> with the pit pump <NUM> in use with HDD rig <NUM>. The drilling fluid recycling system <NUM> is a separate system from the HDD rig <NUM> or other drilling system, and is used to recycle the drilling fluid that is used during drilling operations of the HDD rig <NUM>, and after cleaning the drilling fluid the cleaned drilling fluid is passed through the HDD rig <NUM> for reintroduction back into the borehole. The drilling fluid recycling system <NUM> typically does not control any operations of the HDD rig <NUM>, and the HDD rig <NUM> typically does not control any operations of the recycling system <NUM>. The recycling system <NUM> includes a drilling fluid recycler <NUM> that receives drilling fluid to be recycled from the pump <NUM>. In an example drilling operation, the HDD rig <NUM> drills a borehole <NUM> aided by the drilling fluid <NUM> which is pumped down the borehole <NUM> by the recycling system <NUM>. The used drilling fluid <NUM> together with solids resulting from the drilling operation are ultimately returned to the pit <NUM> where the pit pump <NUM> is disposed. The pit pump <NUM> pumps the used drilling fluid mixed with solids to the drilling fluid recycler <NUM>. In some embodiments, an optional pump <NUM> (shown in dashed lines) can be disposed between the pump <NUM> and the recycler <NUM>, for example in-line, to aid in pumping the used drilling fluid to the recycler <NUM> for recycling. The recycler <NUM> removes the solids in a known manner, with the removed solids <NUM> being collected. The cleaned drilling fluid is then pumped through the HDD rig <NUM> on its way back into the borehole <NUM>. While the pit pump <NUM> is operating, the cooling liquid is circulated from the heat exchanger <NUM> located outside the pit <NUM>, through the cooling liquid inlet <NUM>, through the motor housing <NUM> and out through the cooling liquid outlet <NUM> and back to the heat exchanger <NUM> to cool the cooling liquid before being returned back to the motor housing <NUM> to continue the cooling cycle.

In one embodiment, the volume of the used drilling fluid mixed with solids pumped by the pit pump <NUM> and the volume of the cleaned drilling fluid pumped back into the borehole <NUM> can be determined. The difference between these two volumes provides a determination as to the amount of solids being removed from the borehole <NUM>. A significant difference in the volumes of the used and cleaned drilling fluids can provide an indication of possible leakage of the drilling fluid, for example within the borehole <NUM>, in the pit <NUM>, or elsewhere in the path of the drilling fluid. In addition, the amount of solids being removed provides an indication of the drilling operation and whether the borehole <NUM> is clean enough.

The volume of the used drilling fluid mixed with solids pumped by the pit pump <NUM> and the volume of the cleaned drilling fluid pumped into the borehole <NUM> can be determined using any suitable techniques. For example, mechanical flow meters can be provided at suitable locations at or near the output of the pit pump <NUM> and at or near the output of the downhole pump. In another embodiment, one or more of the volumes can be determined mathematically using variables and parameters measured from various components of the system. In an embodiment, one or more sensors <NUM> (seen in <FIG>) can be provided at or near the outlet of the pump <NUM>. The sensor(s) <NUM> is used to detect a volume of the fluid being pumped by the pump <NUM>. The volume of fluid detected by the sensor <NUM> can then be used to compare against a calculated volume pumped by the pump <NUM> to validate the calculated volume amount. In addition, the torque on the electric drive motor <NUM> can be detected and used to calculate an estimated weight of the drilling fluid in the output of the pump <NUM>.

Claim 1:
A pit pump (<NUM>) to be used within a pit (<NUM>) containing drilling fluid (<NUM>) for use with drilling operations performed by a drilling system (<NUM>), the pit pump comprising:
a pump portion (<NUM>) with an inlet (<NUM>), an outlet (<NUM>), and a pump impeller (<NUM>) for pumping drilling fluid (<NUM>) from the inlet to the outlet;
an electric drive motor (<NUM>) in driving engagement with the pump impeller to drive the pump impeller, the electric drive motor includes a motor housing (<NUM>);
a cooling liquid inlet (<NUM>) in the motor housing through which a cooling liquid can be input for cooling the electric drive motor; and
a cooling liquid outlet (<NUM>) in the motor housing through which cooling liquid can be output after cooling the electric drive motor; characterized in that
the electric drive motor (<NUM>) is reversible whereby a rotation direction of the impeller (<NUM>) can be reversed and a flow of fluid through the pump portion (<NUM>) can be reversed.