Abstract: Methods and apparatus are disclosed for conveying an electrically energized hydraulic pump into a wellbore surrounded by steel casing and thereafter using that hydraulic pump to pump oil, water and gas to the surface of the earth. The apparatus may be used as a well tractor conveyance system to service a perforated steel cased wellbore located in a geological formation that incorporates means to prevent any reverse fluid flow into the geological formation through any perforations in the steel cased wellbore during movement within the wellbore of the tractor conveyance means.

Abstract: A method and apparatus for controlling the production of well treatment fluid is disclosed. The apparatus includes: a sand system, a water system, a pumping system, a blender tub, and a virtual rate control system. The method includes determining an output rate from a sand system; sensing an output rate from a water system; sensing an output rate from a pumping system; sensing the height within a blender tub of a mixture of sand from the sand system and water from the water system; providing a virtual rate control system; and producing a drive signal to the pumping system using the virtual rate control system using a desired rate of well treatment fluid to be delivered to a well, the output rate of the sand system, the output rate of the water system, and the output rate of the pumping system.

Abstract: Embodiments of the present invention generally relate to a cable suspended pumping system. In one embodiment, a method of producing fluid from a reservoir includes deploying a pumping system into a wellbore to a location proximate the reservoir using a cable. The pump assembly includes a motor, an isolation device, a pump, and a power conversion module (PCM). The method further includes setting the isolation device, thereby rotationally fixing the pumping system to a tubular string disposed in the wellbore and isolating an inlet of the pump from an outlet of the pump; supplying a DC power signal from the surface to the PCM via the cable; and supplying a second power signal to the motor, thereby operating the pump and pumping reservoir fluid from the reservoir to the surface.

Abstract: A submersible pumping system for use downhole, wherein the system includes a pump, an inlet section for receiving fluid, a pump motor, and an actively controlled flow restriction device for controlling flow to the submersible pump from an upper fluid producing zone. Active flow control proximate to the submersible pump motor protects the pump motor from overheating.

Abstract: A method for operating a downhole oil water separator and electric submersible pump includes measuring fluid pressure proximate one of the pump intake, separator intake and a bottom of a wellbore. At least one of flow rate and pressure is measured at the separator water outlet. Pump and a water outlet restriction are controlled to maintain an optimum fluid pumping rate and an optimum injection rate of separated water. A flow control system includes a controllable valve disposed in a water outlet of the separator. At least one of a pressure sensor and a flowmeter is operatively coupled to the water outlet. A controller is in signal communication with the at least one of a pressure sensor and flowmeter and in operative communication with the valve. The controller operates the valve to maintain at a selected pressure and/or a selected flow rate through the water outlet.

Abstract: Embodiments of the present invention generally relates to methods and apparatus for operating an artificial lift well. In one embodiment, the well is operated between an on cycle and an off cycle. Preferably, the off cycle is determined by detecting an increase in the pressure differential between the casing pressure and the tubing pressure. In another embodiment, the well is optimized by measuring the production of the well in one cycle of operation. The measured production is compared to the production of a previous cycle. A controller then optimizes the well based on the increase or decrease of the production from the previous cycle.

Abstract: A well system is provided and configured for local and/or global control of a well. The well system may comprise one or more controllable downhole devices. Each of the downhole devices may include a telemetry module, an energy module configured to at least power an actuator, a controller communicably coupled to the telemetry module and one or more sensors, and a controllable component coupled to the actuator. The well system may further include a surface controller comprising a desired state input device configured to accept a desired state and then provide the desired state to the controller via the telemetry module. The controller may compare the desired state to an actual state determined by a sensor and instruct the actuator to adjust the controllable component such that the actual state approaches the desired state. The downhole device may operate autonomously after the initial setting of the desired state.

Abstract: A device, method, and program product detect and break an occurrence of gas lock in an electrical submersible pump assembly in a well bore based upon surface or downhole data without the need for operator intervention. The system provides the ability to flush the pump and return the system back to production without requiring system shutdown. In addition, the system provides an algorithm for controlling a pump operating speed of the electrical submersible pump assembly to maximize production from the well bore.

Abstract: Method for organizing computer operations on a system of parallel processors to invert electromagnetic field data (11) from a controlled-source electromagnetic survey of a subsurface region to estimate resistivity structure (12) within the subsurface region. Each data processor in a bank of processors simultaneously solves Maxwell's equations (13) for its assigned geometrical subset of the data volume (14). Other computer banks are simultaneously doing the same thing for data associated with a different source frequency, position or orientation, providing a “fourth dimension” parallelism, where the fourth dimension requires minimal data passing (15). In preferred embodiments, a time limit is set after which all processor calculations are terminated, whether or not convergence has been reached.

Abstract: Methods and systems for removing water from gas wells are described herein. The water is removed by positioning a pump in a liquid layer below the perforations through which gas enters a gas well and powering a water pump with electrical power generated by an energy recovery system which produces electricity from a gas flow through the energy recovery system to an earth surface.

Abstract: A transmitter generates an acoustic ping in a fluid in a borehole, and a receiver monitors waves resulting from the acoustic ping. Responsive to the monitored waves, an attribute of the fluid is estimated, including a sonic velocity, a mixture of gas and oil, a mixture of water and oil, an amount of sand, an amount of gas, an amount of skin effect, or a depth of fluid. An operation of the artificial lift device is then controlled responsive to the estimated attribute. Alternately, a sonic velocity is estimated for the fluid through an analysis of a sample pumped to the surface or through an analysis of monitored waves. A depth of the fluid is calculated responsive to the estimated sonic velocity for the fluid in the borehole and the monitored T-waves. The operation of the artificial lift device is then controlled responsive to the calculated depth of fluid.

Abstract: An automated closed loop flowback and separation system that allows automated control and remote operation of a flowback operation from a safe distance without any fluid or gas release to the atmosphere. Four-phase separation tanks allow the transport gas, well bore cuttings, produced oil, and produced water to be automatically separated and transported through process piping for reuse or sale, eliminating the need for auxiliary equipment. Flow measurement instruments, pressure transmitters, and level transmitters work in conjunction with an automated blast choke to send data to a programmable logic controller for use in calculating the erosion status of the choke restriction and adjusting the choke to compensate. The programmable logic controller works with a touch-screen or similar human-machine interface to allow remote monitoring and control or automated control of the system. The automated blast choke can vary the choke restriction opening based on the pressure differential and flow rate conditions.

Abstract: Method for reservoir surveillance using a three-dimensional Earth Model (101) to improve and expedite the surveillance at all scales of investigation (field, reservoir, fault compartment, and individual well) and at all time steps (minutes, hours, days, months, years). The new method allows users to rapidly identify anomalous field and well performance (109) and provides capability to investigate root causes of the performance deviation from predicted (110). Animated co-rendered displays (107) of the earth model and actual (104) and simulated (105) production data enable the user to interactively determine model adjustments back at the basic level of the Earth Model, which are then propagated to a geologic model (102) and then to the reservoir simulator (103) to update it (111) in a physically constrained way.

Abstract: Some embodiments include a heavy-oil-based hydrocarbons effluent production installation for the production of hydrocarbons from at least one well. The installation includes an effluent-lightening fluid injection system at the bottom of the well, an effluent-evacuation pump, a plurality of sensors that measure physical units relating to the installation, and an automated device suitable for optimizing the lightening-fluid injection flow-rate and for regulating the pump speed. The automated device regulates the pump speed according to the physical units and a predetermined target production value. The speed of the pump and the physical units are within a predetermined range of values. some embodiments include a hydrocarbons production method in such an installation. Some embodiments make it possible to ensure a minimum consumption of lightening fluid, while ensuring good operation of the pump and good productivity of the well.

Abstract: Systems and methods for managing aquifer operation are included. An exemplary method includes receiving at an analysis computing device, one or more water measurements from a plurality of sites in an aquifer, wherein water measurements are received at a plurality of time points. A site may include one or more groundwater extraction wells. The method may further include calculating well operational data for at least one groundwater extraction well based on the water measurements, wherein the well operational data includes a well efficiency over a time period. Further, the method may include receiving an aquifer objective input via a graphical user interface presented on the analysis computing device. The method may further include generating a pump operation signal based on the well operational data and the aquifer objective input.

Abstract: A controller for controlling the pump unit of an oil well includes a sensor having a first and second probe for placement in the flow of oil from the well bore. Each of the probes contains a heater. A constant power source is selectively connected to one of the heaters. Each of the probes also includes a linear RTD at each of their tips respectively for generating a signal indicative of the temperature measured at each of the first and second probes. A control unit receives signals from the RTD's and determines a flow rate therefrom. A pump control signal is generated in response to the flow rate, wherein the pump control signal continuously varies a predetermined parameter for controlling the flow rate of a pumping unit during operation of the pumping unit.

Abstract: A bottomhole tool and a method for optimizing oil production rate from an oil well with high gas-to-oil ratio and stabilizing thereof in case of occurrence of a gas cone or gas skin conditions are disclosed. The resistance of the adjustable multi-stage flow resistor is determined by a position of a telescoping needle, which in turn is defined by a driving means including a motor and a gearbox. The motor is driven via a cable from a surface by a control means adapted to receive information about the bottomhole parameters from local sensors via a sensor cable. Methodology explaining the principles of maintaining well stability is also disclosed. Automatic adjustment of the bottomhole pressure is maintained over a wide range of operating parameters throughout the life of the well to maximize its oil output.

Abstract: A system for monitoring and controlling fluid flow through a borehole in an earth formation is disclosed. The system includes: a downhole tool configured to be movable within the borehole; and a plurality of interchangeable modules disposed within the downhole tool, the plurality of interchangeable modules including at least a sensor module for detecting a property change in the borehole and a packer module for sealing a portion of the borehole in response to the property change. Each of the plurality of interchangeable modules includes a connection configuration, the connection configuration of one of the modules being removably engageable with at least another of the modules. A method of monitoring and controlling fluid flow through a borehole in an earth formation is also disclosed.

Abstract: A method and apparatus for automating control, remotely monitoring, and controlling a gas extraction assembly, coupled to a gas pipeline section. The gas extraction assembly may be used to increase gas volume, and/or overall gas flow from productive low or high pressure wells, as well as “wake-up” or recover lowered production from depleting wells. Two features of the gas extraction assembly of the present invention is the capability of creating substantial differential pressure, along with the ability to create substantial vacuum pressure on the suction inlet.

Abstract: A transmitter generates an acoustic ping in a fluid in a borehole, and a receiver monitors waves resulting from the acoustic ping. Responsive to the monitored waves, an attribute of the fluid is estimated, including a sonic velocity, a mixture of gas and oil, a mixture of water and oil, an amount of sand, an amount of gas, an amount of skin effect, or a depth of fluid. An operation of the artificial lift device is then controlled responsive to the estimated attribute. Alternately, a sonic velocity is estimated for the fluid through an analysis of a sample pumped to the surface or through an analysis of monitored waves. A depth of the fluid is calculated responsive to the estimated sonic velocity for the fluid in the borehole and the monitored T-waves. The operation of the artificial lift device is then controlled responsive to the calculated depth of fluid.

Abstract: A method for improving the recovery efficiency of storing fresh water into an aquifer, the storing includes injecting the fresh water and extracting the injected fresh water by a single water storage system that includes at least one well penetrating into the aquifer, the method includes: providing a plurality of screens, each screen being located alongside a wall of at least one well, and each screen respectively allowing a flow of fresh water between an associated storage zone in contact with the screen and the well on which the screen is located; controlling the flow of fresh water through each one of the plurality of screens according to parameters provided from a storage model of the aquifer, the storage model describing a behavior of each storage zone.

Abstract: A method of reservoir management linking. The method includes receiving a reservoir volume from a submitter, the reservoir volume modeling hydrocarbons in a reservoir, and determining that the submitter is authorized to submit the reservoir volume and sending notification of the reservoir volume to a first approver. The method further includes storing the reservoir volume on a storage device, receiving approval of the reservoir volume from the first approver, determining that the first approver is authorized to approve the reservoir volume, generating a standardized report associated with the reservoir volume, and displaying the standardized report.

Abstract: A downhole plunger for oil and gas wells comprises an electronic ambient environmental sensor via a cargo bay. Although the sensor is preferably a downhole time, temperature, pressure and flow sensor, the device contemplates the use of any appropriate cargo to ascertain well conditions. The device can also be used to sample fluid. The sensor has a measured data memory.

Abstract: A method of controlling a plunger lift system for a well. The method including the steps of: defining a threshold value for a trigger event, the trigger event initiating operation of the control valve by the controller; defining event-value conditions upon which adjustment of the trigger event is adjusted; determining, upon a calling-event, if the event-value conditions have been satisfied; and adjusting the trigger event threshold value upon satisfaction of the event-value conditions.

Abstract: A method for updating a software of a sub-sea controller (31) located under the sea level. The sub-sea controller manages a plurality of tools in a sub-sea well. An application module (35) is downloaded into the sub-sea controller. The application module is executed using a virtual machine (36) implemented within the sub-sea controller.

Abstract: A method and apparatus for controlling the operation of a flowing or producing well utilising: a downhole located pressure monitoring device which is operative to monitor a characteristic pressure profile of the flowing well, and to respond when a significant deviation to the pressure profile is introduced into the well as a control signal to the monitoring device; and an actuator which is initiated into operation to control any required operation of the well when the monitoring device responds to the control signal.

Abstract: A gas flow system for removing a liquid from a well bore and allowing for gas production is provided. The gas flow system comprises a casing in the well bore for allowing flow of the liquid and gas; a tubing string in the casing for allowing flow of the liquid and gas; pressure measurement devices for use in determining a rate of liquid influx into the well bore; a casing control valve moveable between various positions ranging from fully open to fully closed for controlling flow through the casing; a tubing control valve moveable between various positions ranging from fully open to fully closed for controlling flow through the tubing; and flow measurement devices for determining the rate of flow through the tubing and the total rate of flow.

Abstract: This invention provides for an apparatus that controls a liquid level down-hole of a hydrocarbon producing well by physically monitoring the liquid level down-hole having a down-hole liquid level measurer and a signal device connected to the liquid level measurer that causes a pump to adjust its current liquid output based on the liquid level down-hole as measured by the down-hole liquid level measurer.

Abstract: Well bore servicing equipment is provided. The well bore servicing equipment comprises a first manipulator to grip a well bore work string, to raise the work string, and to lower the work string. The well bore servicing equipment further comprises a controller to receive a work string trajectory input and to automatically control the first manipulator to raise and lower the work string substantially in conformance with the work string trajectory input.

Abstract: A system for the storage of crude oil, natural gas and/or refined petroleum products at an offshore location includes a group of tanker vessels or concrete structures on the ocean floor attached to a manifold. The manifold is connected to sources of crude oil, natural gas and/or refined petroleum products. Each vessel includes a security system and a moving arrangement which allows the vessel to weathervane in response to wind and wave forces.

Abstract: A method for managing information associated with an oilfield operation of an oilfield, the oilfield having a subterranean formation with geological structures and reservoirs therein. The method includes specifying a first site of interest, where a first data source includes data stored at the first site of interest, designating a first abstract role for the first data source, where the first abstract role corresponds to one of a plurality of information lifecycle roles, designating a first abstract stream for the first data source, where the first abstract stream corresponds to one of a plurality of categories of information, and generating a first output associated with the first data source, where the first output includes the first site of interest, the first abstract role, and the first abstract stream. The method further includes presenting the first output, where the oilfield operation is adjusted based on the first output.

Abstract: A control system and control method for controlling a modular apparatus for extracting petroleum and/or generating electricity based on subsurface data as well as market prices of electricity and/or petroleum. One or more probes measure subsurface total pressure, partial pressure of carbon dioxide, partial pressure of hydrogen, oil flow rate, gas flow rate, underground temperature, and/or viscosity of the oil. The control system/method controls the apparatus based on the subsurface parameters by controlling an injection module and/or a gas separator module to increase or decrease output of driver gas. The control system/method may also control the injection module and/or the gas separator module to increase (or decrease) output of driver gas when the market price of electricity decreases (or increases) and/or petroleum increases (or decreases).

Abstract: An automated flowback system allows control and operation of the system from a remote location away from the dangers of high-pressure gases or abrasives traveling at high velocities that cause damage or failure to equipment piping valves. The system provides techniques and mechanical components installed in flowlines in any position without having to cut and thread, weld or fabricate pipe to fit. This system includes an expansion sub with axial adjusting lengths adequate to compensate for variations between two points. The expansion sub is secured and installed into position eliminating field cut and threading, welding or fabrication. The system also includes a blast barrel with an installed choke nipple, choke bean or choke insert with a chosen orifice size for multiple chambered ports. The blast barrel retracts between two fixed points without having to dismantle any connections or be removed from the fluid flow.

Abstract: Disclosed herein is a downhole flow control device. The device includes, a first member defining a first portion of a flow path, and a second member defining a second portion of the flow path, the flow path has a cross sectional flow area defined at least partially by the first member and the second member, a length of the flow path is greater than a largest dimension of the cross sectional flow area, and the cross sectional flow area is adjustable by movement of at least a portion of the first member relative to the second member.

Abstract: A system (100) for selective activation of explosive devices (126, 128, 130, 132) includes a surface controller (102), a downhole controller (106) operable to communicate bidirectionally with the surface controller over a first communication link (108) and a plurality of downhole remote units (114, 116, 118, 120) operable to communicate bidirectionally with the downhole controller (106) over a second communication link (112). One or more sensors (162) are operably associated with the downhole controller (106) and one of the explosive devices (126, 128, 130, 132) is operably associated with each of the downhole remote units (114, 116, 118, 120) such that, responsive to a detonation event, the sensors (162) detect the intensity level of the detonation which is communicated from the downhole controller (106) to the surface control (102) over the first communication link (108).

Abstract: A bottomhole tool and a method for optimizing oil production rate from an oil well with high gas-to-oil ratio and stabilizing thereof in case of occurrence of a gas cone or gas skin conditions are disclosed. The resistance of the adjustable multi-stage flow resistor is determined by a position of a telescoping needle, which in turn is defined by a driving means including a motor and a gearbox. The motor is driven via a cable from a surface by a control means adapted to receive information about the bottomhole parameters from local sensors via a sensor cable. Methodology explaining the principles of maintaining well stability is also disclosed. Automatic adjustment of the bottomhole pressure is maintained over a wide range of operating parameters throughout the life of the well to maximize its oil output.

Abstract: An apparatus and method of measuring a parameter characteristic of a rock formation in an oil well is provided with a device for generating a sensing field within a volume of the rock formation and a device for causing a flow through the volume in the presence of the sensing field, further including sensors responsive to changes in the volume, wherein a sensor response is indicative of the amounts of fluid, particularly hydrocarbon and water saturations and irreducible hydrocarbon and water saturations. Measurements can be made before the flow affects the measuring volume and after onset of the flow through the measuring volume.

Abstract: A device and method can detect, and also break, an occurrence of gas lock in an electrical submersible pump assembly in a well bore based upon surface or downhole data without the need for operator intervention. To detect an occurrence of gas lock, an instantaneous value is monitored using a sensor. Then a controller compares the instantaneous value to a threshold value over a predetermined duration to thereby detect the occurrence of gas lock in the electrical submersible pump assembly. Sensors can include, for example, a differential pressure gauge, a pressure gage located in a pump stage located toward the inlet, a fluid temperature sensor located toward the discharge, a free gas detector located near the pump discharge, an electrical resistivity gage, a flow meter located within surface production tubing, and a vibration sensor attached to a tubing string to measure a vibration signature.

Abstract: A system for performing a task in a borehole, the system including: a downhole tool configured for disposition into the borehole, the downhole tool also configured to perform the task; a processing unit disposed remote to the downhole tool, the processing unit configured for initiating a command signal; and a broadband communication system for coupling the downhole tool and the processing unit, the broadband communication system configured to transmit the command signal to the downhole tool to perform the task.

Abstract: A downhole plunger for oil and gas wells comprises an electronic ambient environmental sensor via a cargo bay. Although the sensor is preferably a downhole time, temperature, pressure and flow sensor, the device contemplates the use of any appropriate cargo to ascertain well conditions. The device can also be used to sample fluid. The sensor has a measured data memory.

Abstract: A downhole formation fluid pumping and a sampling apparatus are disclosed that may form part of a formation evaluation while drilling tool or part of a tool pipe string. The operation of the pump is optimized based upon parameters generated from formation pressure test data as well as tool system data thereby ensuring optimum performance of the pump at higher speeds and with greater dependability. New pump designs for fluid sampling apparatuses for use in MWD systems are also disclosed.

Abstract: A method of optimizing fluid (gas/oil) throughput of a battery complex to monitor and control the flow of an individual well in a field of wells at any particular instance in time and to allocate production of a specific well. The method comprises one or more of the steps of; providing a master control unit within the battery complex; placing an individual control unit on each of the individual wells in said field of wells; arranging a communications network between each of the individual control units at each well in the field and the master control unit in the battery complex; reporting each individual well's gas production factors to the master control unit; and sending a control signal to each individual well to control its production based upon the monitoring of the collective signals received by the master control unit from the field of individual wells.

Abstract: An interface to provide coupling between a downhole sensor and wiring to other electrical equipment. The interface is configured to obtain voltage from a single power line and provide it to the downhole sensor while simultaneously converting sensor data to frequency form for transmission right back over the same power line. In this manner a substantial reduction in downhole wiring may be obtained. This may be particularly beneficial for sensors to be incorporated into downhole equipment where size and space issues are prevalent, particularly in the circumstance of equipment requiring a retrofit in order to accommodate the sensor capacity.

Abstract: An electrical submersible pump that regulates pump flow rate based on sensor measurements of the fluid is disclosed. The sensor measures a property of the fluid being processed. The sensor may be located at the intake, discharge or other area of the pump. The sensor measures the relative proportion of gas in the pumped liquid. The pump flow rate is adjusted to maintain a desired level for the gas in a production environment. The pump may be used to operate and control a seabed gas-liquid separation and centrifugal pump system.

Abstract: A dedicated hydraulic line for transmission of a signal device capable of generating one or more unique signals to one or more tools within a subterranean well. Each tool can be equipped with a reader device for receiving signals from and transmitting signals to the signal device. Each reader device can control operation of the tool associated therewith if the reader device is programmed to respond to signals received from the control device. Hydraulic fluid used to operate the tool can be conveyed via the dedicated hydraulic line or a separate hydraulic line. A separate hydraulic line can be used to reset the tool.

Abstract: A control system for an annulus balanced subsurface safety valve. A system for operating a safety valve in a well includes a piston of the safety valve being responsive to displace due to a pressure differential between chambers exposed to the piston; and a valve controller which alternately exposes at least one of the chambers to pressure in an annulus surrounding the safety valve, and to pressure greater than that in the annulus. A method of operating a safety valve in a well includes the steps of: opening the safety valve by biasing a piston of the safety valve to displace in response to a pressure differential between a chamber exposed to pressure greater than well pressure, and another chamber exposed to well pressure; and closing the safety valve by exposing both of the chambers to the well pressure.

Abstract: Disclosed herein is a downhole communication system. The system includes, a plurality of addressed downhole devices, a plurality of remote devices, and a plurality of conductors. Each of the plurality of conductors is electrically conductively connected to at least one of the plurality of addressed downhole devices and at least one of the plurality of remote devices, the downhole communication system is configured such that at least one of the plurality of devices is able to receive and recognize encoded addresses and encoded data in an electrical signal transmitted at least one of the plurality of conductors electrically conductively isolated from the device configured to be receptive to the electrical signal having the encoded addresses and encoded data.

Abstract: A technique is provided to determine a flow rate of a production fluid. The technique is utilized in a well having a gas lift system. Temperatures are measured along the well to create a temperature profile. The temperature profile is used to determine the flow rate of a produced fluid.

Abstract: A method and apparatus for automating control, remotely monitoring, and controlling a gas wellhead extraction assembly, coupled to a gas pipeline section. The gas wellhead extraction device assembly may be used to increase gas volume, and/or overall gas flow from productive low or high pressure wells, as well as “wake-up” or recover lowered production from depleting wells. Two features of the gas wellhead extraction device assembly of the present invention is the capability of creating substantial differential pressure, along with the ability to create substantial vacuum pressure on the suction inlet.

Abstract: A method is disclosed for controlling production of oil and/or gas from an underground reservoir by means of a closed loop production control system, in which: —an assembly of monitoring sensors (4) monitor the physical properties of hydrocarbon and other fluids within the reservoir; —a plurality of high order and/or low order mathematical reservoir models (5, 7) calculate each an estimate of the physical properties of hydrocarbon and other fluids in the hydrocarbon containing formation and in the wells; —the mathematical reservoir models (5, 7) are iteratively updated in response to data provided by the assembly of sensors such that any difference between the properties monitored by the assembly of sensors and those calculated by each of the reservoir models is minimized; —an optimal mathematical reservoir model (5, 7) or an optimal combination thereof is selected during at least one updating step for which an averaged difference between the calculated properties and the properties monitored by the assembly