Dynamic relative load rate for fluid systems

A method

• for defining, calculating, and evaluating various dynamic relative load rate [DRLR] variables for sets of fluid control devices operating as a fluid system with dimensions of said DRLR variables including, but not limited to a dynamic kPa/cm (psi/inch), kPa/second (psi/second), kPa/unit kPa (psi/unit psi), and MSCM/D/unit kPa (MSCF/D/unit psi), and with said fluid control devices including, but not limited to gas-lift valves that operate in strings of said valves to lift hydrocarbons from onshore and offshore reservoirs with the values of said DRLR variables to be derived from test data, including but not limited to fluid pressure, fluid flow rate, temperature, and time data and static mechanical distance data, including maximum distance of travel of a valve stem, with said test data generated by test equipment and associated fluid energy pulse tests of each member of the set, and which DRLR variable definition permits any fluid control device in the set to be selected as a reference device for comparison when evaluating the loading characteristics associated with the operation of all fluid control devices in the set, and whereby the value of each DRLR variable is determined from one or more characteristics of dynamic test data and static mechanical distance data for each fluid control device, said method comprising the steps:
• (a) acquiring test data as a function of time for one fluid control device using one or more slowly increasing positive or slowly decreasing negative energy pulses, or one or more explosively increasing positive or explosively decreasing negative energy pulses;
• (b) repeating step (a) for each fluid control device in the set of fluid control devices under evaluation, in which each fluid control device is set to operate at a specific temperature, a fluid upstream pressure, and a fluid downstream pressure, with a specific fluid flow rate;
• (c) selecting one or more characteristics from a set of characteristics of test data acquired in step (a) and step (b), with each selected characteristic providing a dynamic event or dynamic property of fluid pressure, fluid flow rate, temperature, and/or time for each fluid control device under evaluation, said characteristics to be used to create a DRLR variable that is common to each fluid control device;
• (d) selecting the dimensions for a DRLR variable from the characteristics selected in step (c) in order to assign a value to the DRLR variable for each fluid control device in the set, with said dimensions based upon combinations of static and/or dynamic variables, and which dimensions may include static approximations;
• (e) designating one fluid control device as a reference fluid control device and establishing the value of the DRLR variable for said reference fluid control device from test data that satisfy the dimensions selected in step (d), whereby a value of the DRLR variable for the reference device and values for all other DRLR variables for the fluid control devices in the set are enumerated as DRLR data in terms, not limited to, but including, kPa/unit kPa (psi/unit psi), kPa/second (psi/second), MSCM/D/unit kPa (MSCF/D/unit psi), and kPa/centimeter (psi/inch);
• (f) plotting the values of DRLR variables enumerated as DRLR data in step (e) on a DRLR graph of the DRLR variable with respect to fluid pressure, to fluid flow rate, to time, or to a mechanical dimension associated with the generation of energy pulses for each fluid control device, said mechanical dimension including a percent open state of a set-valve that generates back pressures on the fluid control devices;
• (g) identifying the characteristic curve of the DRLR data plotted in step (f) for all of the fluid control devices under evaluation, which curve may be of any configuration, depending upon the dimensions selected in step (d), but which curve generally follows a monotonically increasing or a monotonically decreasing path of the DRLR variable;
• (h) defining error-bounds for the curve identified in step (g), with said error-bounds providing limits on the variation of the values of the DRLR variables plotted in step (f);
• and,
• (i) comparing the DRLR values plotted in step (f) and/or the DRLR curve of step (g to the value of the DRLR variable for the reference fluid control device designated in step (e) and to the error-bounds defined in step (h), to ensure that all DRLR data show a well-defined dynamic operating relationship with respect to the reference fluid control device and that all DRLR data fall within said error-bounds, thereby ensuring an acceptable dynamic relative load rate characteristic for all fluid control devices in the set.