Method and apparatus for estimating down-hole process variables of gas lift system
AssigneeKhalifa University of Science and Technology
InventorsIgor Boiko, Mohammad Luai Hammadih, Khalifa Hasan Al Hosani
Life of this patent
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Abstract
A method and apparatus for estimating a down-hole annulus pressure, and/or a down-hole tubing pressure, and/or a down-hole lift gas rate through a gas injection valve of gas lift system, which comprises at least one gas lift choke and at least one gas injection valve and at least one production choke. A state estimator is proposed to obtain the values of these down-hole process variables. The estimator contains a number of local estimators and an interpolation module.
Claims13
A method for determining down-hole process parameters for an artificial gas lift system, comprising the following steps:
- measuring an annulus pressure and/or a surface tubing pressure of the gas lift system;
- operating a state estimator to perform the steps of:
- a) determining a vector signal representative of a gas lift choke opening value and/or a production choke opening value and/or a vector signal representative of the measured annulus pressure and/or the measured surface tubing pressure as input values;
- b) providing a vector signal representative containing estimates of a down-hole annulus pressure about a reference point of an i-th local estimator, and/or a down-hole tubing pressure about a reference point of an i-th local estimator, and/or a lift gas rate through said gas injection valve about a reference point of an i-th local estimator by means of N local estimators where N is greater than or equal to two;
- and
- c) incorporating the estimates provided by all local estimators into a single estimate by means of an interpolation module to determine estimated values of a down-hole annulus pressure, and/or of a down-hole tubing pressure, and/or of a lift gas rate through said gas injection valve;
- and
- generating an output associated with the determined estimated values;
- and
- controlling the artificial gas lift system by using the outputted estimated values of a down-hole annulus pressure, and/or of a down-hole tubing pressure, and/or of a lift gas rate through said gas injection valve.
A state estimator system for determining down-hole process parameters for an artificial gas lift system, the artificial gas lift system comprising a well casing which connects a surface equipment with an oil reservoir;
- a tubing inserted inside said well casing and forming an annulus as a space between said well casing and said tubing;
- a gas lift choke installed between a source of a high-pressure gas and said annulus;
- a gas injection valve installed between said annulus and a volume inside said tubing;
- a production choke installed between a volume inside said tubing and oil processing facilities above the surface;
- the state estimator system comprising:
- a) an electronic receiver configured to receive a plurality of input parameters measured at an upper end of the artificial lift system;
- b) N local estimators where N is greater than or equal to two, each providing based on the plurality of input parameters an 11th vector signal representative containing estimates of a down-hole annulus pressure about a reference point of an i-th local estimator, and/or a down-hole tubing pressure about the reference point of an i-th local estimator, and/or a lift gas rate through a said gas injection valve about the reference point of an i-th local estimator;
- and
- c) an interpolation module that incorporates estimates provided by all local estimators into a single estimate to determine estimated values of a down-hole annulus pressure, of a down-hole tubing pressure, and of a lift gas rate (LGR) through said gas injection valve, in steady and transient modes;
- based on the input parameters measured at the upper end of the artificial gas lift system;
- and
- d) an output device configured to generate an output associated with the determined estimated values to control the artificial gas lift system using the outputted estimated values of the down-hole annulus pressure, and/or of the down-hole tubing pressure, and/or of the LGR through said gas injection valve.
Dependencies are inferred from the claim text.