Gas-Lift Automation
API RECOMMENDED PRACTICE 19G12 (RP 19G12)
DRAFT #4, Dec. 12, 2009
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API RP 19G12 Gas-Lift Automation Page 19
Foreword
This Recommended Practice (RP) is under the jurisdiction of the API Committee on Standardization of Production Equipment (Committee 19).
This document presents Recommended Practices for Gas-Lift Automation. Other API Specifications, API Recommended Practices, and Gas Processors Suppliers Association (GPSA) documents may be referenced and should be used for assistance in design and operation of a gas-lift automation system.
API Recommended Practices may be used by anyone desiring to do so, and diligent effort has been made by the Institute to assure the accuracy and reliability of the data contained therein. However, the Institute makes no representation, warranty, or guarantee in connection with the publication of any API Recommended Practice and hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use, for any violation of any federal, state, or municipal regulation with which an API Standard may conflict, or for the infringement of any patent resulting from the use of an API Recommended Practice or Specification.
Note:
This is the first edition of this recommended practice.
Requests for permission to reproduce or translate all or any part of the material published herein should be addressed to the Director, American Petroleum Institute, 1220 L Street NW, Washington DC 20005-4070
This Recommended Practice shall become effective on the date printed on the cover but may be used voluntarily from the date of distribution.
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Recommended Practices for
Gas-Lift Automation
API RP 19G12
Forward
· This publication is intended to provide recommended practices for the use of gas-lift automation to enhance the functionality and profitability of gas-lift operations for the production of oil and gas.
· This publication is under the jurisdiction of the API Committee on Recommended Practices for use of Production Equipment.
· American Petroleum Institute (API) Recommended Practices are published as aids for the use of equipment and materials by operating companies, as instructions to manufacturers of equipment and materials, and as instructions to manufacturers of equipment or materials covered by an API Specification. These Recommended Practices are not intended to obviate the need for sound engineering practice, nor to inhibit in any way anyone from using, purchasing, or producing products to other specifications.
· The formulation and publication of API Recommended Practices, Specifications, and the API monogram program are not intended in any way to inhibit the purchase or use of products from companies not licensed to use the API monogram.
· API Recommended Practices and Specifications may be used by anyone desiring to do so, and diligent effort has been made by the Institute to assure the accuracy and reliability of the data contained therein. However, the Institute makes no representation, warranty, or guarantee in connection with the publication of any API Recommended Practice or Specification and hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use, for any violation of any federal, state, or municipal regulation with which an API Recommended Practice or Specification may conflict, or for the infringement of any patent resulting from the use of an API Specification.
· Any manufacturer producing equipment or materials represented as conforming with an API Specification is responsible for conforming with all the provisions of that Specification. The American Petroleum Institute does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard or specification.
This Recommended Practice shall become effective on the date printed on the cover but may be used voluntarily from the date of distribution.
Attention Users of This Publication: Portions of this publication may have been changed from the previous edition. In some cases the changes may be significant, while in other cases the changes may reflect minor editorial adjustments.
Note:
This is the first edition of this recommended practice.
Requests for permission to reproduce or translate all or any part of the material published herein should be addressed to the Director, American Petroleum Institute, Production Department, 2535 One Main Place, Dallas, TX 75202.
Introduction
This API recommended practice provides guidelines and tools to facilitate the effective and efficient design, operation, optimization, and troubleshooting of gas-lift wells and systems when using automation systems.
As used in this document, gas-lift automation includes any use of instruments, controls, communications, computer hardware, computer software, databases, and other computer tools that are intended to monitor, control, provide surveillance, detect problems, diagnose the cause of problems, solve problems, and optimize the operation of gas-lift systems for production of oil and gas.
This document may be used as a guide for designing gas-lift automation systems, and as an aide in providing training in how to design, operate, optimize, and troubleshoot these systems.
1. Scope
The scope of this document addresses the following topics:
· Production automation definition.
· Overview of gas-lift automation.
· Fields that need to be served by gas-lift automation.
· Objectives of gas-lift automation.
· Methods of using gas-lift automation.
· Gas-lift automation business drivers.
· Instrumentation and controls for gas-lift automation.
· Communication equipment and systems.
· Computer automation hardware.
· Computer automation software.
· Normal automation applications.
· Special automation applications.
o Continuous single string gas-lift.
o Continuous dual gas-lift.
o Intermittent gas-lift.
o Gas-lift of gas wells.
· Gas-lift database systems.
· Gas-lift optimization capabilities.
· Benefits of gas-lift automation.
· Risks.
· Justification of automation systems.
· Staffing required.
· Training required.
· Case histories of automation successes.
· Case histories of automation failures.
This document does not include information provided in the documents listed in the Normative Reverences in the next section of this document, nor in the Informative References which are listed in the Bibliography.
This document does not recommend any specific automation hardware, automation software, or automation service/supply companies.
2. Normative References
Normative (required) references used in this document include:
API RP 11V5, Operation, Maintenance, Surveillance, and Troubleshooting Of Gas- Lift Installations
API RP 11V8, Recommended Practice for Gas Lift System Design and Performance Prediction
API RP 19G9, Recommended Practice for Design, Operation, and Troubleshooting of Dual Gas-Lift Wells (document being published by API)
API RP 11V10, API Recommended Practice for Design and Operation of Intermittent and Chamber Gas-Lift Wells and Systems
API RP 19G11, Recommended Practices for Dynamic Simulation of Gas-Lift Wells and Systems (document ready for Work Group and Task Group review)
API RP 19G13, Recommended Practice for High Pressure and Sub-Sea Gas-Lift (document currently being drafted)
3. Terms and Definitions
Terms and definitions used in the document are listed here.
3.n
gas-lift automation
The process of using instruments, controls, and automation hardware and software to automate some or all of the functions of gas-lift date acquisition, control, problem detection and diagnosis, and optimization.
3.n
gas-lift, continuous
Gas-lift gas is injected into an oil or gas well at a continuous rate.
3.n
gas-lift, dual
There are two completions (two tubing strings) in the same wellbore, and they are both on gas-lift at the same time.
3.n
gas-lift, intermittent
Gas-lift gas is injected into an oil or gas well on an intermittent rather than a continuous basis.
3.n
gas-lift, single
There is one completion (one tubing string) in the wellbore, and it is on gas-lift.
3.n
host computer system
A computer system that provides data processing, centralized control logic, centralized optimization logic, information access for operating staff, and may provide information transmission to other computer systems such as corporate systems, databases, etc.
3.n
recommendation
Expression in the content of a document conveying that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others, or that a certain course of action is preferred but not necessarily required, or that (in the negative form) a certain possibility or course of action is disapproved of but not prohibited.
4. Symbols and Abbreviations
Symbols and abbreviations used in the document are listed here.
4.n
Bit
The smallest element of data; a 1 or a 0.
4.n
Byte
A byte consists of eight bits.
4.n
CAO
Computer Assisted Operation.
4.n
DCS
Distributed Control System.
4.n
Hertz
Measure of data transmission speed. One hertz is transmission of one byte of data per second.
4.n
IPO
Injection Pressure Operated (gas-lift valve).
4.n
PLC
Programmable Logic Controller.
4.n
PPO
Production Pressure Operated (gas-lift valve).
4.n
RTU
Remote Terminal Unit.
4.n
SCADA
Supervisory control and data acquisition system.
4.n
TLP
Tension Leg Platform.
5. Requirements
Note: This is a draft of the API RP 19G12 document. Once the outlines of each section are complete, they are installed here from the “Outline” document. Each author is then asked to draft his/her sections based on the outline.
5.1 Introduction to Gas-Lift Automaton
5.1.1 Production automation defined (Rick Peters)
5.1.2 Overview of gas-lift automation (Rick Peters)
5.1.3 Objectives of gas-lift automation (Cleon Dunham)
This section discusses the objectives listed below and how they may be realized with a gas-lift automation system. Gas-lift automation systems should be designed and implemented to address specific gas-lift business functions and to enhance specific business drivers.
a. Minimize downtime of gas-lift wells. There are two types of down time or off-production time: planned and un-planned.
Planned downtime occurs when a gas-lift well or system is shut down for some operation reason such as well maintenance, system maintenance, production facility maintenance, safety, as in the case of a hurricane, etc. A gas-lift automation system helps minimize this type of downtime and its associated deferred production by automating the shut-down process so it is performed safely, and by automating the start-up process so it is performed rapidly, but consistent with safe well and facility operations.
Unplanned downtime occurs when a gas-lift well or system shuts down due to any unplanned malfunction or failure in the well, the distribution system, the compression system, or the production system. A production automation system helps minimize this type downtime by immediately detecting the downtime, alerting the production operating staff, and providing them with information on the likely cause(s) of the problem. This helps the operating staff respond quickly to return the well or system to production, thus minimizing deferred production.
b. Enhance gas-lift problem detection and correction. A gas-lift automation system assists with problem detection and correction in various ways.
First, the system automatically and continuously collected the pertinent data (measurements) needed to detect problems. Typically, this consists of measuring the gas-lift injection pressure and rate, and the production pressure. Other measurements may include the injection and production temperatures, and the liquid production rate.
Next, the automation system contains logic to check each value against alarm limits and for other “problem” conditions. This is discussed further in Section 5.1.1.
Then, the system contains logic to help analyze problem conditions and their causes. Common examples of problems that the system can help to analyze are: (1) instability when the casing and/or tubing pressure are surging or heading, (2) multipointing or injecting in multiple valves or a valve and a leak at the same time, (3) gas delivery problems such as blocks or freezing, and (4) production problems such as a plugged choke or a blocked flowline.
Finally, in some cases, the automation system can assist with problem solutions. For example, it can change the gas injection rate if this is needed to improve stability, or it may be able to take corrective actions to remove an injection blockage due to hydrate formation.
c. Optimize oil production from oil wells. Optimization of oil wells is not just problem solving. It is much more. For each well, there is an economic optimum production rate. This is discussed in API Recommended Practice 11V8 and in Section 5.2.4. However, for many reasons, it is rarely possible to operate a well at its optimum rate. This is also discussed further in Section 5.2.4.
Speaking simply, the economic gas-lift production rate occurs when the value of oil (and gas) production, divided by the cost of gas-lift injection and production handling and treating is maximized. Before this point, adding more gas will increase the value of oil and production by more than the cost of adding the gas-lift gas and treating the additional fluid. Beyond this point, the value of the production will be less than the cost.