1. Petroleum Experts Ltd. Janvier Lissanon

2. Gas Lift Optimization Workshop
This workshop addresses theoretical and practical aspects of implementing a Production Management system. Field case studies are used to illustrate the methods used.
The first session introduces the main concepts and elements of the system. This is followed by a well problem diagnosis example.
Gas Lift Design for a single Well
Understanding individual well performance
Optimized gas lift allocation in a multi-well system

3. Gas-Lift Objectives Maximize the oil production today and tomorrow
Production Management can be defined as exercising control over all aspects (technical and organisational) of the production process. Control implies that the rates achieved are due to a conscious effort on the part of the field manager. Each well in a field is produced to a specific plan - production rates are not left to chance.
The objective is to maximise return on investment by maximising oil production within constraints. Constraints can occur at the reservoir, well, gathering network, process and marketing levels. It is the field manager’s responsibility to achieve the economic optimum production within the constraint framework.
Reservoir and well conditions change throughout the life of a field. Production management is a continuous process of surveillance and reaction to these changes. By comparison of forecast and actual production, predictions are improved, and production maximised.
Without a baseline for comparison, interpretation of a programs’s effectiveness is not possible. A properly calibrated well and gathering system model is needed to estimate each well’s production potential. Only by comparing each well’s actual production with its potential can the effectiveness of a particular production strategy be properly assessed.
Maximize the oil production today and tomorrow
Systematic Analysis of individual production system components (well, fluid description, reservoir response, valve response, pipe line behaviour)
Allocate the available gas lift volume in a multi-well system by taking into account the entire network response: a non-linear optimization problem

4. Gas-Lift Design: Objectives
Production Optimisation aims to maximise return of investment by:
Maximising production rates - by producing at the highest rates that can be economically justified.
Minimising production downtime - Well problems must be quickly identified and repaired. This requires an effective surveillance program and a baseline model to compare measured rates.
Identifying production restrictions. Optimisation models will locate the factors limiting production. e.g. compressor capacity, pipeline restrictions, process limits, well productivity. By re-running the model without the restriction, the economic benefit resulting from capital expenditure to remove the restriction can be assessed.
Maintenance planning. Field lift gas allocation, production rate settings etc. can be calculated for maintenance scenarios in order to maximise production when equipment must be taken out of service. e.g. lift gas allocations can be pre-calculated to maximise production when a compressor is unavailable.
Planning for the future. Models can be run for expected future conditions for production forecasting. Timing of the need for artificial lift, additional compression, more wells etc. can be assessed. Prudent planning will allow equipment to be procured and installed at the optimum time in field life. Maintenance of accurate production optimisation models allows preparation of ‘what-if’ contingency plans with minimal delay.
Optimized Gas Lift Design for individual wells:
Finding the optimum design rate per well
Finding the required gas lift gas injection rate and injection depths
Finding unloading valves depths, valve trim sizes and dome setting pressures
Ensuring required design flexibility to changing operating conditions
Check of third party Design (Existing mandrels)

5. Gas-Lift Design: Example
Production planning is often based on extrapolation of past history. While this approach will predict a forecast that should be achievable in terms of the field’s current operating practices, it does not necessarily take account of the field’s potential to produce.
An production system model is required to estimate what the field is capable of producing with optimum operating practices (lift gas allocation, well choke settings, separator pressures etc.)
The effectiveness of the current operating strategy is best evaluated by comparing how close the actual rates are to the production potential.
Wells may not be able to be operated at their potential for a number of reasons e.g. process limitations, sand production, contract or quota restrictions, gathering system limitations. For proper production management, the effect of each restriction on overall production rates must be quantified and a justification as to why the potential rate was not achieved prepared.
This allows the field manager to evaluate on an on-going basis whether capital expenditure to remove production restrictions can be economically justified.

6. The QuickLook plot: Example
A Production Management system can be divided into 2 main sections:
Technical -
Reservoir fluid description (matched PVT model)
Systems Analysis models and software used to match the production performance of each well.
Gathering system model used to perform production optimisation calculations
System constraint description at well, gathering system and process levels
The modelling and optimisation effort cannot succeed without a steady supply of accurate and timely data from the field. The data flow must be designed to minimise the effort required to build and maintain the well models.
A significant component of the management system is the organisation that allows the flow of data
Organisational -
A set of procedures for the efficient acquisition, quality control and display of field well test and downhole pressure survey data.
Procedures for systematic review of model and measured performance.

7. Quicklook Example: Calibrated Model
A Production Management system can be divided into 2 main sections:
Technical -
Reservoir fluid description (matched PVT model)
Systems Analysis models and software used to match the production performance of each well.
Gathering system model used to perform production optimisation calculations
System constraint description at well, gathering system and process levels
The modelling and optimisation effort cannot succeed without a steady supply of accurate and timely data from the field. The data flow must be designed to minimise the effort required to build and maintain the well models.
A significant component of the management system is the organisation that allows the flow of data
Organisational -
A set of procedures for the efficient acquisition, quality control and display of field well test and downhole pressure survey data.
Procedures for systematic review of model and measured performance.

8. Gas Lift Optimisation in a multi-well system
A Production Management system can be divided into 2 main sections:
Technical -
Reservoir fluid description (matched PVT model)
Systems Analysis models and software used to match the production performance of each well.
Gathering system model used to perform production optimisation calculations
System constraint description at well, gathering system and process levels
The modelling and optimisation effort cannot succeed without a steady supply of accurate and timely data from the field. The data flow must be designed to minimise the effort required to build and maintain the well models.
A significant component of the management system is the organisation that allows the flow of data
Organisational -
A set of procedures for the efficient acquisition, quality control and display of field well test and downhole pressure survey data.
Procedures for systematic review of model and measured performance.
Gas Lift is to be allocated in order to maximise oil production
Wells, Pipelines and overall System constraints are to be honoured
Impact of network response on individual well performance is to be accounted for

9. Multi-Well System Liquid Rate Gas Injection Rate Liquid rate

10. Optimization Techniques in a multi-well system
A Production Management system can be divided into 2 main sections:
Technical -
Reservoir fluid description (matched PVT model)
Systems Analysis models and software used to match the production performance of each well.
Gathering system model used to perform production optimisation calculations
System constraint description at well, gathering system and process levels
The modelling and optimisation effort cannot succeed without a steady supply of accurate and timely data from the field. The data flow must be designed to minimise the effort required to build and maintain the well models.
A significant component of the management system is the organisation that allows the flow of data
Organisational -
A set of procedures for the efficient acquisition, quality control and display of field well test and downhole pressure survey data.
Procedures for systematic review of model and measured performance.
The “Equal Slope” Method
Linear Programming
The Sequential Quadratic Programming technique

11. GL#1: Actual well ResponseQ
Starting Point
100
First Calculation
200
Convergence
300
True Response
Gas Lift Gas

12. Comparison EQ-SLP-LP-SQP
∆Q Oil
SQP Response
ES – LP - SLP
∆Q Gas Inj
Gas Lift Gas

13. CRITERIAS FOR A SUCCESSFUL OPTIMIZATION
In summary, an effective production manage system consists of
Organisational procedures that ensure efficient production data gathering, quality control and analysis.
Calibrated computer models for wells, gathering system and production constraints. Validated models are used to determine the production potential to determine the effectiveness of current operations and identify opportunities for improvements.
Commitment to continuous improvement at all levels, from field operators, production engineers and management.
Wells PC must have the network feedback embedded in their expression (1st and 2nd Derivative)
Ability to respect constraints by realistic means
Ability to handle mixed systems (NF wells, ESP-wells, gas lifted wells)
SQP:
non-linear optimization method which accounts for the entire network response: GAP

14. Equal Slope Method

15. Linear Programming

16. SEQUENTIAL QUADRATIC PROGRAMMING
PC is approximated with a quadratic term
Global maximum can be estimated and searching is accelerated

17. VARIOUS OPTIMIZATION TECHNIQUES
In summary, an effective production manage system consists of
Organisational procedures that ensure efficient production data gathering, quality control and analysis.
Calibrated computer models for wells, gathering system and production constraints. Validated models are used to determine the production potential to determine the effectiveness of current operations and identify opportunities for improvements.
Commitment to continuous improvement at all levels, from field operators, production engineers and management.
Equal Slope:
works only if no pipeline response is to be accounted for
cannot handle constraints in optimized fashion
LP/SLP:
can handle constraints but
can not optimize non-linear systems like gas lifted systems
SQP:
Optimization method for Gas Lift Allocation accounting for the entire network response

18. SUMMARY Solid, Consistent and Flexible Gas Lift Design using PROSPER
In summary, an effective production manage system consists of
Organisational procedures that ensure efficient production data gathering, quality control and analysis.
Calibrated computer models for wells, gathering system and production constraints. Validated models are used to determine the production potential to determine the effectiveness of current operations and identify opportunities for improvements.
Commitment to continuous improvement at all levels, from field operators, production engineers and management.
Solid, Consistent and Flexible Gas Lift Design using PROSPER
Ability to analyse, troubleshoot and quantify the benefit of work-over using PROSPER
Optimize the gas lift allocation in a multi-well system with an optimizer which accounts for the entire network response: GAP

19. Optimisation Techniques
Staring Point
100
First Calculation
200
Second Calculation
300
Gas Lift Gas