Spring 2003 Gas-Lift Workshop AbstractsFeb. 4 - 5, 2003Page 1
2003 Spring Gas-Lift Workshop
Abstracts of Presentations
Company(ies) / Author(s) / Title / Abstract / NotesGas-Lift Single Well Analysis Session
Schlumberger / Roger Stinson & Balraj Grewal / Gas-Lift Design and Analysis / The gas-lift design and analysis capabilities of the Baker Jardine (now part of Schlumberger) Pipesim software have been improved significantly. An innovative feature of the software is a feature that sizes ports and calibrates temperature for upper unloading valves based on unloading fluid rate and gas volume requirements.
Other improvements allow gas-lift engineers to customize gas-lift designs by allowing the user to specify the design method to be used, set design biases and safety factors, and design bracketing spacing for future conditions or uncertain conditions. This flexibility allows gas-lift engineers from different backgrounds and experience to customize designs based on specific field conditions, and individual preferences and experience.
Case studies will be presented based on application of this technology.
Weatherford / Ken Hilse / Gas Lift Design Evaluation Using Available Software Models / Gas-lift design calculations for installations, using traditional methods, may result in improper port sizing and transfer tubing pressure selection. These factors can affect the depth of injection, thereby causing reduced production rates and inefficient use of the injection gas.
Well data was submitted on a well for a gas-lift valve re-design. The well was the long string side of a dual that had six side pocket mandrels in place. The short string side did not require gas-lift and remained with dummy valves in the side pocket mandrels. According to operator, this well had never performed to expectations, producing approximately 200 BF/D. A traditional approach was used for the re-design calculations and the new string of PPO valves was installed. The well did not respond to the new installation as anticipated. A pressure/ temperature survey was conducted and the survey indicated that the well was lifting from the second valve.
A re-design of the installation was completed and evaluated using the VPC program and nodal software. The new design was installed and the well responded satisfactorily. A survey and well test established that the well was lifting from the fifth mandrel and the production rate had increased to 400 BF/D.
This presentation summarizes the application of tools that were available to more accurately determine design parameters in this well.
Occidental of Elk Hills / Patrick Lee Matthews / Distributed Temperature (Fiber Optic) Logging of Gas Lift Wells / Distributed Temperature Surveys and fiber optic technology are being used for more and more applications in the oil field. The advantages, of course, are getting a temperature trace of the wellbore top to bottom instantaneously. Occidental of Elk Hills has worked with Sensa, a Schlumberger company, and Welaco Wireline LLC to develop a logging system that provides economical temperature profiles of the wellbore along with bottom hole pressure information to look specifically at gas lift mechanics. Combining this information with Oxy’s Automation and Real Time Surface Monitoring systems gives pictures of downhole gas lift performance not seen before.
An example(s) will be shown of a well unloading after a workover. This has become a great visual aide for training. Other examples including a suspected packer leak, a sliding sleeve leak, and weak/damaged valves in the gas lift string will also be offered and discussed. We have observed valves opening and closing in just a few minutes that could not be detected by conventional slickline pressure/temperature memory gauges.
Gas-Lift Field-Wide Optimization Session
Petroleum Consulting Limited (with Amerada Hess) / Fortune Bikoro / Unlocking the Value in Marginal Mature Fields: 'Chasing the barrels by field-wide gas lift gas allocation optimisation' / Most of the producing wells in IVRRH fields can no longer flow naturally; the gas lift is an important slice of the production pie contributing to approximately 65% of the total oil production.
One of the key aspects of gas lift is the interaction between wells in a gathering network, as the backpressure from additional gas in the flowlines will adversely affect production from all the other wells. The impact of all of the other wells sharing the flowlines in a gathering network is to add to backpressure on an individual well, thereby lowering its production rate as well as the optimal rate of gas injection. Such adverse backpressure effect in IVRRH fields accounts approximately for a production loss of 1,000 BOPD out of a total production of 11,000 Bbls.
The presentation covers the approach taken to the problem of gas lift gas allocation in IVRRH fields by using a network analysis program that optimizes field-wide gas lift allocation, the program combines individual well performance models to build a complete production system model from the sand face through to the separator.
The delegates will learn how this approach has allowed the backpressure effect to be modeled, understood and how substantial oil production gain has been achieved.
Edinburgh Petroleum Services / Alasdiar Brown / On-Line Field Wide Gas-Lift Optimization / Many oil companies currently have initiatives to assess how to maximise the business value returned from their investments in real-time measurement and control systems such as SCADA and SMART wells. One of the most obvious ways of achieving this is by integrating a field-wide optimization system with the real-time measurement system, so that real-time data can be used as optimizer input, and optimizer recommendations can be automatically implemented by control devices in the field.
In this presentation, we describe EPS’s experience of implementing this type of online field-wide optimization system in two gas-lifted fields. We will cover the methodology used to model the entire gas-lift production facilities including the gas distribution system, and will explain how the workflow, integration, maintenance and data management aspects of the online system were addressed. We will also present results which demonstrate how the implementations generated business value, and will describe the lessons learned and how various roadblocks to progress were overcome.
ConocoPhillips / Kenneth Lloyd Martin & Tom Nations / Kuparuk River Field Gas-Lift Optimization and Production Allocation System / The Kuparuk River Field operated by ConocoPhillips Alaska, Inc, (CPAI) has recently implemented a new field-wide gas lift optimization and production allocation program.
This cross application computer program utilizes performance curves with the equal slope incremental gas-oil ratio (IGOR) method to estimate optimum gas lift rates for each well in a compression constrained network of 46 drill sites and over 400 gas lifted wells using 400 mmscf/d of lift gas.
Engineers create a suite of performance curves for each well using well test data, hydraulic models, and nodal analysis to create an inflow performance relationship.
These curves are used to estimate hourly production rates as gas lift rates and flowing tubing pressures fluctuate.
As conditions in the field change, CPAI personnel compute an IGOR target to fully utilize the available compression capacity.
The SCADA system automatically computes new recommended gas lift rates for each well using the equal slope method and adjusts the automated chokes for those wells so equipped.
Benefits of the system include reduced production losses due to testing at suboptimal gas lift rates to determine IGOR behavior, better estimates of IGOR optimum at rates beyond recently tested gas lift rates and optimization of all gas lifted wells to utilize the available compression space.
Occidental of Elk Hills / Patrick Lee Matthews / Occidental of Elk Hills Field Wide Automation/Optimization / A brief overview will be presented of Oxy’s Elk Hills Gas Lift System. A total of 100 wells on are on gas lift producing approximately 10,000 BOPD, 20,000 BWPD and 16 MMCFD produced gas. Daily gas lift usage averages 40 MMCFD. Gas lift at Elk Hills is applied to a multitude of reservoirs and operating conditions making each well unique. The number of wells on gas lift has only shown a net increase of twelve wells in the past eighteen months, but thirty wells were taken off the system and forty two wells added to the system challenging the gas lift system in whole and the engineers/technicians responsible for well surveillance and optimization.
Oxy has implemented field wide automation over the past few years, first concentrating on beam pumped wells and this year (2002) has added automation and real time monitoring to its gas lifted and flowing wells. Examples of Oxy’s real time data gathering system which provides casing pressures, tubing pressures, gas lift rates, flowline temperatures and gas lift supply pressures will be shown. The system has alarms which provide instant notice to surveillance and operating personnel of low gas lift rates, high flowline pressures etc.
The presentation will also include how the real time data system is combined with conventional diagnostic tools such as pressure/temperature traverses, fluid levels, two pen charts and well tests to trouble shoot problem wells. Oxy’s work with distributed temperature fiber optic wireline surveys that provide instantaneous temperature profiles of the well bore top to bottom every few minutes will be highlighted. Optimization of individual wells by converting from continuous injection to intermittent (pilot valve) gas lift and treating the gas lift stream to break downhole emulsions will be reviewed.
Gas-Lift Deepwater and Subsea Session
ChevronTexaco / Shauna Noonan / Gas-Lift Versus Other Lift Methods for Subsea and Deepwater Developments / Gas-lift is not the only lift method being evaluated and used for subsea and deepwater developments. With the technological advances ofdownhole hydraulically driven turbinesand electrically-driven centrifugal pumps, the artificial lift selection process has become more complex.
The issue of lift placement(i.e. base of riser, wellhead or downhole) is also debatable.
This presentation will focus on ChevronTexaco's approach to artificial lift selection for its subsea and deepwater projects using various examples from around the globe. Each example has its own unique outcome and quickly demonstrates the impact of flow assurance on lift selection.
Petroleum Experts / Janvier Lissanon / Deepwater Field Optimization with Riser Lift / Conventionally,individual wells are designed as gas-lifted wells. The allocation of the available amount of gas-lift gas was performed depending upon network configuration. However, in deepwater environment (West Africa, Gulf Of Mexico), a new gas-lift technique has emerged: lifting the riser rather than individual wells. The wells are flowing naturally. The technique allows to maximise the oil production by lightening the weight of the fluid column in the riser and hence reduces the back pressure at the well head.
Riser lift can be applied to individual wells, group of wells, and/or entire field.
A successful riser lift consists in finding the optimum gas-lift rate as a function of the response of the wells, the produced fluid, and the production gathering system. For forecasting purposes, the change in reservoir response with time needs to be taken into consideration.
The presentation will focus on how riser lift can be designed and applied on a daily basis. The presentation will also demonstrate how the future performance of a fully riser lifted production gathering network can be predicted by integrated fluid response, reservoir response, well response and entire network behaviour while respecting all operating constraints.
The benefits of using amodern gas-lift software suiteto achieve an optimum riser lifting to maximize field production will be shown with case studies.
Gas-Lift Facilities Session
Production Associates / John Martinez / Downhole Gas Lift and the Facility / The gas-lift facility is the driving force and the largest capital cos
t component of the system. Excellent production response from gas-lift wells requires that the surface facility provide excellent online performance. This paper reviews the surface equipment and options, and also reviews the impact of facility design on downhole gas-lift operation.
System components
System backpressure and number of wells and operating factor
Power input and system backpressure
Compression options
Dehydration options
Measurement, control, and remote transmission
Flow rate stability and gas injection rate
PEMEX / Miguel Lozada / Self-Sufficient System for Gas-Lift in a Sour Environment / In the southern region of Mexico, in the Mora oil field, which is 60 kilometers from Villahermosa, Tabasco, a project for a self-sufficient system for continuous flow gas-lift in a very harmful sour gas environment was carried out. This was done because gas-lift infrastructure isn’t going to be installed in the short time, because many problems have arisen in the surrounding communities.
The philosophy of this system is to separate the gas from the liquid in order to compress it and inject it into the well as a source of gas-lift, using special coiled tubing for sour gas handling. In addition, a continuous chemical inhibitor injection was carried out to protect the tubing and the coiled tubing from either cracking failure or corrosion, because the H2S and CO2 content in the mixture is too high.
This paper presents the design and the material selection process for this particular application, based on the well productivity. Sizing the equipment and selecting the appropriate material were a special issue for the success of this application, as the cracking and corrosion problems were likely to happen.
During the month of March, 2002, the test of the system was carried out, getting good results, regarding the objective of avoiding the cracking and the corrosion problems. Some problems of instability were presented during the test, but with a modification in the system, these problems were overcome. Nevertheless, some problems of premature failure in the suction valves of the compressor have occurred, which are being addressed at this time.
Due to this test, a major project has been started to install this system in those oil fields that produce sour gas and don’t have any gas-lift infrastructure.
Weatherford / Bryan Butler / Using a Pump for Wet Gas Compression / The RamPump is a single stroke, duplex pump that is hydraulically driven (similar to a hydraulic press).Its long stroke and large plunger diameters result in relatively high volumetric efficiency, allowing the pump to be used as a multiphase pump, compressing either gas or liquids or combinations.
By equipping the pump with HP limiting controls the pump may be operated in a mannersimilar in certain aspects to that of reciprocating compressor, resulting in a "wet" compressor that will operate with similar HP requirements; but whichcan also manage occasional slugs of liquidsas well as solids.
The paper traces the development and application of the RamPump, and discussesfield practices using this equipment.
Gas-Lift Field Reviews and New Technology Session
Altec / John Lebeau / Gas Lifting Gas Wells / The typical production cycle of a gas well in the Gulf of Mexico is that it flows naturally with little or no liquid volumes. Gas production will decrease as the pressure declines and/or the influx of water increases. Traditionally gas well completions in the GOM have not considered artificial lift utilizing gas-lift systems. In the early life of a gas well, artificial lift is not required. However, when the well ceases to flow, gas-lift can be utilized to return a well to production. Utilizing gas-lift systems can increase the total recovery of the reserves.
This presentation will show examples of different methods of lift with total cost and days pay-out.
Schlumberger / Boots Rouen / Gas Lift Gas Wells / Mr. Rouen will discuss liquid loading problems in gas wells and how they can be alleviated by utilizing gas lift. He will describe the components of a gas lift systems and provide numerous case studies including coil tubing gas lift. In addition, the economic benefits of gas lifting gas wells will be described.
ExxonMobil / Pat Underwood & Jacob Null / CO2 Gas-Lift / Presentation will be given on the Postle Field CO2 gas-lift project, including a brief description of the field history and the reservoir. Will describe types of artificial lift and problems associated with corrosion, and wag cycles, leading into why CO2 gas-lift is being used. CO2 gas-lift design, sub-surface and surface will be explained along with start up and optimization. Results of CO2 gas-lift will be included. Jacob Null will describe recent failures and steps toward redesigning of system using composite coiled tubing.