Category Archives: Blog post

Compressor Insights from Detechtion – September 2016

By | Blog post | No Comments


Thought of the Day


Aligning Business Objectives When Natural Gas Producers Lease Compression Assets

The line between operational and maintenance responsibility is often blurred when managing a fleet of compression assets. Additional complexity is introduced when some of the assets are owned and some are leased. In this quarter’s blog, we will look at the different philosophies and metrics for operating and maintaining a fleet of leased compression assets.

When a natural gas production company leases compression assets to service their gathering network, they generally agree to service level agreements around availability and mechanical availability with the compression leasing company.

Availability is generally defined as:

Total Available Runtime Hours – Total Downtime Hours
Total Available Runtime Hours

Total downtime hours include both scheduled downtime for preventative maintenance and compressor overhauls as well as unscheduled downtime for any reason not associated with scheduled downtime.

Mechanical availability is generally defined as:

Total Available Runtime Hours – Downtime Hours Due to Mechanical Issues
Total Available Runtime Hours

The natural gas producer and the compression leasing company agree to terms and service levels around these two metrics and then move to operations. However, these two metrics do not take into account the level of efficiency or utilization that each compressor has delivered for each hour of runtime. Consequently, a leasing company may meet their contractual guarantees of availability and mechanical availability, while opportunities around process losses and inefficiencies caused by the mechanical conditions inside each compressor and cylinder go unrealized as that responsibility remains with the entity responsible for operations. It is in these instances that Detechtion can help bridge the gap between maintenance and operational philosophies. Using Enalysis™, we can help leasing companies meet their service level agreements around availability and mechanical availability and highlight utilization opportunities that can be acted upon and realized by operations.

When a natural gas producer deploys Enalysis™ on those leased assets, operational opportunities that either increase throughput or save on power consumption are quickly identified. These opportunities are sent to the compression leasing company and natural gas producer. Depending on who is responsible for operations dictates how those opportunities are realized.

In a best practice we have observed, there are joint monthly meetings with the leasing company, operating company and Detechtion to ensure that business objectives are aligned. At these monthly meetings, opportunities for increased gas throughput (along with recommended operating changes like pocket adjustments, speed changes, etc.), power savings, and any inefficiencies identified through Enalysis™ are jointly reviewed and prioritized. Whether implemented by the leasing company or by the operator, the benefits are significant. We have found that utilization opportunities average about 1.5% of daily throughput and power savings average about 6% annually.

By deploying Enalysis™ on leased compression assets, natural gas producers can then feel confident that they are getting the most out of their compression investment and the leasing company can drive towards that peak efficiency with the confidence that they are not exposing their compression assets to extreme conditions as they move towards increased availability and mechanical availability through predictive maintenance analytics.

If you are a natural gas producer who leases compression assets or the leasing company that provides them and want to make sure that utilization of those assets is being measured and acted upon, please reach out to us at Detechtion so we can quantify what opportunities exist in a leased compression fleet.


Representative Win


Increased Throughput – Maximizing Power Usage

Proposed

Optimize the client’s compressor station to maximize production and increase overall utilization.

Background

A compressor station composed of two identical reciprocating compressors was commissioned in a high activity field aimed to accommodate high flow rates and variable conditions. Cylinder actions were setup as single-acting to accommodate the variable conditions resulting in high uptime, and swinging gas flow rates. The subsequent year, activity in the field slowed and the rates/pressures steadied. With the steadied pressures and slowly declining gas rates, the two compressors became ideal candidates for optimization as identified through Enalysis™’ Cash Flow at Risk and Incremental Production calculations.

In an on-going effort to improve on and meet production targets, the gas producer opted to pursue the potential for increased production through compressor optimization.

Optimization Methodology

For a reciprocating compressor to be fully optimized for maximum throughput, either or both of the cylinder capacity utilization and the horsepower utilization should be 100%. Through the use of individual compressor performance curves, such as the one below, and a Detechtion Technologies’ Start-up Package of high and low pressure set points, detailed in this edition’s Tech-Tip, compressor units can be evaluated for opportunities to:

  • Increase running speed
  • Adjust cylinder action
  • Reduce added cylinder clearance
  • Optimize suction pressure
  • Decrease recycle set point

Thus resulting in increased utilization and maximum throughput.

Outcome

After a detailed review of the current compressor station operating parameters through Detechtion Technologies’ Enalysis™ system, a new configuration with new high and low pressure set points were presented to the gas producer. With the new configuration, the compressors were capable of flowing more gas at much lower suction pressures than the current plant inlet pressure.

The new pressure set points were programmed into each panel to protect the compressors, the stage 1 cylinders were changed to double acting from single acting, the pockets were adjusted to 1.75” and the suction set-point decreased by 23 psig to pull harder on the field and increase production.

The changes resulted in approximately 4.6 mmscfd of additional throughput for the station as the field production was stimulated by the lower suction pressure. For the time frame that was closely observed, the units sustained an average production increase of 4.6 mmscfd over the following 30 days, equating to an immediate $414,000 in revenue increase for the time frame observed, assuming $3.00/mscf that, when annualized, resulted in $5,037,000 in increased revenue!

Compressor Configurations Power Usage Suction Pressure Discharge Pressure Station Throughput
Before SAHE0”,SAHE0”//DA0”//DA0” 74% 75psig 750psig 11.0mmscfd
After DA1.75”,DA1.75”//DA0”//DA0” 96% 52psig 750psig 15.6mmscfd
Change +22% -23psig 0psig +4.6mmscfd


Tech Tip


The Optimization Life-Cycle

Compressor optimization is an ongoing process aiming to maximize production revenues while minimizing operating costs, all the while holding safety paramount. The engineering approach and delivery to achieve compressor optimization will vary on a case-by-case basis, while the workflow process often remains the same:

  1. Identify Opportunity
  2. Define Optimization Objectives
  3. Create Solution – Start-up Package
  4. Track Results

The steps above highlight the basic framework needed to assess an optimization opportunity. Often times, there are restrictions set by existing business processes, upstream/downstream conditions, parallel/series compression, or facility limits which must also considered but are not detailed in this article. It is important to consider the impact of any process change, in order to anticipate the expected benefit and risk as part of any management of change (MOC) process. With proper planning and execution, compressor optimization often results in a high value return for low cost efforts!

    1. Identify Opportunity

Finding an opportunity is the first step in optimizing a compressor. Whether you are regularly assessing Enalysis™ reports or closely monitoring its operation, here are some questions you can ask yourself to see if an opportunity presents itself:

      1. Is your compressor not meeting the defined objectives it was set out to do?
      2. Is your compressor bypassing or pinching back the suction control valve often?
      3. Is your compressor frequently hitting alarm set points?
      4. Does your Enalysis™ report frequently indicate CFRs or other flags?

If the answer to any of these questions is yes, then you might have an opportunity to improve production or reduce your operating costs!

    1. Define Optimization Objectives

Defining the ideal outcome beforehand can determine the success of the opportunity early on. Accommodating additional production, allowing for increased line pressure, or improving on the current operation are all common scenarios that can typically be defined with some accuracy. By considering a range of operating conditions, we can setup a compressor more capable of handling a multitude of conditions.

When given a range of potential operating conditions, Detechtion will often focus on accommodating a wider array of conditions, instead of running at a fixed point. The reason being is that compressors are often subjected to variable conditions, and any time a compressor pinches back gas with the suction control valve or recycles to regulate pressures, efficiency is lost.

    1. Create Solution – Start-up Package

Using Detechtion’s Curves, Online Simulator, or reaching out to your Engineering Account Manager will enable you to find the optimal solution for your compressor. Assuming we have a 3-stage compressor, and are setting up the compressor to handle the 8 to 10 mmscfd at a discharge pressure range of 700 to 1100psig, Enalysis™' Simulator determined the ideal configuration to be DA2”, DA2"//DA0"//DA0" with the limiting factor being 99% HP Utilization. Upon finding the ideal configuration, we need to verify the compressor can handle the other operating conditions, and make sure we are going to be satisfied with the outcome.

Variable Min Average Max
Configuration DA2",DA2"//DA0"//DA0"
Discharge Range (psig) 700 1000 1100
Flow Range (mmscfd) 8 9 10
Suction Pressure (psig) 58 67 77
HP Utilization (%) 77% 91% 99%

Running two more simulations as seen in the above chart proves that we can operate in our desired minimum to maximum range. The next step is to determine the full operating range for our compressor with the creation of a start-up package.

Detechtion produces start-up packages for our clients which is a document that details the configuration, control points, and shutdown set points required for the compressor to run optimally. The start-up package considers the full range of pressures that the compressor could operate in and limits the conditions so that it will not exceed any potentially catastrophic conditions. For example; Rod Loads, net rod loads, reversals, and low volumetric efficiencies, are factors not visibly evident but could have catastrophic results if not considered.

The process for creating a start-up package may differ depending on your equipment, maintenance practices and/or operating philosophies. The process that Detechtion typically follows is detailed as follows and is based on 4 operating points:

Limiting Factors/Objectives High Shutdowns High Suction Control
Keep Driver Utilization <105% <99%
Keep Rod Loads <95% <90%
Keep Reversals <65% <70%
Corresponding Load Step 1 2
Limiting Factors/Objectives Low Suction Bypass High Suction Control
Keep Discharge Temperatures < Max Allowable < Max Allowable
Keep Volumetric Efficiencies >20% >16%
Keep HP Utilization >30% >25%
Keep Rod Loads <90% <95%
Corresponding Load Step 4 6

Using these 4 operating points as our limiting factors, the following start-up package was created and represents the full operating range along with the control points and shutdowns for our chosen configuration. This documentation and knowledge can now be handed off to the personnel responsible for completing the MOC review and making the adjustments:

Although the objective only required the asset to move between 8-10mmscfd at a 700-1100 psig discharge pressure, the above start-up package indicates that if needed, the compressor can handle flow between 5-10 mmscfd, between a range of 35-77 psig suction pressure while protecting the units if these wider ranges are exceeded. The wider operating band will keep the unit out of recycle ultimately improving the unit’s overall efficiency.

    1. Track Results

After the changes have been made and the compressor is optimized, it is important to ensure that the results were as expected. Detechtion has numerous approaches to assessing the benefits of a configuration change which involves assessing changing trends, verbal feedback, or looking over a time period. Assuming the data is available, comparing the 30 days before and after the optimization provides an excellent resource for assessing the overall outcome of the change and whether or not the opportunity was acted on effectively or if further opportunities exist for optimization.

Key Performance Indicator 30 Day Before 30 Day After Change Comment
Average Production (mmscf) 9 9.2 0.2 $12,000/month Production Gain (@2.00/mscf)
Average Suction Pressure (psig) 70 66 -4
Average Discharge Pressure (psig) 1000 1000 0
Average HP Utilization (%) 85 92 7 $1,020/month increase to fuel cost (@2.00/mscf)
Average Fuel Usage (mscf) 212 229 17
Downtime (hrs) 18 6 -12 $xx,xxx/month saved in personnel callouts

If you are happy with the results, it is time to give those involved a pat on the back for creating positive results, continue monitoring the asset, and look for the next opportunity!

Compressor Insights from Detechtion – May 2016

By | Blog post | No Comments


Thought of the Day


Finding Hidden Revenue In Your Existing Compressor Fleet

The current downturn in commodity pricing has had a massive effect on the capital and operational expenditures of Oil and Gas Producers in North America. With these companies cutting their capital spending and investment, they are no longer able to increase revenues by drilling new wells and must look elsewhere to create business value. While many of these companies are focused on decreasing operating expenses to weather the current downturn, there are other alternatives that can be used to unlock hidden potential in their existing assets.

The three main KPIs to measure the success of a fleet of compressors are utilization, availability and reliability. Most companies employing compression fleets have programs to address availability and reliability, but few address utilization. Common problems in utilization include lost revenue opportunities caused by damaged valves, piston rings or suboptimal configurations. Without a tool to measure these missed business opportunities, the companies are blind to the business intelligence that could highlight them.

If you are responsible for the profit and loss of a group of compression assets and you have not equipped your Reliability, Engineering, and Operations groups with a tool that measures utilization, you will never know if your compression assets are running as close as possible to their true potential. Equally, if you are a member of one of those groups and are given the responsibility to optimize your company’s compression assets, a tool that measures utilization and gives actionable information on how to achieve optimal performance is vital to your success.

At Detechtion, we offer Enalysis™ as that tool. We routinely find 1 ½% to 2% revenue increases by finding opportunities such as:

  1. Unseen production potential
  2. Unseen maintenance issues
  3. Fuel and power overconsumption
  4. Risk of catastrophic equipment failure

If you’ve been limited in investing in the health and potential of your compression fleet due to the current downturn in commodity pricing, now is the time to invest in a tool that will give you visibility into both.

Next Issue’s Topic: The pros and cons of the different operating philosophies in managing compression assets


Representative Win


Total Fleet Performance – Increased Utilization

Proposed:

Continuous optimization of the client’s compressor fleet for maximum throughput and equipment utilization.

Outcome:

Compressor performance is tracked within Detechtion Technologies’ Enalysis™ system every time a compressor’s operating data is entered to generate an Enalysis™ performance report. Clients, therefore, have the ability to track and report compressor fleet performance and various other parameters via Fleet Management Reports and Tools within Enalysis™.

The Performance Graph in Enalysis™ graphs the average performance (compressor flow divided by the total potential flow) of the compressor in a certain region over a period of time. This graph is, therefore, a direct indication of the utilization of the compressor, as determined by the greater of the power utilization and the cylinder capacity utilization, and allows the client to identify the regions where production is not optimized.

The graph shown below represents the performance for the entire compressor fleet of a long term Detechtion client over a period of 5 years. The graph shows a continuous improvement in compressor fleet performance over the last four years and a total, fleet-wide performance improvement of more than 7.5%.

What is the value of 7.5% increase in total fleet performance?

In the case of this client, with a compressor fleet of well over 100 operating units and more than 200,000HP, 7.5% could represent 15,000HP of power used more effectively.

Alternatively, with a reported daily throughput of more than 1,000mmscfd, 7.5% could represent 75mmscfd of increased potential production.

Input your average daily gas price ($/mscfd) to see what this could be worth to your company:

Gas price: $
Throughput: mmscfd

Result: $54,750,000.00/Year

Background:

Maximizing the throughput of a compressor simply means maximizing the capacity of the compressor. In a competitive natural gas gathering application, maintaining the lowest suction pressure can provide a significant production advantage to any gas producer.

To maximize the throughput of a reciprocating compressor there are two concepts in play. The first concept being, the gas has to go through the first stage of a compressor to go through the rest of the unit; hence the importance of maximizing the capacity of the first stage cylinder(s). The capacity can be impacted by clearance devices such as Variable Volume Clearance Pockets (VVCP) or Fixed Volume Clearance Pockets (FVCP) that add clearance to the head end of a cylinder. Clearance can be added to the crank end of a cylinder by adding valve spacers under the valves. The running speed of the compressor and single acting the crank end or head end of a cylinder will also influence the capacity of the machine. The second concept is to increase the capacity of a compressor by increasing the suction pressure; which means that the suction pressure is dictated by the flow of the compressor or vice versa.

The loading curve shown in the figure below shows the optimized performance of a two stage unit at a discharge pressure of 870 psig. The curve can be divided into three segments: the cylinder capacity, the knee and the power section.

  • The cylinder capacity portion of the curve implies a cylinder capacity utilization of 100%, which means no clearance is added to the first stage cylinder(s) and the driver is running at maximum speed. This can be translated on to having the first stage cylinders double acted with no spacers, the VVCP or FVP fully closed and the driver speed set to the maximum.
  • The power section of the curve indicates a horsepower utilization of 100%. In this portion of the curve, clearance devices are generally used to unload the driver and this is translated as an increased capacity while maintaining the horsepower usage to the maximum.
  • The knee of the curve is the only point on an optimized loading curve where the cylinder capacity utilization and horsepower used is at 100%.

For a reciprocating compressor to be fully optimized for maximum throughput, either or both the cylinder capacity utilization and the horsepower utilization should be at 100%.
Through the use of individual compressor performance curves, such as the one above, and a Detechtion Technologies Start-up Package of high and low pressure trip-points, shown below, compressor units can be evaluated for opportunities to:

  • Increase running speed
  • Reduce added cylinder clearance
  • Optimize suction pressure
  • Decrease recycle set point

Thus resulting in increased utilisation and maximising throughput.


Tech Tip


Over/Under Compression in a Rotary Screw Compressor

Screw compressors are a crucial part to the natural gas industry, and typically operate under wide variants of operating conditions in both gathering and process applications. Whether the compressor is experiencing pressure and volume fluctuations, temperature swings or changing gas composition, the screw compressor is a reliable piece of equipment that powers through operational swings without issue. However, this doesn’t mean that the compressor is operating as efficiently as it could be!

Optimization can result in significant power savings and/or reduce the potential for catastrophic failure. It is beneficial to analyse the performance at frequent intervals to ensure your screw compressors continues to operate without issue, at low cost. The most common method to optimize a screw compressor is by adjusting the Internal Volumetric Ratio (Vi). Adjustments to the Vi are recommended when the unit is experiencing over or under compression, or the internal discharge pressure exceeds the max allowable.

The following graphic allows you to visualize the relationship between pressures, Vi and gas composition to better understand the compression process, and the effects those variables have on power requirement. Note that the process highlighted in the graph is as follows:

  1. A volume of gas is captured in the rotors: (At Suction Pressure)
  2. The volume of gas is compressed in the rotors: (Increasing Pressure)
  3. The volume of gas is exposed to the discharge line and expelled: (At Discharge Pressure)


*Note that the graphic is conceptual, and does not account for partial loading due to the slide valve.

For questions regarding the performance of your screw compressors, please contact your Detechtion representative.