| dc.description.abstract | With decreasing oil prices, optimizing existing production is essential to generate as much revenue as possible. When the product sold decreases in value, more volume is required to maintain the revenue levels. Therefore, when oil prices are low, well availability is an important contributor to reaching revenue targets. A major international oil and gas company, with assets in NCS and UKCS, had a goal to better understand which failures impact their asset’s well production availability. The goal of this thesis was to determine Company’s assets’ availability though practical system reliability and maintainability.
This was achieved by reviewing historic production performance data. When commencing this thesis, the goal was to obtain knowledge of how the offshore assets were managed to achieve well availability. It was believed that simple manipulations in excel would provide sufficient information to gain an understanding of how the wells are operated. However, as the thesis progressed, new discoveries were made which required further analysis, and most importantly it has been necessary to consider and recommend how to apply this historic insights to improve future performance.
With data collected from the company’s performance database, PPIT. Based on the data, 1,854 production deferrals were issued during a period of nearly ten years for three separate assets. A total of 102 wells were included in the survey. A total of 822 service years were included in the review. Well equipment failure accounted for 40% of the production volume deferred, platform priorities accounted for 28% and reservoir and well service accounts for 32%.
Planned deferrals accounts for 17% of all production volume deferred. The total planned production volume deferred is 7 million BOE. Thus, 83% of the total production volume deferred is unplanned, which accounts for 35 million BOE. The total deferral duration was over 29,000 days, deferring 42 million BOE.
The reliability of the system is calculated using MTBF. The total MTBF, which includes planned and unplanned deferrals, for all assets is 0.45 years. This means that at any given time, any of the company’s wells are, on average, expected to have deferrals twice a year.
The MTBF for equipment failure is 2.09 years. The main contributor to the low MTBF is the “Surface tree” equipment group. Additional equipment groups which causes low MTBF are the “DHSV” and “HPU/Logic” groups. “Intermediate completion” groups did not have any registered failures, this the MTBF is equal to the total service time.
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The repair time to fix the system is determined by calculating the MTTR. The average MTTR for any deferrals for all assets is 16 days. The equipment average MTTR is 26 days. This is also expected, as the equipment MTTR is only unplanned deferrals.
The overall asset reliability is 61%. The industry average, compared to reliability data from WellMaster RMS, is 60%. This, on average, the Company’s assets are according to the expected average. Asset 1 are below the expected performance average, whilst Asset 3 is above. Asset 2 has very low reliability and measures should implemented to increase the overall reliability.
As the components has a generally high reliability performance, altering component reliability will be less effective as the values are already high. Channing high values to higher values will not dramatically increase the availability of the system. Therefore, the focus should be on reducing the time it takes to repair the systems. If a component has high reliability, but is difficult to fix, the availability of the component may be relatively low. The following is highlighted;
Efforts should be made reducing repair time for Cluster 2 equipment. If the repair time cannot be reduced, better maintainability of the equipment should be developed.
To increase availability of the system, the initial focus should be on reducing the repair time of the components.
A significant amount of the equipment has a reliability above 95%.
Repair time has a big impact on the availability of a product.
Company has an overall good performance on the wells system availability. All the assets range between 84% and 93%. This is considerably higher than what was though prior to the commencement of this thesis. Even though Asset 2 is very low on reliability, it still manages to maintain a good availability of the wells. Thus, the maintainability of the wells systems is a very contributing factor in achieving the desired uptime of a well system.
Based on the information found in this thesis, the major contributor in reducing deferred production, and increasing the availability of a well system, is the maintainability of the wells. If the equipment has low reliability but has a relatively low MTTR, the equipment will remain available most of the time. Therefore, the equipment the company should focus on to improve well system availability is the equipment with high MTTR. A high MTTR will cause more production deferrals than a low MTBF. Therefore, measures should be made by Company to
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gather information related to how effective the company is at fixing failed equipment. This may be the most effective method to increase well availability.
For example, a possible way to increase availability is to install redundant systems on the TR-ASV to ensure continuous production. From this thesis, it was disclosed that the TR-ASV single failures caused large amounts of deferred production. By installing redundant system, deferred production can be lowered by tens of millions of dollars over a period of ten years.
Further, it was discovered that the managing of asset performance may be affected by discussions which are not directly related to the well itself. Asset 3 received a platform upgrade in 2012-2013, which has caused the production capacity on the platform to increase. Thus, all well failures cause a full system deferral. This yields less time to fix problems when they occur as the asset needs the production to perform as required. This causes a sub-optimum and “firefighting” environment.
However, overall, the Company has roughly industry average reliability for most assets. Company is relatively efficient at mending their failures. Thus, the availability of all the assets are reliability high. The high availability of the wells are thought to be due to the efficient maintainability skills of the organization. This thesis has proved that if the reliability of an item is poor, but easy to fix, the availability of the well system may still be high. Thus, Company should focus their time on reducing the maintainability of the system first. | nb_NO |
