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An Introduction to Insight - Erosion Management

Increased oil production through effective erosion management.


Insight
New software provides effective, continuous management of erosion development of chokes and other critical flow line components. The solution safely enables operators to increase oil production, while organizing inspection and maintenance work more effectively.This software is called Insight. While originally developed by Production Technology Integrated AS in cooperation with Statoil, it was acquired by ABB early in 2006 and is now a product in the software suite offered by ABB to enhance production and operation.
Figure 1. Insight: Monitoring erosion rate and accumulated erosion in bend and choke for a well.


Sand production
More than 80% of the oil production from the Norwegian Continental Shelf (NCS) is from sandstone reservoirs. Inevitably, some sand will always be produced together with the oil and gas and thereby cause erosion (sand blasting) of chokes and other critical flow line components, such as bends and manifolds. Throughout the life of the field, the reservoir pressure gradually declines while the water production increases. Both factors contribute to an increasing sand production. Recent experience has shown that several fields that initially did not expect any sand production today have the oil production constrained du to sand production problems.

When a well starts to produce a significant amount of sand, the well is routed to a test separator, which offers better control of the sand quantities being produced. The production is then choked back until the sand rate stabilizes on a low level. The well is then routed back through the production system, but now at a lower oil- and gas rate.


Erosion management
The software, which is currently in use by Statoil on the Gullfaks and Statfjord fields on the NCS, offers easy and user-friendly erosion management of individual wells, and thereby enables the operator to allow a higher oil and gas production. Since all relevant production data are automatically gathered and processed, the erosion potential variations for each well is easily spotted through the production visualization screens. For example, a high gas- oil-ratio (GOR) well has significantly higher erosion potential than a well producing at a lower GOR. However, other parameters are also important for the erosion rate, such as choke setting and sand rate.

The Insight software gives the user access to the erosion history of all defined erosion nodes. Every 24 hours the accumulated erosion for each node is updated. In a case where a flow line node has been exposed to high erosion rates, e.g. due to gas break-through or failure of a sand control mechanism, the incident will be recorded and automatically included in the erosion history of the affected flow line elements. The erosion of the flow line elements is more accurate and security is improved. The erosion management system also contributes to a more effective utilization of the resources that goes into the inspection and maintenance of the production equipment.

The erosion software meets three main purposes. These are:
- Erosion estimates based on advanced erosion models
- Continuous calculation of accumulated erosion from condition monitoring
- Evaluation of the performance of installed chokes

The erosion management software contributes to replace the subjective assessments regarding the sand production impact with facts and real numbers.

Figure 2. Insight erosion models: In addition to physical modelling, the models from DNV perform advanced numerical simulations using particle tracking to calculate erosion speed in chokes. (Illustration: DNV).


Software technology
The erosion management solution is built on Oracle and Java technology, and it communicates with other software systems for production control. The erosion development, choke status, and other relevant production parameters are easily accessible using web technology. Furthermore, third party applications, e.g. for multiphase flow, are also made available through Insight. The Insight software is currently managing erosion in more than 240 production wells in the North Sea.
Figure 3. Choke erosion rounds off the edges of a choke. As a result, the flow area increases, resulting in higher throughput (Cv) than the choke setting would suggest. Production is adjusted by relative movement of the two disks. (Illustration: Statoil)


Results
About 50 wells in the Gullfaks field were restricted due to potential sand production. A total retention of 30.000 b/d has been the results of the traditional sand production strategy. By using the new sand management strategy, this is reduced by about 50%, adding a significant amount to the revenue stream. This is equivalent to about $880,000 a day or $300 million a year with an oil price of $60/bbl. Other fields in the North Sea are now looking into ways to implement this new approach.





Statoil's sand management project
Increasing sand production is a common problem in maturing fields, resulting from declining reservoir pressure and increasing amounts of water. Sand production has an impact on both production and safety, because sand causes erosion of production equipment. In some cases, increasing sand production triggers premature shut down of production wells.

Statoil has more than 400 sand producing wells in the North Sea. The sand producing reservoirs with the lowest formation strength are located in the Gullfaks field. (The reservoir rock disintegrates when it is squeezed between the fingers). As a result, Gullfaks was the first field to systematically enhance sand management through investments in knowledge and technology.

A cooperation between Statoil and DNV was established, and a systematic review of the erosion phenomena was conducted. The major break-through of the sand management project reached surface about two years ago, which made it possible for Statoil to control the oil production according to an Acceptable Sand Rate (ASR) instead of a Maximum Sand free Rate (MSR). As a direct consequence, the oil production from the Gullfaks field has increased.

Insight started as a project for Statoil to develop a software solution for online erosion management of critical flow line elements. The system was to be accessible both from the offshore installation and onshore. The Insight software was installed on the Gullfaks field in 2001, and is today keeping track of the actual wall thickness reduction due to the sand production in chokes and other erosion nodes. Besides from an increased production and improved safety situation, the software provides an economical gain due to condition based inspection and maintenance operation. Based on the experiences from the Gullfaks field, the system is now also in operation on the Statfjord field. Insight was acquired from PTI by ABB in 2006.

Additional information about the sand management project in Statoil is available on NPD web pages “Petroleum resource management/Development and operations” http://www.npd.no.

Source: NPD

Figure 4. Both declining reservoir pressure and increasing amounts of water can cause increasing sand production in mature fields. (Illustration: Statoil)


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Last edited 2006-09-28
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