This page gives the "30,000 ft view" of BOP pressure testing in general and discusses the particular advantages that the GreenLight digital pressure testing software has over analogue testing using circle charts.
The relationship of the blow-out preventer (BOP) and choke manifold (CM) valves in a typical deep-water arrangement is shown in the image below. Often, the choke manifold consists of a couple dozen valves and the BOP consists of multiple rams and annulars stacked one on top of the other. Each test of the BOP consists of three main steps
- placing each CM valve into a state (open or closed) and each valve of the BOP into a state (open or closed)
- determining if the system will hold a low pressure
- determining if the system will hold a high pressure
A single test of the BOP may take on the order of an hour. The full test series of the BOP - which consists of multiple tests - can take on the order of days to complete depending on the complexity of the CM and BOP.
The image below shows 11 Tests performed in about 15 hours on a deep-water rig in the Gulf of Mexico. For each test the CM and BOP valves were in different configurations which is illustrated by the images above the P(t) curve. In Test #1, all valves in the BOP - seven rams and both annulars are open - while in Test #11 the Test Ram and Upper Pipe Ram have been closed. Examples of low pressure and high pressure tests are circled in the images below. The current Federal Regulations that govern pressure testing (30 CFR 250.737), require a low pressure test to stay between 250 and 350 psi for five minutes for it to be considered "passing". Similarly, a high pressure test must stay above the test pressure (5,600 psi for all tests shown below) for five minutes or be confidently predicted to stay above the test pressure for five minutes at some point in the future.
Fundamentally, GreenLight offers a new way - a digital way - to assess the low pressure and high pressure tests which are circled in green in the image below. Digital assessment has several advantages - listed below - over analog assessment. However two advantages stand out as particularly important. First, GreenLight never gets tired and is always consistent in its determination of which curves constitute "passing" tests. Interpretation of circle charts by people is an inherently subjective process - each person may interpret the data somewhat differently. Second, GreenLight has the potential of save time. Instead of having to wait until a "flat line" is observed on a circle chart to consider a test to be "passing", GreenLight can call a high pressure test as "passing" when it can confidently predict when a "flat line" will eventually be observed in the future. The Bureau of Safety and Environmental Enforcement (BSEE) reviewed the operation of GreenLight and has accepted it as a system-of-record in the US Gulf of Mexico since 2015. GreenLight has been used in over 40 offshore locations since that time to generate reports that are routinely audited by BSEE inspectors.
The ability of GreenLight to safely pass a test earlier than is possible with a circle chart has a direct impact on the cost of drilling a well. With a circle chart, a "5-minute flat line" needs to be observed before a test can be passed. With GreenLight, the test can be bled-off as soon as a confident prediction of a "5-minute flat line" at sometime in the future is calculated. The benefit of this is illustrated in the image below. Had the test shown below been called using GreenLight instead of by Circle Chart, the pressure could have been bled-off as soon as the color of the high pressure points changed from yellow to green (i.e., just before 11:15) instead of at about 11:35. That is, using GreenLight could have reduced the duration of the 35-minute high pressure test by about 20 minutes, a savings of 57% (= 25 / 35). Actual savings are typically between 25% and 50% depending on test fluid, etc.
The GreenLight field data shown below was acquired for a subsea BOP. GreenLight has also been successfully used to test surface stacks, ISRs and coiled tubing units and has the potential to be used in a variety of other settings. Feel free to contact us regarding applications that you are interested in pursuing.