Wellhead HIPS with Automatic Testing and Self-Diagnostics

Abstract

A method for diagnostics of a high integrity protection system (HIPS) for protection of a pipeline downstream of a wellhead includes: monitoring for initiation of an automatic trip or manual safety shutdown or full shut-off test; determining the process safety time (PST) that elapses between the time at which the upstream pressure reached the trip setpoint and the time at which the upstream pressure reaches the maximum allowable piping pressure (MAPP) of the downstream pipeline; and verifying that the safety critical isolation valves stroked to the fully closed position within ½ PST and that the downstream pressure did not exceed the MAPP. If the verification is successful, no action is required, whereas if the verification shows that either of those parameters are not met, then the HIPS signals an alarm to operators, and in the case of a manual safety shutdown or full shut-off test, resets the pressure trip setpoint to a lower level.

Description

RELATED APPLICATION [0001] This application is a Continuation-in-Part of U.S. patent application Ser. No. 11 / 648,312 filed on Dec. 29, 2006, which is incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention relates to a method and an apparatus for the operation and testing of a high integrity protection system (HIPS) connected to a wellhead pipeline system. BACKGROUND OF THE INVENTION [0003] In the oil and gas industry, wellhead topside pressure may exceed a maximum allowed pressure within production fluid pipelines downstream of the wellhead due to degraded pipe wall thickness or cost limitations that prevent the installation of full-rated piping. It is therefore necessary that such pipelines be protected against excessive pressure that might rupture the pipe, which would cause environmental pollution and be very expensive to replace. A conventional system used to protect pipelines from over-pressure is the high integrity protection system (HIPS). This i...

AI Technical Summary

Benefits of technology

[0021] In a preferred embodiment, the safety logic solver is programmed to maintain one set of the SSVs in an open position when the parallel set of SSVs is moved to a closed position from an open position during a tight shut-off test. In addition, the safety logic solver is programmed to measure and record the pressure between a pair of the closed SSVs during the tight shut-off test, and to open the VCV between the closed SSVs for a short period of time during the test to relieve or reduce the line pressure.

Problems solved by technology

In the oil and gas industry, wellhead topside pressure may exceed a maximum allowed pressure within production fluid pipelines downstream of the wellhead due to degraded pipe wall thickness or cost limitations that prevent the installation of full-rated piping.

It is therefore necessary that such pipelines be protected against excessive pressure that might rupture the pipe, which would cause environmental pollution and be very expensive to replace.

It is a necessary requirement that the safety of the HIPS be tested regularly since a malfunction in operation of the HIPS presents the risk of significant damage to the pipeline.

The conventional system cannot be tested during its operation.

The interruption of operations has serious financial implications.

This test system is useful for testing surface safety valves in hydraulic circuits, but does not provide safety information of the overall system's ability to perform safety function.

This system, however, has to interrupt production for the diagnostic testing.

The protection system, however, does not provide any valve diagnostic means and is forced to interrupt the production for shut off valves to be fully closed.

This system does not permit a testing of shut off valves without an interruption of production.

This method, however, requires that the production be interrupted for the testing of the hydraulic system.

The system results in an interruption of production and operators intervention.

An additional limitation of existing testing and protection systems relates to diagnostic procedures.

However, this procedure does not take into account the fact that process dynamics and valve stroke time can change with the passage of time.

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