High Integrity Pressure Protection Systems for Production Applications

Abstract

ABSTRACT Through the use of a High Integrity Pressure Protection System (HIPP$) the flare capacity of a well head platform can be reduced to the flowrate required for depressurisation. The HIPPS may also be used to reduce the are capacity of a process plant. By the use of HIPPS, the discharge of hydrocarbons or carbon dioxide due to venting/flaring is reduced. This paper describes the development of HIPPS for the Sleipner B-platform offshore Norway. A 20" multiphase pipeline is protected against overpressure by two 20" quick acting shut down valves (QW installed in series, instead ofpressure safety valves. The valves have been qualified for operation in well stream at a shut-in pressure of 336 bar, and have a closing time of 2 seconds. Each of the QSKS has independent, fail safe instrumentation circuits. A parallel rain of QSV.s has been installed due to the testing requirements. The estimated saving using HIPPS on SLB was $25 mill. The paper also discuss existing and new applications of the HIPPS. INTRODUCTION The Sleirmer Vest is a gas field, containing 33 billion Sm 3 of sales gas 29 million of code oil and; mill. tons of NGL. The development consists of two platforms, a wellhead platform (SLB), and a gas treatment platform (SLT). Platform production is 20.5 mill Sm3/Dof sales gas and 450 Sm3/hrof condensate(including NGL). Sleipner Vest will come on stream in 1996. The well head platform is connected to the treatment platform via a 20" multiphase pipeline. The Sleipner Vest interfiled pipeline has a design pressure of 160 barg, while the wellhead shut-in pressure on Sleipner B is 336 barg. It is therefore necessary to protect the pipeline against the wellhead pressure. The flowrate in the pipeline is 250 kg/s. The main scenarios for over pressure in the pipeline was considered to be hydrate formation, pigging and closing of the inlet valve on Sleipner T. A flare system designed for blocked outlet, i.e. fill flow, is Expensive at the high flow rate required (250 kg). It was therefore decided to use a HIPPS. The HIPPS on Sleipner B is shown in figure 1. PROBLEM DESCRIPTION For this paper HIPPS is defined to be a system for Over pressure protection of process equipment by utilizing dedicated shutdown valves. The HIPPS system protects the equipment against over pressure by closing down the source of the over pressure. HIPPS has been used offshore in production systems for several applications, mostly for tie-ins of new fields to existing platforms, or as a modification to platforms where the flare capacity is limiting for the oil production. A number of different valve types, instrumentation concepts, valve configuration etc. has been used. In terms of equipment, valve configuration etc. API RF'14C, ref. /1/, has traditionally been used for design of process safety systems offshore, but does not describe the application of HIPPS. Overpressure protection by the use of double shut down valves is permitted for wells, but the use of additional PSVS are still recommended by API.