Integrated wellhead packages

Oceantech "Oilswell" Product Line

An Oilswell Panel

Current approach

Most well head system packages are purchased as separate packages namely:-

Hydraulic vendor
RTU/SCADA vendor
Fire and Gas vendor
Solar power system vendor
Field Instrument vendor

The responsibility of integration is left to the end user or his contractor.

has reviewed the current philosophy and by questioning users with regard to operation and maintenance and found that current systems are suffering from these problems

Hydraulic/pneumatic system

Leakage
Mechanical problems with valves and fittings

RTU system

Requires safe area building therefore a larger deck to be outside the hazardous area
Large solar power requirements

Fire and Gas

Same comments as RTU system

Radio Telemetry

Large wattage radio system thus same comments as RTU system

Integrated approach

have developed products and integrated them into a combined wellhead control package. This became possible with the introduction of the Intrinsically Safe RTU/PLC

System responsibility

By integrating the following system components the wellhead package becomes a single source responsibility by one vendor. This also allows the system to be fully tested at the factory before shipment, thus reducing expensive site commissioning time and charges by a number of vendors.

Hazardous Area

The use of intrinsically safe components in the system means that the wellhead control package can be located in the hazardous area, hence, no requirement for a safe area or control room.

Environmental Protection

The Wellhead Control Package is built as a single cabinet to meet Ingress Protection IP65. Further, components located within the cabinet meet IP55 minimum. Thus offering a double protection against the environment.

Integrated Components

Hydraulic package

The feature of the design is that it uses as many maintenance free components as possible. All pipe fittings, as far as pratical, use orbital welded fittings thus providing a lifetime free of maintenance and leaks. The design also removes all ESD logic by mechanical devices and replaces this with more reliable electronic components. Thus the hydraulic pipework is reduced to a minimum.

HPU

This provides the hydraulic power for the system and comprises a reservoir, pumping system, accumulator and pressure protection.

With the use of leak free fittings the pumping system uses electric pumps driven from the Solar power system. Pressure control is provided by Hi/LO pressure switches, with operating logic in the PLC/RTU system. The pumping system, in normal operation, will run for 20 minutes a week. Accumulators are sized per client requirement.

Wellhead Valve control

Is achieved by the use intrinsically safe solenoid valves. By-pass manual valves are fitted around each solenoid valve to permit manual operation and ease of maintenance.

Pipe work is sized to provide quick closure of each wellhead valve. An adjustable needle valve is fitted in each line to set the closing flow to suit the process conditions.

All logic for wellhead valve operation is programmed as part of the PLC/RTU system.

Remote Telemetry System

The Intrinsically Safe PLC/RTU provides the following functions:-

Pump control logic
Wellhead valve control and ESD logic
Monitoring of all parameters
Interface to the telemetry system
Local Diagnostics

Safety System

To meet the requirements of the safety case a simple secondary hard wired relay ESD system is provided. In the rare event of an RTU failure, the safety system will shut the well down safely.

Local/remote control station

Part of the Safety system is the local/ remote control station to permit local operation of the Wellhead. This uses push buttons with status lamps to inform the operator.

All local actions are reported to the RTU system and the SCADA system, thus on a return to remote operation the RTU system is synchronised to the current state of the well.

Fire and gas system

Gas detection is provided by Intrinsically safe Gas detectors connected through the RTU. A separate alarm contact is also fed to the Safety system.

Fire detection is by an intrinsically safe fire cable

Telemetry System

Usually provided by VHF/UHF intrinsically safe radio modem transceiver system operating at 1 watt. Depending on propagation calculation Transmission up to 25Km is achieved. When more than one well site is in the system the multi-routing Radnet protocol is used to provide a secure routing of data at all times.

Solar Power System

Due to the use of intrinsically safe equipment the solar power requirements are very low when compared to conventional PLC technology. A typical wellhead panel uses 4 solar panels.

Field Instrumentation

Intrinsically safe to client requirements

SCADA

Dual redundant or simplex systems, per client requirements. Software uses Windows NT and Scadaplus software

Availability

Designed to be better than 99.8% or better

Typical P&ID

Ocean Technical Systems Ltd.
P.O.Box 752, Sutton, Surrey, U.K. SM2 7RQ
Tel: +44 (020) 8643-2233 Fax: +44 (020) 8643-6444
e-mail: oceantech@oceantechsys.com


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