Cost Effective System Solutions for Deepwater Production Controls
Authors: Allen John 
Published: October 2008

As oil and gas developments move into the more difficult areas of deep water, high pressure, high temperature and potential long offset distances, the challenges posed have to be met. Technology is being developed to meet these demands and to provide cost effective solutions for the future. Long offset tiebacks to shallow waters or the use of floating production platforms in very deep water pose significant problems. Cost effective intervention techniques are becoming critical in verydeep water.

Introduction

Developments in sub sea 'Electrical' controls have made significant progress since the acceptance of Multiplexed Electro-Hydraulic (E/H) control in sub sea oil and gas production controls. Methods and technologies have been developed to enable long offset controls to be implemented 'cost effectively' and for sub sea equipment to be configured in a way which is easier to install (and retrieved) in deepwater.

Techniques to minimize umbilical (constituent parts) and hence cost, as well as to achieve long distant (70 mi.+) transmissions have now been developed and are in service. The availability of lightweight mini Sub sea Control Modules (SCM) which are Remotely Operated Vehicles (ROV) 'handle able' have minimized intervention (installation and retrieval) costs, particularly in deepwater.

The development of additional 'Electrical' sub sea monitoring and control packages such as flow monitoring and separation & pumping has led to the provision of the sub sea distribution of significant levels of electrical power. This evolution in sub sea monitoring has also necessitated higher levels of data handling capability. This has led to innovative pproaches to sub sea system which are not only technically demanding, but due to the nature of the business today, are also highly focused on developing cost effective solutions. As offshore oil and gas developments move into deeper and deeper water, the application of these technologies has an increasing focus on the application to deepwater.

Control System strategies also relate to the flow line. Such systems as High Integrity Pipeline Protection Systems (HIPPS), are aimed at effective cost management with long offset distances. Monitoring packages which provide flow assurance with long distance or difficult reservoirs are also an important development.

Umbilical System Enhancements and Cost Minimization

Minimized Umbilical Solutions.

The umbilical systems for sub sea control have become more compact by the move away from hydraulic controls, towards Electro- Hydraulic (E/H) controls. A typical E/H umbilical is shown in Figure 1. This composite bundle will usually be sheathed and armored, but will contain redundant hydraulic low pressure lines as well as high pressure lines and separate electrical power and communications lines.

Through recent developments (which are now installed and gathering track record in the Industry) these constituent elements have been systematically reduced. As an example the use of Communications superimposed On electrical Power (COPS) removes the need for separate communications and power cores as shown in Figure 2.

The use of High Pressure Intensifiers (HPI) which are located in the sub sea control module, removes the need for high pressure hydraulic supply hoses in the umbilical as shown n Figure 3.