Intelligent Completion for Oil and Gas Production Control in Subsea Multi-lateral Well Applications
Authors: Tubel Paulo , Hopmann Mark 
Published: December 2007

This paper describes a permanently installed, electronically enhanced, downhole completion system for real-time communication, command, and control of oil and gas production in extended reach, multilateral and subsea wells. The system allows the operator to control the production of hydrocarbons inside a wellbore from remote locations, and thus reduces the need for costly interventions to maintain efficient production rates. Key features of the system include automated monitoring, and permanently installed production control systems that consist of multiple downhole electromechanical devices and multiple gauges for monitoring tubing and annulus parameters. The surface unit controls the activities of the modules downhole by requesting data on a periodic basis; commanding the modules to open or close the electromechanical devices; and changing production monitoring parameters to accommodate changes in long-term wellbore conditions. A hardwire cable provides the power and communications link between downhole and surface, while a surface computer provides data acquisition, processing and communications control.

In addition to describing the system, this paper will outline the objectives associated with monitoring and controlling the production of fluids in the wellbore such as optimization of the production in each lateral of a multilateral well, and the ability to reduce the number of interventions necessary in a well.

Introduction

The development of completion equipment has been based on the deployment of devices that perform individual functions inside the wellbore, ie. packers, safety valves, etc. For the most part, these tools work independently of any other component of the completion. Fig. 1 shows this type of completion system. Consequently the acquisition of downhole parameters from electronic sensors and the control of flow in the well bore is not typically accomplished in real time.

The measurement of downhole parameters during the production of a well can be performed by various methods. Some of the more common are: tools that are lowered and retrieved from the wellbore via wireline and permanently mounted downhole tools. Wireline tools are used for the measurement of formation pressure, temperature, and fluid flow. Formation evaluation tools used for the determination of formation porosity, hydrocarbon saturation, and lithology inside the wellbore are also utilized during well production. Permanently mounted pressure and temperature tools are placed on the outside of the production tubing and are connected to the surface data acquisition system through a cable mounted along the outside of the tubing string. The information obtained from these tools is used to maintain production at optimum levels. Field proven, permanently deployed flow meters may also be placed in the tubing string. These meters require the reduction of the production tubing inside diameter to acquire pressure differential measurements for the determination of fluid flow.

The actuation of downhole devices to control flow is performed today via well intervention methods such as slickline or coiled tubing. A mechanical device is attached to coil tubing or wireline, lowered into the wellbore and used to control flow by plugging, checking or choking production intervals. Zone isolation is performed by landing straddle systems or closing permanently mounted sliding sleeves located in the tubing string. Well intervention consumes a great deal of time, halts production and carries the risk of getting tools stuck in the main production bore. P. 119