Intelligent Running Tools for Subsea Drilling and Completion Equipment Using Acoustical Two-Way Communication Between the Subsea Wellhead and the Surface
Authors: Burton J.A. , Cassity T.G. , Taylor B.M. , Martin J.D. 
Published: October 2008

The development of intelligent running tools (smart tools) for subsea drilling and completion equipment is presented. The system provides intelligent feed-back of critical parameters while landing and operating subsea marine wellhead equipment. Two way conmmication is provided between the rig floor and the subsea wellhead and real time data is provided to the operator to allow informed decisions to be quickly made. Many other subsea applications are envisioned for this simple and rugged communication system.

INTRODUCTION

With the recent upturn in subsea drilling and production activities, safety and reliability have continued to grow in importance. To maintain the level of safety required, subsea operators must be able to reliably verify that all operations are performed accurately. In 1987, a cause-of-malfunction survey conducted for marine wellhead equipment showed that a significant number of field problem were not caused by equipment failure, but rather by various types of mislocation errors associated with improper component positioning within the wellhead. Such errors were especially noted during installation of casing hangers and seal assemblies and retrieval of wear bushings. In any case, the misinstallation of a hanger or seal assembly or the failure to properly retrieve a wear bushing could have expensive and potentially dangerous consequences to the drilling program. In the past, subsea operators have had to perform vital operations with minimal feedback to the surface. Standard rig floor indications (which can be vague or misleading, especially in deep water) have been the basic means to tell the rig operator if procedures have been successfully completed.

DEVELOPMENT GOAL

The development goal was to produce a system which could provide real time data to the rig operator while operating in a background mode without interfering with normal rig operations. Further, the goal was to prove the feasibility of using acoustical means of transmitting data from the subsea wellhead to the surface rig floor.

THE SMART TOOL SYSTEM

The smart tool system is shown schematically in figure 1. System components are shown in figure 2. The system consists of three main assemblies:a remote communications and control box,a surface sub, anda subsea smart sub.

A) The remote communications and control box allows the operator to collect data via FM radio while located in a position remote from the drill floor to eliminate interference with normal rig operations, The control box contains a computer which is preprograrmmed with all the pertinent operating parameters for a number of predetermined equipment systems (For example, different wellhead systems, different functions within the wellhead system, etc.). The operator enters the data to tell the computer which specific type of equipment is being used and which operation is being performed. Then, upon request from the operator, the computer initiates two way communications with the surface sub via FM radio and requests the desired information. B) The surface sub in turn requests the required information from the subsea smart sub. Two way communication between the surface sub and the smart sub is provided by sending binary data via acoustical pulses through the drill pipe running string using an FSK (frequency shift keying) communication scheme. Specialized electronic circuits filter the signal from the background noise.