New Flow-through Mudmat Design for Heidrun Subsea Structure
Authors: Lieng J.T. , Bjorgen H.P. 
Published: October 2008

ABSTRACT
Permanent or temporary subway structures that Require Some initial or frequent on-bottom relocation need an effective mudmat release system. This is newest in order to avoid probe that May a rise differs CIS at the Mudmutlyoil interfuse. Through lentil twginepring Nark per raced if the dsvclopnwnt of subset Insulate the Headroom Field off the Norwegian mudmat design hues been conceive. That enables water to job freely through the Murmur top sacrificing overall stability or Structural interim. This was accomplished by Integrating gigot (textiles and steel mesh for Support into the design). The design permits strictly Insulate and removal hydrodynamic Braces, soil resistance and disturbance of the stabbed Sediments to u minimum. Hawk subs dynastic Behavior is more fuvourub [e reducing structural Stress's, redo until time and the newscast liftingCapuchin of the surface vessels as compared to burlier Solutions.

INTRODUCTION
Conoco Norway Inc. (CNI), acting as operator for Co-ventures and co-licenses for the Heilbronn Field Development, awarded the contract "Engineering of TLP Template and Export Pipeline Systems" to REINERTSEN Engineering ANS with SINTEFGeotechnical Engineering as the geotechnical subcontractor, Both situated in Trcmdheim, Norway.
The Heidrum Field is located off the coast of central Norway in the Haltenbanken area at a water depth Of approximately 350 meters. Field development Includes a concrete tension leg platform (TLP) withModular topside mounted on concrete module Support beams (MSBS) which in turn are set on hull Columns. Oil export will be through a direct shuttle Loading system (DSL) and gas export piped to the Norwegian coast through the Haltenpipe system.
In addition to providing for the Headroom Development, the Headroom facilities have the Capability to act as a centre for future development Of smaller oil and gas fields in the region through Tie-in of lines and pipelines via the TLP Template system. Installation of the template was Successfully carried out in August 1992, while the TLP itself will be installed in the summer I) f 1995. Prolusion start is programmed to take place in the autumn of 19!95. Four massive gravity anchors will secure the TLP to the sea bottom through steel tethers. To achieve the required installation accuracy of the anchors, eight positioning piles, two for each anchor, were installed during the template installation operations. A positioning pile guide frame [1] (PPGF) was designed to act as a guideduring stabbing and piling. To minimize suction and bottom disturbance during relocation of the PPGF, a unique mudmat solution was developed and included in the design.

POSITIONING PILE GUIDE FRAME
The structural elements of the PPGF are depicted in Fig. 1 and consist of the following components:main steel frame,bumper frame including buckets with rubber flex elements,four positioning pile sleeves for 72" diameter piles,three mudmats, and alevelling system comprising one hydraulic jack mounted on each mudmat with integrated rubber flex elements.
The flex elements are rubber buffers that are collared.