Auger Predrill Challenges And Innovations
Authors: Javanmardi Kaz , Forster L.D. , Flodberg K.D. , Simon B.W. , Marsh G.L. , Gonzalez Rome , Michel D.L. , Travis T.R. 
Published: October 2008

The sheer challenge of drilling geopressured Auger wells with shallow gas sands, low fracture gradients, and nearly four miles deep in 2860 feet of water from a floating vessel requires effective teamwork, planning, and application of new technologies.

An overview of drilling strategy and application of some innovative technologies during the Auger Predrill program is presented, with emphasis on:Drilling challenges and performance results,Performance of the Two Dri11ing Riser System, andGuidelineless Drilling and Acoustic Positioning System.

INTRODUCTION

The Auger Predrill Team has successfully drilled and cased 10 wells to total depth and drilled 10 additional wells to 20-inch surface casing depth before the installation of the Auger Tension Leg Platform (TLP) in 2860 feet of water in Garden Banks 426. The TLP was installed in December 1993. These wells were predrilled with a semi-submersible drilling rig, the Sonat George Richardson, to have completeable wells for the TLP to accelerate first production and allow the facility to be filled to its 46,000 barrels per day capacity before the next drilling program begins using the TLP rig.

The predrill wells were planned and implemented with three major objectives in mind:Change the traditional teamwork concept by combining and sustaining the synergistic efforts and expertise of nine contractor companies and the Auger engineering and operations personnel.Solve the expensive borehole instability problems experienced during the exploratory program.Accommodate the Auger TLP well System for producing operations concurrent with well completion, drilling, and workover operations.

Many innovative ideas have been implemented during the predrill program to address potential drilling problems and to optimize performance.

A Two Riser System (TRS) was used which allowed the use of the large diameter casing program (36-inch, 26-inch, 20-inch, 16-inch, 11 3/4-inch, and 7-inch) necessary to reach total well depths of up to 22000 feet* and provide an effective high rate completion. The TRS consists of a 26-inch riser and 30-inch subsea diverter, and a convent ional 21-inch riser and subsea BOP stack. This el iminated the expensive and risky deep underreaming in direct ional holes and tight casing clearances associated with a conventional single riser (21-inch OD) system.

A specially developed underwater acoustic positioning system was used which enabled the Auger wells to be drilled using guidelineless guidebases without an expensive multi well template or other potential troublesome mechanical guidance systems. The acoustic system consists of a seabed array of 5 intelligent transponders mounted in rigid which form a precision reference grid against which a measurements are made to an accuracy of ±4 inches.

Mud solidification technology (Slag-Mix) was used to overcome the costly contamination problems of conventional cements and to reduce mud discharge.

Other simple innovations such as an ROV-operated subsea BOP connection tightening tool and a through-riser TA cap running/retrieving tool were used to eliminate the need to pull the riser and the subsea BOP stack.