Auger Well Completions - Sand Control Installation and Mechanical Design
Authors: Norton S.J. , Smith C.D. 
Published: October 2008

Nine producing wells have been completed on the Auger TLP. The results have been better than anticipated with average production rate capability exceeding 11,000 BOPD and 25 MMCFGPD per well. Completing wells from a TLP in 2,860 ft of water posed several unique challenges from an equipment as well as an operational standpoint. This paper discusses the completion operations from gravel packing through tree stack-up noting the original plans and changes that were made during the program. Special procedures for perforating, stimulating and gravel packing, special equipment requirements and material selection are discussed.

INTRODUCTION

The Garden Banks Block 426 Field (Auger), located 137 miles offshore in the Gulf of Mexico, was discovered in May 1987 and is presentlyproducing over 55,000 BOPD and 115 MMCFGPD. The TLP is anchored in 2,860 ft of water. Auger is a salt dome/structural trap encompassing five pay sands of Plio-Miocene age ranging in depth from 15,000 to 19,700 ft subsea. The three deepest pay sands are oil bearing while the two shallower zones contain gas. The hydrocarbon column heights range from800 to 1500 ft. The sands are unconsolidated to moderately consolidated, having been deposited by oceanic turbidity currents.

Bottomhole pressures range from 10,440 to 12,800 psi while bottomhole temperatures (BHT) are rather cool for these depths at 160 to 205 -F. Permeabilities taken from whole core data ranged from 150 md in the lowermost and largest pay sand, to an average of 900 md in the upper gassand. However, pressure transient analysis from lower oil sand wells now shows the permeability to be more on the order of 400 md, partially explaining why the wells are flowing at rates higher than initially anticipated, Porosities rangefrom 24 to 29%.

To be economically viable, Auger requires high rate wells. Given the initial well parameters, it was anticipated that the wells in the main oilsand would flow on the order of 6,400 BOPD and 10 MMCFGPD, The production facility was designed to process a sustained rate of 46,000 BOPD and 125 MMCFGPD with a peak capacity, for short periods of time at certainconditions, of 55,000 BOPD and 150 MMCFGPD. A facility expansion study is underway.

COMPLETION CHALLENGES

Inflow Issues

Well inflow relationships, using Darcy radial flow and initial well parameters, indicated that the Auger oil wells were capable of rates exceeding 10,000 BC)PD if the wells had minimal impairment, However, due to their unconsolidated nature, the wells required sand control and minimal impairment could not be assumed.

At depths up to 20,600 ft (MD), these gravel packs would be the deepest in the Gulf of Mexico. In addition, the 250 ft gross intervals and 12,800 psi bottom hole pressure also made them some of the longest and highest pressured gravel pack installations. Unfortunately, historical sand control data suggested that depth, interval length, and bottom-hole pressure (completion fluid weight) all tended to increase impairment. Trends showed that completion skins in Auger type wells might exceed 60 (completion efficiencies c 10%).