Production Modules - Prudhoe Bay Field
Authors: Sharpe T.A. 
Published: December 2007

Introduction

A small ceremony took place in Houston on May 11, 1970, marking the culmination of 8 months of intensive engineering, purchasing and fabrication activity (Fig. 1). Invited members of the oil companies participating in the Prudhoe Bay Unit area witnessed the departure Prudhoe Bay Unit area witnessed the departure down the Galveston ship channel of the first barges loaded with production modules for the North Slope of Alaska. It was to be 3 months later, on Aug. 9, after a voyage of some 9,000 miles, through hurricanes in the Gulf of Mexico, through the Panama Canal, up the West Coast, across the Bay of Alaska, through the Aleutians at Dutch Harbor and around Point Barrow into the pack ice of the Beaufort Sea, before this equipment was to arrive at Prudhoe and the giant crawler transporters lifted the modules bodily off the deck of the barges, carried them over the jetty and along 20 miles of gravel road to set them onto steel pile foundations at the site of Gathering Center 1 (Fig. 2).

This was the completion of the initial stage of the program to develop and install oil/gas separation facilities in time to meet the anticipated Trans-Alaska Pipeline commissioning program (Fig. 3).

FIELD DEVELOPMENT PLAN

The lease areas of SOHIO, ARCO-and Humble in the Prudhoe Unit have been divided operationally so that BP Alaska Inc. is responsible as operator on behalf of SOHIO for the western half and ARCO for the eastern half.

Briefly, the field development plan for the BP operations area calls for the production of 825,000 B/D from wells drilled on 640-acre spacing (Fig. 4). Well pads will have from four to eight wells grouped on them and will be directionally drilled. The oil to be taken through 6-in. bundled flowlines to gathering centers, each centrally located with respect to the wells which it is to serve.

The temperature of the oil at the well-head is expected to be in the region of 190 deg. F and, in order to minimize dehydration problems, the bundles of lines will be insulated so that the temperature at the second-stage separators will not be lower than 130 deg. F. The physical properties of the oil indicate that in relatively properties of the oil indicate that in relatively short lines pumpability is a practical proposition down to -40 deg. F, but in case of a proposition down to -40 deg. F, but in case of a prolonged shutdown at the wells or of the production prolonged shutdown at the wells or of the production units and particularly when any water is present in the crude, arrangements have been made for the gathering lines to be cleared of oil by pigging and purging with gas. The high pressure separators can store enough gas to purge 45 miles of 6-in. flowline with 50 psi gas and be replenished from solution gas in each flowline as it is depressured before pigging. A typical gathering center schematic flow diagram is shown in Fig. 5.

Separated oil from the gathering centers will be pumped into a transit line system connecting all three centers to the Trans-Alaska Pipeline system origin pump station located centrally between the BP and ARCO operating areas.