Deepwater Satellite Subsea Development In Mississippi Canyon

Abstract

ABSTRACT Satellite subsea completions with flowline connections to existing shallow water production facilities have proven to be an economical means of developing reserves in deep waters in the Gulf of Mexico. Application of existing, field proven technology and equipment minimizes the time required from project approval to initial production. This development approach was used to complete three wells in the Gulf of Mexico, Mississippi Canyon Block 401 and 445 in water depths from 1355' to 2088' in less than 13 months from project approval. Separate flowline and umbilicals were installed for each well using the lay-away technique. Existing subsea equipment installation procedures were extended to deeper water depths during the completion of these wells. INTRODUCTION The Mississippi Canyon 400 Unit is located approximately one hundred miles southeast of New Orleans, Louisiana, in the Gulf of Mexico (Figure 1). The Mississippi Canyon 400 Unit consists of Blocks 356, 357, 400, 401, 444, and 445. Initial exploration in the area began in 1987 with the drilling of a well in Block 356. In 1988, two gas wells were drilled in block 401, Mississippi Canyon (MC) 401-1 and MC 401-2. In October 1992 MC 445-1 was drilled as a portion of this three-well subsea gas development. The water depth is 1355' at MC 401-1, 1697' at MC 401-2 and 2088' at MC 445-1. Engineering studies were begun in July 1992 to review options for developing the existing Block 401 wells and other potential wells in the area. Project approval was obtained in October, 1992 and initial production was on line in July, 1993. This paper describes the selection of the subsea trees, installation equipment, controls system, and installation procedures. SYSTEM ENGINEERING The initial engineering work included evaluation of available technical options for connecting the prospective wells to an existing platform in West Delta (MD) 152, located in 373' water depth. Various development scenarios were considered with well counts ranging from two to five. A strong emphasis was placed on using existing technology to reduce the development time due to the fast track project schedule and minimize the overall installed cost of the system. Several field development options were briefly considered until three preferred cases could be identified and given a more detailed analysis. These cases included:Case 1: Individual flowlines and umbilicals from each well to the platform.Case 2: A subsea manifold installed near MC 401- 1 as the central commingling point for all satellite production flowing to the platform, and the central distribution point for controlling each well.Case 3: Individual flowlines and umbilicak from the platform to the two existing wells in MC 401, plus a separate driIling template/manifold system for the wells farthest from the platform (five well case only). Each case was further evaluated with three different flowline options, including all rigid steel flowlines, all flexible flowlines, and combination steel line pipe with flexible pipe pigtails. Cost estimates for each case were developed based on budgetary quotations of components and services which affect only the relative difference between options. The analysis indicated Case 1 to be the most cost effective option.