RIASSUNTO
Abstract
The Coulomb field is the 6th field of the ultra deepwater GoM Na Kika subsea development. The two subsea tie-back wells in the Coulomb development (the C-2 and the C-3) were completed in April and May of 2004, in 7,570' of water depth. When completed, the Coulomb wells held the industry record for the deepest water depth subsea completions in the world. The subsea trees and the surface-controlled subsurface safety valves also represented the deepest set to date.
The development planning included selection of the optimum completion design to address a wild-cat in the northern block, which had not previously been penetrated. While the conceptual sand control design was based on data from the previously appraised southern block.
The execution phase was performed on a Generation 5 Moored Mobile Offshore Drilling Unit (MODU) with no prior experience in deepwater completions. Value creation activities were employed to raise the awareness and competence of the rig team to transform improvement opportunities into high performance goals. The Heave-Compensated Landing System (HCLS)1 was used to install the subsea tree, tubing head spool and well jumpers from anchor handling vessels, hence expanding the scope of activities performed off the critical path of the rig and contributed significantly to the record-breaking pace.
Completion fluid, workstring and treatment fluid were carefully selected and tested for well-specific conditions. Specific challenges included the quick turn around completion design and execution on a wild cat, optimizing the drill/complete sequence to complete in uncertain mineralogies, high day rate leading to a desire to be ""quick but good??, cooling effects due to huge riser volume and long riser trip times. Through extensive preparation and the use of several innovative concepts, record performance was achieved.
This paper also gives an overview of the application of internal plastic coating of the production string in the Coulomb wells. Through nodal analysis with a match to the well performance data, it is demonstrated that the reduced tubing friction associated with the use of internal plastic coating in the tubing has been estimated to yield a 15% increase in daily production in these wells. Success in this application further proves the effectiveness of today's new and novel coating system.
Introduction
The Coulomb field is located 144 miles southeast of New Orleans and covers two leases, MC613 (66.7% Shell, 33.3% Petrobras) and MC657 (100% Shell). The two-well program involved the development of gas and associated liquids from two subsea clustered well locations in water depths of 7,570 feet. The Coulomb field consists of a single reservoir that is structurally separated into two accumulations. The larger, southern accumulation which had been proven and appraised by the downdip exploration well and an updip appraisal sidetrack. The smaller, northern accumulation remains unpenetrated. Both accumulations are located at approximately 16,500' TVDss.
The wells were tied back to the Shell-BP Na Kika host, located in MC474 in 6,340 feet of water about 27 miles from the wells (Fig.1). The host incorporates the concept of a dispersed subsea development tied- back to a centrally located semi-submersible shaped ""Na Kika host?? facility. The host and subsea structure is designed for other tie-backs to enable furtherdevelopment in the field. The production from both wells were commingled through a single 8?? flowline and controlled by a network of subsea umbilicals. Both wells came on stream June 2004 at rates exceeding expectations. Application of internal plastic coating to the bore of the production tubing provided a more uniform surface thereby lowering the frictional pressure drop. This contributed to the higher production rates from these well.