Abstract

The Cannonball field is a one Tcf gas condensate development offshore Trinidad producing at an initial rate in excess of 800 MMcf/D from three wells. The completion design selected was 7" inch production tubing with an open-hole gravel pack (OHGP). The initial well (CAN01) has produced at an initial rate of 320 MMcf/D. The calculated deliverability of this well is 415 MMcf/D. This paper discusses the completion basis of design, detailed engineering assurance of the design, qualification of critical engineered equipment, and actual results.

Introduction

Trinidad's gas production has increased dramatically over the past 10 years. In 1996, local gas production exceeded oil production for the first time as the twin island Caribbean state of Trinidad and Tobago moved from a predominantly oil producing country to a major gas producer. The gas growth has been driven by an increase in local demand and construction of a liquefied natural gas (LNG) infrastructure which now includes four Trains. BP Trinidad and Tobago LLC's (bpTT) share of the gas supply to the local market has grown from less than 350 MMcf/D in 1994 to over 2 Bcf/D by mid-2007 with production coming predominantly from several prolific gas fields located off Trinidad's East Coast (Fig. 1).

The Cannonball field is located approximately 35 miles off the southeast coast of Trinidad in 240 ft of water (Fig. 1). The discovery well, Ironhorse-1 ST1, was drilled in 2002. In 2005, a minimal structure (nine slot four pile) production platform was installed and three development wells were drilled and completed with a jack-up cantilever drilling rig. Initial production commenced on March 12, 2006 following pipeline hook-up and commissioning. The Cannonball field was brought on production at a sustained rate in excess of 800 MMcf/D.

SPE 810451 published in 2003 and titled "Trinidad's First 500 MMcf/D well: Fact or Fiction?" discussed the Ironhorse discovery well and presented the engineering challenge of an ultra-bore completion (9" inch production tubing). The right scoping process discussed in this paper present the various tubing sizes evaluated and articulates the decision to select 7" inch production tubing.

Geologic Overview

The Cannonball West gas field is located in the Columbus basin, 35–40 miles off the southeast coast of Trinidad in water depths of 240 feet. It is comprised of a single reservoir unit, the 33 (TP65) sand, situated at -12,334 ft TVDSS (Fig. A-1). The accumulation was discovered in 2002 by the exploration well, Ironhorse-1 ST1, which targeted the reservoir down dip in the Sparrow fault block delineated by bright seismic amplitudes (Fig. 2). The reservoir was over pressured at 6400 psi with a temperature of 220°F.

The gas is trapped by major extensional faults to the west and east and a stratigraphic updip seal to the southeast. The down-dip limit is a gas / water contact inferred from a seismic "flatspot" that conforms to structure to the northwest of the Ironhorse penetration at -13,000 ft TVDSS. This interpretation is supported by wireline log evidence from the Ironhorse well showing a gas-down-to of at least -12,622 ft TVDSS.

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