Abstract

Expandable sand screen technology has gained interest from operating companies since proving its reliability in various environments and configurations. Both mechanics of deployment operation and fluid handling procedures have been validated and consolidated through field runs, showing dependability, improved logistic efficiency and overall performance comparable with standard operations. These results confirmed margins to enhance the project targets to high complexity scenarios and encouraged widening the candidate selection criteria towards more demanding environments.

To progress the technology further, an operating company identified an opportunity to challenge the advantages of expandable sand screen technology in a gas storage well openhole sidetrack. This application required deployment and expansion of a screen assembly through a milled casing window to provide necessary sand control for the target zones as well as isolation of upper shale and shale breaks located between the sands.

This paper will demonstrate how the various challenges were faced and solved through planning and execution, specifically in the following areas:

  • wellbore construction options

  • fluid procedures

  • one trip system reliability

  • zonal isolation requirements

  • sand retention capabilities of the screen

  • production enhancement

Introduction

The Minerbio field is located in the Po Valley, approximately 20 km North from Bologna, producing gas and consisting of two productive layers (C1 and C2) which have been identified at depths between 1300 and 1400 meters, with permeability ranges from 10 mD to 500mD. The reservoir sands are sand and shale layers with some thin sand/silt interbeds composed of sediments of the Porto Garibaldi formation which were deposited in the Pliocene period in a turbidite environment, while the cap rock is formed by Santerno shale. Experience indicates that these unconsolidated sands require sand control completions for efficient reservoir management. The conversion of the Minerbio field from production to storage was implemented in late 1970s. The pressure cycles induced by alternate phases of production and injection, typical for storage wells, reinforced the requirement for sand control completions. The increased gas demand pushed for the development of this reservoir with the drilling of new wells in the early 1990s. The project discussed in this paper refers to this phase of the gas storage cluster development.

The Minerbio #83 well was completed as a production well in November 1990. The original completion included an openhole gravel pack performed from the 7 in. 23#/ft casing inside pool C Sand body, with average permeability of 60 – 80 mD. The open hole was enlarged to 12 in. and then treated with 20–40 Mesh Gravel using Gel pack techniques with 4 in. 12- gauge wire wrapped screens. Production, maintained for 10 years, was suspended in 1999 for a possible screen failure.

Project Objectives

The workover of this well was planned in 2003 in order to reestablish cluster stock volumes. Feasibility studies were implemented in order to meet the main targets of production and economics. Productivity expected was 1MMSCM/d during production phase and 0.5 MMSCM/d during injection phase while CAPEX and OPEX analysis was conducted after completion scenarios' risk assessment and well construction process optimization.

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