Case History of a Successful Selective Horizontal Openhole Gravel Pack With Zonal Isolation in Deep Water Field
Authors: Machado Fernando A. 
Published: October 2008

This paper describes the successful experience of a horizontal openhole gravel pack integrated with zonal isolation in a deepwater reservoir and how this application was approved as an innovative and effective system for selective production in horizontal openhole gravel pack. Also, it will be described some recent applications such as the 1076 m long selective horizontal openhole gravel pack and the use of a large bore horizontal OHGP with zonal isolation.

Introduction

In the early 2001 one challenge was presented: two unconsolidated sandstones separated by a shale barrier should be completed with an Open Hole Gravel Pack. Also, it was estimated that water breakthrough would reach the lower zone first. It was necessary a sand face completion system that would permit the complete isolation of the lower zone when water production becomes prohibitive.

In order to obtain higher production rates, producing crude from more than one layer in deepwater and unconsolidated sandstones using sub-horizontal and horizontal wells drove the need for an innovative solution: the use of two existing devices that had never been joined before, the Expandable Casing Packer (ECP) and the Diverter Valve.

Thus, it was possible to perform an openhole gravel pack in two highly permeable and unconsolidated sandstones, separated by a shale barrier.

Several openhole horizontal wells have been completed with this technique in deepwater Campos Basin. In one of these wells the effectiveness of this technique has been already proved when water breakthrough happened in the lower sandstone, using an inflatable device.

The lower zone was successfully isolated, decreasing the water cut from 68% to zero. Moreover, the low intervention cost to achieve this goal must be highlighted.

This innovative application proves that. Selective horizontal openhole gravel packs are feasible now, allowing the production of more than one zone if there is a shale barrier dividing the reservoir.

Horizontal Openhole Gravel Pack Design with Low Viscosity Carrier Fluids

The procedures for carrying out horizontal openhole gravel pack completion with the water pack system were originally developed by Penberthy et al1 in a field simulator approximately 460m long. This simulator, which was equipped with pressure sensors, tubes along its entire length to simulate the fluid losses and acrylic windows, allowed the feasibility of carrying out gravel pack completion throughout the entire horizontal extension to be analyzed, depending on certain parameters such as: pump flow, return flow, relationship between ID screens / OD wash pipes, sand concentration, etc.

The identification of primary sand decantation waves in the direction of the lateral facing the bottom of the well (Alpha) and in the opposite direction (Beta), allowed the visualization of the gravel placement process on the screen - casing annulus and the development of a simulator to characterize the parameters necessary for carrying out operations in the field.

Gravel Placement in High Deviated and Horizontal Wells

The gravel placement in deviated wells (until 45°) starts at the bottom of the well and continues until it covers the top of the screen.