Abstract

Over the last years, expandable screens technology has become more mature and many oil and gas wells are now equipped with such sand control. This paper intends to present typical applications through three case studies.

The first case regards a gas well in Indonesia, where gas reserves are found in many thin layers spread over several hundreds of meters. Traditional sand control methods do not allow flexible and cost effective protection of many thin layers. Expandable screens were installed in a cased hole after a work-over with the aim to maximize gas reserves despite weak sand formation. The paper addresses the erosion concern related to this configuration.

In the second case, an old oil well in Cameroon was side tracked in order to reach marginal reserves. Frac-packing, preferred sand control method in Cameroon, was not practical considering the small drilling diameter, the high well angle, the dependency to stimulation boat availability and the economical constraints. Instead, expandable screens were installed in open hole, allowing cutting the cost down while providing very good well performance. Expandable screens open new opportunities to access additional reserves that were not economical with traditional technology.

At last the third case demonstrates the feasibility of utilizing expandable screens in a high profile deep water development in Nigeria. The paper describes three water injection wells where expandable screens were successfully installed in an open hole, and addresses the challenging deployment from a floating rig.

Introduction

Since expandable screens were introduced on the market in the early 2000's, they have been thoroughly evaluated within the company and progressively used in wells with increasing stakes. If the first application was an exploration well where expandable screen purpose was only to protect from sand production during a DST, the latest application aims at validating the technology in high profile deep water projects.

Basically, sand control solutions can be divided in stand alone screens and gravel packs. In the first case the interface between well and reservoir is the screen filter media itself, when in the latter case (frac packs, open hole gravel pack) the interface between well and reservoir is the contact between the formation sand and the gravel.

Stand alone screens have the benefit to be a cost effective solution, as long as the field conditions are within their envelop of applicability. Typically stand alone screens have a very good track record in clean and well sorted sands, and wells operated under a controlled manner. When sand characteristics or well operating conditions are less favorable, the next choice is to use gravel packing, which is more tolerant to fine and dirty sand as well as harsh well start up's. However gravel packing introduces more complexity, higher cost, and some other limitations such as sensitivity to shale or less potential for zonal isolation.

Expandable screens can be seen as a middle ground between stand alone screens and gravel packs. They can still be classified as stand alone screens as the screen is in direct contact with the formation sand. By supporting the formation sand and avoiding the creation of a low permeability pack around the screen due to sand re-mixing, they are expected to extend the envelop of operability and to be suitable in sand of lower quality. Compared to gravel packing, it still allows zonal isolation thanks to expandable packers, and it avoids any compatibility concern when pumping gravel slurry in shaly formations. In addition, it removes any need for pumping, reducing complexity and dependency to stimulation vessels, which can be a strong concern in some area.

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