Patent Application
20150068742
The field of this invention is completions and more particularly in unconsolidated formations that produce methane hydrate where there is a need for sand control and flow distribution to protect the screen while stabilizing the borehole.
Methane hydrate exists as a solid substance in layers that contain sand and other sediment. Hydrate to methane gas and water must be accomplished in order to produce the methane gas. The production of methane hydrate means dissociating methane hydrate in the layers and collecting the resultant methane gas through wells and production systems. To dissociate methane hydrate that is stable at low temperature and under high pressure, there must be an (1) increase the temperature , (2) decrease the pressure, (3) or both. The optimum methane hydrate production method is one based on the “depressurization method.” However, since methane hydrate layers are unconsolidated sediments, sand production occurs with the methane gas and water. Because removal of the methane, water, and sand, wellbore stability becomes an issue that cannot be overcome with conventional sand control methodologies. Economical and effective measures for preventing sand production and solving borehole stability issues require a novel approach to completion methodology. The proposed method to control sand production and provide better borehole stability comprises providing a shape memory polymer foam filter that does not depend on the borehole for containment for sand management. The shape memory polymer will be utilized such that a flow path would not be exposed that would permit the production of sand from the borehole. One other issue related to the “depressurization method” of methane hydrate production is the uniform application of a differential pressure across the reservoir interface. The method further comprises a porous media under the shaped memory polymer foam filter that can be varied in number and permeability to balance the differential pressure applied to reservoir being produced. This improves borehole stability via uniform drawdown and flow from the exposed reservoir. While these techniques could be used in a conventional open hole or cased hole completion, it is desirable to under ream or expand the borehole size to help increase reservoir exposure and decrease flow velocities at the sand management/reservoir interface. Additionally, consolidated proppant or sand is deposited adjacent the shape memory foam as it is not the objective to fully occupy the borehole with the foam after it crosses its critical temperature. Instead, in recognition that the hole can be enlarged with initial reaming to reduce fluid velocities or alternatively additional methane production destabilizes the formation and can enlarge the borehole, the consolidated proppant or sand can be an outer protective layer to the foam. Its ability to self-adhere contains the foam and protects the foam from erosive velocity effects of the produced methane.
Several references that employ memory foam in sand control applications are as follows:
Flow balancing devices are generally discussed in the following references:
Those skilled in the art will better appreciate additional aspects of the invention from a review of the detailed description of the preferred embodiment and the associated drawings while appreciating that the full scope of the invention is to be determined by the appended claims.
In a completion for producing methane the bottom hole assembly has a base pipe with porous media within it for equalizing flow along the base pipe. A shape memory polymer foam surrounds the base pipe with porous media. The borehole can be reamed to reduce produced methane velocities. Surrounding the shape memory polymer is an exterior layer of consolidated proppant or sand that can self-adhere and/or stick to the polymer foam. The proppant or sand can be circulated or squeezed into position although, circulation is preferred. The borehole may enlarge due to shifting sands in an unconsolidated formation as the methane is produced. The bottom hole assembly helps in fluid flow equalization and protects the foam and layers below from high fluid velocities during production.
Referring to
In
The combination of flow balancing with the self-adhering proppant or sand 9 covering the memory polymer foam 3 and to some extent adhering to the foam allows for a longer service life as the layers of filtration remain serviceable longer in adverse conditions such as borehole collapse and potential for erosion caused at least in part by flow imbalance induced high gas velocities.
The proppant/sand 9 can be a commercially available product such as Sandtrol®. The foam is available as GeoFORM®. Alternatives can be alloy memory foam or screens of various designs that do not change dimension with thermal stimulus. The screens can be constructed so that they can be radially expanded for borehole support or to reduce the volume needed for the proppant/sand 9. The flow balancing feature can be a porous annular shape or insert plugs in the base pipe or screen materials that vary in mesh size at different opening locations.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
