Patent Application
20160290109
The field of the invention is gravel packing of screens at subterranean locations where gravel pack movement is a risk that can expose screen portions to high velocity fluid flow which can be erosive of the screen.
Completions frequently combine sections of screens that are connected directly or with short sections of blank pipe. The process of gravel packing is well known in the industry and comprises of depositing “gravel” typically a specialized sand in the annular space surrounding the screen assembly. The gravel is pumped through surface tubing into a tool known as a crossover and into the annular space that surrounds the screens. The gravel stays in the annular space but the carrier fluid goes through the screens and into an internal annulus between the screen and another pipe known as a wash pipe and back up into the wash pipe and out of the borehole through the crossover to an upper annulus above the production packer. One of the purposes of the gravel pack is to protect the screens from the erosive effects of high velocity gases by presenting a line of defense that diffuses the flow to protect the screen. The gravel also retains some of the solids carried with the production before those solids hit the screen to prolong screen useful life or to increase throughput during the life of the screen.
The nature of stacks of screens is that that the stack has dead zones where there are no screen openings. The delivered gravel tends to keep moving past these dead zones as the carrier fluid keeps moving until it finds screen openings to flow through and into the wash pipe. In horizontal completions this does not present a major issue as the gravel stays put due to the force of gravity so unpacked zones opposite connecting pipe does not risk exposing of screen in the event of a gravel pack shift. In wells that are closer to vertical than horizontal this can be a situation that allows some of the gravel pack to shift or settle by gravity away from the initial placement location to the annular space about the blank pipe separating the screen sections. This settling or shifting can leave portions of the screen assembly exposed to undesirable high velocity fluid, normally gas that can erode holes in the screens rendering such screens inoperative for their intended purpose.
For high deviation wells (close to horizontal), gravel packing may be used using low density proppant that have the propensity to float and be easily dragged by fluid flow. Gravel movement away from the screen could lead to screen exposure, formation sand production through the bare screen and potential screen erosion.
In the past efforts to avoid gravel pack voids have tried putting screened openings in the blank pipe connecting screen sections in an effort to encourage deposition of gravel outside the blank portions, mainly to enhance distribution of flow toward the screen sections.
A references discussing gravel packs and issues encountered in them is U.S. Pat. No. 7,934,555. External sleeves that swell to form isolators for expanded pipe in a borehole are discussed in general in U.S. Pat. No. 7,320,367.
The present invention addresses the gravel voids in boreholes by providing sleeves in those areas that have their smallest dimension when running in and when gravel is deposited and then swell in the presence of well fluids to take up the voids in the gravel pack around the connectors. In this way collapse of the existing gravel pack or low density proppant movement away from the screens is prevented while an effective gravel pack around the screens is assured. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
A gravel pack of screen sections separated by blank pipe is accomplished with sleeves around the blank sections that have a smaller run in dimension to allow the gravel to get past the sleeves during the gravel packing. When the gravel packing is complete the sleeves swell or otherwise enlarge to fill the voids where no or insufficient amount of gravel has been deposited. The presence of the enlarged sleeves prevents settling or shifting of the gravel pack away from the screens because voids that would otherwise have been there are filled with the enlarged sleeves.
As shown in
Those skilled in the art will appreciate that while one sleeve 30 is shown between screens 10 and 12 that additional sleeves are contemplated adjacent each blank section 16 below a given screen. The sleeves can swell or can be ingredients that mix to create a material that fills the annular space or other means of eventual enlargement after the gravel packing is accomplished such as a shape memory polymer or alloy that reverts to a larger size when crossing its critical temperature on exposure to well fluids or applied heating or an inflatable member to mention a few possible variations. Another possibility is a material that not only grows in dimension for reasons of support of the gravel but that also has some porosity to allow production flow axially between screen sections. The various materials or reactants are known in the art and the common feature is sufficient structural integrity while spanning the annular space to keep the gravel positioned adjacent the screen sections while preventing gravel collapse that would otherwise leave the screen sections exposed. The sleeves permit the gravel to be distributed and then enlarge to a gravel pack at an adjacent screen to allow the gravel to remain in place against the force of gravity in wells that are not completely horizontal. The sleeve can be the length of section 16 or shorter. It can be one piece or multiple pieces which grow at the same or at different rates. It can be a split sleeve or a seamless sleeve put over the blank section 16 on assembly of the screen sections. In a swelling embodiment such as an elastomer rubber the sleeve can have an external coating which is removed in the borehole environment by heat or chemical action as a delay mechanism for the growth in diameter such as by swelling to allow time to complete the gravel pack before the dimension increases in section 16. The porous embodiment can be an open cell foam.
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:
