Methods for placement of sealant in subterranean intervals

The present invention relates to subterranean treatments and, more particularly, in one or more embodiments, to introducing a relative-permeability modifier into a subterranean interval ahead of, or in conjunction with, a sealant.

In subterranean treatments, it is often desired to treat an interval of a subterranean formation having sections of varying permeability. Consequently, it may be difficult to obtain a uniform distribution of the treatment fluid throughout the entire interval. For instance, the treatment fluid may preferentially enter portions of the interval with high permeability at the expense of portions of the interval with lesser permeability. In some instances, these intervals with variable permeability may be water-producing intervals. In other instance, the portion of an interval with high permeability may be an elbow or turn in a well bore, into which the treatment fluid may preferentially enter. In yet another embodiment, the portion of an interval with high permeability may be a junction of a multi-lateral well, into which the treatment fluid may preferentially enter.

In an attempt to facilitate the uniform distribution of sealants throughout an entire interval, a variety of techniques have been used to divert the sealant to less permeable portions of the interval. For example, when the goal is to seal inflow from a long interval with multiple sections of varying permeability, sealants may be placed using packers or other such devices to focus the sealant into target intervals to help insure that the sealant does not travel into only the sections with relatively high permeability. Other such techniques may have involved, among other things, the injection of particulates, foams, or blocking polymers (e.g., crosslinked aqueous gels) into the interval so as to plug off the high-permeability portions of the subterranean formation, thereby diverting subsequently injected fluids to less permeable portions of the subterranean formation. While each of these diversion techniques has been used successfully, there may be disadvantages. Plugging off the high-permeability sections may not be suitable for a producing interval, for example, because the injected solution (or material) may reduce or stop the flow of hydrocarbons in addition to the achieving a desired diversion of the treatment fluid. Therefore, to return the interval to production, expensive and/or time-consuming remedial treatments may be required to remove the injected solutions (or materials). Furthermore, techniques geared toward injecting solutions (or materials) designed to plug off high-permeability intervals of the formation may require expensive zonal isolation, which may be inaccurate, leading to inadvertent plugging of and/or damage to the hydrocarbon-bearing sections.

The present invention relates to subterranean treatments and, more particularly, in one or more embodiments, to introducing a relative-permeability modifier into a subterranean interval ahead of, or in conjunction with, a sealant.

In one embodiment, the present invention provides a method of treating an interval of a subterranean formation having a permeability that varies comprising: identifying the interval to be treated; introducing a relative-permeability modifier into the interval, wherein the relative-permeability modifier modifies the interval to have a more uniform effective permeability to water-based fluids, wherein the relative-permeability modified comprises a water-soluble polymer; and introducing a sealant into the interval, wherein the more uniform effective permeability of the interval allows for a more uniform treatment of the interval by the sealant than would be allowed without treatment of the interval with the relative-permeability modifier.

In one embodiment, the present invention provides a method of treating an interval of a subterranean formation having a permeability that varies, the method comprising: identifying the interval to be treated; introducing a relative-permeability modifier into the interval, wherein the relative-permeability modifier modifies the interval to have a more uniform effective permeability to water-based fluids, wherein the relative-permeability modifier is water soluble and comprises a polymer that has been hydrophobically modified with an alkyl group with 4 carbons to 22 carbons present on an amino group in quaternized form; monitoring the pressure of the interval; adjusting the introducing of the relative permeability modifier into the interval based at least partially on the monitored pressure so that the interval retains a water permeability sufficient to allow injection of water at a rate of about ¼ barrel per minute at a differential pressure no more than 90% of a fracture gradient of the interval; and introducing an aqueous-based sealant into the interval, wherein the more uniform effective permeability of the interval allows for a more uniform treatment of the interval by the aqueous-based sealant than would be allowed without treatment of the interval with the relative-permeability modifier.

The features and advantages of the present invention will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention.

The present invention relates to subterranean treatments and, more particularly, in one or more embodiments, to introducing a relative-permeability modifier into a subterranean interval ahead of, or in conjunction with, a sealant.

Embodiments of the present invention relate to using a relative-permeability modifier (e.g., water-soluble hydrophobically modified polymers) as a pre-flush to treat an interval of a subterranean formation having variable permeabilities prior to injection of a sealant. As used in this disclosure, the term “relative-permeability modifier” refers to a polymer that selectively reduces the effective permeability of a subterranean formation to water-based fluids. In general, the relative-permeability modifier should be used to modify the interval to have a more uniform effective permeability than prior to the treatment. Modification of the interval to have a more uniform effective permeability should facilitate uniform treatment of the interval with the sealant. As the interval has been modified to have a more uniform effective permeability, a more uniform distribution of sealant introduced into the interval should be obtained than would otherwise be achieved without this permeability modification. Otherwise, the sealant may preferentially enter portions of the interval with high permeability at the expense of portions of the interval with lesser permeability. As desired, embodiments of the present inventions use of the relative-permeability modifiers generally may, for example, alleviate the necessity of using packers or other such mechanisms to focus the sealant into target areas.