Abstract:
Methods for cleaning or stimulating a well include providing an isolation device, providing a penetration device, isolating a zone, and penetrating a portion of the formation utilizing the penetration device. Isolating and penetrating may occur in a single trip into the well. The isolation device may include one or more packers. The penetration device may be a pulsating/oscillating hydrajet that introduces fluid pressure waves into the formation.

Description:
BACKGROUND 
       [0001]    Oilfield operations such as production enhancement require tools for cleaning of casing, deposits from near well bore areas, perforations, and screens. In wells with increased water production, waterflood projects, and geothermal wells, scale and deposit buildups are often a major cause of decreased production. These buildups can cause a choking effect, which increases the bottomhole pressure required to maintain flow capacity. Conventional methods of removing buildup-milling, acid wash, wireline broaching, and even replacing the production string and flowlines-are often either expensive or provide only limited success. 
         [0002]    Another method involves a fluidic oscillator. The fluidic oscillator creates pulsed jets, which cause alternating bursts of fluid. These bursts of fluid create pulsating pressure waves within the well bore and formation fluids. These pressure waves can break up many types of near well bore damage, helping restore and enhance the permeability of the perforations and near well bore area. The pressure waves expand spherically providing 360° coverage as the tool moves through the interval. As damage is removed, the waves penetrate deeper into the formation. Fluidic oscillator well cleaning has been effective in removal of deposits from the near well bore area, including the following: perforations, and screens; perforating damage; scales of all types; formation fines; paraffins and asphaltenes; mud and cement damage; emulsions; drilling damage; and water and gas blocks. Fluidic oscillator well cleaning has also been effective in the following applications: primary stimulation of high permeability formations; preparation prior to stimulation treatments; preparation for gravel packing or frac packing; clean out fill from open hole or casing; alteration of injection profiles; and correct placement of treating chemicals. 
         [0003]    Generally, a fluidic oscillator is deployed on coiled tubing, requiring a dedicated trip out of the well bore for removal of the fluidic oscillator. For example, U.S. Pat. No. 6,976,507 describes a typical fluidic oscillation device, deployed on coiled tubing, used for near well bore cleaning. 
       SUMMARY 
       [0004]    The present invention relates generally to well stimulation and/or cleaning. More specifically, the present invention relates to a method of isolating a zone and penetrating or cleaning a formation using an isolation tool and a stimulation/cleaning tool. 
         [0005]    In one embodiment, a method for cleaning a well comprises: providing an isolation device, providing a penetration device, isolating a zone, and penetrating a portion of the formation utilizing the penetration device. Isolating and penetrating may be done in a single trip into the well. 
         [0006]    In another embodiment, a method for stimulating a well comprises: providing an isolation device, providing a penetration device, isolating a zone, and penetrating a portion of the formation utilizing the penetration device. Isolating and penetrating may be done in a single trip into the well. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a side view of a cleaning/stimulation operation using one embodiment of the method of the present invention. 
           [0008]      FIG. 2  is a side view showing another embodiment according to the present invention. 
           [0009]      FIG. 3  is a side view of yet another embodiment according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Referring to  FIG. 1 , in a single trip, isolation device  100  and penetration device  105  may be lowered into well  110 . Once isolation device  100  and penetration device  105  are adjacent to formation  115 , isolation device  100  may be used to isolate zone  120 , which may include at least a portion of formation  115 . After zone  120  has been isolated, penetration device  105  may penetrate at least a portion of formation  115  located within zone  120 . 
         [0011]    Isolation device  100  may be one or more packers, which are set to isolate zone  120 . More specifically, isolation device  100  may be a straddle cup packer. Alternatively, isolation device  100  may be two or more packers that are set on either end of zone  120 . Thus, penetration device  105  may enhance a standard selective injection packer (SIP) process by inducing pressure pulses between the cups of a straddle cup packer, allowing for deeper matrix penetration. 
         [0012]    Penetration device  105  may be a pulsating/oscillating hydrajet that jets fluid into formation  115 . Penetration device  105  may be a low frequency, large amplitude wave generating tool, such as, for example, a 2-⅞″ DeepWave® stimulation services tool, commercially available from Halliburton Energy Services, Inc. of Duncan, Okla. under license from Wavefront Energy and Environmental Services, Inc. of Ontario, Canada. Such a low frequency, large amplitude tool may be particularly useful for stimulating perforations. It may improve chemical treatments such as matrix acidizing, scale inhibition, remedial sand/proppant control and conformance. This may involve a shockwave or “thumping” at from several seconds per cycle up to minutes per cycle. 
         [0013]    In another embodiment, penetration device  105  may be a high frequency, small amplitude tool, such as, for example, a Pulsonix® TF (tuned frequency) tool, commercially available from Halliburton Energy Services, Inc. of Duncan, Okla. Such a high frequency, small amplitude tool may be particularly useful for cleaning scale off casing, or removing deposits from the near well bore area, perforations, and screens. For example, it may remove perforating damage, scales of all types, formation fines, paraffins and asphaltenes, mud and cement damage, emulsions, drilling damage, or water and gas blocks. This type of tool may also be useful for enhancement of placement and effectiveness of treatment fluids, primary stimulation of high permeability formations, preparation prior to stimulation treatments, preparation for gravel packing or frac packing, cleaning out fill from open hole or casing, alteration of injection profiles, or correct placement of treating chemicals. This may involve fluid oscillation in fluid flow and pressure at hundreds of hertz. For example, at a 200 psi pressure drop, the range may be from 300 to 600 Hz. Paraffin may be cleaned with solvents and scale may be cleaned with mild acid, solvents, or water. 
         [0014]    Regardless of the type of penetration device  105  used, penetration of formation  115  is preferably facilitated via fluid pressure pulses or waves  125  introduced by penetration device  105 . Depending on the type of penetration device  105 , fluid pressure waves  125  may have a low frequency and a large amplitude or fluid pressure waves  125  may have a high frequency and a small amplitude. Various other combinations of frequency and amplitude may also be desirable. Some examples of desirable low frequency/large amplitude ranges include a 1 second pressure rise of 1300 psi followed by 9-10 seconds of pressure decline. 
         [0015]    Referring now to  FIG. 2 , penetration device  105  may be run below isolation device  100 , allowing for a single trip cleaning and/or stimulation job. Mandrel  130  with  0 -rings  135  may straddle port section  140  of isolation device  100 , allowing for all fluid to exit penetration device  105  to accomplish cleaning until ready to stimulate. Spear or retrieving head (not shown) may then be run on wireline to retrieve mandrel  130 . Then plug  155  configured to seat in standing valve  160  may be dropped to block flow through penetration device  105 , causing fluid to exit pressure treating ports  165  in isolation device  100  for stimulation. Plug  155  may then be retrieved by running rod overshot (not shown) and pulling plug  155 , preventing the need for pulling a wet string. 
         [0016]    This approach may be desirable, for example, when penetration device  105  is a pulsating/oscillating hydrajet and zone  120  includes a methane bed. 
         [0017]    Referring now to  FIG. 3 , penetration device  105  may be a Pulsonix® TF oscillator insert (not shown) at ports  165  in isolation device  100 , thus inducing oscillation of the stimulation job. The insert may be preinstalled or dropped via a mandrel with a retrieving neck  180 . After the treatment, the insert may be retrieved on wireline or slick line, allowing the string to be drained while pulling out of hole. Caged ball  185  at bottom may not be needed if the insert is preinstalled. 
         [0018]    The methods of this disclosure are equally applicable to coil tubing or any other tubular, such as a jointed tubular. Because the penetration device  105  and the isolation device  100  are both run inside of the tubular, there are no extra trips needed to pull them. Thus, the methods of this disclosure provide a hybrid solution for SIP applications using penetration devices  105  for increased pinpoint injection efficiency or for formation damage cleaning/removal in non-through tubing applications. These methods combine the advantages of fluid pressure waves with the ability to run the penetration device either by installation in a tubular at surface prior to running in well  110  or via dropping the penetration device from surface and allowing it to seat inside the tubular. This is accomplished by combining the penetration device with the features of a retrievable jetting tool mechanism to allow the penetration device to be retrieved via either a sandline or applying annulus pressure to force the penetration device up the tubing where is can be captured at surface via a TIW style valve. 
         [0019]    Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.