WO2017083444A1 - Monitoring diversion degradation in a well - Google Patents

Abstract

A degradable diverter is placed in a flow path to divert fluid flow and exposed to degradation conditions, and after sensing a response to a pressure wave to determine the diverter has degraded, placing the well in service. Also, a treatment sequence is initiated according to a treatment schedule, a degradable diverter is placed in a flow path to divert treatment fluid, and, before completing the treatment, an interruption of the treatment schedule is followed by sensing a response to a pressure wave generated in the well to determine the status of the degradable diverter. Also, in a series of stages a degradable diverter is placed in a flow path, a response to a pressure wave is sensed to confirm placement, fluid flow is diverted, and the sequence repeated for subsequent stages.

Description

MONITORING DIVERSION DEGRADATION IN A WELL

CROSS REFERENCE TO RELATED APPLICATION S)

[0001] The present application claims priority to U.S. Non-Provisional Application Serial

No. 14/939,723, filed November 12, 2015, which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Existing methods to detect failure of zone isolation or diverter material include post-treatment pressure analysis or chemical traces recording. Other methods use distributed pressure or vibration sensors, such as an optic wire, pre-installed into casing or coiled tubing. The analysis of reflected pressure waves has been used to detect fractures or bottom irregularities, and also to determine or confirm the proper placement of diverters in fractures or bridge plugs in the wellbore. There are patents describing ways to analyze pressure wave reflections, such as US 2011/0267922, US 2012/0018150 and US 7819188.

[0003] The industry has an ongoing requirements for the development or improvement of well treatment methods involving the installation and/or removal of temporary diverters prior to production or otherwise placing the well in service.

SUMMARY OF DISCLOSURE

[0004] In one aspect, embodiments of the present disclosure relate to monitoring the degradation of a degradable diverter used to plug a fluid flow path, within the wellbore or connected to the wellbore, using the reflection of tube waves, which are also referred to herein as pressure waves. In some embodiments, the degradation of the diverter is confirmed before placing the well in service, e.g., to produce reservoir fluids through the flow path plugged by the diverter. In some embodiments, the functionality of the diverter for diversion is confirmed, e.g., following interruption of a treatment schedule involving shut in of the well.

[0005] In some embodiments, a method for treating a well comprises: (a) placing a degradable diverter in a flow path of the well to divert fluid flow from the flow path; (b) exposing the degradable diverter to degradation conditions; (c) sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has substantially degraded; and (d) after determining that the degradable diverter has substantially degraded, placing the well in service and flowing fluid through the flow path.

[0006] In some embodiments, a method for treating a well comprises: (a) initiating a treatment sequence according to a planned treatment schedule comprising introducing treatment fluid into the well in a plurality of stages; (b) placing a degradable diverter in a flow path of the well to divert treatment fluid from the flow path; (c) interrupting the treatment schedule comprising shutting in the well; (d) sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has degraded; and (e) after determining that the degradable diverter has not degraded, resuming the treatment sequence.

[0007] In some embodiments, a method for treating a well comprises: (a) placing a degradable diverter in a flow path of the well to divert treatment fluid from the flow path; (b) sensing a response to a pressure wave generated in the well to confirm the placement of the degradable diverter; (c) diverting fluid flow from the flow path; (d) repeating (a) - (c) one or more times for a plurality of respective degradable diverters placed in respective flow paths; (e) exposing the diverters to degradation conditions; (f) sensing a response to a pressure wave generated in the well to determine whether the degradable diverters have degraded; and after determining that the degradable diverters have degraded, placing the well in service and flowing fluid through the flow paths.

[0008] Other aspects and advantages of the disclosure will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 is a pressure wave trace diagram for a series of tests in a simulated borehole, according to embodiments of the disclosure.

[0010] FIG. 2 is a schematic diagram of a borehole being tested for the degradation of diverter balls, in accordance with embodiments of the present disclosure. [0011] FIG. 3 is a schematic diagram of a borehole being tested for the degradation of diversion materials in hydraulic passages connected to the well, such as perforations or fractures, in accordance with embodiments of the present disclosure.

[0012] FIG. 4 is a process flow diagram for treatment of a well involving monitoring of diverter degradation in accordance with some embodiments of the disclosure, [per claims 1-15]

[0013] FIG. 5 is a process flow diagram for treatment of a well involving checking diverter degradation after interruption of a treatment schedule in accordance with some embodiments of the disclosure, [per claims 16-19]

[0014] FIG. 6 is a process flow diagram for treatment of a well involving monitoring of diverter placement and degradation in accordance with some embodiments of the disclosure, [per claims 20-21]

DEFINITIONS

[0015] "Above", "upper", "heel" and like terms in reference to a well, wellbore, tool, formation, refer to the relative direction or location near or going toward or on the surface side of the device, item, flow or other reference point, whereas "below", "lower", "toe" and like terms, refer to the relative direction or location near or going toward or on the bottom hole side of the device, item, flow or other reference point, regardless of the actual physical orientation of the well or wellbore, e.g., in vertical, horizontal, downwardly an d/or upwardly sloped sections thereof.

[0016] Borehole or wellbore - the portion of the well extending from the Earth's surface formed by or as if by drilling, i.e., the wellbore itself, including the cased and openhole or uncased portions of the well.

[0017] Break in - sudden loss of wellhead pressure or rapid increase in treatment fluid flow rate, e.g. when a fracture is initiated in a formation.

[0018] Casing/casing string - Large-diameter pipe lowered into an open hole and cemented in place. [0019] Closed end - an end of a tube at which there is little or no compliance, e.g., a capped pipe, and producing a positive reflection to a positive pressure wave.

[0020] Cluster - a collection of data points with similar characteristics.

[0021] Confirm - to make sure or demonstrate that something is true, accurate, or justified; verify; substantiate.

[0022] Deconvoluting - algorithmic processing to reverse the effects of convolution on recorded data.

[0023] Degradable - a material capable of breaking down, or chemically deteriorating, or changing state as by dissolution, sublimation or melting.

[0024] Degradation conditions - conditions at which the process of degrading a degradable material can initiate or continue.

[0025] As used herein, a degradable diverter placed in a flow passage has "substantially degraded" when the process of degrading has progressed to the point where fluid can readily pass through the flow path.

[0026] Depth - includes horizontal/lateral distance/displacement.

[0027] Derived (data) - obtained from a specified source. For the avoidance of doubt, data derived from a specified source may comprise or consist of the original data per se.

[0028] Determine - to establish or ascertain definitely, as after consideration, investigation, or calculation.

[0029] Diversion - the act of causing something to turn or flow in a different direction.

[0030] Diversion material - a substance or agent used to achieve diversion during stimulation or similar injection treatment; a chemical diverter.

[0031] Diversion pill - a relatively small quantity of a special treatment fluid blend used to direct or divert the flow of a treatment fluid.

[0032] Divert - to cause something to turn or flow in a different direction. [0033] Diverter - anything used in a well to cause something to turn or flow in a different direction, e.g., a diversion material or mechanical device; a solid or fluid that may plug or fill, either partially or fully, a portion of a subterranean formation.

[0034] Flow path - a passageway, conduit, porous material or the like through which fluid may pass.

[0035] Fluid communication - connection via a flow path.

[0036] Fluid hammer - a pressure surge or wave caused when a fluid in motion is suddenly forced to stop or change direction.

[0037] Formation - a body of rock that is sufficiently distinctive and continuous that it can be mapped, or more generally, the rock around a borehole.

[0038] Fracture - a crack or surface of breakage within rock.

[0039] Hydraulic fracturing or "fracturing" - a stimulation treatment involving pumping a treatment fluid at high pressure into a well to cause a fracture to open.

[0040] Initiate - to cause a process or action to begin.

[0041] Injection - pumping fluid through the wellbore into the reservoir for storage or to maintain pressure and/or in a flooding operation.

[0042] Instantaneous shut-in pressure or ISIP — the shut-in pressure immediately following the cessation of the pumping of a fluid into a well.

[0043] Interval -a space between two points or times, e.g., the space between two points in a well.

[0044] Lateral - a branch of a well radiating from the main borehole.

[0045] Liner - A casing string that does not extend to the top of the wellbore, but instead is anchored or suspended from inside the bottom of the previous casing string.

[0046] Measure - to ascertain the value, number, quantity, extent, size, amount, degree, or other property of something by using an instrument or device. [0047] Minibreak - a brief, unscheduled interruption of a well treatment lasting less than

24 hours such as for example interruption stop for refueling the pumps, stop because of accidents, thunderstorm, insufficient supply of proppant/water.

[0048] Modify - to make partial or minor changes to (something), typically so as to improve it or to make it less extreme.

[0049] Monitor - to observe, record or detect the progress or quality of something over a period of time; keep under systematic review for purposes of control or surveillance.

[0050] Open end - an end of a tube at which there is a large compliance, e.g., a large

(relative to the tube) tank or a lateral flow passage connection such as at a perforation or fracture open to the wellbore, and producing a negative reflection to a positive pressure wave.

[0051] Overlapping - partly coinciding in time or spatial dimension(s).

[0052] Perforation - the communication tunnel created from the casing or liner into the reservoir formation, through which fluids may flow, e.g., for stimulation and/or oil or gas production.

[0053] Perforation cluster - a group of nearby perforations having similar characteristics.

[0054] Pill - any relatively small quantity of a special blend of drilling or treatment fluid to accomplish a specific task that the regular drilling or treatment fluid cannot perform.

[0055] Pressure wave - a periodic pressure disturbance in which alternating compression and rarefaction are propagated through or on the surface of a medium without translation of the material; also known as a tube wave or Stoneley wave.

[0056] Pressure signal emitter - a non-pumping device specially adapted to form a pressure wave in a wellbore, usually in communication with the high pressure side (outlet or discharge) of a fluid pump.

[0057] Progression - a movement or development toward a destination or a more advanced state, especially gradually or in stages; a succession; a series.

[0058] Proppant -particles mixed with treatment fluid to hold fractures open after a hydraulic fracturing treatment. [0059] Proppant pumping schedule - a pumping sequence comprising the volume, rate, and composition and concentration of a proppant-laden fluid, and any associated treatment fluids such as an optional pad, optional spacers, and an optional flush.

[0060] Receiver - an electrical or computer apparatus that converts a signal to a file, sound, or visual display.

[0061] Refracturing or refrac - fracturing a portion of a previously fractured well after an initial period of production. The fractures from the earlier treatment are called "pre-existing fractures".

[0062] Regularly changing frequency - a frequency (cycles per time) that varies in an ordered pattern.

[0063] Remote - distant or far away.

[0064] Reservoir - a subsurface body of rock having sufficient porosity and permeability to store and transmit fluids.

[0065] Re-stimulation - stimulation treatment of any portion of a well, including any lateral, which has previously been stimulated.

[0066] Revise - alter in light of developments.

[0067] Sending - cause (a message or computer file) to be transmitted electronically.

[0068] Shut in - closing a wellbore at the surface, e.g., at or near the Christmas tree, blowout preventer stack

[0069] Shut-in pressure or SIP - the surface force per unit area exerted at the top of a wellbore when it is closed, e.g., at the Christmas tree or BOP stack.

[0070] Simulate - to create a representation or model of something, e.g., a physical system or particular situation.

[0071] Stage - a pumping sequence comprising a proppant pumping schedule and a diversion pill pumping schedule, including pads, spacers, flushes and associated treatment fluids. [0072] Stimulation - treatment of a well to enhance production of oil or gas, e.g., fracturing, acidizing, and so on.

[0073] Sweep circuit - an electronic or mechanical device which creates a waveform with a regularly changing frequency or amplitude, usually a linearly varying frequency and a constant amplitude.

[0074] Treatment - the act of applying a process or substance to something to give it particular properties.

[0075] Treatment fluid - a fluid designed and prepared to resolve a specific wellbore or reservoir condition.

[0076] Well - a deep hole or shaft sunk into the earth, e.g., to obtain water, oil, gas, or brine.

DETAILED DESCRIPTION

[0077] In the following description, numerous details are set forth to provide an understanding of the present disclosure. However, it may be understood by those skilled in the art that the methods of the present disclosure may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In the summary and this detailed description, each numerical value should be read once as modified by the term "about" (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. Also, in the summary and this detailed description, it should be understood that a range listed or described as being useful, suitable, or the like, is intended to include support for any conceivable sub-range within the range at least because every point within the range, including the end points, is to be considered as having been stated. For example, "a range of from 1 to 10" is to be read as indicating each possible number along the continuum between about 1 and about 10. Furthermore, one or more of the data points in the present examples may be combined together, or may be combined with one of the data points in the specification to create a range, and thus include each possible value or number within this range. Thus, (1) even if numerous specific data points within the range are explicitly identified, (2) even if reference is made to a few specific data points within the range, or (3) even when no data points within the range are explicitly identified, it is to be understood (i) that the inventors appreciate and understand that any conceivable data point within the range is to be considered to have been specified, and (ii) that the inventors possessed knowledge of the entire range, each conceivable sub-range within the range, and each conceivable point within the range. Furthermore, the subject matter of this application illustratively disclosed herein suitably may be practiced in the absence of any element(s) that are not specifically disclosed herein.

[0078] In some embodiments, degradable diverter is used to plug a fluid flow path, within the wellbore, e.g., a bridge plug, or connected to the wellbore, e.g., a fracture, and degradation is monitored using the reflection of tube waves, which are also referred to herein as pressure waves or an interrogating signal. The pressure waves can be generated either by a special pressure signal emitter or by a fluid hammer, e.g., by suddenly stopping a treatment fluid pump in such a way that a pressure wave results. When a pressure wave reflects from an interface or change in the tubular media, the reflection is related to the original wave, but modified by the character of the reflector.

[0079] According to some embodiments herein, the pressure waves reflected to the surface or other sensor location are from a wellbore plug such as a ball, or an open fracture. The reflection from a wellbore plug, normally having the same sign as the interrogating signal, implies that the sealing ball did not degrade. The change or disappearance of reflections from the wellbore plug indicates degradation of the plug and lost sealing of the zone and/or readiness for production or injection.

[0080] Conversely, in some embodiments, a sealed fracture in which a diverter has been placed produces no reflection, or a small or undetectable reflection, and appearance of a reflection from the perforation interval with a negative sign compared to the interrogating signal can indicate degradation of diversion material and the establishment or restoration of a hydraulic connection between the wellbore and a fracture, suggesting that the fracture is readied for production or injection as the case may be.

[0081] Two extreme types of pressure wave reflection are thus of particular interest in some embodiments: those of a closed end wellbore, and those of an open end. A closed end is one in which there is little or no compliance at the reflector; a capped pipe is an example of this. An open end is one in which there is a large compliance at the reflector; a pipe ending in a large tank is an example of this. Such compliance can consist of a significant sealed volume of fluid, a free surface, or a connection to a reservoir, such as a hydrocarbon reservoir. The fluid flow characteristics of the connection between the two affect the magnitude of the reflection; a free flowing connection, i.e., an open end, produces the largest reflection; a non-flowing connection, i.e., a closed end, similarly produces a large reflection; and a connection with significant flow resistance produces a smaller reflection. At some point the impedance or resistance of the connection approximates the characteristic impedance of the pressure wave media, i.e., the wellbore, casing or other material having a surface interfacing the fluid filling the wellbore. At this point all of the incoming energy may be absorbed by the resistance of the connection, leading to no reflection at all, and this non-reflecting end is referred to as a terminator.

[0082] With reference to the example shown in FIG. 1, PVC pipe used as a simulated well bore was interrogated with a positive pressure wave. A small hydraulic accumulator was attached to the pipe via a ball valve at 101 m (331 ft) from the pressure source to imitate an open fracture connected to the well. The far end of the tubing located at 165 m (541 ft) was capped to imitate a sealed bridge plug. When the ball valve was closed to imitate a fracture sealed by a diverter for reflection traces 1 and 2, there was no simulated perforation reflection 10 at 101 m, and a full end reflection 12. In the case of traces 3 and 4, the ball valve was opened to simulate an open fracture, giving a low resistance connection to a compliant volume and yielding an open end type reflector. This reflection 10 was visible as an inverted or down-going pulse. The far end gives a positive reflection 12, which is proportionally reduced by partial reflection 10. In this manner, the interpretation of the pressure wave reflections is illustrated for purposes of some embodiments disclosed herein. [0083] With reference to the embodiments illustrated in FIG. 2, the pressure wave 14 is generated in the well 16 by pressure signal emitter or source 18 and/or by a sharp stop of the fracturing pump 20, and is propagated downhole. The reflections are received at pressure sensor 22. The pressure wave reflection 24 is formed by the partially degraded ball 26 seating on bridge plug 30. The remaining signal wave portion 28 passing the plug 30 forms reflection 32 at the intact ball 34 seated on the bridge plug 36. The reflection 24 is weak if present at all, and may not be detected.

[0084] The embodiments of FIG. 2 have potential application in a multistage operation wherein degradable balls 26, 34 are used to seal respective bridge plugs 30, 36 to isolate intervals in respective stages. After the stimulation, the balls 26, 34 degrade to permit production. Monitoring of the degradation of the balls 26, 34 in some embodiments, involves an analysis of the detected reflections 24, 32 for their presence as well as amplitude. In the case of degraded ball 26 the reflection 24 from bridge plug 30 is weak and/or may be absent, whereas the reflection 32 from the next bridge plug 36 is detected and is strong. If the ball 26 were not degraded, the reflected wave 24 would have strong positive amplitude compared to the interrogating pressure pulse 14, and there would be no passing wave 28 and thus no reflected wave 32 would be detected.

[0085] In the embodiments illustrated in FIG. 3, wherein like reference numerals indicate like parts and features, the pressure wave 14 is generated in the well 16 by pressure signal emitter or source 18 and/or by a sharp stop of the fracturing pump 20, and is propagated downhole as in FIG. 2, and the reflections received at pressure sensor 22. In this case, the pressure wave reflection 42 is formed by the open hydraulic fracture 44. Diversion material 46 seals the perforations 48 or other hydraulic passages in the fracture 50, whereas the fracture 44 is hydraulically connected to the well via perforations 52. These perforations are only partially sealed with diversion material 54 that has been degraded. The pressure wave 14 passes fracture 50 without reflections, and reflects from fracture 44.

[0086] The embodiments of FIG. 3 have potential application in a diversion operation in new fracturing treatments or in refracturing treatments, wherein diversion material 46 is pumped to seal the hydraulic connections between the fractures 44, 50 and the wellbore 38 before the next successive stimulation stage. Monitoring of the degradation of the diverting material 46 is done by analysis of the reflected waves coming from the depth of particular fracture. At the end of a stimulation stage, before sealing, the fracture from the stage will produce reflection with strong negative amplitude compared to the interrogating signal. After sealing the fracture with diversion material 46 the reflection from that interval will become weak or disappear. When the diversion material degrades, there will again be a strong reflection from that depth with negative amplitude, indicating that the fracture is ready for returning the well to service.

[0087] To monitor degradation of a ball or diverter material occurring over an order of several minutes, in some embodiments, multiple frequent pressure pulses can be generated from the interrogating signal, e.g. every 1 second to 3 minutes, or every 10 to 30 seconds, and degradation can be determined from a change in the reflected pulses, i.e., appearance and strengthening in the case of perforation plugs, or weakening and disappearance in the case of bridge plugs. Where a well is a hybrid of FIGs. 2 and 3, i.e., may contain bridge plugs and perforation plugs, the reflections at each plug type can be distinguished by the different signs as noted above, e.g., positive sign reflections for the bridge plugs and negative sign reflections for the open fractures.

[0088] In some other embodiments, fast degradation events can be monitored using a sweep signal having a period longer than the event, which is generated by a special pulsing source, e.g., a modified fracturing pump. Splitting the sweep signal into shorter overlapping intervals and deconvolution of the reflections can show any change in the reflector and therefore degradation.

[0089] In some embodiments, to monitor degradation occurring over longer periods, e.g., from 0.5 to 24 hours, such as 1 to 4 hours, in addition to or in place of a special pulsing source, the fluid hammer generated every time the fracturing pump(s) are stopped can be used, such as, for example, firac pump stopping before and after placing the ball or diversion material, as well as after minibreak, ISIP test, break in, end of stage, and so on.

[0090] In some embodiments, to measure of degradation over a period of 1 or more days, if desired, a pulsing source and reflection detector can be left in place on location connected to the well after completion of the stimulation treatment. The pulsing source can send multiple pulses or sweep signals over a day. Because of the relatively long monitoring time, a high number of pulses or long sweep pressure signals can be used, with stacking of the reflections detected to improve signal to noise ratio so that a relatively small, weak and/or inexpensive pressure signal emitter can be used. Gradual changes in the reflected waves can reveal kinetics of long-term degradation of a ball or diversion material. The measurement tool, in some embodiments, can automatically send data to a remote location for analysis.

[0091] Monitoring of the degradation of the degradable diverters in some embodiments can be used to change one or more operating parameters of the well, e.g., in response to the changes in the observed reflections, proportional changes in the operation of the well can be instituted, in some embodiments automatically, or a decision to begin producing the well and//or the zones ready to be placed into production (or injection) can be made based on actual measured degradation, rather than an estimated time. This can be an advantage when downhole conditions are not precisely known and/or other factors make a precise determination of the degradation time otherwise unpredictable, and according to some embodiments herein the well can be placed into production earlier than the period estimated for complete degradation if this is the case, or production can be delayed until complete degradation is confirmed if it is not the case. For example, the time required for the degradation of diversion materials and/or wellbore plugs is sensitive to fluid salinity, pressure, and temperature, as well as the physical condition and quality of the diverter or plug itself, which may degrade differently under (generally unknown) downhole conditions, and the use of a laboratory master curve may not give a precise prediction of the kinetics of the process.

[0092] With reference to FIG. 4, a process flow diagram illustrates some of the steps, operations, events, tasks, or features for treatment of a well according to the method 100, involving monitoring of diverter degradation in accordance with some embodiments of the disclosure. In operation 102, a diverter, which may be a mechanical diverter or a chemical diversion material, is placed in the wellbore, perforation, fracture or the like, e.g., a bridge plug isolating a first portion of the wellbore from a second portion of the wellbore, or diversion material placed in a perforation, fracture, etc.,; and in step 104, fluid flow is diverted past the diverter, e.g., in a later pumping operation of the same stage and/or another stage(s) of the treatment. After placement 102, e.g., during diversion 104 or other progression of the treatment, or after completion of the stimulation treatment, the diverter is exposed to degradation conditions in operation 106. Degradation conditions can include pressure and temperature conducive to degradation, contact with a solvent or chemical reactant, which may be present or exist in the downhole environment or may be introduced and/or activated in a distinct step.

[0093] To check the degradation status of the diverter element, a pressure wave is generated in operation 108 and the response sensed in step 110. In some embodiments, analysis of the data from the pressure wave interrogation is performed in operation 112, and if desired, the data and/or analysis may be reported, e.g., to a remote location or control system. In some embodiments, the degradation status is monitored in operation 114, and after determining that the degradable diverter has substantially degraded, in step 116, the well is placed in service, e.g., production or injection of fluids from or to the reservoir or otherwise flowing fluid through the flow path of the (degraded) diverter.

[0094] By performing an operation, the present disclosure may refer to placing the well in service for example by flowing through the previously plugged path; but it may also be forcing the degradation of the diverter for example by pumping an acid or alkaline compound, this can also be other operation such as opening a sleeve or flowing back in order to improve the configuration of the well for further hydrocarbon production.

[0095] With reference to FIG. 5, there is shown a method 200 for treatment of a well involving checking diverter degradation after interruption of a treatment schedule in accordance with some embodiments of the disclosure. In the method 200, treatment of the well is initiated in step 202 per a planned treatment schedule, which may include schedules for proppant pumping or other treatment fluid introduction into the well and for mechanical or chemical diverter placement 204, and treatment progresses past at least one diverter placement 204 until the planned treatment is interrupted in event 206. Before resuming the treatment, the status of the diverter(s) is checked by pressure wave generation 208 and response sensing 210, e.g., to determine that the diverter is still intact and/or has not degraded to the point that diverter functionality is impaired. If needed or desired, the treatment schedule can be adjusted in step 212, and in operation 214 the treatment is resumed according to the original treatment schedule or the modified treatment schedule. Following further treatment, in some embodiments, the method may further proceed, in a manner similar to actions 108 to 116 in FIG. 4, with pressure wave generation 216, response sensing 218, analysis and/or reporting of the data 220, degradation status monitoring 222, and fluid flow 224 through the flow path(s), e.g., by placing the well in service.

[0096] With reference to FIG. 6, there is shown a flow diagram for the method 300 for treatment of a well involving monitoring of diverter placement and degradation in accordance with some embodiments of the present disclosure. The method 300 proceeds with diverter placement 302, followed by pressure wave generation 304, and response sensing 306 to confirm proper diverter placement prior to fluid flow diversion 308. Next, in operation 310 steps 302 to 308 can optionally be repeated as desired for one or more subsequent stages. Following completion of the desired stage(s), the diverter(s) is(are) subjected to degradation exposure 312, and the method 300 may further proceed, in a manner similar to actions 108 to 116 in FIG. 4, with pressure wave generation 314, response sensing 316, processing and/or reporting of the data 318, degradation status monitoring 320, and fluid flow 322 through the flow path(s), e.g., by placing the well in service.

EMBODIMENTS LISTING

[0097] In some aspects, the disclosure herein relates generally to well re-stimulation methods and/or workflow processes according to the following Embodiments, among others:

[0098] Embodiment 1 : A method for treating a well, comprising: (a) placing a degradable diverter in a flow path of the well to divert fluid flow from the flow path; (b) exposing the degradable diverter to degradation conditions; (c) sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has substantially degraded; and (d) after determining that the degradable diverter has substantially degraded, placing the well in service and flowing fluid through the flow path.

[0099] Embodiment 2: the method of Embodiment 1, wherein the degradable diverter comprises a mechanical diverter, such as a ball received in a bridge plug seat.

[00100] Embodiment 3 : the method of Embodiment 1 or Embodiment 2, wherein the degradable diverter comprises a chemical diversion material. [00101] Embodiment 4: the method of any one of Embodiments 1-3, wherein the flow path comprises a perforation and/or fracture in communication with the well.

[00102] Embodiment 5 : the method of any one of Embodiments 1-4, wherein the flow path comprises a first portion of the wellbore isolated from a second portion of the wellbore by the diverter.

[00103] Embodiment 6: the method of any one of Embodiments 1-5, further comprising continuously or periodically generating the pressure wave and sensing the response to monitor the placement of the diverter, degradation of the diverter, or a combination thereof.

[00104] Embodiment 7: the method of any one of Embodiments 1-6, wherein the placement or degradation of the diverter or both are monitored by changes in the sensed response.

[00105] Embodiment 8: the method of any one of Embodiments 1-7, wherein the pressure wave is generated at a frequency from 1 per second to 1 per minute.

[00106] Embodiment 9: the method of any one of Embodiments 1-8, wherein the pressure wave generation comprises a sweep circuit comprising a regularly changing frequency.

[00107] Embodiment 10: the method of any one of Embodiments 1-9, wherein the pressure wave has overlapping intervals.

[00108] Embodiment 11 : the method of any one of Embodiments 1-10, further comprising deconvoluting the sensed response, e.g., to improve sensitivity and allow weak emitter signal such as signal to noise ratio less than 10 dB.

[00109] Embodiment 12: the method of any one of Embodiments 1-11, further comprising automatically sending data derived from the sensed response to a remote receiver.

[00110] Embodiment 13 : the method of any one of Embodiments 1-12, wherein the pressure wave is generated by a fluid hammer.

[00111] Embodiment 14: the method of Embodiment 13, wherein the fluid hammer is formed by suddenly stopping pumping of treatment fluid, e.g., into the well.

[00112] Embodiment 15: the method of any one of Embodiments 13-14, wherein the fluid hammer is formed at a time in the operation that is one or more or all of the following: before diverter placement, after diverter placement, after a minibreak, for an instantaneous shut-in pressure (ISIP) test, for break in, at the end of a stage, or a combination thereof.

[00113] Embodiment 16: the method of any one of Embodiments 1-15, wherein the pressure wave is generated by a pressure signal emitter device in communication with the well.

[00114] Embodiment 17: The method of any one of Embodiments 1-16, wherein the flowing of the fluid in (d) comprises producing reservoir fluid, or wherein the well comprises a production well.

[00115] Embodiment 18: The method of any one of Embodiments 1-17, wherein the flowing of the fluid in (d) comprises fluid injection into a subterranean formation, or wherein the well comprises an injection well.

[00116] Embodiment 19: The method of any one of Embodiments 1-17, wherein

[00117] Embodiment 20: The method of any one of Embodiments 1-17, wherein

[00118] Embodiment 21 : The method of any one of Embodiments 1-20, wherein

[00119] Embodiment 22: The method of any one of Embodiments 1-21, wherein

[00120] Embodiment 23 : A method for treating a well, comprising: (a) initiating a treatment sequence according to a planned treatment schedule comprising introducing treatment fluid into the well in a plurality of stages; (b) placing a degradable diverter in a flow path of the well to divert treatment fluid from the flow path; (c) interrupting the treatment schedule comprising shutting in the well; (d) sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has degraded; and (e) after determining that the degradable diverter has not degraded, resuming the treatment sequence; wherein the method is optionally according to none or any one of the methods of Embodiments 1-22.

[00121] Embodiment 24: The method of Embodiment 23, wherein the resumption of the treatment sequence is according to the planned treatment schedule. [00122] Embodiment 25: The method of Embodiment 23 or Embodiment 24, wherein the resumption of the treatment sequence is according to a new treatment schedule revised in response to the interruption.

[00123] Embodiment 26: The method of any one of Embodiments 23-25, further comprising exposing the diverter to degradation conditions.

[00124] Embodiment 27: The method of Embodiment 26, further comprising sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has degraded.

[00125] Embodiment 28: The method of Embodiment 27 further comprising after determining that the degradable diverter has degraded, flowing fluid through the flow path.

[00126] Embodiment 29: A method for treating a well, comprising: (a) placing a degradable diverter in a flow path of the well to divert treatment fluid from the flow path; (b) sensing a response to a pressure wave generated in the well to confirm the placement of the degradable diverter; (c) diverting fluid flow from the flow path; (d) repeating (a) - (c) one or more times for a plurality of respective degradable diverters placed in respective flow paths; (e) exposing the diverters to degradation conditions; (f) sensing a response to a pressure wave generated in the well to determine whether the degradable diverters have degraded; and after determining that the degradable diverters have degraded, placing the well in service and flowing fluid through the flow paths; wherein the method is optionally according to none or any one of the methods of Embodiments 1-28.

[00127] Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this disclosure. For example, any embodiments specifically described may be used in any combination or permutation with any other specific embodiments described herein. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus- function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 1 12(f) for any limitations of any of the claims herein, except for those in which the claim expressly uses the words 'means for' or 'step for' together with an associated function without the recitation of structure.

Claims

CLAIMS What is claimed is:

1. A method for treating a well, comprising:

(a) placing a degradable diverter in a flow path of the well to divert treatment fluid flow from the flow path;

(b) exposing the degradable diverter to degradation conditions;

(c) sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has substantially degraded; and

(d) after determining that the degradable diverter has substantially degraded, performing an operation and flowing fluid through the flow path.

2. The method of claim 1, wherein the degradable diverter comprises a mechanical diverter.

3. The method of claim 1, wherein the degradable diverter comprises a chemical diversion material.

4. The method of claim 1, wherein the flow path comprises a perforation or fracture in communication with the well.

5. The method of claim 1, wherein the flow path comprises a first portion of the wellbore isolated from a second portion of the wellbore by the diverter.

6. The method of claim 1, further comprising continuously or periodically generating the pressure wave and sensing the response to monitor the placement of the diverter, degradation of the diverter, or a combination thereof.

7. The method of claim 6, wherein the placement or degradation of the diverter or both are monitored by changes in the sensed response.

8. The method of claim 6, wherein the pressure wave is generated at a frequency from 1 per second to 1 per minute.

9. The method of claim 6, wherein the pressure wave generation comprises a sweep circuit comprising a regularly changing frequency.

10. The method of claim 9, wherein the pressure wave has overlapping intervals, and further comprising deconvoluting the sensed response.

11. The method of claim 6, further comprising automatically sending data derived from the sensed response to a remote receiver.

12. The method of claim 1, wherein the pressure wave is generated by a fluid hammer.

13. The method of claim 1, wherein the pressure wave is generated by a pressure signal emitter device in communication with the well.

14. The method of claim 1, wherein the flowing of the fluid in (d) comprises producing reservoir fluid.

15. The method of claim 1, wherein the flowing of the fluid in (d) comprises fluid injection into a subterranean formation.

16. A method for treating a well, comprising:

(a) initiating a treatment sequence according to a planned treatment schedule comprising introducing treatment fluid into the well in a plurality of stages;

(b) placing a degradable diverter in a flow path of the well to divert treatment fluid from the flow path;

(c) interrupting the treatment schedule comprising shutting in the well;

(d) sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has degraded; and

(e) after determining that the degradable diverter has not degraded, performing an operation or resuming the treatment sequence.

17. The method of claim 16, wherein the resumption of the treatment sequence is according to the planned treatment schedule.

18. The method of claim 16, wherein the resumption of the treatment sequence is according to a new treatment schedule revised in response to the interruption.

19. The method of claim 16, further comprising exposing the diverter to degradation conditions; sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has degraded; and after determining that the degradable diverter has degraded, flowing fluid through the flow path.

20. A method for treating a well, comprising:

(a) placing a degradable diverter in a flow path of the well;

(b) sensing a response to a pressure wave generated in the well to confirm the placement of the degradable diverter;

(c) diverting fluid flow from the flow path;

(d) exposing the diverter to degradation conditions;

(e) sensing a response to a pressure wave generated in the well to determine whether the degradable diverter has degraded; and

(f) after determining that the degradable diverter has degraded, performing an operation and flowing fluid through the flow path.

21. A method for treating a well, comprising:

(a) placing a degradable diverter in a flow path of the well;

(b) sensing a response to a pressure wave generated in the well to confirm the placement of the degradable diverter;

(c) diverting fluid flow from the flow path;

(d) repeating (a) - (c) one or more times for a plurality of respective degradable diverters placed in respective flow paths;

(e) exposing the diverters to degradation conditions;

(f) sensing a response to a pressure wave generated in the well to determine whether the degradable diverters have degraded; and

(g) after determining that the degradable diverters have degraded, placing the well in service and flowing fluid through the flow paths.