US20060076134A1 - Well stimulation - Google Patents
Well stimulation Download PDFInfo
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- US20060076134A1 US20060076134A1 US10/963,436 US96343604A US2006076134A1 US 20060076134 A1 US20060076134 A1 US 20060076134A1 US 96343604 A US96343604 A US 96343604A US 2006076134 A1 US2006076134 A1 US 2006076134A1
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- Prior art keywords
- tubing
- formation
- acid
- well
- diverter
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- 230000000638 stimulation Effects 0.000 title description 15
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 76
- 239000002253 acid Substances 0.000 claims abstract description 74
- 238000000034 method Methods 0.000 claims abstract description 27
- 239000011159 matrix material Substances 0.000 claims abstract description 20
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 claims description 7
- 239000005711 Benzoic acid Substances 0.000 claims description 3
- 235000010233 benzoic acid Nutrition 0.000 claims description 3
- 238000005755 formation reaction Methods 0.000 description 54
- 239000012530 fluid Substances 0.000 description 21
- 238000011282 treatment Methods 0.000 description 16
- 239000000463 material Substances 0.000 description 12
- 238000004519 manufacturing process Methods 0.000 description 11
- 238000002347 injection Methods 0.000 description 9
- 239000007924 injection Substances 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 7
- 229930195733 hydrocarbon Natural products 0.000 description 7
- 150000002430 hydrocarbons Chemical class 0.000 description 7
- 230000035699 permeability Effects 0.000 description 6
- 238000006073 displacement reaction Methods 0.000 description 5
- 238000005086 pumping Methods 0.000 description 5
- 238000010306 acid treatment Methods 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000010420 art technique Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 235000005985 organic acids Nutrition 0.000 description 2
- 230000037361 pathway Effects 0.000 description 2
- 239000011435 rock Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000003180 well treatment fluid Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 235000011054 acetic acid Nutrition 0.000 description 1
- 150000001243 acetic acids Chemical class 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 230000009969 flowable effect Effects 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 150000004674 formic acids Chemical class 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 150000002913 oxalic acids Chemical class 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
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- 238000006467 substitution reaction Methods 0.000 description 1
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Images
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/27—Methods for stimulating production by forming crevices or fractures by use of eroding chemicals, e.g. acids
Definitions
- a well for the production of hydrocarbons may be stimulated by one or more procedures.
- the purpose of stimulation is to increase the permeability to the flow of hydrocarbons. These procedures may increase the permeability to values not only equal to the original natural permeability prior to drilling. If a hydrocarbon reservoir has acceptable saturation, but insufficient permeability for economic development, stimulation procedures may also increase the permeability to a value justifying the cost for development of the reservoir.
- Matrix acidizing is a common way to stimulate a well by pumping acid into the near wellbore region to dissolve formation damage and create pathways for the hydrocarbons.
- Various acids may be used to Improve production by dissolving formation damage or creating new pathways around the borehole depending on the nature of the formation, rock, or the types of damage which may exist.
- an acid solution Is pumped under pressure down the well and into the perforations around the well, chemically removing contaminants as well as rock structure itself.
- FCP fracture closure pressure
- pumping acid into the matrix of the formation may cause a hydraulic fracture of the formation and create an undesirable flow path between wells. It Is therefore essential to keep the pressure and rates of the fluid below fracture closure pressure (FCP).
- FCP fracture closure pressure
- the FCP is a function of formation parameters and pressure.
- Treatment fluid can be directed exclusively towards a low-permeable zone using mechanical aids or the flow itself can be blocked at individual perforations using e.g. ball sealers that seal the perforation.
- ball sealers that seal the perforation.
- the most common materials used to divert the acid are particulates that are poorly soluble in acid, but soluble in hydrocarbons for effective cleanup so as not to obstruct the production.
- stimulation is often performed with benzoic acid flakes, emulsified acids, oil soluble resins, foam and self-viscosifying acids as a diverting material.
- One method is to use chemical diversion during the matrix stimulation treatment and this can be accomplished by adding diversion material in stages at the surface such that the diversion material is separated by stages of acid and pumping the stages of acid and diversion material commingled through the tubing without mixing.
- These stimulation treatments are normally pumped at high rates and at high treatment pressures and therefore they are called High Rate Matrix stimulation methods.
- the diversion volumes are large compared to the total treatment volumes and the diverting materials are physically very coarse. Therefore, the High Rate Matrix stimulation methods often cause severe operational problems, such as stuck pipes or tubing, or the FCP is in many cases even exceeded during the treatment causing the formation to fracture.
- a coiled tubing which is basically a second smaller tubing disposed within the production tubing (first tubing) running from the well to the surface.
- Coiled tubing is widely used in the oil and gas industry for completion, production and work-over operations.
- Some of the oilfield operations in which such a secondary tubing is used are completion operations in which the second tubing can be used to transport fluids from the surface down into the well.
- the treatment fluids in the prior art technique involving coiled tubing are pumped through the interior of the second tubing and into the well to perform the particular required operation which can take place at a predetermined location or in a predetermined depth.
- the second tubing may remain suspended in the well for continuous use, and it may extend from the surface to the bottom of the well.
- the second tubing may also extend to an intermediate point between the surface and the well bottom.
- the second tubing may possibly also be temporarily suspended into the well for the duration of a particular operation during which the tubing may be raised and/or lowered to various levels in the well. Upon completion of the operation, the tubing may be retracted so as to be used in another operation or be transported to another well.
- the prior art technique often poses a potential hazard to the environment and pollution is often the unsuccessful outcome in situations where the formation is blocked with diversion materials and the treatment pressure at the same time approaches or even exceeds the FCP.
- the tubing is then filled with a mixture of acid and diversion material, and further pumping is not possible without unavoidable fracturing of the formation.
- the tubing content of acid and diversion material possibly solid then inevitably have to be circulated out back to surface and discharged to the sea where both the acid and the diversion material present a high degree of hazard to the environment.
- the formation is pre-flushed by acid that is injected into the formation through-said second tubing.
- the acid treatment is initiated through the second tubing, whilst taking fluids back to surface via the first tubing inlet until the acid reaches the end of the second tubing.
- the initial step of Injecting a relatively small amount of acid into the formation through the second tubing causes the formation pressure to decrease. This will improve the injectivity into the formation so the annular volume (between the first and the second tubing) of non-reactive fluid can be injected to the formation, without exceeding the FCP.
- the injection occurs by displacement of the annular volume by well treatment fluid.
- substitution of said liquid could also, in a less preferred embodiment, be accomplished by it being displaced through the top from the bottom end (at the formation) with the aid of the inner (second) tubing.
- benzoic flakes dissolved in methanol achieves a highly flowable diverter that can flow into all parts of a formation and provide good diversion without exhibiting defects due to segregation in the tubing delivering it.
- the formation being a chalk formation.
- FIG. 1 shows a sectional view of a well showing the initial step of displacing fluid in second tubing by acid whilst taking fluid back to surface through first tubing inlet
- FIG. 2 shows a well being pre-flushed with acid through the second tubing
- FIG. 3 shows a well with diverter in the second tubing
- FIG. 4 shows a sectional view of a well showing the step of injecting the annular volume of non-reactive fluid (between first and second tubing) into formation by displacement with acid,
- FIG. 5 shows a sectional view of well showing displacement of fluid in the second tubing by diverter
- FIG. 6 shows a sectional view of a well having diverter present in the second tubing and acid present in the first tubing at the formation
- FIG. 7 shows a sectional view of a well where the acid is being displaced by a non-reactive fluid
- FIG. 8 shows a sectional view of a well where the acid is being displaced by a non reacting fluid
- FIG. 9 shows a sectional view of a prior art well with a single tubing having acid and diverter commingled through the tubing.
- FIG. 1 discloses a well having a casing 3 extending throughout the wellbore, which is usually secured in place by e.g cement.
- the casing 3 is perforated 5 adjacent to the production formation 20 to provide flow passages for fluids from the formation 20 into the casing 3 .
- a first tubing or production tubing I has a sliding door 6 and a tubing Inlet 12 extends into the casing 3 and has a packer 19 (already known in the prior art) for isolating the production interval of the well-bore.
- a second tubing 2 extends down within the production tubing 1 into the well-bore and has an inlet 11 .
- the second tubing which is commonly called coiled tubing, may be wound around a reel or wheel and Is passed into the well through an—already known—injector head.
- the second tubing and production tubing further comprises a system of valves (not shown) having means for individually and independently regulating and turning off the fluid flow through first and second tubings at both inlet and welbore end.
- the second tubing usually passes through a blowout-preventer (not shown either) to facilitate regulation of the well-bore pressure.
- the coiled tubing usually consists of a singular tubing but may consist of two or more tubings.
- the outcome of matrix acidizing depends highly on the pressure at which diverter and acid are injected and the aim of the current matrix stimulation method is to deploy acid at the highest pressure possible without exceeding of the pressure at which the formation breaks down and a fracture is generated.
- the pressure at which the formation breaks down is called the fracture closure pressure (FCP).
- FCP fracture closure pressure
- the pressure may be monitored. Monitoring of the wellbore pressure facilitates injection of acid whenever the pressure is adequate for acidizing and diverter whenever the pressure drops to a level inadequate for acidizing thus optimizing utilization of the stimulation fluids.
- the non-reactive liquid, present in the second 2 (coiled) tubing is displaced by acid (illustrated by being a little darker in FIG. 1 ).
- the acid 8 which e.g. can be a 15% HCl, is then pumped in from the top of the second tubing 2 whilst taking fluid back via the first tubing 1 , thus essentially maintaining formation pressure at the wellbore.
- the tubing 1 is then closed and the acid treatment is initiated with a pre-flush of acid (bull-heading) to the formation via the second tubing as shown in FIG. 2 .
- the purpose of initially injecting of a pre-flush of acid 8 through the second tubing is to open up the formation so as to increase its injectivity sufficiently to absorb the volume of non-reactive fluid present in the first tubing 1 (production tubing) without exceeding the fracture propagating pressure of the formation. Field testing shows that this is advantageously done by injecting approximately 50 bbl (barrel) of acid.
- the acid pre-flush is advantageously finished by displacement of acid in the second tubing by diverter 9 as shown in FIG. 3 .
- the main acid treatment is then started by injection of the (annular) volume of non-reactive liquid present in the first tubing 1 into the formation by displacement with acid 8 as shown in FIG. 4 .
- the flow is kept at rate such that the pressure does not exceed the FCP pressure.
- the acid injection preferably continues until the pressure starts to decrease.
- a pressure insufficient for acidizing may at any time during the well stimulation procedure cause injection of diverter 9 .
- FIG. 5 shown by a pressure drop
- a batch of diverter is pumped into the main treatment fluid and further to the formation via the second tubing (coiled tubing), as shown in FIG. 6 .
- the diverter will follow the main stream, which is also the path of least restriction, into the formation and preferably block off the coming acid accession to recently stimulated areas in the formation.
- FIG. 9 The worst operational scenario during prior art methods of matrix stimulation with diverter 9 is illustrated in FIG. 9 .
- the FCP is exceeded and further pumping into the formation will invariably create fracture of the formation. Further, the string content has to be circulated back to surface and disposed off.
- the acid utilized may be any of the aqueous solutions of acid commonly employed for acidizing formations.
- the solution of acid may be an aqueous solution of hydrochloric acid and hydroflouric acid, which is employed for acidizing formations.
- Certain organic acids can be utilized alone or in combination with inorganic acids.
- Organic acids Include formic, acetic and oxalic acids.
- hydrochloric acid Is utilized it should be in a concentration from about 5 to about 30 percent.
- the concentration of hydroflouric acid will range from about 0.3 to about 8 percent.
Abstract
Methods of conducting matrix acidizing in a well in a formation by simultaneously or alternatingly injecting an acid and a diverter into the formation through tubing. The acid is injected into the formation through a first tubing and the diverter is injected into the formation through a second tubing. The second tubing may extend within said first tubing and the formation may be a chalk formation.
Description
- A well for the production of hydrocarbons may be stimulated by one or more procedures. The purpose of stimulation is to increase the permeability to the flow of hydrocarbons. These procedures may increase the permeability to values not only equal to the original natural permeability prior to drilling. If a hydrocarbon reservoir has acceptable saturation, but insufficient permeability for economic development, stimulation procedures may also increase the permeability to a value justifying the cost for development of the reservoir.
- Matrix acidizing is a common way to stimulate a well by pumping acid into the near wellbore region to dissolve formation damage and create pathways for the hydrocarbons.
- Various acids may be used to Improve production by dissolving formation damage or creating new pathways around the borehole depending on the nature of the formation, rock, or the types of damage which may exist. In acidizing a well, an acid solution Is pumped under pressure down the well and into the perforations around the well, chemically removing contaminants as well as rock structure itself. However, if the pressure exceeds the fracture closure pressure (FCP), pumping acid into the matrix of the formation may cause a hydraulic fracture of the formation and create an undesirable flow path between wells. It Is therefore essential to keep the pressure and rates of the fluid below fracture closure pressure (FCP). The FCP is a function of formation parameters and pressure.
- Low acid pressure injection rates often cause other problems, because when acid is injected at low rates the most reactive parts of the formation in a group of perforations or zones may take up all the acid. With continued reaction at low injection rates it is even more likely that only these more reactive perforations or zones will receive acid.
- As acid is pumped it preferably flows along the most permeable path into the formation. The acid opens up these paths even more, and the process becomes self-perpetuating; and less permeable, damaged zones are almost guaranteed not to receive adequate treatment. Some technique to divert the treatment fluid is therefore essential. Such technique is called diversion.
- There exist a variety of diversion techniques. Treatment fluid can be directed exclusively towards a low-permeable zone using mechanical aids or the flow itself can be blocked at individual perforations using e.g. ball sealers that seal the perforation. In order to cover all zones as completely as possible, a frequent practice is to use diverting materials in combination with stages of acid.
- The most common materials used to divert the acid are particulates that are poorly soluble in acid, but soluble in hydrocarbons for effective cleanup so as not to obstruct the production.
- Because of both Its solubility in hydrocarbons and its capability to build up filter cakes within the holes created by the acid, and thereby forcing the acid to divert, stimulation is often performed with benzoic acid flakes, emulsified acids, oil soluble resins, foam and self-viscosifying acids as a diverting material.
- One method is to use chemical diversion during the matrix stimulation treatment and this can be accomplished by adding diversion material in stages at the surface such that the diversion material is separated by stages of acid and pumping the stages of acid and diversion material commingled through the tubing without mixing. These stimulation treatments are normally pumped at high rates and at high treatment pressures and therefore they are called High Rate Matrix stimulation methods. The diversion volumes are large compared to the total treatment volumes and the diverting materials are physically very coarse. Therefore, the High Rate Matrix stimulation methods often cause severe operational problems, such as stuck pipes or tubing, or the FCP is in many cases even exceeded during the treatment causing the formation to fracture.
- These problems can be partly avoided by using a coiled tubing which is basically a second smaller tubing disposed within the production tubing (first tubing) running from the well to the surface. Coiled tubing is widely used in the oil and gas industry for completion, production and work-over operations. Some of the oilfield operations in which such a secondary tubing is used are completion operations in which the second tubing can be used to transport fluids from the surface down into the well. The treatment fluids in the prior art technique involving coiled tubing are pumped through the interior of the second tubing and into the well to perform the particular required operation which can take place at a predetermined location or in a predetermined depth. The second tubing may remain suspended in the well for continuous use, and it may extend from the surface to the bottom of the well. The second tubing may also extend to an intermediate point between the surface and the well bottom. The second tubing may possibly also be temporarily suspended into the well for the duration of a particular operation during which the tubing may be raised and/or lowered to various levels in the well. Upon completion of the operation, the tubing may be retracted so as to be used in another operation or be transported to another well.
- As will be familiar to those having operating experience with well stimulation by matrix acidizing, the prior art technique often poses a potential hazard to the environment and pollution is often the unsuccessful outcome in situations where the formation is blocked with diversion materials and the treatment pressure at the same time approaches or even exceeds the FCP. The tubing is then filled with a mixture of acid and diversion material, and further pumping is not possible without unavoidable fracturing of the formation. The tubing content of acid and diversion material (possibly solid) then inevitably have to be circulated out back to surface and discharged to the sea where both the acid and the diversion material present a high degree of hazard to the environment.
- It is an object of the invention to provide a method for diverting acid into all intervals of a formation via a diverting agent, which method further minimizes chemical consumption and prevents discharge of acid and diverting material to the sea.
- This is achieved by the present invention as defined by the claims relating to methods of conducting matrix acidizing in a well in a formation by simultaneously or alternatingly injecting an acid and a diverter into the formation through tubing, said acid being injected into the formation through a first tubing and said diverter being injected into the formation through a second tubing. The second tubing may extend within said first tubing and the formation may be a chalk formation.
- Having acid and diverter in both the first and the second tubing respectively makes it possible to inject one of these fluids at the precise moment where the particular treatment fluid is needed in the matrix acidizing process thus improving the utilization of well treatment fluids.
- It is a further object of this invention to increase the pressure during acidizing and thereby to improve permeability of a the formation and stimulate said formation to produce increased volumes of hydrocarbons.
- Increasing the pressure at which acid is injected into the formation improves the matrix stimulation of a well since the higher pressure forces the acid further into the formation. Accordingly an even better exploitation of especially the acid can be accomplished by monitoring of the pressure e.g. at the wellbore or formation to facilitate an almost instantaneous injection of acid whenever the pressure is approaching FCP pressure or/and injection of diverter whenever the pressure decreases to a level inadequate for the matrix acidizing of the well.
- In a preferred embodiment the formation is pre-flushed by acid that is injected into the formation through-said second tubing.
- Preferably, the acid treatment is initiated through the second tubing, whilst taking fluids back to surface via the first tubing inlet until the acid reaches the end of the second tubing. The initial step of Injecting a relatively small amount of acid into the formation through the second tubing causes the formation pressure to decrease. This will improve the injectivity into the formation so the annular volume (between the first and the second tubing) of non-reactive fluid can be injected to the formation, without exceeding the FCP. Advantageously the injection occurs by displacement of the annular volume by well treatment fluid. However the substitution of said liquid could also, in a less preferred embodiment, be accomplished by it being displaced through the top from the bottom end (at the formation) with the aid of the inner (second) tubing.
- The use of benzoic flakes dissolved in methanol achieves a highly flowable diverter that can flow into all parts of a formation and provide good diversion without exhibiting defects due to segregation in the tubing delivering it.
- The formation being a chalk formation.
- The invention will be described in detail in the following with reference to the drawing in which
-
FIG. 1 shows a sectional view of a well showing the initial step of displacing fluid in second tubing by acid whilst taking fluid back to surface through first tubing inlet, -
FIG. 2 shows a well being pre-flushed with acid through the second tubing, -
FIG. 3 shows a well with diverter in the second tubing, -
FIG. 4 shows a sectional view of a well showing the step of injecting the annular volume of non-reactive fluid (between first and second tubing) into formation by displacement with acid, -
FIG. 5 shows a sectional view of well showing displacement of fluid in the second tubing by diverter, -
FIG. 6 shows a sectional view of a well having diverter present in the second tubing and acid present in the first tubing at the formation, -
FIG. 7 shows a sectional view of a well where the acid is being displaced by a non-reactive fluid, -
FIG. 8 shows a sectional view of a well where the acid is being displaced by a non reacting fluid, and -
FIG. 9 shows a sectional view of a prior art well with a single tubing having acid and diverter commingled through the tubing. - Referring more particularly to the drawings,
FIG. 1 discloses a well having acasing 3 extending throughout the wellbore, which is usually secured in place by e.g cement. Thecasing 3 is perforated 5 adjacent to the production formation 20 to provide flow passages for fluids from the formation 20 into thecasing 3. A first tubing or production tubing I has a slidingdoor 6 and a tubing Inlet 12 extends into thecasing 3 and has a packer 19 (already known in the prior art) for isolating the production interval of the well-bore. Asecond tubing 2 extends down within theproduction tubing 1 into the well-bore and has aninlet 11. The second tubing, which is commonly called coiled tubing, may be wound around a reel or wheel and Is passed into the well through an—already known—injector head. - The second tubing and production tubing further comprises a system of valves (not shown) having means for individually and independently regulating and turning off the fluid flow through first and second tubings at both inlet and welbore end. The second tubing usually passes through a blowout-preventer (not shown either) to facilitate regulation of the well-bore pressure. The coiled tubing usually consists of a singular tubing but may consist of two or more tubings.
- The outcome of matrix acidizing depends highly on the pressure at which diverter and acid are injected and the aim of the current matrix stimulation method is to deploy acid at the highest pressure possible without exceeding of the pressure at which the formation breaks down and a fracture is generated. The pressure at which the formation breaks down is called the fracture closure pressure (FCP). To facilitate a more precise pressure in the wellbore, the pressure may be monitored. Monitoring of the wellbore pressure facilitates injection of acid whenever the pressure is adequate for acidizing and diverter whenever the pressure drops to a level inadequate for acidizing thus optimizing utilization of the stimulation fluids.
- When initiating the stimulation of a well as shown in
FIG. 1 , the non-reactive liquid, present in the second 2 (coiled) tubing is displaced by acid (illustrated by being a little darker inFIG. 1 ). Theacid 8, which e.g. can be a 15% HCl, is then pumped in from the top of thesecond tubing 2 whilst taking fluid back via thefirst tubing 1, thus essentially maintaining formation pressure at the wellbore. - The
tubing 1 is then closed and the acid treatment is initiated with a pre-flush of acid (bull-heading) to the formation via the second tubing as shown inFIG. 2 . The purpose of initially injecting of a pre-flush ofacid 8 through the second tubing is to open up the formation so as to increase its injectivity sufficiently to absorb the volume of non-reactive fluid present in the first tubing 1 (production tubing) without exceeding the fracture propagating pressure of the formation. Field testing shows that this is advantageously done by injecting approximately 50 bbl (barrel) of acid. The acid pre-flush is advantageously finished by displacement of acid in the second tubing bydiverter 9 as shown inFIG. 3 . - Preferably, the main acid treatment is then started by injection of the (annular) volume of non-reactive liquid present in the
first tubing 1 into the formation by displacement withacid 8 as shown inFIG. 4 . The flow is kept at rate such that the pressure does not exceed the FCP pressure. The acid injection preferably continues until the pressure starts to decrease. However, a pressure insufficient for acidizing may at any time during the well stimulation procedure cause injection ofdiverter 9. - When the
main treatment acid 8 starts to react with the formation,FIG. 5 shown by a pressure drop, a batch of diverter is pumped into the main treatment fluid and further to the formation via the second tubing (coiled tubing), as shown inFIG. 6 . The diverter will follow the main stream, which is also the path of least restriction, into the formation and preferably block off the coming acid accession to recently stimulated areas in the formation. - When the path into the formation is blocked by
diverter 9, the treatment pressure will increase thus indicating thatacid 8 would be diverted to other parts of the formation. When the pressure has increased to a level adequate for acid treatment but preferably still below FCP,acid 8 is injected via the first tubing. This treatment is then continued until pressure has again dropped to a level sufficiently below FCP-pressure. Themain treatment acid 8 is displaced to perforations, as shown inFIG. 7 and 8. - The worst operational scenario during prior art methods of matrix stimulation with
diverter 9 is illustrated inFIG. 9 . The FCP is exceeded and further pumping into the formation will invariably create fracture of the formation. Further, the string content has to be circulated back to surface and disposed off. - The acid utilized may be any of the aqueous solutions of acid commonly employed for acidizing formations. The solution of acid may be an aqueous solution of hydrochloric acid and hydroflouric acid, which is employed for acidizing formations. Certain organic acids can be utilized alone or in combination with inorganic acids. Organic acids Include formic, acetic and oxalic acids. When hydrochloric acid Is utilized, it should be in a concentration from about 5 to about 30 percent. When combined with hydrochloric acid, the concentration of hydroflouric acid will range from about 0.3 to about 8 percent.
- Although the method has been described as comprising diverter in the second tubing and acid in the first tubing it is clear that the opposite condition may as well be the case without departing from the scope of the invention.
Claims (8)
1. A method of conducting matrix acidizing in a well in a formation by simultaneously or alternatingly injecting an acid and a diverter into the formation through tubing, said acid being injected into the formation through a first tubing and said diverter being injected into the formation through a second tubing.
2. A method according to claim 1 , wherein before said acid and said diverter are injected alternatingly through the first and the second tubings respectively, the formation is pre-flushed by acid that is injected into the formation through said second tubing.
3. A method of conducting matrix acidizing as defined in claim 1 , wherein said diverter comprises benzoic acid diluted in methanol.
4. A method of conducting matrix acidizing as defined in claim 1 , wherein said formation is a chalk formation.
5. A method of conducting matrix acidizing in a well in a formation by simultaneously or alternatingly injecting an acid and a diverter into the formation through tubing, said acid being injected into the formation through a first tubing and said diverter being injected into the formation through a second tubing, said second tubing extending within said first tubing.
6. A method according to claim 5 , wherein before said acid and said diverter are injected alternatingly through the first and the second tubings respectively, the formation is pre-flushed by acid that is injected into the formation through said second tubing.
7. A method of conducting matrix acidizing as defined in claim 5 , wherein said diverter comprises benzoic acid diluted in methanol.
8. A method of conducting matrix acidizing as defined in claim 4 , wherein said formation is a chalk formation.
Priority Applications (2)
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US10/963,436 US20060076134A1 (en) | 2004-10-12 | 2004-10-12 | Well stimulation |
EP05388085A EP1647668A1 (en) | 2004-10-12 | 2005-10-11 | Well stimulation |
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US10/963,436 US20060076134A1 (en) | 2004-10-12 | 2004-10-12 | Well stimulation |
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US20060076134A1 true US20060076134A1 (en) | 2006-04-13 |
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US10/963,436 Abandoned US20060076134A1 (en) | 2004-10-12 | 2004-10-12 | Well stimulation |
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EP (1) | EP1647668A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110107830A1 (en) * | 2008-07-15 | 2011-05-12 | Troy Fields | Apparatus and methods for characterizing a reservoir |
RU2475624C2 (en) * | 2008-03-11 | 2013-02-20 | Хэллибертон Энерджи Сервисиз, Инк. | Improved water-based insulating liquids and relating methods |
CN113027402A (en) * | 2021-04-07 | 2021-06-25 | 孙淑芳 | Oil well acidizing is separated stifled and is used crowded sour device |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7832485B2 (en) | 2007-06-08 | 2010-11-16 | Schlumberger Technology Corporation | Riserless deployment system |
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US6138760A (en) * | 1998-12-07 | 2000-10-31 | Bj Services Company | Pre-treatment methods for polymer-containing fluids |
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US7017665B2 (en) * | 2003-08-26 | 2006-03-28 | Halliburton Energy Services, Inc. | Strengthening near well bore subterranean formations |
-
2004
- 2004-10-12 US US10/963,436 patent/US20060076134A1/en not_active Abandoned
-
2005
- 2005-10-11 EP EP05388085A patent/EP1647668A1/en not_active Withdrawn
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US3244234A (en) * | 1962-02-26 | 1966-04-05 | Pan American Petroleum Corp | Apparatus for reducing hydraulic friction |
US3797575A (en) * | 1972-06-19 | 1974-03-19 | Halliburton Co | Additives for temporarily plugging portions of subterranean formations and methods of using the same |
US4249609A (en) * | 1978-04-10 | 1981-02-10 | Shell Internationale Research Maatschappij B.V. | Method for forming channels of high fluid conductivity in formation parts around a borehole |
US5207778A (en) * | 1991-10-24 | 1993-05-04 | Mobil Oil Corporation | Method of matrix acidizing |
US5402849A (en) * | 1992-09-28 | 1995-04-04 | Mobil Oil Corporation | Use of dual density spacer fluids to improve cementing efficiency in horizontal wellbores |
US5507342A (en) * | 1994-11-21 | 1996-04-16 | Mobil Oil Corporation | Method of selective treatment of open hole intervals in vertical and deviated wellbores |
US6138760A (en) * | 1998-12-07 | 2000-10-31 | Bj Services Company | Pre-treatment methods for polymer-containing fluids |
US6367548B1 (en) * | 1999-03-05 | 2002-04-09 | Bj Services Company | Diversion treatment method |
US7017665B2 (en) * | 2003-08-26 | 2006-03-28 | Halliburton Energy Services, Inc. | Strengthening near well bore subterranean formations |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
RU2475624C2 (en) * | 2008-03-11 | 2013-02-20 | Хэллибертон Энерджи Сервисиз, Инк. | Improved water-based insulating liquids and relating methods |
US20110107830A1 (en) * | 2008-07-15 | 2011-05-12 | Troy Fields | Apparatus and methods for characterizing a reservoir |
US8991245B2 (en) * | 2008-07-15 | 2015-03-31 | Schlumberger Technology Corporation | Apparatus and methods for characterizing a reservoir |
CN113027402A (en) * | 2021-04-07 | 2021-06-25 | 孙淑芳 | Oil well acidizing is separated stifled and is used crowded sour device |
Also Published As
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EP1647668A1 (en) | 2006-04-19 |
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