EP1647668A1 - Stimulation de puits - Google Patents

Stimulation de puits Download PDF

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Publication number
EP1647668A1
EP1647668A1 EP05388085A EP05388085A EP1647668A1 EP 1647668 A1 EP1647668 A1 EP 1647668A1 EP 05388085 A EP05388085 A EP 05388085A EP 05388085 A EP05388085 A EP 05388085A EP 1647668 A1 EP1647668 A1 EP 1647668A1
Authority
EP
European Patent Office
Prior art keywords
tubing
formation
acid
well
diverter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05388085A
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German (de)
English (en)
Inventor
Jens Thorlak
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Total E&P Danmark AS
Original Assignee
Maersk Olie og Gas AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Maersk Olie og Gas AS filed Critical Maersk Olie og Gas AS
Publication of EP1647668A1 publication Critical patent/EP1647668A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK 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

  • the invention relates to a method of matrix acid stimulation of formations with simultaneous coiled tubing deployed diversion.
  • 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.
  • figure 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 1 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 figure 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 well-bore.
  • 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 figure 2.
  • a pre-flush of acid bull-heading
  • 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 figure 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 figure 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.
  • 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 figure 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.
  • 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 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.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Geology (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
EP05388085A 2004-10-12 2005-10-11 Stimulation de puits Withdrawn EP1647668A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US10/963,436 US20060076134A1 (en) 2004-10-12 2004-10-12 Well stimulation

Publications (1)

Publication Number Publication Date
EP1647668A1 true EP1647668A1 (fr) 2006-04-19

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Family Applications (1)

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EP05388085A Withdrawn EP1647668A1 (fr) 2004-10-12 2005-10-11 Stimulation de puits

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US (1) US20060076134A1 (fr)
EP (1) EP1647668A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8376041B2 (en) 2007-06-08 2013-02-19 Schlumberger Technology Corporation Apparatus and method for engaging a tubular

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080224087A1 (en) * 2007-03-14 2008-09-18 Ezell Ryan G Aqueous-Based Insulating Fluids and Related Methods
US8991245B2 (en) * 2008-07-15 2015-03-31 Schlumberger Technology Corporation Apparatus and methods for characterizing a reservoir
CN113027402A (zh) * 2021-04-07 2021-06-25 孙淑芳 一种油井酸化解堵用挤酸装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3244234A (en) * 1962-02-26 1966-04-05 Pan American Petroleum Corp Apparatus for reducing hydraulic friction
US5507342A (en) * 1994-11-21 1996-04-16 Mobil Oil Corporation Method of selective treatment of open hole intervals in vertical and deviated wellbores
US6367548B1 (en) * 1999-03-05 2002-04-09 Bj Services Company Diversion treatment method

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3797575A (en) * 1972-06-19 1974-03-19 Halliburton Co Additives for temporarily plugging portions of subterranean formations and methods of using the same
GB1565637A (en) * 1978-04-10 1980-04-23 Shell Int Research Method for froming channels of high fluid conductivity in formation parts around a bore hole
US5207778A (en) * 1991-10-24 1993-05-04 Mobil Oil Corporation Method of matrix acidizing
US5320172A (en) * 1992-09-28 1994-06-14 Mobil Oil Corporation Method for improving cement placement in horizontal wells
US6138760A (en) * 1998-12-07 2000-10-31 Bj Services Company Pre-treatment methods for polymer-containing fluids
US7017665B2 (en) * 2003-08-26 2006-03-28 Halliburton Energy Services, Inc. Strengthening near well bore subterranean formations

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3244234A (en) * 1962-02-26 1966-04-05 Pan American Petroleum Corp Apparatus for reducing hydraulic friction
US5507342A (en) * 1994-11-21 1996-04-16 Mobil Oil Corporation Method of selective treatment of open hole intervals in vertical and deviated wellbores
US6367548B1 (en) * 1999-03-05 2002-04-09 Bj Services Company Diversion treatment method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8376041B2 (en) 2007-06-08 2013-02-19 Schlumberger Technology Corporation Apparatus and method for engaging a tubular

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US20060076134A1 (en) 2006-04-13

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