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
  • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
  • E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
  • E21B43/2406—Steam assisted gravity drainage [SAGD]
• • 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
  • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
  • E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
  • E21B43/2406—Steam assisted gravity drainage [SAGD]
  • E21B43/2408—SAGD in combination with other methods

Definitions

• This invention relates to recovering heavy oil from an underground reservoir using a staged process involving, in the first stage, steam assisted gravity drainage, and in the second stage, non-condensible gas injection and reservoir pressurization.
• SAGD Steam assisted gravity drainage
• UTF Underground Test Facility
• AOSTRA Alberta Oil Sands Technology and Research Authority
• the upper well was used to inject steam and the lower well was used to produce a product mixture of heated oil and condensed water.
• the chamber extended along the length of the horizontal portions of the well pair. Oil that had originally filled the chamber sand was heated, to mobilize it, and drained, along with condensed water, down to the production well, through which they were removed.
• the chamber was thus filled with steam and was permeable to liquid flow. Newly injected steam moved through the chamber and supplied heat to its peripheral surface, thereby enlarging the chamber upwardly and outwardly as the oil was mobilized and drained together with the condensed water down to the production well.
• This process is described in greater detail in Canadian patent 1 ,304,287 (Edmunds, Haston and Cordell). The process was shown to be commercially viable and is now being tested by several oil companies in a significant number of pilot projects.
• the Kisman patent teaches injecting a non-condensible gas, such as natural gas, into the more depleted section to raise its pressure and equalize it with the pressure in the relatively undepleted section. By this means, the loss of steam from the one section to the other can be curtailed or minimized.
• the Kisman patent further teaches that pressurizing the more depleted section with natural gas has been characterized by an increase in production rate from that section, if the production well penetrating the section is produced during pressurization.
• Each section is penetrated by one or more wells completed for SAGD operation, preferably one or more pairs of horizontal injection and production wells.
• the process comprises: (a) injecting steam into the first section of the reservoir to practice SAGD and produce contained oil, until the steam/oil ratio rises sufficiently so that further production by SAGD from the section is substantially uneconomic; (b) then reducing or terminating steam injection into the first section and injecting non-condensible gas into the section to maintain it pressurized; (c) continuing to produce oil from the first section while it is pressurized; and (d) concurrently with step (c), injecting steam into the adjacent second section to practice SAGD therein and produce contained oil; (e) while preferably maintaining the first section pressurized to substantially the same pressure as exists in the second section during step (d).
• Steps (b) and (c) constitute a post-steam wind-down of oil production from the first section. Over time, oil production rate will drop off during wind- down and eventually it will again become uneconomic to justify continuing to produce the first section. However it may still be desirable to continue maintaining pressurization in the first section to limit steam loss from the second section.
• the process provides a strategy for sequentially producing adjacent sections across the reservoir. It takes advantage of gas pressurization to prevent steam leakage from a less depleted section undergoing SAGD to a mature, more depleted section. It also maximizes production from each section by subjecting it to sequential SAGD and pressurization production stages.
• DESCRIPTION OF THE PREFERRED EMBODIMENT comprises: (a) directionally drilling one or more pairs of wells from ground surface into a reservoir first section, to provide generally parallel, horizontal, co-extensive, spaced apart, upper and lower well portions extending through the section, and completing the wells for SAGD production; (b) establishing fluid communication between the injection and production wells of each pair, for example by circulating steam through both wells, to heat the span between the wells by heat conduction, and then displacing and draining the oil in the span by injecting steam through the upper injection well and opening the lower production well for production; (c) practising SAGD in the reservoir first section by injecting steam through the injection wells and producing the produced heated oil and condensed water through the production wells while operating said production wells under steam trap control; (d) preparing a second adjoining section of the reservoir for SAGD production by carrying out the provision of wells and establishing fluid communication between the wells of each
• thermocouples • measuring the downhole temperature at the injection and production wells of an operating pair, using thermocouples; • establishing the temperature differential between the two wells and throttling the production well to maintain the differential at a generally constant value (say 7°);
• the invention is characterized by the following advantages:
• a finite steam-producing plant can be applied in sequence to a plurality of adjacent sections of the reservoir, without severe steam loss from a section undergoing SAGD to an adjacent depleted section.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)

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• 1998
  • 1998-10-26 CA CA002251157A patent/CA2251157C/en not_active Expired - Lifetime
• 1999
  • 1999-10-26 EP EP99952188A patent/EP1125037A1/de not_active Withdrawn
  • 1999-10-26 WO PCT/CA1999/000996 patent/WO2000025002A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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