Method for preventing influx of fluid during fracturing of an offset well

Abstract

Method is provided for preventing fluid from entering a well, such as a producing well, during a hydraulic fracturing treatment in another well completed in the same reservoir. Degradable ball sealers or degradable particulate material is injected into the well and pressure is maintained in the well during the fracturing treatment to prevent influx of fluid.

Claims

1. A method for preventing influx of fluid into a first well having casing during or immediately after the time of a hydraulic fracturing treatment of a second non-intersecting well completed in the same reservoir, comprising: providing a quantity of ball sealers and degradable particles; injecting the quantity of ball sealers or degradable particles together into the first well in a carrier fluid to plug or partially plug perforations or ports in the casing of the first well; and hydraulically fracturing the second well while maintaining pressure in the first well so as to maintain plugging or partial plugging of the perforations or port in the first well, thereby preventing influx of fluid from the second well into the first well as a result of hydraulically fracturing the second well.

2. The method of claim 1 wherein the carrier fluid is water or fracturing fluid.

3. The method of claim 1 wherein the quantity of ball sealers and degradable particles is sufficient to provide partial or complete shut-off of the perforations.

4. The method of claim 1 wherein a surface pressure is maintained via a slow injection rate on the first well during the hydraulic fracturing of the second well.

5. The method of claim 4 wherein the surface pressure is maintained via the slow injection rate until pressure decreases around the second well after the hydraulic fracturing.

6. The method of claim 4 wherein the surface pressure is maintained via the slow injection rate until pressure decreases around the first well after the hydraulic fracturing.

7. The method of claim 1 wherein the ball sealers and degradable particles each comprise a degradable polymer.

8. The method of claim 7 wherein the degradable polymer comprises polyester.

9. The method of claim 1 wherein the ball sealers and degradable particles each comprise a metal degradable material.

10. The method of claim 1 wherein production from the first well is restarted after completion of the hydraulic fracturing of the second well.

Description

BRIEF DESCRIPTION OF THE DRAWING(S)

(1) FIG. 1 is an isometric view of two horizontal wells completed in the same naturally fractured reservoir.

DETAILED DESCRIPTION OF THE INVENTION

(2) Referring to FIG. 1, well 10 and well 20 are completed in naturally fractured reservoir 25. The wells are completed by perforations 12 in well 10 and 22 in well 20. Alternatively, openings in casings 14 and 24 may be provided by ports controlled by sliding sleeves or any other types of opening in casings 12 and 22.

(3) The following procedure may be followed when well 10 is to be hydraulically fractured and it is desired to prevent influx of fracturing or reservoir fluid into well 20. Before injection of fracturing fluid into well 10 or soon after injection begins, degradable ball sealers 30 or degradable particles 31, or both, together or separately, may be injected into well 20 in a carrier fluid such as water or a fracturing fluid. Injection of fluid into well 20 is continued and sufficient ball sealers or degradable particles are injected to provide partial or complete shut-off of all perforations 22 in well 20, i.e., ball sealer or degradable particle injection may continue until a “ball-out” of well 20 is observed. A ball-out will be defined for purposes herein as an injection rate less than 0.1 barrels per minute. Preferably, a slow injection rate will be continued in well 20 to maintain pressure at the perforations at least above estimated reservoir pressure around the well during the fracturing treatment, so as to ensure that flow into the well does not unseat a ball or backflow particles. Alternatively, pressure in the wellbore at the perforations may be obtained above fracturing pressure to ensure that no fluid enters the well. The surface pressure may be maintained on well 20 during the hydraulic fracturing treatment of well 10 and until pressure decreases around well 10 and well 20 after the treatment. This will allow a much smaller injection of fluid into well 20 than would be required without use of the ball sealers 30 or particulate material 31 and leave a lower water saturation around producing well 20, providing a higher production rate.

(4) Degradable ball sealers and degradable particles may be obtained from pumping service companies in the industry.

(5) A variety of degradable materials may be used in the ball sealers or particulate material. For example, the degradable material may be a polymer that degrades in contact with water, such as a polyester. Other degradable materials such as metal degradable material that degrade under reservoir conditions are also widely available in industry.

(6) After the hydraulic fracturing treatment is completed in well 10, production may be restarted from well 20. Ball sealers or particles 31 may degrade before being produced with production from well 20, or they may not be recovered if fully degraded. Degradation of ball sealers 30 or particles 31, however, will assure that no perforations are plugged by using ball sealers to seal perforations 22.

(7) Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.