Method And Apparatus For Producing Multiple Zone Oil And Gas Wells

Abstract

Two or more oil and gas zones are produced by allowing production from at least one zone to drain down to a common chamber where production from the zones is comingled and lifted to the earth's surface. A separate gas bent is provided for each zone to the earth's surface.

Description

BACKGROUND OF THE INVENTION

The field of the invention relates to multiple zone wells which require one or more of the zones to be artificially lifted. This method and apparatus is suitable for wells producing oil, saltwater, fresh water or other liquid with or without natural gas in one or more of the zones.

A prior art device is shown in U.S. Pat. No. 2,618,339. This device discloses apparatus for comingling multiple zone well production. The apparatus is arranged in the well so that the upper zone production travels down the casing and allows gas entrained in the liquid to break out and pass to the surface. No provision is made, however, for separate handling of the lower zone gas. The device does not provide a check valve to prevent high pressure in the lower zone from passing through the tool and into the upper zone where such liquid may not be recoverable. Also, the pump intake is positioned above the packer which is not necessarily a desirable position in the case of a low pressure, low production, lower zone. A further prior art device, shown in U.S. Pat. No. Re 26,319, discloses a flow control device for producing multiple zone wells which have sufficient drive in the producing zones to cause the fluid to flow into the well bore where it is metered through predetermined orifices and comingled at a point whereby gas from a higher pressure zone can assist in lifting production from a lower pressure zone. An additional prior art device, shown in U.S. Pat. No. 3,509,941, discloses a confluent production apparatus wherein one zone or the other or both zones can be produced. Check valves are provided in the passages from each zone so that flow is prevented between the zones but no provision is made for separate handling of gas from the lower zone nor is the position of the pump intake desirable, because the pump intake is above the packer between zones and is, therefore, above the lower zone. An additional prior art device, shown in U.S. Pat. No. 3,559,740 discloses method and apparatus for use with hydraulic pump and multiple completion well bores. This patent discloses a separate vent for the lower zone gas. It also discloses various selector heads which provide production from either one or both of the zones and provides for chokes to meter production from the zones. However, none of the prior art devices show or disclose apparatus which adequately drains production from zones in a multiple zone well; wherein one or more zones have such low pressure that production is reduced in total or in part by reason of hydrostatic pressure in a column of the liquid in the well bore being lifted from the zone to a pump intake, and also provide separate venting of gas from each zone.

It is, therefore, a primary object of this invention to provide a multiple zone producing arrangement which provides for lifting of one or more low pressure zones.

It is a further object of this invention to provide a multiple zone production apparatus which provides separate venting of the gas from each zone.

It is a further object of this invention to provide a multiple zone production apparatus which provides for separate measurement of the gas from each zone.

It is a further object of this invention to provide a multiple zone production apparatus which conserves hydrocarbons and prevents loss of fluid or gas from a high pressure zone into a lower pressure zone in the same well bore.

SUMMARY OF THE INVENTION

These and other objects of this invention are fulfilled, broadly, with a multiple zone producing apparatus and method which provides a chamber for comingling fluid from the production zones at a point below the upper zone. As an additional feature, the comingling takes place beneath the lower zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view partially in elevation and partially in section of a well bore with well casing and apparatus according to this invention which may be used to produce a multiple zone well in accordance with this invention.

FIG. 2 is an alternative embodiment of FIG. 1 showing gas lift means to produce the liquid from the well.

FIG. 3 is an alternative embodiment of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the preferred embodiment, FIG. 1, casing 10 is shown in a well bore through two producing horizons 12 and 14. Perforations 16 and 18 in the upper and lower producing zones, respectively, allow production from these zones to flow into the casing 10. A packer 20 is sealingly engaged with the casing 10 between the perforations 16 and 18 to isolate the producing zones from each other. Gas from the upper zone 12 flows into the casing 10 through perforation 16 and is designated UG. Gas may be dissolved and/or entrained in the upper zone liquid production designated U. Some of the upper zone gas UG can break out of the liquid U and flow upward through the casing 10 to be gathered from outlet 22 in the casing at the top of the well bore. The volume of UG gas passing through this outlet can be measured and then used for gas lift purposes, sold into a pipeline, or used for another purpose. Production LG from lower zone 14 flowing into casing 10 through perforation 18 may flow upward into a passage 24 in a head or barrier portion 26 connected to packer 20. This gas can then pass into a tubing string 28 which extends to the top of the well bore where it may be measured and disposed of in one of the ways mentioned for the UG gas. Liquid production U from the upper zone can gravitate or flow downward through passage 30 and head 26 and thence through tubing 31 connected to passage 30. A check valve 32 is incorporated in the flow path for liquid U permitting flow into chamber 34 from the upper zone but preventing back flow from chamber 34 to passage 30. Lower zone liquid production L flows into casing 10 through perforation 18 and enters chamber 34 through ball check valve 36 which prevents back flow from chamber 34 to perforation 18. A pump 38 is positioned in the tubing string 40 immediately above chamber 34 where production U and L are comingled and admitted to the pump intake and lifted to the surface. Pump 38 may alternatively be a plunger pump operated by sucker rods or a hydraulically operated piston pump which has a piston-type motor section that operates a piston-type pump. A hydraulic pump would require an additional tubular conduit extending from the surface of the well bore to the pump. The additional pipe could be located inside tubular string 40 as illustrated in FIG. 2 as tubing string 42 which is illustrated for gas lift purposes. The additional string for the hydraulic pump could alternately be located beside tubing string 40 in a manner well known by those with skill in the art.

Referring to FIG. 2, an apparatus used in gas lifting a well according to this invention is illustrated. A concentric tubing string 42 is run inside the long tubing string 40 and is used to inject gas through gas lift valves 44 to lift the comingled liquids L and U from chamber 34. In this embodiment, gas to lift the comingled fluid is injected at 46 into tubing 40 and is admitted through gas lift valves 44 into the concentric tubing string 42 to lift the comingled fluid through concentric tubing string 42. A packing arrangement 48 which may be a landing nipple or a packer or other suitable device is used to seal between tubing string 40 and tubing string 42 to permit a gas lift arrangement. Other arrangements for gas lift are well known to those with skill in the art and any one of a number of arrangements may be used to gas lift the liquid from chamber 34.

Referring to FIG. 3, an apparatus used in lifting a well according to this invention, casing 110 is shown in a well bore through two producing horizons 112 and 114. Perforations 116 and 118 to the upper and lower producing zones respectively allow production from these zones to flow into the casing 110. A packer 120 is sealingly engaged to the casing 110 between the perforations 116 and 118 to isolate the producing zones from each other. The flow of upper and lower zone gas and liquid is generally the same as described hereinbefore except that the head or barrier portion 126 is simplified to have fewer passages. Lower zone gas LG flows through passage 124 into tubing string 128 connected thereto. Upper zone liquid production flows through check valve 132 into passageway 133 in body 126. A tubular string 131 is connected to body 126 in alignment with passage 133 to conduct upper zone liquid U to chamber 134. Check valve 136 admits lower zone production liquid L into chamber 134 and prevents back flow therefrom. Tubing string 140 is sealingly engaged to head 126 by means of a suitable connection 127. Tubing string 131 is sealingly engaged to tubing string 140 by a suitable connection 135, so that back flow from chamber 134 is prevented into the upper zone by check valve 132 and back flow from chamber 134 is prevented to lower zone by check valve 136. A suitable plunger pump 138 may be used to lift the liquid from chamber 134 through tubing string 140. It should be understood that pump 138 may be a hydraulically operated pump. It should also be understood that a gas lift arrangement similar to FIG. 2 could be used to lift fluid from chamber 134 through tubing string 140 to the top of the well bore. These and other means for lifting fluid well known to those skilled in the art may be used in lifting the fluid from chamber 134 according to this invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In multiple zone well production apparatus comprising:

a well casing passing through upper and lower producing zones in a well bore, said casing having upper and lower openings through which production from said upper and lower zones can flow, respectively, into the well casing;

barrier means in said casing between said upper and lower openings, said barrier means having a plurality of longitudinal passages and having means in one of said passages for securing a first tubular string extending to the top of the well bore to said barrier means;

chamber means below said barrier means, said chamber means communicating with said lower zone;

tubular means connected to said barrier means and said chamber means, said tubular means communicating with said one passage for conducting fluid in the lower zone to said first tubular string;

a second tubular string below said barrier, said second tubular string connecting another of said passages to said chamber for conducting fluid from said upper zone to said chamber;

means for lifting fluid from said chamber to the top of the well bore;

a third said passage in said barrier means; and

a third tubular string communicating with said third passage and extending to the top of the well bore for conducting gas from the lower zone to the top of the well bore.

2. In multiple zone well production apparatus adapted to be set in a well casing passing through upper and lower producing zones in a well bore, the casing having upper and lower openings through which production from the upper and lower zones can flow, respectively, into the well casing, the apparatus comprising:

barrier means in the casing between the upper and lower openings;

said barrier means having a first longitudinal passage with means for securing a first tubular string to said barrier means, said first tubular string extending to the top of the well bore;

chamber means below said barrier means, and chamber means communicating with said lower zone;

tubular means connected to said first longitudinal passage in said barrier means and said chamber means for conducting fluid in the lower zone to said first tubular string;

a second longitudinal passage in said barrier;

a second tubular string below said barrier, said second tubular string connecting said second passage to said chamber means for conducting fluid from said upper zone to said chamber means;

means for lifting fluid from said chamber means to the top of the well bore;

a third said passage in said barrier means; and

a third tubular string communicating with said third passage and extending to the top of the well bore for conducting gas from the lower zone to the top of the well bore.

3. Apparatus according to claim 2 wherein said chamber means is located at least as low as the lower zone.

4. Apparatus according to claim 2 wherein said chamber means is located below the lower zone.

5. Apparatus according to claim 2 wherein said means for lifting fluid comprises a plunger pump.

6. Apparatus according to claim 2 wherein said means for lifting fluid comprises gas lift means.

7. The method of producing liquid from a well bore passing through two producing zones with barrier means in the well bore between the zones comprising the steps of:

passing liquid from the upper zone into a chamber located below the barrier means;

passing liquid from the lower zone into said chamber;

lifting liquid from said chamber to the top of the well bore; and

venting gas from the lower zone to the top of the well bore.

8. The method of producing liquid from a well bore passing through two producing zones comprising the steps of:

draining liquid from the upper zone into a chamber located at least as low as the lower zone;

draining liquid from the lower zone into said chamber;

lifting liquid from said chamber to the top of the well bore; and

venting lower zone gas to the top of the well bore through a tubular member.

9. The method of claim 8 comprising the additional step of measuring the volume of gas produced from the lower zone.

10. The method of producing liquid from a well bore passing through two producing zones comprising the steps of:

draining liquid from the upper zone into a chamber located at least as low as the lower zone;

draining liquid from the lower zone into said chamber;

lifting liquid from said chamber to the top of the well bore; and

venting the upper zone gas to the top of the well bore.

11. The method of claim 10 wherein said step of venting the upper zone gas comprises venting the upper zone gas to the top of the well bore through the casing annulus.

12. The method of claim 10 comprising the additional step of measuring the volume of gas produced from the upper zone.