Selective Completion Using Triple Wrap Screen

Abstract

This invention relates to a completion system for a well drilled in the earth and especially for a well drilled to an oil and gas producing formation. It relates to a system for selectively producing fluid from either an upper or lower zone and for providing sand control facilities for each zone. A tubing string is suspended in a well bore and has an upper sand screen and a lower sand screen which are adjacent the upper and lower producing zones respectively. A packer is set in the annulus about the tubing between the two sand screens. An upper sleeve valve is mounted in the tubing string and is surrounded by the upper sand screen. Plug valve means are provided in the tubing string between the two sand screens. By selectively opening or closing the sleeve valve and the plug valve, production can be selectively opened from either the top or lower zones or both.

Description

RELATED PATENT APPLICATIONS

This application is related to co-pending patent application Ser. No. 77,492 filed Oct. 2, 1970, entitled "Multi-Layer Well Screen" for William G. Bearden and George C. Howard.

BACKGROUND OF THE INVENTION

This invention relates to a well completion system for selectively producing fluids from either an upper or lower zone and in which these zones produce fluids containing sand. It relates especially to a system for producing fluid selectively from either zone through special sand filters.

SETTING OF THE INVENTION

Oil and gas are produced from underground formations through well bores drilled from the surface to the formation. Sometimes oil and gas are found in the pores of consolidated rocks or sand. When this oil is produced through the well bore, it is relatively free of any particles or sand. However, many oil and gas wells produce fluid from underground formations which are not consolidated; that is, the various sand particles which make up the rock are not strongly attached to each other. In such formations when the fluid is produced, it carries entrained sand with it. This sand causes serious damage to well equipment and greatly restricts production of such fluids. In producing oil and gas from such underground formations, some method must be provided to restrain the sand inflow into the well. Perhaps the most widely used method of preventing the inflow of sand is the use of a gravel pack placed in the annular space in the well bore between a slotted liner and the formation. The voids between the gravel grains is small enough to prevent inflow of sand particles but still permits flow of fluid.

In conventional gravel packing technique, a perforated liner is connected to the lower end of a string of tubing which is suspended in the well bore. Gravel is circulated (or carried) into the annular space about the liner with the aid of a circulating fluid. This is usually a time consuming and very expensive operation. After the liner is placed in the well, washed and closely sized gravel is circulated into the well at the surface a little at a time, to a stream of circulating fluid forced down the well under pump pressure. Normally the fluid and entrained gravel are forced downwardly through the string of tubing. The gravel is discharged into the well cavity around the liner and the circulating fluid returns to the surface through the annular space. Reverse circulation can be used in which the descending stream of fluid and entrained gravel passes down through the annular space between the tubing string and the casing, the gravel being deposited in the well cavity and the fluid being returned to the surface through the string of tubing.

Frequently two vertically separated zones containing oil and gas are not permitted by government regulations to be produced simultaneously where the fluid can co-mingle in the wellbore. Occasionally it is desired to complete a well selectively such that when the lower producing zone has been depleted, the upper (selective) zone can be recompleted to without a rig workover. This means that upon original conventional gravel packing completion, the wellbore must be set up such that two intervals are perforated (one set of perforations at each productive zone) with a gravel pack and SxL (sand control means) opposite each set of perforations. This will ordinarily require about four round trips to set up the completion in the above manner. A round trip is the running (lowering) and pulling of an entire assembly (such as a string of tubing) with a rig on location. Rig time can cost $50 to $60 per hour for wells located on land. Furthermore, special and costly equipment in the form of packers and wash pipes are necessary in the conventional gravel packing method. This gravel packing procedure is successful in most cases but is time consuming and expensive. The present invention discloses a system for selectively producing from either an upper or lower zone whereby all the equipment necessary for controlling sand production and for switching from one zone to the other is set when the string of tubing is first run in the well bore. All that is required thereafter is wireline work in which the selective sleeves are changed in position in order to allow switching from one zone to another. This is accomplished without a rig and is therefore relatively inexpensive.

BRIEF DESCRIPTION OF THE INVENTION

This invention concerns a well completion system in which a casing is set through an upper unconsolidated formation and a lower unconsolidated formation. The casing has upper perforations and lower perforations at the elevation of the two zones. A string of tubing is suspended in the well bore. The tubing string contains a sleeve valve which is set adjacent the upper perforations of the casing. A first sand screen surrounds this sleeve valve. The lower end of the tubing string is connected to a second or lower sand screen. A plug valve is set in the tubing string between the two sand screens. The sleeve valve and this plug valve means are operable from the surface. A packer is set about the tubing between the two sand screens. Thus, by selectively opening or closing the sleeve valve and the plug valve, production can be had from either the upper or lower zone.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objectives and a better understanding can be had of the invention by the following description, taken in conjunction with the drawings in which:

FIG. 1 is a schematic drawing of a well completion according to this invention.

FIG. 2 illustrates in greater detail the upper sand screen and associated sleeve valves.

BETAILED DESCRIPTION OF THE INVENTION

Attention is first directed to FIG. 1 which shows a well bore 10 having casing 12 which is set through an upper petroleum productive zone 14 and a lower producing zone 16 separated by a non-productive layer 15 such as shale. Zones 14 and 16 are each unconsolidated zones, i.e. In the absence of preventative action, entrained sand is produced with the produced fluid. Casing 12 has upper perforations 18 and lower perforations 20 which are at the elevation of zones 14 and 16 respectively.

A tubing string 22, through which the fluid is to be produced, is suspended in the well bore. The tubing string, sometimes called a "completion string", is provided with an upper sand screen 24 and a lower sand screen 26 which are placed at about the levels of perforations 18 and perforations 20 respectively. These sand screens are a special type sand screen which is described in co-pending application Ser. No. 77,492 supra. These are special type multi-layer filters which have been found in many cases to be more efficient and longer lasting than gravel pack. In most cases no gravel packing is needed with these multi-layer sand screens. Typically these screens comprise a filter of a plurality of concentric screens spaced radially from one another, the opening in any one screen being no larger than the openings in any screen of larger diameter and no smaller than the openings in any screen of smaller diameter. An upper packer 28 is provided in the annulus about tubing string 22 at a point slightly above upper screen 24. A lower packer 30 is placed about tubing 22 between screens 24 and 26. Various packers are suitable for this operation. For example, the packer designated "Husky M-1" manufactured by Brown Oil Tool of 7400 E. Slauson Avenue Los Angeles, Calif. is quite suitable for packer 28 and a Brown Oil Tool packer model "DBL" is quite suitable for packer 30.

Tubing 22 is provided with two valves which permits the upper part of the tubing string to be in fluid communication with either the interior of the upper or lower sand screens. As shown in FIG. 2 this includes a sleeve valve or valves 32 which is inserted in the tubing string interior of upper screen 24 and a valve means or plug means 34 in the tubing string between the two sand screens. A suitable valve 32 is a model L sliding sleeve valve commercially available from Baker Oil Tools, Inc. A suitable plug means 34 is designated a Model F non ported seating nipple, also available from Baker.

Attention is directed to FIG. 2 for a more detailed illustration for an upper sand screen 24. As can be seen, this sand screen is placed about a slotted liner 40 and has an inner layer 42, an intermediate layer 44 and an outer layer 46. Each of these layers are formed preferably by wire wound in a spiral with selected spacing between the adjacent turns all as described in said application Ser. No. 77,492. The upper end and the lower end of the annulus between tubing 22 and the filter are closed by any means such as bushings with o-rings or packing 23 and 25.

Referring back to FIG. 1, a pump 48 or any other type artificial lift, if needed, can be provided above packer 28. The equipment shown in FIG. 1 permits sand free fluid to be produced selectively from either the upper or lower zones. The sleeve valve 32 and the plug valve 34 can be opened or closed from the surface using simple wireline equipment.

The equipment shown in FIG. 1 can all be set on one trip after the lower packer has been set by wireline. [If desired, both packers and the completion string can be run on the same trip. All that is necessary in this case is to use compatible packers, i.e. a mechanical packer (such as Brown Oil Tool Husky) as the lower packer and a hydrostatic (such as Baker Oil Tools, Inc. Model FH) packer as the upper packer. In this method wireline work is eliminated.] Lower sand screen 26 is supported at this stage from packer 30 by tailpipe 27. All that is then necessary is running the completion string (tubing 22, screen 24, plug 34, packer 28 etc.) in sequence as is shown on FIG. 1. (All components screw into each other.) When the completion string is in the hole, a seal assembly in the tubing string below plug 34 and not specifically shown, is stung into the lower packer 30. The upper packer is then set by weight and/or rotation. The tubing is then "hung off" in the tree and the well placed on production. Specific details of each step of this "running" operation are not given as they are known to those skilled in the art.

While the above description has been made in detail, various modifications can be made thereto without departing from the spirit or scope of the invention.

Claims

We claim:

1. A system for completing a well having an upper unconsolidated producing formation and a lower unconsolidated producing formation which comprises:

a casing having upper perforations and lower perforations at the elevations of said upper and lower formation respectively;

a string of tubing in said casing, said string having no other string within its interior;

a sleeve valve in said string of tubing at the elevation of said upper zone;

an upper sand screen surrounding said sleeve valve;

a lower sand screen connected to the lower end of said string of tubing;

a packer placed about said string of tubing between said upper and said lower sand screen filters;

a tubing valve means at a selected location in said string of tubing between said sleeve valve and said lower sand screen operable from the surface to open or close said string of tubing at said selected location.

2. A system as defined in claim 1 including a packer about said tubing string above said upper sand screen.

3. A system as defined in claim 1 in which said upper and lower sand screens each comprise a filter of a plurality of concentric screens spaced radially from one another, the opening in any one screen being no larger than the openings in any screen of larger diameter and no smaller than the openings in any screen of smaller diameter.