Patent Application
20100065274
1. Field of the Invention
The present invention relates to an apparatus and method for perforating well casing and/or a subterranean formation. More particularly, the present invention relates to an apparatus and process wherein a propellant is conveyed into a well within a shaped charge.
2. Description of the Related Art
Hydrocarbon producing wells typically include a casing string positioned within a well bore that intersects a subterranean oil or gas deposit. The casing string increases the integrity of the well bore and provides a path for producing fluids to the surface. Conventionally, the casing is cemented to the well bore face and subsequently perforated by detonating shaped explosive charges. These perforations extend through the casing and cement a short distance into the formation. In certain instances, it is desirable to conduct such perforating operations with the pressure in the well being overbalanced with respect to the formation pressure. Under certain overbalanced conditions, the well pressure exceeds the pressure at which the formation will fracture, and therefore, hydraulic fracturing occurs in the vicinity of the perforations. As an example, the perforations may penetrate several inches into the formation, and the fracture network may extend several feet into the formation. Thus, an enlarged conduit can be created for fluid flow between the formation and the well, and well productivity may be significantly increased by deliberately inducing fractures at the perforations.
Techniques for perforating and fracturing a formation surrounding a borehole are known in the art. The common technique of hydraulically pressurizing the borehole to expand or propagate the fractures initiated by the projectile can be expensive due to the preparation required for pressurizing a portion of a borehole. Typically, pressure around a production zone in the borehole is increased by pumping fluids into that portion of the well to obtain the high pressures necessary to expand the fracture in the production zones. This operation is generally time intensive and costly making these techniques unattractive for either multiple zone wells or wells with a low rate of production.
Gas generating propellants have been used in place of hydraulic fracturing techniques to create and propagate fractures in a subterranean formation. In one conventional arrangement, a perforating gun having shaped charges is fitted with a propellant charge and conveyed into the well. This propellant charge may be formed as a sleeve that surrounds a charge tube in which the shaped charges are secured. As is known, flammable or combustible material such as propellants require careful handling during all aspects of manufacture, transportation and deployment. Thus, protective measures are taken throughout all these phases to prevent unintended detonation of the propellant.
Thus, it is one object of this invention to provide methods and systems for safely and efficiently fracturing a well, particularly in connection with a perforation activity. Still other objects will become apparent below.
The present invention provides devices and methods for safely and efficiently fracturing a formation. In one aspect, these devices and methods are adapted to perforate and fracture the formation in a single trip. An exemplary device for perforating and fracturing a subterranean formation includes shaped charges and a volume of a gas generator (or gas generating material). When activated, the gas generator forms a high-pressure gas that includes steam. The high-pressure gas expands to stress and fracture the formation. The gas generator is activated by a downhole energy source. Suitable gas generating materials include hydrates and hydroxides. Theses classes of material can be activated using thermal energy released by detonation of shaped charges. Other materials that can be employed with the gas generator include oxidizers and material such as metals that increase the available heat for the activation of the gas generator.
In embodiments where the gas generator is used in connection with a perforating gun, one or more parts of the gun can be formed from the gas generator. For example, one or more casings for the shaped charges can be formed from the gas generator. In situations where fracturing is not done in connection with another activity such as perforating, an exemplary device having a volume of a gas generator can be conveyed down using a suitable conveyance device.
The above-recited examples of features of the invention have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto.
For detailed understanding of the present invention, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:
As will become apparent below, the present invention provides a safe and efficient device for fracturing a subterranean formation. In aspects, the present invention uses a gas generating material that, when activated, produces a high-pressure gas having a steam component. The steam can be a fraction or substantially all of the high-pressure gas generated. Merely for convenience, suitable materials that decompose to release water will be referred to as steam-producing materials. Exemplary materials include hydrates and hydroxides. Hydrates are compounds formed by the union of water molecules with some a primary material. Common hydrates include gypsum (calcium sulfate dihydrate), barium chloride dihydrate, lithium percholorate trihydrate and magnesium carbonate pentahydrate. Hydroxides are compounds that contain one or more hydroxyl groups. Common hydroxides include magnesium hydroxide. As should be appreciated, such materials can be manufactured, transported and deployed without the safeguards typically used when handling combustible materials such as propellants. Embodiments utilizing steam-producing material for fracturing are discussed in greater below.
Referring initially to
In one embodiment, the perforating gun 10 is configured to perforate and fracture a formation in a single trip, the perforations being enumerated with P and the fracturing action being enumerated with F. As will be described more fully below, the material for producing a high-pressure gas for fracturing the formation 13 is carried in a suitable location along the gun 10.
Referring now to
In still other embodiments, one or more elements making up the perforating gun 10 can be formed from the steam-producing material. For example, a casing 36 of the shaped charge 16 can be formed partially or wholly from a steam-producing material. In another arrangement, a volume of steam-producing material 38 can be positioned inside the casing 38. In still other arrangements, the carrier tube 20, charge tube 16 or other component of the perforating gun 10 can be formed at least partially of a steam-producing material.
Referring now to
In one variant, the detonation step 100 can generate a gas or other material at step 190 that activates the steam-producing material at step 150. For example, the gas or other material can chemically interact with the steam-production material. Such an interaction (i.e., chemical activation) can be used in combination with or in lieu of thermal activation. Other activation methods, which may or may not use detonation of a shaped charge, include pressure activation and electrical activation. Advantageously, a gas generated at step 190 can be used to supplement the high-pressure gas formed at step 160 to stress the formation at step 170.
It should be appreciated that while the
In certain applications, an oxidizer may be used in conjunction with the gas generating material. Suitable oxidizers include potassium sulfate and potassium benzoate. The oxygen released by the oxidizers can combine with a metal fuel such as zinc and/or with carbon or hydrogen (e.g., rubber). Also, materials such as calcium sulfate hemihydrate can function as both a hydrate and a high temperature oxidizer. Additionally, material can be used in conjunction with the gas generating material to increase the available heat of reaction. Suitable material includes a metal such as finely divided aluminum.
The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope of the invention. Thus, it is intended that the following claims be interpreted to embrace all such modifications and changes.
This application is a continuation of and claims priority to U.S. patent application Ser. No. 11/252,958 filed Oct. 18, 2005.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11252958 | Oct 2005 | US |
| Child | 12624195 | US |
