The present invention relates to flocculation and dewatering systems for separating solid-liquid mixtures. More particularly, the present invention relates to flocculation and dewatering systems for recycling and reconditioning subterranean treatment fluids and methods of use thereof,
Subterranean operations such as drilling, mineral exploring and geological coring often require fluids that are introduced into the subterranean environment for the completion of desired tasks. For example, drilling fluids, also commonly referred to as drilling muds, are used in most modern drilling operations. In a drilling operation, a drilling fluid provides a number of important functions, which includes preventing formation fluids from entering the wellbore, carrying out drill cuttings, suspending drill cuttings while drilling is paused, and keeping the drill bit cool and clean. Overall, drilling fluids provide stability to a wellbore during a drilling operation. Some fluids are referred to as “drill-in fluids.” Drill-in fluids are specialty drilling fluids designed for drilling through the reservoir section of a wellbore. The reasons for using a specially designed mud are: (1) to drill the reservoir zone successfully, often a long, horizontal drainhole; (2) to minimize damage and maximize production of exposed zones; and (3) to facilitate the well completion needed, which can include complicated procedures. Drill-in fluids are often brines comprising only solids of appropriate particle size ranges such as salt crystals or calcium carbonate and polymers. Generally, only additives essential for filtration control and cuttings carrying are present in a drill-in fluid. The term drilling fluids as used herein includes drill-in fluids.
There are many different types of drilling fluids including water-based, oil-based, polymer-based, clay-based, and synthetic-based fluids. While the composition may vary, a drilling fluid is generally composed of a fluid (liquid or gas) and may further comprise various additives including, but not limited to, polymers, salts, clays, and viscosifiers. The exact composition of a drilling fluid may be engineered to meet the specific needs of a drilling operation based on factors such as rock formation, type of petroleum being recovered, environmental concerns, and the like. A drilling fluid is usually homogeneous and mixed prior to circulation in a subterranean environment. However, once a drilling fluid is introduced to a wellbore, its composition can change drastically. For example, drill cuttings such as rocks, sand, shale, grit, and other contaminants can become suspended and mixed in the drilling fluid during a drilling operation. These solids inevitably make their way up as part of returned fluids as the drilling fluid is returned to the surface.
While drilling fluids provide numerous advantages, there are several drawbacks. For example, drilling fluids can be very costly and, while the exact cost depends on the operation, can take up a significant portion of the total cost of drilling a well. Moreover, the long term effects that drilling fluids have on the environment may be uncertain. These important considerations have spurred efforts to recondition returned drilling fluids so that the drilling fluids may be recycled and reintroduced in a wellbore.
In conventional drilling operations, the drilling fluids are recirculated after removing the drilling cutting and other solid contaminants from the fluid. This recycling and reconditioning process generally involves recovering the returned drilling fluid at the surface, removing drilling cuttings and undesirable drill solids, and recirculating the reconditioned drilling fluid into the well. The removal or separation of solids from the drilling fluids is typically done using a size exclusion screen. Smaller solids may further be removed, at least partially, by additional processing equipments such as a hydrocyclone or centrifuges. A hydrocyclone or a centrifuge separate suspensions by density and generate two types of fluids, an overflow and an underflow. The composition of the overflow is the same or very similar to a new drilling fluid and may be reintroduced into the wellbore without further treatment. On the other hand, the underflow is a concentrated fluid comprising much of the unwanted solids present in the returned fluid.
There are, however, limitations on current separation techniques. For example, in a typical recycling and reconditioning process, only about 50-80% of the returned fluid may be separated into overflow. This means that a significant volume of underflow is left over. Because this underflow typically needs further treatment before it can be disposed or reused, there are considerable cost and time considerations.
The present invention relates to flocculation and dewatering systems for separating solid-liquid mixtures. More particularly, the present invention relates to flocculation and dewatering systems for recycling and reconditioning well treatment fluids and methods of use thereof,
In one embodiment, a method comprises: providing a returned fluid comprising: a fluid; and a solid contaminant; introducing the returned fluid into a solid-liquid sorter thereby separating the returned fluid into an overflow and underflow; flocculating the underflow in a flocculating chamber thereby forming a flocculated fluid; and dewatering the flocculated fluid using a dewatering rack.
In one embodiment, a method comprises: providing a returned fluid comprising: a drilling fluid wherein the drilling fluid has been circulated in a subterranean environment; flowing the returned fluid through a hydrocyclone thereby separating the returned fluid into an overflow and an underflow; flocculating the underflow in a flocculation chamber thereby forming a flocculated fluid; dewatering the undertow in a dewatering rack; and introducing the overflow into a mixing unit comprising: a basin.
In one embodiment, a method comprises: providing a returned fluid comprising: a drilling fluid wherein the drilling fluid has been circulated in a subterranean environment; flowing the returned fluid through a hydrocyclone thereby separating the returned fluid into an overflow comprising reusable drilling fluid and an underflow comprising solid contaminants; introducing the underflow in a flocculation chamber comprising: a trough comprising an injection port for introducing a flocculant, thereby forming a flocculated fluid; and introducing the flocculated fluid to a dewatering rack comprising: at least one filtration collection bag situated in at least one collection basket; and a filter press; and dewatering the underflow by pressing the filtration collection bag with the filter press.
The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the preferred embodiments that follows.
The following figures are included to illustrate certain aspects of the present invention, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.
The present invention relates to flocculation and dewatering systems for separating solid-liquid mixtures. More particularly, the present invention relates to flocculation and dewatering systems for recycling and reconditioning well treatment fluids and methods of use thereof,
The present invention provides systems and methods for recycling and reconditioning returned fluids. As used herein, “returned fluid” generally refers to a treatment fluid that has been introduced to a subterranean environment and that has been circulated back up to the surface. Suitable examples of returned fluids for use in conjunction with the present invention include, but are not limited to, drilling fluids, completion fluids, and combinations thereof. Fluids suitable for use in conjunction with the present invention may be water-based, oil-based, polymer-based, clay-based (e.g., bentontite), synthetic-based, and the like,
In particular, an example of a returned fluid may be a drilling fluid that has been used in a drilling operation and that includes various solid contaminants such as drill cuttings, rocks, sand, shale, grit, assorted debris, and other solid contaminants. As shown in
It is believed that the present invention provides superior separation of solid-liquid mixtures compared to typical separation systems and techniques. Specifically, it is believed that the present invention would provide a higher ratio of overflow to underflow as compared to typical separation systems and methods. As used herein, “overflow” refers to a separated portion of a returned fluid that may be reused and recycled. As used herein, “underflow” refers to a separated portion of a returned fluid that requires reconditioning to recover reusable and recyclable portions of a treatment fluid. Typically, the overflow may be reused without further reconditioning. The underflow generally comprises solid contaminants such as those accumulated while a returned fluid is circulating in a subterranean environment. In a drilling operation, solid contaminants may be drill cuttings, rocks, sand, shale, grit, assorted debris, and other solid contaminants which can become suspended and mixed in the drilling fluid during a drilling operation. In some embodiments, the overflow comprises reusable treatment fluids which may be introduced into the mixing unit 126. Moreover, the present invention is able to recondition the underflow so that a large portion is reusable in a subterranean operation and thus recyclable. The solid contaminants which are separated are typically not reusable. It is also believed that the present invention provides superior efficiency in the reconditioning of the underflow as compared to typical separation systems and techniques. This superior efficiency is in part related to the superior mixing and flocculating characteristics of the flocculating chamber 104, in particular, the flocculating trough 106. It is believed that the geometry (e.g., the slope of the trough) of the flocculating trough 106 unexpectedly enhances the mixing and flocculation of the underflow. This ability to recondition returned fluids for subsequent reuse in subterranean operations enables the operator to save considerable costs.
Another advantage of the present invention is that the elements of the flocculation and dewatering system 100 have been configured (e.g., geometrically, volumetrically, etc.) and optimized to ease the handling of large amounts of returned fluids. Yet another advantage is that some or all of the elements of the present invention have been designed to be portable. The present invention also provides a single system which is able to function in two separate modes: reconditioning mode (
To facilitate a better understanding of the present invention, the following examples of preferred embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.
In some embodiments, the solid-liquid sorter 102 may sort a solid-liquid mixture such as a suspension by density using centrifugal force. For example, a solid-liquid sorter 102 will separate a returned fluid such as a drilling fluid which has been circulated in a subterranean environment into a relatively lower density fluid (overflow) comprising relatively fewer solid contaminants and a relatively higher density fluid (undertow) comprising relatively more solid contaminants. Suitable examples of solid-liquid sorter 102 include, but are not limited to, centrifuges, shaker beds, helix tubular sorters, counterspinning screens, vibrating beds, filter boxes and/or hydrocyclones.
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The methods of the present invention generally comprise providing a returned fluid comprising a fluid; and a solid contaminant; introducing the returned fluid into a solid-liquid sorter thereby separating the returned fluid into an overflow and an underflow; flocculating the underflow in a flocculating chamber 104 thereby forming a flocculated fluid; and dewatering the flocculated fluid using a dewatering rack 110.
The fluid may be a liquid or gas-based fluid. In some embodiments, the returned fluid may comprise a drilling fluid wherein the drilling fluid has been circulated in a subterranean environment. Flowing the returned fluid through a hydrocyclone may separate the returned fluid into an overflow and an underflow. The overflow may comprise reusable drilling fluid. The underflow may comprise solid contaminants. In some cases, the overflow may be introduced into a mixing unit 126 comprising a basin 128. In some embodiments, the underflow may be flocculated in a flocculation chamber 104 and dewatered in a dewatering rack 110. In some embodiments, the underflow may be dewatered by pressing the filtration collection bag 118 such as by pressing a filter press 124,
Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.
The present invention is related to co-pending U.S. application Ser. No. ______ [Attorney Docket No. HES 2011-IP-046463U1] entitled “NOVEL INJECTION FLOCCULATION AND COMPRESSION DEWATERING UNIT FOR SOLIDS CONTROL AND MANAGEMENT OF DRILLING FLUIDS AND METHODS RELATING THERETO,” filed concurrently herewith, the entire disclosure of which is hereby incorporated by reference.