Patent Publication Number: US-11391141-B1

Title: Reverse helix agitator

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the priority as a continuation of U.S. Nonprovisional patent application Ser. No. 17/508,424, filed Oct. 22, 2021, which is a continuation-in-part to U.S. Provisional Patent Application No. 63/169,509, filed Apr. 1, 2021, the contents of which are hereby incorporated by reference in its entirety. 
    
    
     FIELD OF TECHNOLOGY 
     This disclosure generally relates to technology for separating gas and solids from a liquid well fluid that is pumped to a surface location. 
     BACKGROUND 
     Oil wells are often equipped with pumps to bring oil to the surface. The pumping action is considered artificially lifting the oil. Often, the type of device utilized for artificially lifting the oil to the surface is a downhole pump. In a typical arrangement wherein a downhole pump is utilized, the oil well is normally equipped with a casing, a string of tubing ran inside the casing, a downhole assembly attached towards the bottom of the string of tubing, and the downhole pump attached near the bottom of the string of tubing. Oil is pumped up the string of tubing to the surface by the downhole pump. 
     In many oil wells, horizontal directional drilling techniques are used to extract oil. Typically, the oil well bore extends from the surface downward into the ground; at a desired depth the well bore turns to a horizontal direction roughly parallel with the surface. The location where the well bore turns is considered the kickoff point. The downhole pump is typically secured just above the kickoff point. Traditionally an anchoring device is used to secure the string of tubing or the downhole assembly to the casing. 
     Oil produced from the underground reservoir often contains entrained and free gases. Downhole pumps are not typically configured to efficiently pump liquid with entrained or free gases. If the entrained and free gas is not separated from the oil, the gas will be pulled into the downhole pump. When gas is pulled into a downhole pump, the downhole pump&#39;s efficiency and capacity will be reduced. The gas will compress and expand with the action of the pump, therefore wasting the energy output of the downhole pump and causing increased wear and failure frequency to the pumping system. 
     Gas and liquid separators have been utilized to remedy this problem. Generally, the gas and liquid separator is a device that, by utilizing the different properties of the two substances, affects the separation of the liquid, which is usually a mixture of oil, water, and gas. The separator allows them to be more efficiently moved to the surface through different conduits. 
     Anchoring devices used to secure the string of tubing to the casing generally comprise a structure that mechanically connects the string of tubing and the casing to prevent or reduce independent movement of the string of tubing. Gas which has been separated from the oil by a separator flows in the annulus between the casing and string of tubing, past the anchoring device, and toward the surface. Once past the anchoring device, the gas may continue to flow toward the surface through the annulus between the casing and the string of tubing. The structure of the anchoring device is an object which restricts the flow of the gas. The structure of the anchoring device is often configured to minimize its cross-section so to reduce the restriction on the flow of gas. 
     SUMMARY 
     The present invention disclosed herein includes improvements to a downhole assembly. An improved device for separating entrained gas from oil, and an improved anchoring device for increasing the flow of separated gas past the anchoring device is disclosed herein and claimed. For the purpose of this application, the downhole assembly is understood to be the entire assembly connected to the bottom of the downhole pump seating nipple. A downhole assembly is typically comprised of a dip tube, an anchoring device, a sand separator if required, a slotted or perforated body, an upper perforated tube, an optional lower perforated tube, a first helix, and a first reverse helix. The top of the downhole assembly is attached to the bottom of a downhole pump seating nipple. The downhole pump is attached to the string of tubing at the pump seating nipple. The two aspects of the present invention can be considered as the agitation device and the flow through assembly. A downhole pump may fit inside the string of tubing, in which case it is known as an insert pump, or may be connected directly to the tubing string, in which case it is known as a tubing pump. 
     The first aspect of the invention is an agitation device. The agitation device is comprised of the dip tube, the first helix, the first reverse helix, and the slotted body. The agitation device is configured to cause entrained gas to be separated from oil. Shear stress and centrifugal force introduced by the agitation device cause the gas and oil to separate. Oil with entrained gas is pulled into the holes of the slotted body. The dip tube extends downward through the slotted body with the inlet opening of the dip tube positioned near the bottom of the slotted body. Oil with entrained gas which has been pulled into the holes of the slotted body is pulled downward to the inlet of the dip tube. Suction pressure from the downhole pump causes the oil and water to be pulled into the dip tube and artificially lifted to the surface by the downhole pump through the string of tubing. 
     On the exterior surface of the dip tube, at a location below the holes on the slotted body, a first standard helix and a first reverse helix is attached. The first standard helix and the first reverse helix are adapted to extend from the dip tube&#39;s exterior face to the close proximity of the interior surface of the slotted body. Given this configuration, the oil with entrained gas that is pulled downward while in the slotted body, must circulate through the helixes. The standard helix and reverse helix configuration cause increased shear stress and centrifugal force. The stresses and forces cause the oil and gas to separate. The helixes may further be perforated to allow gas to flow upward through the helixes and increase shear forces as fluid flows over and through the perforations. 
     The first standard helix is a helix that is configured to flow in one circular direction. The first reverse helix is a helix that is configured to flow in the opposite circular direction. Multiple helixes and reverse helixes can be configured in a particular embodiment. 
     The second aspect of the invention is the flow through assembly. The flow through assembly is comprised of the lower perforated tube, the upper perforated tube, and the anchoring device. Alternatively, a monolithic tube with perforations above and below the anchoring device will provide the same function. Separated gas flows upward toward the surface from the agitation device. The separated gas may enter the lower perforated tube, flow through the center flow channel of the anchoring device, and out of the upper perforated tube. This adaption allows for the gas to flow upward with a reduced amount of resistance from the structure of the anchoring device. The separated gas may also exit the holes of the slotted body and the perforations of the lower perforated tube into the annulus between the casing and tubing string below the anchoring assembly. Perforations of the assembly above and below the anchoring device allow for maximum flow area for separated gas to rise towards surface and away from the downhole pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with accompanying drawings, wherein: 
         FIG. 1  is an exemplary downhole assembly shown in a well casing; 
         FIG. 2  is a cross-section of a downhole assembly with a dip tube installed; 
         FIG. 3  is a downhole assembly showing one helix and one reverse helix; 
         FIG. 4  is a downhole assembly showing two helixes and two reverse helixes; 
         FIG. 5  is a downhole assembly showing four helixes and four reverse helixes; 
         FIG. 6  is a downhole assembly showing two helixes and one reverse helix; 
         FIG. 7  is a downhole assembly showing one helix and one reverse helix without a flow through assembly; 
         FIG. 8  is a detailed drawing of an exemplary flow through assembly; 
         FIG. 9  is an exemplary helix; and 
         FIG. 10  is an exemplary helix with perforations. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     General 
     The present invention will now be described with occasional reference to the specific embodiments of the invention. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     Unless otherwise indicated, all numbers expressing quantities of dimensions such as length, width, height, and so forth as used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless otherwise indicated, the numerical properties set forth in the specification and claims are approximations that may vary depending on the desired properties sought to be obtained in embodiments of the present invention. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from error found in their respective measurements. 
     Figures Detail 
       FIG. 1  is an exemplary downhole assembly  101  shown contained in a well casing  102 . For the purpose of this application the downhole assembly  101  is understood to be the entire assembly connected to the bottom of the downhole pump seating nipple and above the tail pipe. The downhole pump is attached to the bottom of the string of tubing and above the downhole assembly by the pump seating nipple. The top of the downhole assembly  101  is attached to the bottom of the downhole pump seating nipple. At the bottom of the downhole pump the seating nipple fluidly connects the downhole pump to the string of tubing. The string of tubing extends from the top of the downhole pump seating nipple to the surface. The downhole pump is adapted to artificially lift oil from the downhole assembly  101  to the surface. Oil is artificially lifted to the surface by pumping force exerted by the downhole pump and flows upward through the string of tubing. 
     Many wellbores are horizontal wells wherein horizontal directional drilling techniques are used to extract oil. Typically, the oil wellbore  104  extends from the surface downward into the ground. At a desired depth the wellbore  104  turns to a horizontal direction which is roughly parallel with the surface. The location where the wellbore  104  turns is considered the kickoff point. In a horizontal directional drilling application, the downhole assembly  101  is typically secured just above the kickoff point. The wellbore  104  is the hole drilled into the ground in which the casing  102  is placed. An anchoring device  105  is used to secure the downhole assembly  101  to the casing  102 . The downhole assembly  101  is also used in vertical wells. In a vertical well application, the downhole assembly  101  is secured at a desired depth. 
     A downhole assembly typically comprises a dip tube  106 , an anchoring device  105 , a sand separator  107 , a slotted body  108 , an upper perforated tube  109 , a lower perforated tube  110 , a first standard helix  301 , and a first reverse helix  302 . The slotted body  108  is comprised of one or more holes  111  (individually a hole  111 ), an exterior surface  112 , an interior surface  202 , a bottom  113 , and a peak  114 . The holes  111  can be circular, slotted, a multitude of perforations, or any other configuration appreciated by a person of ordinary skill in the art. The slotted body  108  has a hollow interior that can accommodate solids, gases, and fluids to pass through. Oil with entrained gas may be located between the exterior surface  112  of the slotted body  108  and the casing  102 . The dip tube  106  is comprised of an inlet  303 , an upper connection  205 , an exterior face  201 , and a pipe  204  connecting the upper connection  205  with the inlet  303 . 
     Oil with entrained gas may be pulled into the holes  111  by force exerted from the downhole pump. The inlet  303  of the dip tube  106  is adapted to be at a lower elevation relative to the holes  111 . Typically, the inlet  303  of the dip tube  106  is located near the bottom  113  of the slotted body  108 . The downhole pump seating nipple is attached to the dip tube  106  such that a suction pressure from the downhole pump is present at the inlet  303  of the dip tube  106 . Suction at the inlet  303  of the dip tube  106  causes the oil to flow through the holes  111 , downward through the slotted body  108 , and to the inlet  303  of the dip tube  106 . The inlet  303  of the dip tube  106  is adapted such that oil can enter the dip tube  106 . Oil pulled into the dip tube  106  by the downhole pump then flows upward through the dip tube  106 , through the downhole pump, and up to the surface. 
     Oil and other liquid in the wellbore often contains entrained gases. Downhole pumps are not typically configured to efficiently pump liquid with entrained gases or free gas. If the free and entrained gas is not separated from the oil, the gas will be pulled into the downhole pump. When free or entrained gas is pulled into a downhole pump, the downhole pump&#39;s efficiency and capacity will be reduced. The gas will compress and expand with the action of the pump, therefore wasting the energy output of the downhole pump. 
     The two aspects of the present invention can be considered as the agitation device and the flow through assembly. The agitation device comprises the dip tube  106 , the first standard helix  301 , the first reverse helix  302 , and the slotted body  108 . The agitation device is adapted to cause entrained gas to be separated from oil and liquid. Shear stress and centrifugal force introduced by the agitation device cause the gas and liquid to separate. Liquid with entrained gas is pulled into the slotted body  108  near the peak  114  of the slotted body  108 . The dip tube  106  extends downward through the slotted body  108  and the inlet  303  is positioned near the bottom  113  of the slotted body  108 . Liquid with entrained gas which has been pulled into the holes  111  of the slotted body  108  is pulled downward to the inlet  303  of the dip tube  106 . Suction pressure from the downhole pump causes the liquid to be pulled into the dip tube  106  and artificially lifted to the surface by the downhole pump. 
       FIG. 2  is a cross section of a downhole assembly  101  with a dip tube  106 . The exterior face  201  of the dip tube  106  is understood to be the surface of the tube. On the exterior face  201  of the dip tube  106 , below the holes  111  of the slotted body  108 , a first standard helix  301  and a first reverse helix  302  is attached. The first reverse helix  302  is attached to the exterior face  201  at an elevation relatively lower than the first standard helix  301 . If more than two helixes are used, each subsequent helix would be lower. 
     The first standard helix  301  and the first reverse helix  302  are adapted such that they respectively extend from the exterior face  201  of the dip tube  106  to close proximity of the interior surface  202  of the slotted body  108 . Alternatively, the helixes may extend from the exterior face  201  of the dip tube  106  all the way to the interior surface  202  of the slotted body  108 . The helixes can be connected to both the interior surface  202  and the slotted body  108  or either the interior surface  202  or the exterior face. Given this configuration, the liquid with entrained gas which is pulled downward while in the slotted body  108  must circulate through the helixes. The standard helix and reverse helix configuration cause increased shear stress and centrifugal force. The stresses and forces cause the liquid and gas to separate. The helixes may further be perforated to allow gas to flow upward through the helixes and generate additional shear forces by allowing liquid to move between the vanes of the helix. 
     The various versions of helixes disclosed herein are referred to as helix or helixes. In addition, the term helix or helixes may be used to refer to either reverse helixes or standard helixes. A standard helix is a helix that is adapted to cause rotation in one direction. In contrast, a reverse helix is a helix that is adapted to cause rotation in the opposite direction as the standard helix. 
     The first helix is a helix that is configured to flow in one circular direction. The first reverse helix is a helix that is configured to flow in the opposite circular direction. Multiple helixes and reverse helixes can be configured in a particular embodiment. A helix is considered to be a plate with a desired pitch attached to a pipe. In the present invention, the pipe is the dip tube  106 . Different variations of pitch and length can be employed for use in the agitation device. The length and pitch of the helix for this invention are not important. What is important is the combination of a standard helix and a reverse helix. By combining a standard helix with a reverse helix, the shear stress incurred by the oil entrained with gas is increased, therefore causing the entrained gas to be released. Gas released is considered separated gas. 
     Multiple variations of helixes can be used in the agitation device. For example, multiple sets of standard helixes and reverse helixes can be adapted. Helixes with multiple plates can be used. A helix with multiple plates is a helix that has two distinct plates the run the length of the helix. A double helix is a helix with a second plate. A standard helix will be comprised of standard plates wherein in a reverse helix will be comprised of reverse plates. For example, a double helix that is a standard helix may have a first standard plate  901  and a second standard plate  902 . A double helix that is a reverse helix may have a first reverse place and a second reverse plate. 
     The helixes may be adapted with helix perforations  1001  to allow separated gas to move upward after being released from the oil. Helix perforations  1001  may include holes cut into the plates of the helixes. For example, a helix might have multiple holes cut on the center of the surface of a plate. Alternatively, a helix plate might have cuts at the inner or outer portion of the plate. The helixes are discussed further in the detail of  FIGS. 9-10 . 
     In  FIG. 2  the dip tube  106  can be seen extending from the inlet  303  upward through the slotted body  108 , the lower perforated tube  110 , the anchoring device  105 , the upper perforated tube  109 , and to the top  103  of the downhole assembly  101 . The dip tube  106  is positioned near the center of each elements of which the dip tube  106  extends upward through. Oil with entrained gas is pulled into the holes  111 . The slotted body  108  has a hollow interior  203  which oil with entrained gas can flow through. The hollow interior  203  encompasses the space between the interior surface  202  of the slotted body  108  and the exterior face  201  of dip tube  106 .  FIG. 3  is a downhole assembly  101  showing a first standard helix  301  and a first reverse helix  302 . The dip tube  106  along with the helixes are shown in an exploded view removed from the other elements of the downhole assembly  101 . The exemplary embodiment shown in  FIG. 3  reflects the adaptation of one standard helix and one reverse helix. The helixes are located relatively lower in elevation compared to the holes  111  on the slotted body  108 . 
     In  FIG. 3  a flow through assembly is adapted to the downhole assembly  101 . The flow through assembly comprises the lower perforated tube  110 , the upper perforated tube  109 , and the anchoring device  105 . Alternatively, the upper and lower perforated tube may be combined with the anchoring assembly as one piece. A more detailed description of the flow through assembly is provided in the description of  FIG. 8 . 
       FIG. 4  is a downhole assembly  101  showing two standard helixes and two reverse helixes. In this embodiment, a first standard helix  301 , a first reverse helix  302 , a second standard helix  401 , and a second reverse helix  402  are adapted to the dip tube  106 . The dip tube  106  along with the helixes are shown in an exploded view removed from the other elements of the downhole assembly  101 . The exemplary embodiment shown in  FIG. 4  reflects the adaptation of two standard helixes and two reverse helixes. The helixes are located relatively lower in elevation compared to the holes  111  on the slotted body  108 . 
       FIG. 5  is a downhole assembly  101  showing four standard helixes and four reverse helixes. In this embodiment, a first standard helix  301 , a first reverse helix  302 , a second standard helix  401 , a second reverse helix  402 , a third standard helix  501 , a third reverse helix  502 , a fourth standard helix  503 , and a fourth reverse helix  504 , are adapted to the dip tube  106 . As many helixes can be adapted to the dip tube  106  as reasonably allowed by the size of the dip tube  106 . The dip tube  106  along with the helixes are shown in an exploded view removed from the other elements of the downhole assembly  101 . The exemplary embodiment shown in  FIG. 5  reflects the adaptation of four standard helixes and four reverse helixes. The helixes are located relatively lower in elevation compared to the holes  111  on the slotted body  108 . 
       FIG. 6  is a downhole assembly  101  showing two standard helixes and one reverse helix. In this embodiment, a first standard helix  301 , a first reverse helix  302 , and a second standard helix  401  are adapted to the dip tube  106 . The dip tube  106  along with the helixes are shown in an exploded view removed from the other elements of the downhole assembly  101 . The exemplary embodiment shown in  FIG. 6  reflects the adaptation of two standard helixes and one reverse helixes. The helixes are located relatively lower in elevation compared to the holes  111  on the slotted body  108 . As shown in  FIG. 6 , an uneven number of standard helixes and reverse helixes can be adapted to the dip tube  106 . 
       FIG. 7  is a downhole assembly  101  showing a first standard helix  301  and a first reverse helix  302 . The dip tube  106  along with the helixes are shown in an exploded view removed from the other elements of the downhole assembly  101 . The exemplary embodiment shown in  FIG. 3  reflects the adaptation of one standard helix and one reverse helix. The helixes are located relatively lower in elevation compared to the holes  111  on the slotted body  108 . The embodiment shown in  FIG. 7  does not include a flow through assembly. A standard tubing anchor  701  is adapted to the downhole assembly  101  to secure the downhole assembly  101  to the casing  102 . In this embodiment, a standard tubing anchor  701  commonly used in the industry is adapted for use with the improved agitation device disclosed herein. 
       FIG. 8  is a detailed drawing of an exemplary flow through assembly. The second aspect of the invention is the flow through assembly. The flow through assembly is comprised of the lower perforated tube  110 , the upper perforated tube  109 , and the anchoring device  105 . A dip tube  106  extends through the approximate center of the elements of the flow through assembly. The lower perforated tube  110  has an inner surface  802   b . The upper perforated tube  109  has an inner surface  802   a . The anchoring device  105  has an inner surface  802   c . The three inner surfaces can be referenced as an inner surface  802 . Between the exterior face  201  of the dip tube  106  and the inner surface  802  of the lower perforated tube  110 , the upper perforated tube  109 , and the anchoring device  105 , is a flow channel through which separated gas may flow. The flow channel between the exterior face  201  of the dip tube  106  and the inner surface  802   a  of the upper perforated tube  109  is the upper flow channel  806 . The flow channel between the exterior face  201  of the dip tube  106  and the inner surface  802   b  of the lower perforated tubed  110  is the lower flow channel  807 . The lower flow channel  807 , the center flow channel  801 , and the upper flow channel  806  are fluidly connected such that gas can flow through the channels. 
     The upper perforated tube  109  has one or more upper perforations  803  which gas can flow through so to exit the upper perforated tube  109 . As shown in  FIG. 8 , there are a multitude of upper perforations  803 . The lower perforated tube  110  has one or more lower perforations  804  which gas can flow through. As shown in  FIG. 8 , there are a multitude of lower perforations  804 . 
     A anchoring device  105  further comprises a structure  805  that connects the downhole assembly  101  and the casing  102 . Separated gas flows between the casing  102  and downhole assembly  101  up past the anchoring device  105  and toward the surface. Once past the anchoring device  105 , the separated gas may continue to flow toward the surface between the casing  102  and the string of tubing. The structure  805  of the anchoring device  105  is an object which restricts the flow of the gas. The structure  805  of the anchoring device  105  is often configured to minimize its cross section so to allow reduce the restriction on the flow of gas. 
     The flow through assembly as disclosed herein, additionally allows separated gas to flows upward toward the surface from the agitation device by passing through the center flow channel  801  of the anchoring device  105 . The separated gas may enter the lower perforated tube  110  through the lower perforations  804 , flow through the center flow channel  801  of the anchoring device  105 , and out of the upper perforated tube  109  through the upper perforations  803 . This adaption allows for the gas to flow upward with a reduced amount of resistance from the structure  805  of the anchoring device  105 . 
     The lower perforated tube  110  may be fluidly connected to the peak  114  of the slotted body  108  such that the lower flow channel  807  is fluidly connected to the slotted body  108 . Fluids and gases may communicate through a fluid connection. Separated gas may flow through the slotted body  108  into the lower flow channel  807 . Alternatively, the downhole assembly  101  may be configured without a lower perforated tube  110 . In such embodiment the center flow channel  801  may be fluidly connected to the slotted body  108 . In such embodiment, the anchoring device  105  may be connected to the slotted body  108  or a pipe may connect the anchoring device  105  to the slotted body  108 . 
       FIG. 9  is an exemplary helix. The exemplary helix shown may be a first standard helix  301  attached to the exterior face  201  of the dip tube  106 . In the embodiment shown, the first standard helix  301  is comprised of a first standard plate  901  and a second standard plate  902 . The exemplary helix is a double helix. A reverse helix is a helix that rotates around the dip tube  106  in the rotational direction opposite to the standard helix  301 . 
       FIG. 10  is an exemplary helix. The exemplary helix shown may be a first standard helix  301  attached to the exterior face  201  of the dip tube  106 . In the embodiment shown, the first standard helix  301  is comprised of a first standard plate  901  and a second standard plate  902 . The exemplary helix is a double helix. In the exemplary helix, the first standard plate  901  and the second standard plate  902  further comprise of helix perforations  1001 . The embodiment shown reflects the use of holes cut in the plates. 
     Explanation of Exemplary Language 
     While various inventive aspects, concepts and features of the general inventive concepts are described and illustrated herein in the context of various exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. 
     Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the general inventive concepts. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions (such as alternative materials, structures, configurations, methods, devices and components, alternatives as to form, fit and function, and so on) may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the general inventive concepts even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure; however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated.