Methods and systems for hydrostatic testing a pipeline

A method of hydrostatic testing a selected section of a pipeline having fluid flow therethrough, including the steps of introducing into the pipeline a pig train including a leading seal pig, a supply liquid slug, a first isolation tool, a test liquid slug and a second isolation tool; permitting the train to traverse the pipeline interior by the force of fluid flow until the lead isolation tool is forwardly of and the second isolation tool is rearwardly of the selected selection of the pipeline; securing the position of the pig train by applying exteriorly of the pipeline appropriate signals to actuate the isolation tools to each engage and seal the interior of the pipeline trapping the test liquid slug therebetween; and pumping liquid from the supply liquid slugs into the test liquid slug to a hydrostatic testing pressure. In addition to testing, the pipeline can be repaired by moving the pig train into position where a defective area can be isolated by additional isolation tools.

REFERENCE TO PENDING APPLICATIONS

This application is not based upon any pending domestic or international patent applications.

REFERENCE TO MICROFICHE APPENDIX

This application is not referenced in any microfiche appendix.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to methods for hydrostatic testing a section of a pipeline that employs a pig train including plugging tools, at least one sealing pig, slugs of fluid between the sealing pig and plugging tools and a pumping system for increasing the hydrostatic pressure interior of the pipeline between spaced apart plugging tools.

2. Description of the Prior Art

The invention herein discloses methods and systems for hydrostatic testing a pipeline.

In North America, Europe and other industrialized areas of the world, vast quantities of fluids, including liquids and gases, are transported through pipelines. These fluids include crude oil, lubricating oil, natural gas, gasoline and so forth. These pipelines are often of considerable length and extend over all types of geographic terrains. Many pipelines today are located underneath rivers and lakes and growing mileages of pipelines are located on the surface of the earth covered by seawater, that is, submerged or subsea pipelines.

In the event of damage, deterioration from age, or changing conditions including need for modification or structural changes to a pipeline, a serious problem rises as to the manner in which the flow of liquid, either fluid or gases, through the pipeline can be controlled during repair, maintenance and testing. Most pipelines in use today are continuously filled with liquids or gases. Since the volume contained in a relatively long length of pipeline is great, the value of the contained fluid is great. In addition, in most instances if it is necessary to repair, replace or test a pipeline it is not feasible to drain the pipeline due not only to the cost of the contents but many of the products carried by pipelines are deleterious to the environment. Many governmental restrictions around the world prohibit discharging pipeline contents into the environment for the purpose of facilitating repair, maintenance or testing.

One method used to test or repair a pipeline is to isolate and evacuate a section of the pipeline by using internally transportable plugging devices or pigs. In order to employ a plugging pig it is necessary to be able to stop the pig at a pre-selected location and by internal means, closing the plugging pig to seal the interior of the pipeline against further fluid flow. When repair, maintenance, testing or so forth is completed, it is then necessary to release the grip of the plugging pig to permit it to resume passage through the interior of the pipeline by the force of fluid flow. In this way, the plugging device in the form of a fluid transportable pig, can be removed from the pipeline after its use has been completed and the pig reused for further applications.

A commonly used method to stop flow in a pipeline temporarily is by the utilization of a product commercially available under the trademark STOPPLE® as manufactured and supplied by T.D. Williamson, Inc. of Tulsa, Oklahoma. A method of use of the STOPPLE® plugging system includes installing an access fitting followed by boring a large diameter hole at each of two extremities of the pipeline to be worked on or tested, inserting a plug in each large hole and pivoting the plug about a transverse axis to plug the pipe. After the repair work is done, the plugs are pivoted back and removed from the hole and large flanges are secured on the fittings. While this system functions successfully in areas where the pipe is readily accessible from the earth's surface, in many locations accessibility is a continuous problem and this is particularly a burdensome problem with pipelines running under lakes, rivers and especially pipelines running on the ocean floor. For this reason and in recent years plugging tools or plugging pigs have been developed. These devices are insertable in the pipeline for movement by fluid flow and can be actuated at a selected point to grip the interior wall while simultaneously sealing the interior wall of the pipeline against fluid flow. The invention herein includes methods, systems and devices for employing such plugging pigs in pipelines particularly for hydrostatic testing of pipelines.

For additional information relating to the background of the subject matter of this invention, reference may be had to the following United States patents and publications:

PatentNumberInventorTitleRE33,160GuthrieMethod and Apparatus For Inspecting Lateralet al.Lines3,746,026HerringPipeline Plugging Pig3,750,711ConklinMethod and Apparatus For Testing For Leakset al.In Pipes3,837,214GuestSelf-Propelled Pipeline Plug3,908,682ThompsonMethods and Apparatuses For Remotely andReleasably Sealing A Pipe Line4,026,329ThompsonMethod and Apparatus For Remotely andReleasably Sealing A Pipeline4,314,577BristerInstallation, Hydrostatic Testing, Repair andModification of Large Diameter Fluid Trans-mission Lines4,441,328BristerMethod and Apparatus For Forming ATemporary Plug In A Submarine Conduit4,484,602GuthriePacker For Sealing Lateral Lines4,691,728MathisonElectronic Test and Seal Apparatus andMethod4,854,384CampbellPipeline Packer4,991,651CampbellPipeline Packer For Plugging A Pipeline AtA Desired Location5,139,576DavisMethod and A Horizontal Pipeline PigLaunching Mechanism For SequentiallyLaunching Pipeline Pigs5,272,646FarmerMethod For Locating Leaks In A FluidPipeline and Apparatus Therefore5,372,162FreyRepair Device For The In Situ Repair ofPipes, And A Method of Repairing Pipes5,433,236ZollingerApparatus For Moving A Pipe Inspectionet al.Probe Through Piping5,842,816CunninghamPig Delivery and Transport System ForSubsea Wells5,983,948Yagi et al.Method of Repairing An Existing PipelineIncluding A Main Pipe and A Branch Pipe6,022,421Bath et al.Method For Remotely Launching Subsea PigsIn Response To Wellhead Pressure Change6,348,869AshworthPipe Leak Detection

BRIEF SUMMARY OF THE INVENTION

The methods and systems of this invention for testing a length of a pipeline includes the use of at least two isolation tools introduced into the pipeline. The isolation tools having means for being propelled by fluid flow (liquid or gas) through the pipeline. Further, the isolation tools have means by which they may be set at selected locations and actuated for sealing the pipeline against fluid flow therethrough. Specifically the isolation tools each have facilities for receiving a signal applied from the exterior of the pipeline to initiate the steps required for gripping the interior of the pipeline to stop movement through the pipeline and for sealing the interior of the pipeline against fluid flow.

A sealing pig is introduced in the pipeline a pre-selected time or distance prior to the introduction of the first isolation tool. The sealing pig is typically a pig that does not include moving parts or communication systems but includes only cups or discs that extend from a central body to slidably engage the interior wall of the pipeline. The cups or discs of the sealing pig slide on the interior of the pipe wall as moved along by fluid flow. When the fluid flow stops, the sealing pig stops since it has no means of locomotion. Further, the sealing pig has no means whereby it can be commanded to stop nor can the speed of movement of the sealing pig be effected by externally applied signals since the sealing pig is solely controlled by the speed of movement of the fluid through the pipeline.

After a sealing pig is introduced into a pipeline, such as by the use of a pig launcher, the interior of the pipeline may be filled with a selected fluid that is different from the fluid normally flowing through the pipeline. For instance, after a sealing pig is introduced a quantity of fluid, such as water, can be introduced into the pipeline. This fluid that is introduced into the pipeline and that is different from the fluid or gas that is normally flowing through the pipeline is referred to as a “first testing liquid slug”. After the pre-selected quantity of the liquid slug is introduced into the pipeline, then the first isolation tool is immediately introduced.

After the first isolation tool is introduced, a time delay or liquid volume displacement occurs before a second isolation tool is introduced. The spacing between the first and second isolation tools is selected in accordance with the time delay or liquid volume displacement of launching the second isolation tool. That is, the speed of travel of the liquid in the pipeline multiplied by the time of delay between launching the first and second isolation tool, or a measured volume of liquid is pumped, thereby determines the spacing between the two isolation tools. This spacing can vary according to the intended purpose. When the purpose is to hydrostatically test a portion of the length of a pipeline, the spacing between the isolation tools equal to the length of the pipeline to be hydrostatically tested. This can vary from a few feet to several miles.

After the second isolation tool is introduced into the pipeline in a preferred practice of the invention a second or follow up slug of liquid is introduced into the pipeline in a quantity as required for the procedure to be employed. After the required follow up slug of liquid is introduced into the pipeline, a trailing seal pig is launched into the pipeline.

Thus the basic system of this invention is a pig train made up of a lead seal pig, a leading liquid slug, a lead or first isolation tool, a test liquid slug and a second isolation tool and a trailing seal pig, if needed. Thus, in addition to the pigs making up a basic train for use in practicing the invention, that is a seal pig and two isolation tools, the train includes a leading liquid slug between the leading seal pig and the leading plug pig and a test slug between the two isolation tools.

The system further includes a pump for pumping liquid from the leading liquid slug past the lead isolation tool and into the test slug. When the system is used for a pipeline located on the earth's surface, the pump can be located exteriorly of the pipeline. To provide access from the pump to the interior of the pipeline, small diameter branch fittings are secured to the pipeline, such as by welding, and then by using a hot tapping system the pipeline is penetrated. This can be accomplished while the pipeline is under pressure by employing hot tapping equipment illustrated and described in the following patents:

PatentNumberInventorTitle4,579,484SullivanUnderwater Tapping Machine4,880,028Osburn et al.Completion Machine5,439,331Andrew et al.High Pressure Tapping Apparatus6,012,878HicksPressure Balanced Subsea Tapping Machine6,648,562Calkins et al.Apparatus For Tapping A Hole In A Pipeline

Instrumentation is contained in a control module portion of at least one of the isolation tools for measuring and recording fluid pressure in the test section to provide the hydrostatic testing information obtained by the use of the system of the invention. Each isolation tool as employed in the invention will consist of at least three sections, including a gripper module, a packer module and an instrument module. The gripper and packer modules typically include hydraulic cylinders and therefore a source of hydraulic fluid pressure is employed in each isolation tool.

The invention herein uses a pig train formed of a combination of isolation tools (plugging pigs), batching pigs, and liquid batches, also referred to as “slugs”, which can be propelled along inside the pipeline. This test “train” can be set, a hydrostatic test performed and the train moved along to the next position, and the whole sequence repeated, without the need for welding on test heads, filling the pipeline with test medium, draining the pipeline of test medium and removing the test heads—as in a conventional hydro-testing approach. Therefore, the concept of this invention has the benefit of faster and/or lower cost pipeline hydrostatic testing. The invention herein makes it possible to hydrostatically test relatively short sections of a new pipeline just behind the pipe welding crew during the construction process—resulting in commissioning of new pipelines sooner than by conventional testing methods.

With an additional isolation tool in the pig train, an in-service pipeline can be hydrostatically tested and leaking or failed sections can be repaired while maintaining operating pressure in the pipeline, eliminating the need to completely remove the pipeline from service and without draining down or blowing down the pipeline to remove product therefrom.

The methods of this invention may be used for post-construction proof that a pipeline is capable of withstanding the intended design or operating pressure. Another purpose for this invention may be to qualify an in-service pipeline for an increase in operating pressure over what it has been operating at heretofore in the event the pipeline requires re-rating. The methods of this invention are useful for pipeline hydrostatic testing to meet governmental or industrial code requirements, as well as for insuring general safe operating practices.

A section of a pipeline may be hydrostatically tested and isolated for repair, using a “pig train” (a combination of isolation tools and batching pigs), in relatively short or long sections. The “isolation tools” referred to in this document may also be termed “plugging pigs” and are special purpose “smart” pipeline pigs that are designed to travel along in the pipe, propelled by the flow of product (by pumping or compression), stopped at selected locations and activated by a through-the-pipe-wall communication device to engage the inside diameter of the pipeline with grips and packers to hold back pressure in the pipeline. The isolation tools can then be commanded to release, following equalization of pressure, by external communication devices. “Seal pigs” as referred to herein may be termed “batching pigs” and are designed to provide a tight seal with the pipe wall while traveling along inside a pipeline as propelled by fluid flow and to contain a “batch” or “slug” of fluid that may be of a different type than that within the pipeline ahead or behind the pig train.

The basic configuration of the hydrostatic testing plugging pig train consists of a sealing pig in front, followed closely by a lead isolation tool with a short “make-up” batch or slug of test medium (water or other incompressible fluid) in between. The lead isolation tool is followed by any practical length of test medium and a second isolation tool oriented in the opposite direction in order to hold test pressure in the test section when both isolation tools are set and their packers energized. The length of this test section can be determined by taking into consideration testing time, hold time (for leak detection), elevation changes of the pipeline, which can result in variation of pressure along the test section, and other factors.

A problem exists with elevation changes in that when using water or other liquid as the test medium, pressure will vary significantly with elevation change (approximately 15 psi for every 33 feet of elevation due to the effect of gravity or “head”) along the length of the test medium slug. This may limit the length of the test section due to the possibility of over pressuring the pipeline by the packer module.

In the case of new construction where there is no need to isolate operating pressure during repairs of failed or leaking sections, the trailing isolation tool may be followed closely by another seal pig with a slug of make-up test medium in between. In the case of an operating pipeline, where a defective section of pipeline needs to be isolated from operating pressure during repair, a third isolation tool may follow the second isolation tool by some practical distance with a slug of test medium in between primarily to maintain a fixed distance behind the second isolation tool and to prevent a compressible gas “bubble” from seeping into the test section.

The main purpose of the make-up media is to provide make up volume during test pressurization and to prevent a compressible gas “bubble” from seeping into the test or isolation media. Another purpose of the trailing “make up” slug is to carry a fluid such as methanol or glycol to allow drying of an on-stream gas line while the pig train moves along. The hydrostatic test slug (water or mostly water) leaves a wet pipe wall which results in gradual loss of test medium volume as the train moves down the pipe. This make-up slug can serve the dual purpose of providing make-up medium and drying the line behind the test train.

As previously stated, pumping up the test section utilizes hot-tapping with two small pipe nipples welded to the pipe on either side of an isolation tool with a pumping manifold installed in between by way of temporary external piping. This manifold transfers test medium from a leading slug during pressure testing and returns it to the leading slug during depressurization. Test pressure pumping may also be accomplished by the use of on-board pumping capabilities with a passageway through an isolation tool to transfer liquid into the test section.

If a leak is discovered and located in an operating pipeline, the pig train of this invention can be advanced until the leak is straddled by an isolation section of the train. The isolation tools to either side of the leak can be set and the isolated section of pipe containing the leak can be depressurized and repaired without draining or venting product beyond the relatively short isolated section. After repairs, the isolation tools can be unset and the train moved along to the next test section.

Because of the chance of having a rupture during hydrostatic testing of an operating pipeline, an additional isolation tool may be included to block ambient pipeline pressure downstream of the pig train while a different isolation tool can be set to block ambient pipeline pressure upstream of the pig train. In this case, the additional isolation tool prevents the dislodging and movement of the other isolation tools toward the rupture, possibly saving damage and loss of much or all of the hydrostatic test media. This extra step may be necessary because isolation tools typically only hold pressure in one direction and may be dislodged if pressure is reversed.

In a deep subsea environment a huge hydrostatic head exists on the outside of the pipeline so hydrostatic testing of the pipeline takes on different problems. When the pipeline in question is a gas line, the internal pressure may be low compared to the external pressure. The methods of this invention are advantageous in finding and isolating leaks. If two isolation tools are moved into a pipeline with a fluid slug between them, they can be set and let the external (ambient) hydrostatic head of the water column provide the test pressure. If a pressure rise occurs between the isolation tools, then a leak is present. In this case, since the external pressure is greater than the internal pressure the leak can be located and isolated without moving the pig train. The pipeline could then be repaired or a repair clamp installed for repair at a later date.

In the case where the gas pressure in a subsea pipeline is higher than the ambient pressure, a plugging pig train with two outward looking isolation tools with a slug of water between can be launched into the pipeline and moved along by the internal hydrostatic pressure of a surface riser water column balancing pressure with the external ambient pressure, and with gas at a higher pressure than ambient sub-sea hydrostatic pressure on the other side of the pig train. In this case, the water column in the riser balances the ambient pressure while a hydrostatic pump at the surface is used to provide the testing pressure. The lead isolation tool is set, pressure is pumped up, the trailing isolation tool is set, pressure in the riser is released, resulting in test pressure remaining in the slug between the isolation tools. A sensed pressure drop would indicate a leak. Alternatively, an on-board pump can provide the additional test pressure between the isolation tools when set, eliminating pressure cycles in the riser.

A better understanding of the invention will be obtained from the following detailed description of the preferred embodiments and claims, taken in conjunction with the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the invention that is now to be described is not limited in its application to the details of the construction and arrangement of the parts illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. The phraseology and terminology employed herein are for purposes of description and not limitation.

Elements illustrated in the drawings are identified by the following numbers:

This invention provides systems and methods to test a portion of the length of a pipeline. The test can be of various types but basically constitute hydrostatic testing, that is testing the reaction of the pipeline to fluid pressure in the pipeline. Such tests can be made for many reasons. As an example, a length of a pipeline can be tested to see if there are leaks in the pipeline within the test section. The pipeline sections can be tested to determine whether it is capable of withstanding increased fluid pressure. This need arises frequently when pipelines that have been constructed and operated for several years are considered for upgrade to increase the flow rate which mandates increasing the pressure of fluid moving through the pipeline.

The invention herein makes use of devices that are sometimes referred to as “plugging pigs” but which will be referred to herein as “isolation tools”. Pipeline pigs of this type typically are formed by a packer module in cooperation with a gripper module. These components can be manufactured separately and then joined to form an integral unit in which the components work in cooperation with each other. A “gripper module” means a section of the pipeline pig that can be actuated to grip against the interior wall of the pipeline and thereby lock the pig assembly into a temporarily fixed position in the pipeline. A packer module is an apparatus that can be expanded to close fluid flow through the pipeline.

The system for practicing the invention is in the form of a train of elements introduced by a launching device into the interior of the pipeline. InFIG. 1, a section of a pipeline is illustrated, broken into sections10A,10B and10C. The basic elements making up the pigging train illustrated inFIG. 1is a lead seal pig12contained with pipeline section10A; a lead isolation tool generally indicated by the numeral14contained in pipeline section10B; a second isolation tool generally indicated by the numeral16contained in pipeline section10C; and a trailing seal pig18that is also contained within pipeline section10C.

In addition to the physical apparatus making up the train of components as illustrated inFIG. 1for performing hydrostatic testing of the interior of the pipeline, a leading liquid slug20is introduced into the interior of the pipeline filling the space between lead seal pig12and lead isolation tool14. Between lead isolation tool14and second isolation tool16, there is a test slug22, that is, a column of water traveling in the pipeline between the first and second isolation tools. Between second isolation tool16and trailing seal pig13is a trailing liquid slug24.

FIG. 1illustrates the placement of the train of isolation tools, seal pigs, and liquid slugs within pipeline10as used in the process of conducting a hydrostatic test of the pipeline through a length of the pipeline designated as D2that contains test liquid slug20. This length D2could be a little as a few feet, such as testing a weld joint or a single joint of pipe, or can be as much as several miles. To hydrostatically test the pipeline through the length of D2it is necessary to increase the hydrostatic pressure of the test liquid slug22. In order to do this, two small pipe nipples26A and26B are affixed to the exterior of the pipeline and the pipeline is hot tapped to provide access to the interior. Nipples26A and26B are welded to the pipeline to either side of lead isolation tool14. After the nipples are welded to the pipeline, by the use of hot tapping equipment, such as is available from T.D. Williamson, Inc. of Tulsa, Okla., holes are drilled through the pipe wall and into the interior of pipe10. Thereafter piping28A and28B can be affixed to the pipe nipples26A and26B to connect to a pumping manifold30. By means of a pump within manifold30test media liquid can be extracted from leading liquid slug20and pumped into test liquid slug22thereby raising the hydrostatic pressure in the test liquid slug. Within piping manifold30instrumentation is provided to measure and record the pressure applied to test liquid slug22which represents the hydrostatic pressure applied to section D2of the pipeline. The instrumentation within pumping manifold30can include facilities for measuring and recording the maximum pressure to which the pipe section D2is subjected. Further, after a predetermined pressure is applied to test liquid slug22, pressure can be maintained for a period of time and a record made as to whether the pressure decreases indicating whether there is a leak in the pipe section D2.

After completing the hydrostatic testing of pipe section D2by pumping fluid from leading liquid slug20into test liquid slug22and making a record of fluid pressure measurements, the pressure can be relieved by allowing fluid flow back into slug20. The pipe nipple26A and26B can then be closed and the pumping manifold and piping28A and28B can be removed. Thereafter, the entire train of equipment illustrated inFIG. 1can be moved along by releasing the gripper and packer modules making up each of the isolation tools14and16.

FIG. 7illustrates one embodiment of an isolation tool. In the embodiment ofFIG. 7, a packer module32is shown connected by universal joint34to a gripper module36. Gripper module36is, in turn, connected by a universal joint38to a control module40.

Each of the isolation tools14and16provides a system for closing fluid flow through the interior of a pipeline10. The isolation tools are transported through pipeline10by the force of fluid flow. Each isolation tool can be remotely controlled to grip the interior of the pipeline to stop travel through the pipeline and remotely controlled to form a seal that terminates fluid flow. This type of tool is known in the industry as an “isolation tool” since it can be used to isolate portions of a pipeline.

Isolation tools14and16each includes instrumentation that is utilized to react to a remote signal to cause the tool to set itself in a selected position within pipeline10. This instrumentation is well known in the pipeline industry and is not part of the invention herein. Stated another way, the invention herein is not concerned with the electronics by which isolation tools14and16are remotely controlled by means from exterior of the pipeline but is concerned with systems and methods of making use of such tools for hydrostatic testing pipelines.

InFIG. 1, isolation tools are indicated generally by the numerals14and16. An example of an isolation tool is illustrated in more detail inFIG. 7. As illustrated in this figure the isolation tool is in the form of a train of components flexibly coupled together and configured to travel within a pipeline as a unit and for isolating a portion of the pipeline by closing off fluid flow through it. The isolation tool as shown inFIG. 7includes, as major components thereof, a packer module32, a grip module36and a control module40. The rearward end of the packer module32is attached to the forward end of gripper module36by a ball joint34. The rearward end of grip module36is secured to the forward end of control module40by a ball joint38. Ball joints34and38are representative of mechanical means of flexibly connecting the basic elements of the isolation tool to each other so that the tool can move around bends in a pipeline without putting stress on the individual connected components.

Control module40includes a housing which is typically tubular as indicated with closed ends and in which the forward closed end includes a portion of ball joint38. Positioned on the exterior of the tubular housing are radially extending elastomeric discs42that have exterior diameters that are less than that of the pipeline (not shown inFIG. 7) in which the isolation tool is employed. Discs42function essentially to support the control module centrally within the interior of a pipeline and to slidably seal against a pipeline interior wall.

Within control module40there is electronic instrumentation that functions in accordance with known techniques familiar to those in the pipeline pigging and isolation tool industry by which signals can be received from the exterior of a pipeline. Hydraulic control compartment controls the application of hydraulic fluid pressure to gripper module36and packer module32.

An example of a grip module as used in the isolation tool of this invention is illustrated inFIGS. 5 and 6.FIG. 5shows a pipeline10in which grip module36is positioned. Grip module36includes an elongated central body frame member44that is shown to be of hexagonal cross-section inFIG. 6. Radially extending from frame member44are six radially extending rails46. Each of rails46is in the form of a flat metal plate with a rail edge48that is inclined relative to the central body longitudinal axis. Slidably received on each rail edge48is a grip saddle50, each having an inclined edge52that slides on a rail edge48. Affixed to each of the grip saddle50is a grip shoe54that has a serrated surface as seen inFIG. 5to non-slidably engage pipeline interior wall58. The angular relationship between rail edge48and grip saddle inclined edge52is such that the grip shoe surface56engages the pipeline interior surface58in a parallel relationship.

Secured to a side wall of each of rails46is an actuator body60, seen inFIG. 6, each of which slidably supports a double ended piston62. An intermediate portion of each piston62is secured to a grip saddle50so that the displacement of each grip saddle and in turn each grip shoe54that slides on an edge48of each rail46is controlled by a piston62. Each of the actuator bodies60includes an actuating cylinder. When pressure is applied to the actuating cylinders, pistons62function to move the grip saddles50and thereby grip shoes54in the direction towards or away from pipeline interior wall58.

It is important that the grip shoes54are not in engagement with the interior surface of pipeline, such as surface58as seen inFIG. 5, as the isolation tool moves through the pipeline prior to reaching a point where closure of the pipeline is required. For this reason the grip module36, as seen inFIG. 5, includes wheels64that roll along the interior surface of the pipeline.

As seen inFIG. 7, grip module36is connected at its rearward end to ball joint38that is positioned between the grip module and control module40. As a part of each of ball joints34and38as seen inFIG. 7a coiled spring66is employed for the purposes of preventing relative rotation between the components making up the isolation tool train.

An embodiment of a packer module, indicated by the numeral32inFIG. 7, is illustrated in the cross-sectional view ofFIG. 4. Packer module32includes a tubular body68having an external cylindrical surface70and, at one end thereof, a radially extending fixed forward flange72. The tubular body68includes a portion defining a cylinder wall74with an internal cylinder surface76. Centrally received within cylindrical surface76is a double ended piston rod78. Secured to a rearward end of piston rod78is a radially extending rearward flange80. Piston rod78has a threaded opening in the rearward end thereof that receives a threaded end of a ball joint82. Rearward flange80is captured between the rearward end of piston rod78and ball joint82. Secured to a forward surface of rearward flange80is a backup flange84that is slidably received on external cylindrical surface86. Backup flange84is opposed to fixed forward flange72.

Received on external cylindrical surface86is a first elastomeric packer88and an identical second elastomeric packer90. Each of the elastomeric packers88and90is, in radial cross-section, frusto-conical, that is, each has sloped wall surfaces. Each of the elastomeric packers have an internal cylindrical surface92that is slidably positioned on external cylindrical surface86. Each of the elastomeric packers has an outer pipe wall contacting surface94and opposed side wall surfaces96.

Slidably received on tubular body external cylindrical surface70is a backup ring98having opposed sidewalls102that taper towards an outer circumferential surface104. Side wall surfaces102of backup ring98mirror the side wall surfaces96of elastomeric packers88and90.

Extending radially from piston rod78is a piston106having an outer cylindrical surface that sealably engages internal cylindrical surface76.

Affixed at the rearward end of cylinder wall74is a cylinder head108having an opening110therein that slidably receives piston rod78. Thus there is created within internal cylindrical wall74a cylindrical area112that, when pressure is applied thereto tends to move piston rod78forwardly towards the right, and consequently rearward flange80and backup flange84towards the right, to compress elastomeric packers88and90against forward flange72. This action causes the outward displacement of the elastomeric packers so that the outer circumferential surfaces94thereof engage the interior wall of a pipeline to thereby close fluid flow through the pipeline. That is, when fluid pressure is applied to cylindrical area112, as dictated by control module40, elastomeric packers88and90are squeezed and radially outwardly expanded to close fluid flow through the pipeline.

To support the plugging module ofFIG. 4, a number of rearward wheels116are employed. In the same way, forward wheels118support the forward end of the plugging module away from a pipeline internal wall as the isolation tool train moves through a pipeline.

The typical isolation tool as identified by tools14and16ofFIG. 1include, as a part thereof, as have been described, a control module40that typically includes a power source in the form of a battery. Further, the control module typically includes a hydraulic pump powered by battery power that is used to actuate the packer module32and gripper module34.FIG. 7illustrates a modified isolation tool that has each of the components as have been discussed with respect toFIG. 1but, in addition, includes first and second auxiliary power modules120and122. First power module120is connected to the rearward end of control module40by a universal joint124and second power module122is connected to the rearward end of first power module120by a universal joint126. Power modules120and122are providing auxiliary and enhanced power, particularly battery power, for operating an on-board hydro-test pump or for the actuation of the other components making up an isolation tool.FIG. 7illustrates flexible conduits128and130. These flexible conduits interconnect the various elements of the isolation tool for purposes of supplying electrical energy and hydraulic fluid pressure from one component to another. For instance, one of the flexible conduits may be used to supply hydraulic pressure to actuate packer module32and gripper module36. The flexible conduits can also be employed for providing electrical power from one unit to another such as electrical power from power modules120and122to a pump contained in control module40. Further, one of the flexible conduits128and130ofFIG. 7may be employed for the transmission of pipeline liquids, such as liquid from leading liquid slug20passed lead isolation tool14and into the test liquid slug22as shown inFIG. 1. That is, one of the conduits128and130may be employed as required for hydrostatic testing the section of the length of the pipeline indicated by designation D2onFIG. 1.

FIG. 1of the drawings shows the use of two plugging pigs14and16to conduct a hydrostatic test of a length of pipe indicated by the designation D2.FIG. 2illustrates an alternate embodiment of the methods and systems of this invention that is particularly useful in the case of an operating pipeline where a defective section of the pipeline needs to be isolated from operating pressure during repair. In this case a third isolation tool132is employed. The third isolation tool132follows isolation tool16and is separated by a liquid slug134. The function of liquid slug134is to maintain a fixed distance behind second isolation tool16and to prevent a compressible gas bubble from seeping into the test liquid slug22that is contained between isolation tools14and16. Thus, liquid slug134makes up an isolation section between isolation tools16and132. In the arrangement ofFIG. 2the lead seal pig12, lead liquid slug20, lead isolation tool14, first liquid slug22, second isolation tool16, trailing liquid slug24, and trailing seal pig18functions for essentially the same purposes as described with respect toFIG. 1. In summary, the difference betweenFIGS. 1 and 2isFIG. 2provides an additional isolation tool132to provide for an isolation liquid slug section134.

A main purpose of each of make-up medium slugs20and24is to provide make-up volumes to test liquid slug22during test preparation and to prevent a compressible gas bubble from seeping into either the test liquid slug22or the isolation liquid slug134.

Another purpose of the trailing liquid slug24can be to carry a liquid, such as methanol or glycol, to allow drying of new or on-stream gas line while the pig train moves along. The test liquid slug22when hydrostatic testing a pipeline is nearly always water or mostly water and leaves a wet pipe wall which results in gradual loss of test slug volume as the train moves along the length of the pipeline. This trailing liquid slug which may also be termed a “make up liquid slug”, then can serve the dual purpose of providing make-up liquid to isolation liquid slug134and drying the interior wall of the pipeline behind the test train.

FIG. 3shows an additional alternate embodiment of the systems and methods of this invention for hydrostatically testing a pipeline.FIG. 3adds toFIG. 2the use of an additional isolation tool, that is, a fourth isolation tool136that provides for a second isolation liquid slug138between it and isolation tool14. Second isolation liquid slug138is supplementary to leading liquid slug20as described with reference toFIGS. 1 and 2but, in addition, the fourth isolation tool136helps isolate the basic test system from the downstream pressure of an operating pipeline, in the event of a rupture in the test section, in order to prevent isolation tool14from being pushed toward the rupture resulting in damage to the tool.

As previously stated, pressure within test liquid slug22is provided by a pumping manifold30and piping28A and28B connected to pipe nipples26A and26B which are hot tapped onto the exterior of the pipeline10. This system works satisfactorily when the pipeline10is on the earth's surface but represents a problem if the pipeline hydrostatic test section D2is on an ocean floor, that is, subsea or even if on the floor of a lake or river. For these applications test pumping pressure may be accomplished by on-board pumping capabilities provided by one or more of the isolation tools14and16. As illustrated inFIG. 7, within control module40is instrumentation140which includes systems for measuring and recording the hydrostatic pressure applied to the pipe section D2. Also included within control module40is an actuation hydraulic pump142to apply hydraulic fluid pressure to packer module32and gripper module36so these devices can be set and unset as dictated by signals conveyed from exterior of the pipeline. In addition, an isolation tool may contain, such as within control module40, an on-board test pump144powered by an on-board battery146. On-board test pump144is connected to draw liquid from leading slug22and pump this liquid past isolation tool14and into test liquid slug22to increase the hydrostatic pressure on the length of the pipeline D2. This is accomplished without the use of pumping manifold30, piping28A and28B and without the necessity of installing pipe nipples26A and26B. If the hydrostatic test section22is of relatively short length, such as if the length of this section was only sufficient to test a weld joint or a joint of pipe, then the power required to drive on-board test pump144could be supplied from on-board battery146. On the other hand, if the length of pipeline D2that is being hydrostatic tested is relatively long, substantial additional power or energy source is required and thus, as is illustrated inFIG. 7, the use of auxiliary power modules120and122would likely be required. The number of power modules obviously can vary according to the quantity of fluid required to hydrostatically test pipeline section D2according to the volume thereof which is directly related to the internal diameter of the pipe and the length of the pipe section D2.

Referring back toFIG. 7, if the hydrostatic fluid to be injected into test liquid slug22is to be moved by power supplied from within the pipeline, the test fluid can flow from a fluid inlet148on the rearward end of second power module122, through flexible conduit130to a fluid outlet150on packer module32. If auxiliary power modules120and122are not employed, fluid inlet148would typically be positioned on the rearward end of control module40.

The invention thus provides a unique system that is in the form of a pig train made up of pipeline pig components that are moved by the force of fluid flow through the interior of a pipeline, which components include at least two isolation tools, at least one seal pig and a power pumping system for moving fluid under pressure into the interior of the length of the pipeline between the two isolation tools to hydrostatically test the pipeline. The system is adaptable for use to hydrostatically test pipelines on the earth's surface or in subsea environments.