Methods and apparatus using a hydrocarbon gel to isolate mainline valves in a pipeline during a hydrotest

In accordance with illustrative embodiments of the present invention, the existing valves in a crude oil, gas, or other product pipeline are positively sealed off to allow a pressure test to be made of a section or segment of the pipeline between the valves. The section is packed with a hydrocarbon or aqueous liquid. A mixture of a highly viscous hydrocarbon based gel material and a lost-circulation material are injected into the pipeline segment adjacent each valve to form plugs in the line. The gel plugs are squeezed under pressure against the internal components of each valve to cause all leakage paths therein to be bridged over and sealed off. The pipeline segment then is pressure tested to determine if there are any leaks therein, after which the gel is flushed out of the line and broken down into a linear pumpable state for disposal.

This invention relates generally to the testing of a section or segment of 
an oil, gas, or other product pipeline, which has existing valves at the 
opposite ends of the segment, with a hydrocarbon liquid or water under 
pressure (hereafter referred to as "testing" or "pressure testing"). More 
particularly the present invention relates to new and improved methods and 
apparatus for positively sealing off any leaks in such valves so that the 
line segment may be tested in a reliable, efficient and economical manner. 
BACKGROUND OF THE INVENTION 
A large diameter pipeline that is used to convey fluid products such as 
crude oil or gas over long distances, for example between an oil field and 
a refinery, between pipelines or between unloading facilities and storage 
terminals, must occasionally be tested to confirm that there are no leaks 
in the line which could pose a hazard to the environment, waterways or to 
individuals or property along the route. Testing also must be performed on 
all operational pipelines after a leak has been located and repaired, or 
as required by regulation. 
To test a pipeline, a procedure generally known as pressure testing may be 
used. This involves pressurizing a hydrocarbon liquid in the line to a 
predetermined value, and monitoring the pressure and temperature of the 
liquid in the line to determine if there are any leaks. Although a test of 
an entire pipeline system conceivably could be accomplished in a single 
operation, it is more typical for a series of independent tests to be made 
of relatively short-length segments thereof. The pipeline system is 
typically divided into segments by existing valves. These valves may be 
anywhere from a few feet to several miles apart. Since testing involves 
temporary shut-down of the pipeline, which adversely impacts the operation 
of refineries, terminals and other facilities which depend upon its 
throughput, there is a compelling need to conduct testing operations as 
quickly, reliably and economically as possible. 
To conduct a meaningful test of a pipeline segment, there must be assurance 
that the test segment is positively isolated. If the valves that are used 
to isolate the test segment leak during the test, it is not possible to 
determine from pressure and temperature data whether the pipeline segment 
itself will hold pressure or not. Therefore some means should be provided 
to positively seal off these valves during the test so that if the test 
pressure drops off, the leak must be somewhere in the segment, not at a 
valve. 
In the past, one process that has been used involved cutting the pipeline 
and installing test headers to isolate the mainline valves during testing. 
This procedure is very labor intensive and costly, takes a considerable 
amount of time, and is destructive to the pipeline. Another technique 
required blind flanges or a thin metal plate to be inserted between 
existing flanges. However, this labor intensive method might require 
draining the line product before installation of the "blinds". Thus the 
problem of providing a quickly implemented, economical and reliable way to 
positively seal off a mainline, a branch line or a cross-over valve during 
a test of a pipeline segment remains unsolved. 
An object of the present invention is to provide new and improved methods 
and apparatus for positively sealing off existing valves in a pipeline 
which obviates the foregoing problems and difficulties with prior schemes. 
Another object of the present invention is to provide new and improved 
methods and apparatus of the type described where a hydrocarbon gel 
mixture that can be easily injected into, and removed from, an inner 
region of a pipeline adjacent an existing valve is used to positively seal 
off the valve during a pressure test. 
Still another object of the present invention is to provide new and 
improved methods and apparatus of the type described where a 
hydrocarbon-based highly viscous gel having a lost-circulation material 
suspended therein is injected into the pipeline adjacent existing valves. 
The injected gel bridges over and seals off any leakage paths in the valve 
so that a segment of a pipeline having the valve therein can be tested. 
SUMMARY OF THE INVENTION 
These and other objects are attained in accordance with the concepts of the 
present invention through the provision of a pipeline testing procedure 
where a segment or section of the pipeline contained within existing 
valves is filled or packed with a hydrocarbon liquid under pressure and 
then each of the valves is sealed off by injecting a mixture of a 
hydrocarbon liquid-based, highly viscous crosslinked gel and a 
lost-circulation material into the interior of the pipeline segment at 
locations adjacent each valve to form gel plugs at each location. The gel 
plugs squeeze against the respective valve elements and their seats. If 
any leakage paths are present therein, the gel will extrude through the 
leaks and lost circulation material will bridge over and seal off all such 
paths so that water or hydrocarbon pressure can be maintained within the 
interior of the line segment during the test, unless, of course, the 
segment leaks. After completion of the test, the respective gel plugs are 
flushed out of the line, for example, by opening the point of injection 
and allowing the water or hydrocarbon liquid to displace the gel under 
pressure into a nearby tank or transport truck. After flushing, no 
appreciable solid matter is left in the pipe. Then the gel is broken down 
into a linear pumpable state so that it may be disposed of in an 
environmentally sound manner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
With reference to the drawing FIGURE, a section or segment 9 of a pipeline 
10, which may, for example, have a diameter in the order of about 2-48 
inches or more, is shown as having existing valves 11 and 12 connected at 
the opposite ends thereof. The valves 11 and 12 typically could be a 
variety of valve types, i.e., gate, ball, plug and the like, which may be 
equipped with typical block and bleed ports 44. The pipeline 10 may be 
from several feet to many miles long, and a large number of the valves 11 
and 12 may exist to divide the line into a large number of individual 
segments 9. Each segment 9 may be, for example, from a few feet to several 
miles long, dependent on elevation changes along the line and other 
factors. As is well known to those familiar with this art, the large size 
existing valves 11 and 12 have a propensity to leak due to age, corrosion, 
debris or defect, to an extent which will prevent testing of the pipeline 
segment 9 unless something is done to prevent leakage of the valves. Of 
course if either of the valves 11 or 12 leaks into an adjacent section of 
the pipeline, there is no way to determine from pressure and temperature 
data taken from the segment 9 whether there is a leak therein or not. 
In accordance with this invention, however, the valves 11 and 12 are sealed 
off by injecting a gel plug into the segment 9 adjacent each valve which 
enables a meaningful pressure test of the segment to be performed. 
For purposes of simplification, the right side of the drawing shows only 
those equipment components which are used to isolate the existing valve 
11. It will be recognized that an identical set of equipment components 39 
also is located adjacent the other valve 12 and used to isolate it in the 
same way. Two crews may be employed to operate both sets of equipment 
simultaneously or one crew may seal off the valve 11 and then shut-down 
and seal off the other valve 12, or vice-versa. After each of the valves 
11 and 12 has been sealed off, then a test can be made of the pressure 
integrity of the segment 9 using the equipment components shown at the top 
center of the FIGURE. 
The test components that are used in connection with the present invention 
include a tank 13 that is filled with hydrocarbon liquid or water and 
connected by a line 14 to a pump 15 whose discharge side is connected to 
the interior of the segment 9 by a flow line 16, a control valve 17 and a 
coupling such as a hot tap 18. The pump 15 usually is a positive 
displacement device such as a multi-plex pump. Gauges 40 and 41 are used 
to monitor the pressure and temperature of the hydrocarbon liquid in the 
segment 9, and a recorder 42 may be used to provide a test record. These 
can be located in the near vicinity of one of the valves 11 or 12, or 
somewhere along the segment 9 near the center thereof. 
The gel plug injection equipment includes another hot tap 19 or the like, 
which is made a short distance (for example about 1-2 feet) from the 
existing valve 11. The tap 19 connects a control valve 20 and a line 21 to 
the discharge side of a pump 22 via a tee 23. The pump 22 is connected to 
the outlet of a batch mixer 24 by a flow line 25, and the mixer is 
connected to a drain outlet on a tank 26 by another line 27. The tank 26 
has a fairly large capacity, and initially is filled with hydrocarbon 
liquids. A valve 30 and a line 31 from the tee 23 in the flow line 21 are 
used to provide a sampling point 32 where certain characteristics of the 
gel being pumped into the interior of the pipeline segment 9 through the 
line 21, the valve 20 and the hot tap 19 can be monitored. 
A gel mixture that is formed by operation of the above components is 
injected into the interior of the pipeline segment 9 through the hot tap 
19 to provide a gel "plug" 36 adjacent the mainline valve 11. The gel 
comprises an organic gel including a non-polar, liquid hydrocarbon and a 
gelling amount of a gelling agent mixture of a phosphate ester component 
which is composed predominately of ethyl oleic phosphate and an alkali 
metal aluminate to form a product that is viscoelastic and cohesive. These 
types of gels are more fully described in U.S. Pat. No. 4,537,700 which is 
incorporated herein by reference. The preferred liquid hydrocarbons are 
crude oil, diesel, kerosene, or other normally liquid, aromatic or 
aliphatic hydrocarbons or chlorinated derivatives thereof. The mixture 
further includes a suspended lost-circulation material, which preferably 
consists of cellophane or polyester flakes or chips. Although cellophane 
flakes or chips are the preferred lost-circulation material, other 
materials that may be used are sawdust, cracked pepper, naphtha, small 
mothballs or waxy resin beads. Other flake, granular and fibrous 
substances well known to those skilled in the art as lost circulation 
materials also may be used. 
The gelling agent may be mixed with the hydrocarbon liquid at the mixer 24 
via a pump 37 through an injection line 38 to provide a concentration 
range of from about 15-50 gallons gelling agent per 1,000 gallons gel. An 
activator also may be added to form the viscoelastic characteristics of 
the gel at the mixer 24 via a pump 35 through an injection line 34 to 
provide a concentration range of from about 15-50 gallons activator per 
100 gallons gel. Alternatively, the gelling agent and activator may be 
added to tank 26. In this alternative, circulating line 28 goes from the 
mixer 24 through an access port 29 in the top of the tank 26 and extends 
down to near the bottom wall thereof as shown in dotted lines. In this 
manner the lines 27 and 28 and an auxiliary pump (not shown) in the mixer 
24 may be used to circulate between the tank 26 and the mixer 24 to mix 
the gelling agent, activator or other substances and additives with the 
hydrocarbon liquid in the tank. The lost-circulation material is added at 
the mixer 24 as indicated by the arrow 33, preferably in a range from 
about 0.25 to about 1 percent-by-weight. The alkali metal aluminate is 
added to the mixture through line 34 and pump 35. 
The gel is pumped by pump 22 through line 2 1, control valve 20 and hot 
plug 19 and is injected into the segment 9 in a selected volume such that 
the plug 36 has an appropriate length, e.g., about 50 feet or more if 
needed. When injection of the plug 36 is completed the pump 22 is shut 
down and the valve 20 is closed. A similar gel plug 36 is formed adjacent 
valve 12 through hot plug 19' and control valve 20' in fluid communication 
with substantially identical gel injection equipment 39. The hydrocarbon 
liquid in the segment 9 then is pressurized through operation of the pump 
15, which squeezes the gel against the internal components of the valve 11 
so that it seeks out and bridges over any leaks therein. The pipeline 
segment 9 then can be pressure tested with assurance that any leaks which 
are discovered are in the segment rather than in a valve. 
OPERATION AND USE 
To pressure test a segment 9 of the pipeline 10, the fluid product in the 
segment may be left in the pipeline segment; alternatively, the fluid 
product may be replaced by water or another liquid hydrocarbon. All 
existing valves to contain the segment are closed. The liquid is "packed" 
into the segment 9 by pressurizing to a pressure which will ensure that 
there are no compressed air pockets therein, but well below the test 
pressure, e.g., to half the test pressure The gel is injected into the 
interior of the segment 9 at each end thereof adjacent the test sides of 
the respective valves 11 and 12 as shown in the FIGURE. The basic gel 
mixture is formed in the mixer 24 combining the gelling agent, activator 
and lost circulation material with the hydrocarbon liquid therein. The 
proper amount of gelling agent is added to the mixer 24 by using the pump 
37 and flow line 38. The proper amount of activator is supplied to the 
mixer 24 by using the pump 35 and the flow line 34, which causes 
substantially immediate gellation. The proper amount of lost circulation 
material also is dumped into the mixer 24 and is held in suspension by the 
constituents of the gel. The pump 22 is operated at the necessary pressure 
to inject a predetermined volume of gel and suspended lost-circulation 
material into the line segment 9 adjacent the valve 11. As mentioned 
above, the preferred length of the plug 36 may be about fifty (50) feet or 
more in a 2-48 inch diameter pipeline, dependent upon the size of the 
leakage at the valve. 
After the pump 22 is shut down and the valve 20 closed the pressure is 
raised to the predetermined test pressure, generally in the range of 
200-500 psi, by operating the pump 15 or a smaller unit. If there are any 
leaks in the internal parts of the valve 11, the right end of the plug 36 
will be squeezed against the valve and will seek out and flow into all 
leakage paths that exist. In short order, these leakage paths will be 
bridged over by the lost-circulation material as the gel migrates through 
any leaks to form a bubble- tight seal. The pipeline segment 9 then may be 
tested by applying pressure thereto with the pump 15. Test pressures and 
temperatures are monitored on a continuous basis by the gauges 40 and 41 
and are recorded at 42. 
A drop in test pressure over a period of time which cannot be correlated 
with a temperature change indicates that there is a leak somewhere in the 
segment 9 that needs to be located and repaired. If the test pressure 
holds steady over a number of hours, it can be concluded that the segment 
9 has no leaks which need attention. When the test is completed, a vent, 
e.g., one associated with the 2 inch control valve 17 is opened to bleed 
down the pressure in the line segment 9. The head or break tank 13 and the 
pump 15 of the test unit may be located near the center of the segment 9, 
or a fairly short distance from one of the valves 11 or 12 and may be a 
pump dedicated to the pressure test or contract or an existing facility 
pump. 
After the pressure test is completed, each gel plug 36 is flushed out of 
the segment 9 at each end and into an available transport tank by opening 
an available flow port, for example, the 2 inch injection valve 20 near 
the mainline valve 11, or pumped out the injection valve 20. The plug at 
the other end of the segment 9 also may be removed through components 19' 
and 20'. After removal, the gel is broken down into a linear pumpable 
state. 
Although not shown in the FIGURE, other valves in the system which 
typically are found along the pipeline segment may be sealed off in the 
same manner as disclosed above. Where a bypass valve or a branch line 
valve is located fairly close to one of the existing valves 11, 12, both 
valves may be sealed off simultaneously by using the same gel plug 36, 
although it may have to be lengthened. 
It now will be recognized that new and improved methods and apparatus have 
been disclosed for sealing off mainline, branch or bypass valves in a 
pipeline system so that individual segments thereof may be pressure tested 
in a quick, reliable and economical manner. These new methods avoid the 
installation and use of various expensive and destructive mechanical 
devices, e.g., test headers and/or blind flanges. After a test of the 
pipeline segment is completed, the gel plug may be flushed out, broken 
down and disposed of in an environmentally sound manner. 
Since certain changes or modifications may be made in the disclosed 
embodiment without departing from the inventive concepts involved, it is 
the aim of the appended claims to cover all such changes and modifications 
falling within the true spirit and scope of the present invention.